The internet, and the tuning world, and especially the tuning world on the internet, is full of shit talkers. No matter if it's people lying to help their their business, or people talking shit because they genuinely believe they're right, there's more wrong than right info out there.
Which is why, aside from a few exceptions from people who have PROVEN to me they know their shit, I only listen to proof, facts, data, whatever- Opinion means zero from 99% of the world to me.

The thing is, a LOT of people, even HUGE groups of people, can be suckered in by someones claims. Fuck, it's how a lot of businesses make money; all based on a lie.

I came across a cracking one recently.
​I don't know the origins of these lies, maybe it's just habitual, but this is someone that a certain group of people treat like a god, and for a LONG time too, many many years, and think is an "Ex F1 Engine Designer" (Is he? Fuck knows, Googling his name finds he's been around the tuning scene for a very long time, but that's it, and what he comes out with doesn't sound like one to me).

I noticed him (without having a clue who he was or what people thought of him) making very confident but dubious comments a while ago on Facebook, but whatever, I ignored them.
But then I saw him slagging off some cheap Chinese inlet manifold, and for quite an odd reason too, so I had to comment, and I'm glad I did. And it went like this...

His comment that finally made me bite was...

I couldn't resist saying something this time, so I replied...

He replied in no uncertain terms what his feelings were about this...!

And went STRAIGHT in there with the big "Do you know who I am?" internet Ronnie Pickering comment...

So I asked who, hoping he would dig himself a hole, and he reeled off some BIG claims...

And dig a hole for himself he did, I mean... This is a Mountune Focus WRC inlet plenum....

So I asked him why 'Dave', who he worked for, used them, if they're so bad and stupid...

And he makes an excuse, which basically meant his name dropping was meaningless. And also odd, as Mountune's BTCC efforts were mostly on the turbocharged Cosworth YB in the mid 80s on. And yes, the Cosworth YB inlet has trumpets too lol.

BUT he also claims he worked on the highest power Formula One Turbo engine ever, ie the BMW M12/13. BUT this is the BMW M12/13 inlet, complete with huge trumpets...

So I asked him about that, and he makes another lame excuse...

So we end up having a rather odd little conversation where he tried to deflect the argument and said something else that makes zero sense about uneven flow to cyls...

So he tried the old "If they were so good, why isn't EVERYTHING fitted with them" line...

Then for some reason he again tried to justify his point by showing what the entire universe knows- That not EVERY engine runs trumpets. No shit Sherlock...

So of course, I replied with my own picture...

And after that he unfortunately stopped replying. I think maybe he knew he was rumbled. But he's literally treated like a legit god of tuning among a certain bunch of people, as they believe he's an ex F1 Engine Designer.
Maybe he is? But if nothing else, that proves just because someone has had a job, doesn't mean they are right!

Also, just as it's interesting, here's a few more pics of the current modern F1 Turbo engines take on the inlet trumpets in the plenum thing. This Honda motor uses two big trumpets, adjustable length too, one for each bank of cyls it seems.

People make a REALLY big deal about a lot of things when it comes to the specs of tuned cars, but personally, I think most people obsess over the wrong things. 
And turbo brand is one of them. Fact is, contrary to popular belief and sales talk, turbos are not magic, and if the general specs are the same, the general performance will be the same. Exact? Hell no. Similar enough that other factors make a far bigger difference? Hell yes. And this feature shows that above all else I think.

This comparison came about after a friend of mine got his FD RX7 mapped, and it made 600bhp on the dot, and to be fair performs bloody well. But I did wonder what it was like compared to other peoples, as spec wise it wasn't quite the same as what most do.
Luckily it turned out, the vast majority of the UKs powerful rotaries use this same mapper on this same dyno, meaning there's tons of comparable dyno graphs about, so while it's different days, that's no big deal in the UK as it's the same drab weather 247/365, so it's as fair a comparison as humanly possible.

Obviously you'll get people making excuses 'I had a misfire' 'My dog ate my homework' and so on, but the simple fact is ALL of these cars were mapped, and ALL of these results were publicly posted, so there clearly wasn't any massive issues with any of them or they wouldn't have been mapped in the first place. So no excuses!
The only car I know from the list is the HX50 one, and I know that was missing a fire ring in the wastegate so it was leaking like fuck, slowing spool and hindering it holding boost at high rpm, and compression test was showing under 5bar on all rotor faces (not bedded in fully and wide tolerances rather than fucked), but whatever, I expect a few of these cars had minor things like that so no excuses for anyone, it's as fair as a comparison as possible.

To make it comparable, I only bothered with cars that made over 500bhp, and as only one of the cars made serious power below 5000rpm, I only compared above that, as that's before the start of most of the cars performance powerbands begin anyhow. 

​And here's the graph...

That is a fairly confusing jumble of lines, but I'll do my best to explain it all to you...

Two cars, both with the biggest turbos and the biggest ports, made by far the least power at 5000rpm, barley over 200bhp.
​Most were in the middleground, and one was already making great power by then, one with small ports, a middle sized turbo, but MOST IMPORTANTLY, a lot of boost.
This boost thing is a funny one, and one you only see really with rotaries and stuff with real lairy cams etc- Basically anything with bugger all low down power when N/A- Basically, the powerband, at lower boost levels, isn't from whenever full boost is (like it is on most milder builds), it's from whenever the ports or cams allow the real powerband to begin, just like N/A.
BUT once you crank the boost above about 1.5bar/23psi, the positive effects of the boost MORE than counteracts this, and you once again end up with an engine that the powerband starts whenever full boost hits, and this car running 26psi shows it well, already over 400bhp at 5k.
The only anomaly here is the brown line, which I had as an engine with big ports, a big turbo, and fairly low boost. Yet seems to be doing well. It's possible I was given the wrong info on this cars spec...

By 6000rpm the big 76mm HKS T51R engine with the giant J ports has woken up, as has the car with the 67mm Holset HX50 25cm and a half bridge, and they're now matching the power of the two street ported cars running BorgWarners.
The EFR equipped car and the one with the big 72mm turbo are 40bhp down by this point.
The 'Anomaly' brown line car (which I'm sure I've been given the wrong spec for!) is about 40bhp up from that middle batch.
And as before, the big big boost small port car is absolutely flying, making over 550bhp already!

By 7000rpm, the situation is getting very different. The big boost small port car has already gone beyond peak power, and is now only in the middle of the pack.
The big port big 72mm turbo car has really woken up and has gone from last to making more power than a car that was making over 100bhp more than it just 2000rpm earlier.
All the BorgWarners are starting to tail off a little, probably due to the fairly small turbine housing choices? Just a guess knowing how they're often chosen, but rotaries do like a big turbine.
The 'anomaly' car is still doing well, but starting to flatten out, which again says to me the spec isn't what I thought it was.
And the two cars with the big turbine flow, the 25cm HX50, and the HKS T51R, are going up like a rocket.
Aside from the unknown 'anomaly' car, the HX50 and T51R cars are 50bhp+ ahead of the rest now.

Another 500rpm and aside from the three with the biggest turbine flow, and decent size ports, ie the 72mm turbo one, the T51, and the HX50 25cm, things are dropping down.
But the HX50 and T51R cars have now both gone 600bhp+ over 50bhp more than the next closest car.

By 8000rpm, while pretty much everyone is at peak or beyond, some cars are still FAST and still well worth revving. The T51R car has just about peaked and is still well over 600bhp, the Holset HX50 is still making 580bhp, and even the 72mm turbo one is doing ok, and would probably have really benefitted from a few more psi boost as it was running 17psi vs the HX50 and T51s 20psi.
The rest, well they're all still making 480bhp+, so FAST still, and defo worth revving out to this rpm, aside from the poor old big boost small port car, which has widly ran out of puff and the power has fell off a cliff, now making barely over 350bhp- In the real world the driver would've changed up at 7500rpm at the latest.

By 8500rpm, only the two 70mm+ inducer turbos on big port engines are still barely dropping, but the next two biggest, 66mm BW and 67mm Holset are still making over 500bhp so defo worth revving them this high.
By now the other four cars aren't even comparable.

By 9000rpm there's only two engines still in the game, albeit past their peaks, and lo and behold they're the two with the biggest turbos and biggest ports.

SO WHAT ENGINE DID BEST? Well, let's compare some averages...

Realistically, on something FD RX7 weight, 'FAST' begins at 400bhp.
So let's look how wide was the '400bhp or more' powerband...

Winner here was one of the ones with the least low down power, because it could hold it up top, the giant J port T51R SPL car! 3250rpm worth of 400bhp+ power band.

Joint second, was the car that was flying from low down, but tailed off big time up top, the smallest port car, and the car with fairly small ports but a big turbo that held on well up top, both with 3000rpm worth of 400bhp+

Joint third was the Holset HX50 25cm car, and the big 72mm turbo car, with 2750rpm of 400bhp+

Here's the full 'how long over 400bhp' results- 
1st- HKS T51R SPL J-Bridge 20psi- 3250rpm
2nd- BW S365SXE 26psi small street port- 3000rpm
3rd- BW S366 15psi Street Port- 3000rpm
4th- 67mm Holset HX50 25cm, 20psi half bridge- 2750rpm
5th- Full bridge, 72mm turbo, 17psi- 2750rpm
6th- BW S400 full bridge 17psi 2500rpm
7th- BW S363 street port 19psi 2250rpm
8th- BW EFR9174 19psi bridge 2250rpm

But 'over 400bhp' is a bit misleading when some made over 200bhp more than that!
So let's look at the average power they made above the magic 400bhp mark, which is probably the BEST comparison of what would be the fastest in the real world, as their powerbands are all fairly close in size...

Well first and last place are the same, but the rest, not so much!

Average power beyond 400bhp...
1st- HKS T51R SPL J-Bridge 20psi- 563bhp
2nd- 67mm Holset HX50 20psi half bridge- 523bhp
3rd- BW S365SXE 26psi small street port- 518bhp
4th- Full bridge, 72mm turbo, 17psi- 514bhp
5th- BW S400 full bridge 17psi- 511bhp
6th- BW S363 street port 19psi- 489bhp
7th- BW S366 15psi Street Port- 488bhp
8th- BW EFR9174 19psi bridge- 474bhp

What about their average power levels through the rev range when they're at 80% or more of their peak number? Well ok then...
1st- HKS T51R SPL, J-Bridge, 20psi- 599bhp
2nd- 67mm Holset HX50 25cm, 20psi, half bridge- 545bhp
3rd- BW S365SXE 26psi small street port- 528bhp
4th- Full bridge, 72mm turbo, 17psi- 525bhp
5th- BW S400 full bridge 17psi- 522bhp
6th- BW S366 15psi Street Port- 502bhp
7th- BW S363 street port 19psi- 498bhp
8th- BW EFR9174 19psi bridge- 474bhp

So how wide was the powerband when they were over 80% of their peak power? Let's see...
1st- HKS T51R SPL J-Bridge 20psi- 2750rpm
2nd- BW S365SXE 26psi small street port- 2750rpm
3rd- Full bridge, 72mm turbo, 17psi- 2500rpm
4th- 67mm Holset HX50 20psi half bridge- 2250rpm
5th- BW S400 full bridge 17psi- 2250rpm
6th- BW EFR9174 19psi bridge- 2250rpm
7th- BW S366 15psi Street Port- 2000rpm
8th- BW S363 street port 19psi- 2000rpm

SO what hell have we actually learnt from this? Well, that's a matter of opinion to some extent, but I can tell you what I think...

Does brand matter? NO.
The RX7 scene in the UK is allllll about the BorgWarner turbos. Well considering they were generally in the bottom of the lists, and the 'old fashioned' Holset, HKS, and the 72mm (think it was a Turbonetics?) were generally near the top, I think this assumption many have, is wrong.
TBF I've always known this, I said it countless times, but it's how it is, turbos aren't magic, and aside from a few exceptions, technology hasn't changed hugely, so like for like, the wheels, ie the important factor, from any of these brands are within a few % of each other, and the biggest names are often far from the best, just the most hyped.

Boost helps a LOT-
Is it a surprise the car running 6psi more than the rest did better than lower boost cars with similar turbos? No. Boost is king above EVERYTHING else. If you want your car to perform, no1 thing IMO is to enable to to be safe at big boost. Nothing else will gain you as much as big boost can. 

Good turbine flow gives MORE overall gains than faster spool will-
It's only an educated guess of course, but looking at the powerbands, I'd say most of these BorgWarners had pretty small turbine sides, IMO too small for a big power rotary, and it shows in the results.
Peppier low down, but then lose out massively overall, giving less overall performance.
If you want low rpm performance, I'm not sure a rotary is for you.
Perhaps the clearest example of this is the car with "The highest tech" turbo, the EFR9174. At £1500+ it was probably the most expensive, over three times the HX50 for sure, was a ball bearing, billet wheel, stainless housing, Indy Car developed, proper bit of kit. Yet was near the bottom of the list for everything, despite being 75bhp up from the big T51 at 5000rpm.
And why? The 74mm turbine wheel, which is one of the smallest if not the smallest in this test is going to be one factor. Possibly compounded with a small A/R housing, as that seems to be the done thing with a most UK rotaries.

You gain MORE overall performance building for a high rpm powerband than a low rpm one-
​Again, it's all about the flow. Big ports might kill low rpm performance, but what it loses low down, providing you have the rest of the spec to match, you will MORE than gain up top. Fuck, the T51R J Port car was TOP of every chart, all the averages, widest powerband, despite having the LEAST low rpm power...!

Your turbo spec needs to match your engine spec-
Big turbo and small ports, small turbo and big ports. It's a mismatch that doesn't really work. Sometimes can kill the performance at both ends of the graph, giving you less spool than you expected, but less top end too.
The EFR is probably the best example of this one again too. Decent amount of boost, big ports, but with a fairly small turbine side on that turbo, it stayed near the bottom of the pack from low to high rpm.

SO WHAT ONE WOULD I CHOOSE?
From these results alone? The T51R SPL car, without doubt. It kicked ass.
It might not come alive until after 5000rpm, but it's right up there with the rest of the pack by 5750rpm making over 400bhp, but makes over 500bhp 750rpm later, over 600bhp 750rpm after that, and holds over 650bhp to the 9000rpm limiter, and no doubt would've carried on making massive power to 10,000rpm if they turned the limiter up. And at only 20psi too. Biggest power, biggest powerband, biggest averages, biggest rpm, it just wins everywhere aside from low rpm power.
But if you want that because you don't understand what gears are for, go buy a diesel.

The BIG boost car would be massive fun on the road, a great laugh, super drivable and a tyre smoker, but the fact it's on it's ass beyond about 7.5k is hard for me to accept from a rotary.

Bang for your buck, it's the HX50 car. A turbo you can get for £500 brand new. That fits to an off the shelf old skool Greddy manifold (most BWs need different/newer manifolds otherwise the turbo hits the intake manifold), and so on.
Since this dyno a lot of things have improved on the car- Mostly a better wastegate setup that doesn't massively leak, and a better intercooler, so I'm keen to see how it goes next time it gets mapped on that dyno, and I can show you comparison data in a later post about that too...

Cheers.
Stav

​Fitment to the Volvo housings is much the same as the ones above, but with the added bonus of enabling a HE221W to be fitted to even 1980s Volvo turbo manifolds as they also used this same oddball flange.
In fact, these housings can be used for anyone wanting a HE221W with T3 flange, as that's what these Volvos actually are, just with that strange circular indent- Simply get the flange machined flat and it's normal T3 fitment- That's fairly common the other way around actually, ie machining the flange flat on Volvo manifolds to fit T3 turbos.

The stock HE221W actuator is actually slightly longer than needed on these Volvo housings, but if you wanted the compressor outlet to face the same way as standard (often not if you're running a bigger intercooler etc) you'd need to rotate the housing/core anyhow (dead easy, just a circlip), but as you can see, it'd fit straight to the stock manifold and downpipe.

As well as these two Volvo housings I checked, there's other, older Volvos that use a TD04HL on the Redblock engine, so you can easily fit a HE221W to these too.
​

What A/R size is my Holset turbine housing?

Holset don’t use A/R, they, like Mitsubishi, KKK, Trust, and others, use cm2 to measure turbine housing size.
A/R and cm2 isn’t directly comparable, cm2 is a static measurement, A/R isn’t, but you can still get pretty close if you want to compare. On a HX35/GT35 sized turbine wheels, 12cm is generally accepted to be about 0.89 A/R, but the larger the turbo the smaller A/R any given cm2 would be the equivalent of, with 14cm generally being considered to be just A/R 0.80 on GT40/HX40/S300 sized turbine wheels, and conversely, on a tiny turbine a 6cm housing could still be the equivalent of A/R 0.80.
Because of this use your common sense, use your eyes, and do your research. A 25cm HX55 might sound like a super huge housing when you’re used to 9cm housings on HY35s, but a HX55 is practically twice the size and a 25cm housing is actually not that big.
You can use the housing sizes on other stuff as comparisons too. With most Subaru turbos using cm2, and Mitsubishi Evo ones also, you can compare those to the similar smaller Holsets.
And for bigger ones, well the famous Trust turbos used on countless big power Japanese cars used cm2 as well. The T88 34D, a 1000bhp capable unit, like an older fashioned version of a HX55, and often seen on Skylines, Supras, and RX7s, tended to be a 22cm housing, as was the 38GK version. The Trust T78, a 700bhp turbo, so HX40/HX50 size, but older fashioned, was generally 17 to 24cm housings. The Trust T67 turbo, similar to a HY35 in capability, but again, older design, also had similar housing sizes, 8cm and 10cm most commonly, but 12cm and 16cm was also used. Even Trust’s version of the TD04, good for ~300bhp, used a 8.5cm housing.

There's a common list of A/R to CM2 that goes around the internet, and it's spoken about and published by people who make out they're experts in the field, but IMO it hints at how clueless they really are, and it says this...

6 cm2 = 0.41 A/R
7 cm2 = 0.49 A/R
8 cm2 = 0.57 A/R
9 cm2 = 0.65 A/R
10 cm2 = 0.73 A/R
11 cm2 = 0.81 A/R
12 cm2 = 0.89 A/R
14 cm2 = 1.05 A/R
16 cm2 = 1.21 A/R
18 cm2 = 1.37 A/R
21 cm2 = 1.61 A/R

NO! Fuck no. As said, A/R vs CM2 totally depends on the turbine size, and the above is only about right for TD04 sort of size turbines.

In REALITY, it's more like THIS...
HE221W- 6cm- 0.47, 8cm- 0.60, 9cm- 0.68
HX35- 16cm- 0.98, 14cm- 0.90, 12cm- 0.80, 10cm- 0.65

HX40- 18cm- 1.05, 16cm- 0.92, 14cm- 0.85

HX52- 16cm- 0.85, 13cm- 0.73, 11cm- 0.60
HX55- 28cm- 1.42, 25cm- 1.26, 19cm- 0.96, 16cm- 0.78, 14cm- 0.71, 12cm- 0.62

And obviously, any turbos that are in between sizes of the above for their turbines, so HY35, HX32, whatever, you can extrapolate from there obviously...

​Who’s safe to buy off?
I think this can be summed up with “Any well proven company”. In the UK the Holset specialist seller from an aftermarket tuning point of view has always been Compressor Racing, they've been around for years, supplied thousands of Holset turbos to people.

On the other end of the scale, I have still been stung buying what was meant to be 'good used' ones from a certain Polish eBay seller who often has a lot of Holsets listed- In reality it was a badly worn one sprayed with silver paint to not look too shit in the pics. Mad thing is, he's still out there selling painted up old junk, and for barely cheaper than new ones either. Seems madness buying that shiz just to try and save a few quid.

Lately I've seen a few other overseas sellers promoting their Holset sales with some proper shady stuff. Half truths and flat out lies. And it's working too. Boils my piss...

​HX20- According to Holset literature, the compressor, at least the biggest version, is good for 275bhp, making it similar to a Mitsubishi TD04, a turbo it shares a lot of components with. HX20s are very rare though, and I honestly don’t recall seeing one in my life to be honest, on an OEM or tuned engine...!

HX55- This is the equivalent of a Garrett GT42 or BorgWarner 9180, the HX55 is capable of around the 1000bhp mark when pushed hard, though I’ve seen a couple of people claim 50-100bhp more than that. Housing wise, the smallest you commonly see is a 19cm internally gated housing, and then there is 22cm and 25cm non-wastegated housings also quite commonly found, and while most are T6 flange, T4 versions exist.
Most HX55s have v-bands holding both the compressor and turbine housings on, but there’s a less common version with a bolt-on turbine housing, which I’ve seen 22cm and 25cm T4 flange housings for.
For their size they’re impressive bits of kit, and on 4ltr engines like 1UZs they make serious power from just 3500rpm on even with the biggest 25cm housing, which is well impressive for a turbo good for 4 figure power numbers!

To make things even more confusing, in the last year or so of the HX naming scheme, Holset decided to badge HX52s as HX55s, despite having the small 70mm exducer turbine wheel and housing. So that's worth keeping an eye out for.

Check out these HX55 videos below-
833bhp at just 1.5bar  from a HX55 on a BMW M50 engine in a stunning E36 BMW

950bhp HX55'd 2JZ Soarer

R33 Skyline drift car running a stock bottom end 1UZ and a Holset HX55 25cm. 640bhp at the wheels at just 1.3bar, 600nm torque by just 3800rpm​

​HE300/HE341/HE351
This covers everything from (I think?) HX30 equivalent units, and certainly HX32/HY35 equivalents (Sometimes known HE341 or HE351, but some 341s are purely HX35 wheel size), and HX35/40 hybrid equivalents (Sometimes also known as HE351), but mostly they are the ever popular HX35 size.
Most have nothing drastically different in wheel design from the HX versions, though some have the same size but better designed wheels, and more have billet compressor than the HX versions do.
As with all HE's, the newest ones tend to just be called HE300WG or HE300FG, so you literally can't use the name for much, and you need to know the specs! In recent months I've seen HE300s that were basically HY35 turbines and big billet HX40 compressors, but also straight up normal HX35 spec turbos also called HE300s. Cheers Holset!

There are VGT versions of the above, the ones with V/VG/VE at the end, and as ever, they’re a similar design, just a VGT turbine housing. Generally the VEs perform to the same peak power levels as the non VGT versions, but they spool much sooner, up to 1500rpm sooner.

HOLSET HE400 SERIES-
These are basically the successor to the HX40 series, but some, like all the HE turbos, have upgrades that make them closer in power capability to the next size up turbos in some versions.
HX40s seemed to max out at 60mm inducer compressors, but seen slightly larger on HE400s.
All the turbine wheels I've seen so far are normal HX40 sizes, but some have even higher flowing wheel designs, which is nice.
As ever, most are normal HX40 spec, but that's no bad thing as the HX series turbos are still up there with the best of them even today.

If you just want to smoke your tyres, do skids, burnouts, and powerslides, fuck yeah, have all the power you want and forget the rest, and that can be a whole lot of fun in a RWD car, mega fun.
But massive wheelspin in a FWD is pretty much super gay and not fun at all, and with 4wd your car is either insanely powerful or something's set up very wrong.

Fact is, if you want to actually go fast, it's about way more than just power, and a lot of people don't seem to be able to grasp that fact.
I'm not on about handling and stopping either, that's a whole different subject, I'm purely on about getting this power to the ground- Traction!

You see a lot of people, a hell of a lot of people unfortunately, really chuffed with their car, saying how 'fast' they are, as they smoke the tyres in 4th or whatever just by going full throttle.
But, err, if your car is wheelspinning, it's not going to be that fast until that stops, and in a lot of cases cars with half the power but decent traction will be leaving you for dead.
I'm not sure if these people truly believe their car is quick and have never actually raced or timed it to realise that their wheelspinning mess is actually nothing special, but practically everyone with a tractionless mess act like their cars are rapid when they're not.

One of the most common things you see is people really proud that their engine spools fast and smokes the tyres constantly, while also slating cars with with similar power but far less torque and low down power (due to bigger or no turbos, less capacity, more rpm, etc) as 'dogs' at lower rpm just because they haven't got a ton of torque.
But the fact is, thanks to the more sensible/usable torque levels they have for the amount of grip they have, these 'dogs' are often far faster in reality.
FWD and tuned diesel owners are worst for this, but grip affects almost everyone with big power on road tyres.
​
The bullshit talked about grip, or lack of, works the other way too, as the people constantly say FWD cars are useless with more than 200bhp/250bhp/300bhp (depends who you're talking to) are wrong as well.
Yes FWD is useless even at 200bhp with tons of torque, shit tyres, and an open diff, but even with 500bhp+ I've experienced road legal FWD cars that put all the power down from 2nd gear on, and with rear wheel drive cars you've got even less excuse to have no grip. Fuck, if you've got 4wd and big traction issues then you either need to sort your shit out or something is broke.

So yeah, having no traction means your is gonna accelerate slow no matter how powerful your engine is, and here's the various ways to help fix that...

                             YOUR TYRES!                         

The number one way to improve your traction is tyres. And as blatantly obvious as that is, people still ignore it, and I'd say there's far more big power cars on skinny normal road tyres wheelspinning everywhere, than ones running decent tyres and actually going fast.

The difference in traction under acceleration between the same size tyre, one a normal but decent brand road tyre, and one a road legal semi-slick, is massive.
I've experienced, many times, cars go from wheelspin in 4th with good 'normal' tyres to full traction most the time even in 2nd with a set of semi slicks of the same size.
This, providing there's no standing water, is actually the same in the wet too; it's only standing water when semi-slicks can be a bit crap.

People's reason/excuses for not running decent tyres like this is always stupid too; either that they're rubbish in the wet, which I don't really agree with anyhow, or that they don't last long, which is a false economy when they instead have a powerful car that's a complete waste of time and not actually very fast as it has no grip.

Tyre size is another big one- People rarely even fit the widest tyre they can get under their standard arches, never mind go as far as modify their arches to fit wider ones for decent traction.
This is also usually ridiculous as they end up spending ten times the money doing that will cost on other pointless upgrades. In fact it's that daft that people will fit the biggest wheels they can fit under the arches as they think it looks cool, but then fit way skinnier tyres just to help wheel fitment! You can't have it all, and what do you want? People to think your car looks cool, or for it to be as fast as you tell everyone it is?

Finally, tyre pressure- It can make a big difference to traction, and as long as your car isn't hugely heavy you can often run lower than the typical 30-35psi most people have theirs set at.
It's certainly worth looking at, especially as it's pretty much a free mod, and in drag use people often run barely 10psi depending on car and tyre type, and while this has an adverse effect on handling, on some lightweight cars some people still run under 20psi on the road and circuit, so it's worth some experimentation to see what suits you.

                   YOUR DIFFERENTIAL(S)                

So many “Oh my God my car is soooo fast, my wheels are spinning in 9th gear” type people are wrong. Only one of their wheels are spinning, and their car isn't fast at all, as it's got an open diff or a really crap factory LSD.
Just like decent tyres, the massive difference a decent LSD makes to traction over an open diff is hard to imagine unless you experience it. It really is night and day, and in my book worth every penny. A hard used performance car with an open diff, even a pretty low power one, is not for me; I hate it.
There are lots of performance advantages of a decent LSD, but we're talking about getting your engines power down in this feature,  and that's where a limited slip diff really is most obviously felt.

With an open diff power just goes to the wheel with the least grip, which means one wheel quite easily spins up while the other has no power going to it all, and the end result of that is no forward movement and just pretty much sitting there spinning one wheel like a dick.

With a decent LSD, power is forced to both wheels regardless of what has the most grip, which not only of course massively increases traction for that reason, but even WHEN the wheels are spinning, especially with a plate-style LSD, as both still have the power going to them rather than just one, there's still a lot more traction and therefore forward movement even when wheelspinning. 
It's hard to imagine unless you've experienced it, but the amount of acceleration even when wheelspinning hard when you've got a good aftermarket limited slip (or locked/weldeds/spool) diff can be pretty incredible on some cars.
Please bear in mind though I saw a 'GOOD' LSD, as quite a few factory LSDs are barely better than being an open diff, especially once they get older, so don't just think because your car has a LSD as standard that it's effective- Often far from it!

          YOUR SUSPENSION GEOMETRY           
When it comes to getting power down, maximising tyre contact patch is key to making the most of what you have.
The most obvious factor here is to minimise camber on your driven wheels, BUT if you're really serious about putting the power to the floor it gets a bit more complex than that.
Most suspension designs have dynamic camber change, ie when your suspension lifts or squats, the camber angle changes. Some suspension designs change more drastically than others, so exactly how much you need to cater for this depends on your cars own setup, I can't advise you on exact numbers, but if you're serious about traction, you got to take this in to account.
Upon acceleration, a cars front end naturally lifts, generally reducing the camber angle of the front tyres, and the rear end squats, increasing the camber angle of the rear tyres. Because of this, on FWD cars a small amount of negative camber is often no bad thing as it can turn to zero camber as the front lifts slightly, and on RWD cars, zero camber, or even some positive camber, is often used on cars looking for maximum straight line grip, as this counteracts the natural negative camber increase that happens as the back end squats.

           YOUR WEIGHT DISTRIBUTION              

As mentioned in the geometry bit, when accelerating, the front lifts and the rear squats, and of course, you want to have as much weight over your driven wheels as possible, so why not do something about that?

Thanks to the rear end naturally squatting, RWD cars have it easier when it comes to grip, as the whole car is pushing down on the driven wheels, but regardless of this fact, moving any weight you have to the rear end is never a bad thing to help maximise acceleration grip; unless your car has so much rear end grip it instead does huge wheelies and tries to flip over that is...

On FWD cars the weight distribution issue can be much more important. The front end of a car naturally goes light upon acceleration, which is the last thing you want when it comes to grip, so anything you can do to keep weight over the front wheels the better.
Obviously this is no easy task, as you're limited to what you can fit under the bonnet, but this is why many FWD drag cars fit the fuel cell up front, and some people have even tilted the engine forward a little to help with the weight distribution.

Weight distribution is more than front and rear though- It's left to right, and this can have a major effect on traction due to how much force is put on each tyre. I've seen cars get major improvements in traction my making the corner weights over each driven wheel to be as equal as possible, therefore equalising their grip; to the extent some have said it was more effective than when they changed from an open diff to a LSD!
This is something which can be done by physically moving parts around the car, as well as small changes to ride height if you have coilovers. To even remotely accurately do this you need a set of corner weights, but this is something many tuning shops have and are more than happy to do for you.

While in general adding weight is never ideal, if traction is your main goal and you're still struggling with other methods, adding weight to the very front of a FWD car via thick metal undertrays or weights behind the front bumper, or to the very rear of a RWD car, either with weights behind the rear bumper or added to the boot, is sometimes done to push the driven tyres as hard in to the road/track surface as possible.

Finally, weight transfer from suspension movement. As I've explained, you need to keep the weight on the driven wheels as much as you can, and that generally means allowing a RWD car to squat the rear and lift the front, and conversely trying to prevent a FWD cars front end from lifting and the rear from squatting.

For FWD cars this tends to mean stiff rear suspension to help prevent squat, and various clever ways to prevent front suspension lift (which unfortunately depend on your stock suspension design, so I can't list them all here).
While jacked up rear ends are also sometimes popular, most the fastest FWD people tend to agree it's no big benefit, if at all.

For RWD cars they tend to want to allow the front to lift without lifting the wheels clean off the ground, and allowing the rear end to squat. A fairly soft rear end is a clear start point, and on the front things like soft and relatively long travel suspension, often with no anti-roll bar, allows the front end to naturally lift but also can help prevent the car lifting its wheels, which, while looking cool as hell, gives you zero steering, and potentially massive problems when you come back down to earth!

           LIMITING YOUR TORQUE LEVELS        

Last, but DEFFO not least, I'm going to talk like torque is a bad thing. As sometimes it is!


This is probably the most ignored factor when it comes to traction, as who'd want to willingly give up performance? Only a mad man, surely?
Well there's two things here. Despite the myth diesel and V8 owners like to loudly shout at every opportunity, torque doesn't really win races, and if you're spinning you ain't winning, so you're better off having less torque, so less wheelspin, but more acceleration.


This tactic is common on modern turbocharged drag and track cars, and is part of the reason so many are so fast and controllable in recent years, with things such as boost by gear (ie lower boost in lower gears), boost by speed (similar to boost by gear but works it out with speed) and boost by rpm (ie mapped to the boost rises slower and more progressively than they naturally could, to prevent a big spike of boost spinning the wheels), all easily configurable on a good ECU, as well as clever traction control systems that can limit wheelspin by slightly lowering torque when wheelspin is sensed without killing the power and slowing the car down like many factory systems.


The thing is though, while you may think these are pretty hi-tech and extreme tuning methods, this is actually way more normal and common than you many think. Many factory turbo cars, even some that are 25 years or more old, come with boost by gear or rpm as standard. Yes, many cars have it set, from the factory, that their boost pressure is lower in lower gears and/or rpm to reduce wheelspin, all controlled via the ECU and factory boost solenoid.


Even without clever ECU tricks like boost by gear or other traction control methods, a good engine spec and a good mapper can massively improve traction simply by creating an engine with a good power delivery.
Huge torque, or just sudden increases in torque, when you've not got the grip to use the aforementioned, is pointless  and will prevent you reaching your performance goals, but are easily avoided.


A big part of the reason Prochargers and Rotrex units (ie centrifugal superchargers) are so popular among V8 drag racers and FWD track cars, is because of the linear power delivery they give, with no huge torque spikes to spin the wheels, and a very progressive increase in power all the way to the rev limiter, making for a tractable, controllable, and predictable car with massive peak power levels but far less wheespin than a typical car of the same power equipped with a positive displacement supercharger, nitrous, or a typical turbocharged setup, purely as they tend to give huge and peaky torque curves.


Other engine spec changes can help this too on traction-limited cars. Increased capacity rarely increases peak power, but certainly increases torque, so should be avoided if you're already struggling for grip. Small turbos at high boost means big torque and eaiser to drive, but a bigger turbo at lower boost for the same power can often give a better power delivery for a grip limited car, which is also kinder on the engine too. Using rpm to make power means less torque needed for any given power level, which again can actually be a useful thing if you're struggling for grip.

And that's it for now folks! Hope you've enjoyed this feature and found it useful, and of course show anyone else you know who may get a use out of it too.

I've actually got about 10 other features in progress right now, just, thanks to life getting in the way (I have some very kind Patreon donators, but the total is still very low so I certainly don't make a living doing this, or even close!), I've just not finished the others yet, but I do these at any opportunity I can, so please, watch this space!

Since the death of car magazines and internet forums, and the rise of YouTube videos and Facebook groups, the amount of misinformation and pure bullshit about tuning is higher than ever. It's fucking unreal what gets said and how often, and it's making me a bit disillusioned with the whole scene, but it's also made me want to clear a few things up lately, as reading pure shit constantly is doing my head in.

Probably the worst piles of bullshit I hear is about turbos, so let's clear some stuff up in ten very important points.

​Apologies for the swearing and less than sexy layout of this feature, but this is me saying what I think and explaining some stuff rather than trying to look impressive...


No1- IF YOU'VE NO EXPERIENCE ON THE SUBJECT, PLEASE, SHUT THE FUCK UP
This is the worst thing of all, not just on turbos, but everything. Seems most the people who shout the loudest with their advice are the people who know the least.

On a certain car group I'm a member of that's mostly turbo related, the two main people who reply to peoples questions seem to have zero experience and reply with complete and utter shite almost all the time, but comment so often and so confidently, to anyone who didn't know who they were, ie most people, they'd sound like people who know what they're on about.
Shit like this, on Facebook, on YouTube, and in magazines, is what's killing the scene for me most of all.

Unfortunately a lot of tuners these days will give iffy advice too, either to suit their agendas and sales, or because they're clueless on that exact subject but won't ever admit to it as they have to be seen as the all seeing gods of tuning to their customers. Fucking minefield out there.

No2- TURBO SIZING ISN'T THAT HARD-
One of the most common things I see is people (never with any experience of the turbo/engine/anything) going "OH EM GEE, THAT TURBO WILL NEVER SPOOOOL" just because it's not a fucking tiny little turbo, even if the engine is pretty big.
Don't just guess if something will spool. Either go from your past experiences or do a bit of Googling for proven results and you can make a VERY educated guess by looking at other cars and engines and turbos, even if neither are exactly what you're using.

Unless you're using a horribly specced mismatch of a turbo, or some ancient piece of shit, both of which are very rare these days in all honesty, turbos of a similar size/spec all spool similarly enough or any given size to make a very good guess on how it will work.

Wondering how a 900bhp turbo will spool on a 4ltr for example? Well about the same as a 450bhp turbo does on a 2ltr. Simple. It's not that hard. (THIS is one I see loads of with Toyota 1UZ engines- You can spool a fucking HX55 on one EASILY, but people fit turbos more suited to engines almost half the size, and wonder why they make crap power!).

Wondering how much faster a twin scroll turbo setup of any given size spools vs a single scroll one that's otherwise pretty much the same? Roughly 600-1000rpm faster in general. 2Ltr single scroll setups with ~600bhp capable turbos like GT35s and HX35s are full boost by around 4500rpm typically (seen 5000+ on GT35s with wild cams and the biggest housing though- Shite!), and proven as low as 3500rpm with a good twin scroll setup and 12cm HX35s for example.

No3- BALL BEARING TURBOS DON'T MAKE VERY MUCH DIFFERENCE TO SPOOL-
Fact. Despite being one of the most common myths. I've even posted a video of the owner of Xona Rotor saying the same thing, and he sells the fuckers. It's a mix of sales speak and bullshit that says it makes a big difference.
A Holset HX35, a Garrett GT35, and whatever other similar 600bhp turbo with similar size turbine wheels and housings spool about the same IF all else is equal. This is fact, no matter how many times pricks say one is "An old diesel truck turbo" and one is some kind of superduper thing. It's bollocks.

​In theory it helps, and it does, but by a really small amount, an amount you often can’t even feel. Wheel design, housing design, manifold design, exhaust design, cam spec, mapping, ALL SORTS, all make a way way bigger difference, ie a really noticeable difference, vs it being BB or not.

​The REAL advantage of BB turbos is they can take higher thrust loads for better reliability in extreme use. Though that's all relative to how good/bad the non-BB version would be of course- My friends GTX2860R Gen2 has massive thrust (ie in out) play and it's only done a few thousand road and dyno miles, albeit at 33psi boost.

No4- JUST BECAUSE THE TURBO IS CAPABLE OF A CERTAIN POWER DON'T MEAN YOU WILL MAKE THAT POWER...
Lots of people think this, and it ain't gonna happen. This isn't just the case with running a turbo at very low boost, but most commonly people buying, say, a 600bhp turbo, running 1.4bar or some medium amount of boost, then wondering why they've not got 600bhp (Hint- Most the time you'll be at more like 2bar or more to truly max a turbo out unless it's a very small turbo for the engine size).

These days this issue is coming about thanks too all these tiny but very flashy turbos with funky compressor wheels rated at big power but still running teeny tiny turbine wheels and housings (ie a huge mis-match for most engines, and more sutied to twins on insane power GTRs etc). Things like the smaller Garrett GTXs and so on are big ones for this, as they might be rated at whatever power, but they're not gonna do that aside from on a pretty tiny engine, or as twin turbos on a medium size engine (Such as twins on a Nissan GT-R V6 or Toyota V8), as they've not got the turbine flow to max out on larger capacity engines. Ever notice the truly powerful engines have actual big turbos with big turbines? Yes, that’s because you need it.

What goes in has to come out of an engine, and while better designed wheels help, size is still king.
Take the Garrett GTX2871R rated at 560bhp, or even the new G25-660 turbo rated at 660bhp. They both have tiny 54mm turbine wheels, smaller than a stock little CT12B off a 1JZ VVTi. I don't care how fancy a turbine wheel is, with that size, you're either not going to max out one of them on anything but sub-2ltr engine at mega boost, or your pre-turbine backpressure will be astronomical.

​You'd not make even half of many of these turbos rated power if you was daft enough to fit one to a larger engine, as it's as much about turbine flow as compressor.
Even looking at Garrett's own turbine maps shows it's no magic- The GTX2871R turbine with the biggest housing flows about 21lb/min, the G25-660 one with the biggest housing flow about 24lb/min. Both less than a GT30R turbine does with the biggest housing at 26lb/min, despite the GT30R rated at a good 100bhp less.

So even IF you make the power, you'll be making it with a far less happy/healthy/reliable engine than if you did with a bigger or 'older' turbo that had a bigger turbine wheel.​

No5- TURBINE SIZE IS KEY-
While little turbine wheels and housings help spool, and are fine on suitably small engines, what goes in has to come out, and the smaller the turbine wheel and/or housing, the less can come out, which means less power per psi boost, and less engine reliability.

When chosen right, this is just a trade-off, you just give up a bit of power for a bit of spool, with no reliability issues, and still ballpark correct power.
In fact if going for the maximum power and torque but fastest possible spool, you can build an engine like they would a rallycross engine, that's been specced to handle big boost and big backpressure from a relatively small turbine side with no issues and be loving life. Unfortunately most engines aren't specced like that.

But more often than not these days, people think running the tiniest housings and wheels they can find for any turbo they think can do the power they're after is the right thing to do with no bad consequences, as they have zero understanding that turbine flow matters. Because of this the result is often way too small, so they often struggle to make the power they do, and even more often have reliability issues due to the massive pre-turbine backpressure.

Pre-turbine backpressure is the no1 killer of turbo engines (behind shit mappers!), and both killers are pretty invisible to most, and other stuff gets blamed for the problems.
The less turbine flow you have, the harder time your engine has to stay alive. Heat issues and far less resistance to det, are the biggest problems, problems which people tend to first realise when they're shitting out head gaskets and pistons a lot, or needing to run race fuel when other similar engines with bigger turbines don't...

There's plenty of examples where there's two similar engines, running similar power, but one is highly strung and less reliable than the other, just as it runs a smaller turbine side in an attempt to get faster spool.

Unless you've specced the engine to suit, it's simply not worth trying to gain a tiny bit of spool considering what you give up just to get that.

And remember the basics- The bigger the capacity, the bigger the turbine flow needs to be for any given power. What will make 600bhp on a 1.8ltr might have a turbine side too small to even make 400 on a 3ltr...

No6- LAG VS BOOST THRESHOLD-
What most people call 'Lag' isn't lag, it's just not being in the boost threshold.

The rpm where your turbo can't make boost, that's being out the boost threshold.

Lag is your turbo response when within the boost threshold.

You put your foot down at 2000rpm and it don't come on full boost until 4000rpm isn't lag, that's being out the boost threshold.

You put your foot down at 4000rpm and any delay then is LAG.

But how much 'lag' is there on even slightly modern turbos when truly within the boost threshold? Even fucking big ones? Some vs being naturally aspirated, but in real world terms, very little, not enough to win or lose a race unless you're rallying.

Even something like a Holset HX35 on a 2ltr with a single scroll manifold (Bad idea btw when twin scroll often spools it 1000rpm faster). Boost threshold would be fairly high, full boost not until 4.5k, but do you think there's any real delay between planting your foot to the floor and fucking off down the road like a rocket when you're within the boost threshold (ie 4.5k+)? No. Pretty much zero, even for things like drifting etc.

No7- BOOST = TORQUE.
If you're grip limited or haven't got the strongest engine or transmission out there, torque can do more harm than good, BUT if that's not an issue, torque is always fun! Despite this, a lot of people seem to be confused why they haven't got lots of it despite having lots of power.

The answer is mostly boost. The biggest thing to make high torque numbers is boost pressure, and many cars, especially at 1bar or less, even the smallest fastest spooling turbos, can feel almost like a powerful N/A engine with most the power up top and fairly low torque, but the identical engine with another half a bar of boost can feel like a totally different engine with ridiculous amounts of low and midrange torque.

The lower the rpm you can make boost, the bigger the torque numbers tend to be for any given boost level, but the more low down torque you have, the harder it tends to be on engine internals, especially conrods, so it's a double edged sword in some ways!

Good example of boost giving torque and transforming how and engine feels was the old 13B rotary in my RX7. It was a large street port engine running a fairly small HKS T04E. At 0.8bar, despite being full boost by 3000rpm, wasn't really "fast" until at least 5.5k when the ports really came in to their own, then it screamed up to 8k; feeling much like a tuned N/A engine. At 1.5bar though, despite peak power not feeling much different up at 8k, it was a rocket ship with a ton of torque right from 3k to the limiter now. It was tons more fun at 1.5bar and easier to drive faster, but if I didn't have the massive grip to cope with it, it would've been slower to be honest, but still, more fun...!
I like boost!

No8- LEARN TO CHANGE FUCKING GEAR-
Unless you've made a tragic and totally mismatched engine or gearing setup, there is pretty much zero excuse to be caught off boost unless you have no idea how to fucking drive and change gear.

Putting your foot down at low rpm then blaming the turbo for you not going fast is fucking lame. No, it's your fault for being at low rpm. Your fucking fault. Even if you got a tiny turbo, you'd be going a lot faster if you had the sense to be at a higher rpm.
Even if you got a standard turbo on a petrol car that is on boost by 2500rpm, you'd accelerate a lot faster if you made sure you was in the right gear so you was already at 5k+. I've got an Impreza at the moment, 2ltr, and a tiny little TD04 that even 1.6s spool easiy. Yes it spools at low rpm, but to do fast I'd still drop a gear or two from cruising rpm so I'm at at least 5k to accelerate as hard as I can, as I'm not stupid.

You could have a GT25 or a GT35 on your 2ltr, and while the GT25 will be faster at 3k, it will still be slow, and but would be FAR faster at 5k. But the GT35 will be FAR faster at 5k regardless.

God help you if you drive a highly strung N/A engine- Any engine even approaching 100bhp per litre, even with fancy variable valve timing to help low down power, the real powerband starts at at least 6000rpm on non-turbo lumps, and by then even fucking massive turbos are at full boost.

You ever wonder why so many 'fast' cars look so average when the owners give them some beans? It's because people are fucking useless and don't understand how to change gear, that's why! Most owners are a waste of a good car...

No9- WHAT YOU GIVE UP LOW DOWN, YOU USUALLY GAIN UP TOP, SOMETIMES MORE! -
People fucking obsess over low rpm performance, and think a bigger turbo gives a smaller powerband, so would don't want to run one as they think it won't have a decent power band, but on modern engines, that actually rev, this is usually bollocks, and it's often the opposite.

Most modern turbo engines safely rev to around 7500rpm, some 1000rpm more, and even the lowest safe revvers these days are no more than 1000rpm less.

But, despite this, most modern turbo engines make peak power at least 1000rpm lower than their safe rev limit, so there's room for more if you can make it worth it...

A typical fairly small turbo engine making like 150bhp per litre, so a 300bhp 2ltr etc, makes good power from 3000-3500rpm and peaks out 6000-6500rpm. So you've usually got a 3000-3500rpm power band.

A typical bigger turbo engine, say 250bhp per litre, so a 500bhp 2ltr etc, makes good power from about 4000rpm, but tends to pull hard with no let up until 7500-8000rpm. So you've got a 3500-4000rpm power band, ie the same or fucking BIGGER, not smaller.

Even if you only pulled hard to 7k, and in all honesty you've probably done something badly to have an engine that spools that late but dies out that soon, you've still got the same size powerband as a smaller turbo, just higher in the rev range, and you also happen to have 100-200bhp more!

You can make a fucking mess of things, with small downpipes, shit manifolds, badly matched turbos, stupid cam specs, and so on, and make a powerband smaller than it needs to be, but these days you'd have to fuck things up good and proper to make a powerband much smaller with a larger turbo unless you go to a REALLY fucking big turbo.

If things are specced and built right, you can have a fucking big powerband. Even with some 600-650bhp turbos, on 2ltr engines, with good overall specs, good twin scroll setups etc, you see cars making big power from 3500rpm all the way to 8000rpm, that's a massive power band, way bigger than any factory turbo engine, but while also having about TWICE the bhp per litre of even the hottest factory turbo engines these days.

This sort of shit is especially good on Honda engines that love a good rev. When N/A they don't really come alive until 6k+, but rev to 8k+, but provided you can drive you still won't ever fall out the power band. Even a fucking gigantic turbo is on full boost by time the N/A car is in the powerband anyhow, so even with insane, really fucking insane power, with a huge turbo, you'll still have a bigger powerband than stock...

No10- YOU DON'T 'GET WHAT YOU PAY FOR'
Turbos are all kinds of prices, from sub £200 eBay specials to £2000 swanky ones, and everything in between. But is a £2000 ten times better than a £200 one? Or even a £1000 twice as good as a £500 one? Personally, I'd say no.

Cheapy eBay ones, well that's where it's real a gamble. Personally I think a lot of these under-perform as the typical type of person that runs one is a clueless cheapskate so the car is an unreliable underperforming piece of shit in general due to the mistakes and lack of care/knowledge from the owner, rather than the turbo being truly shite, but still, it's a gamble and not one I've ever made personally yet.

Another thing you see for a couple hundred quid, is used and sometimes new turbos off trucks and so on. This is FINE if you know exactly what the fuck you looking at, but most people don't. People see "HX35" or "GT40" or "T4" and think it will be ideal for them, not realising there's a 1000 variations of almost every turbo type on the planet, and 90% of them are not suitable for you.
The vast majority of turbos, even ones on some of the more powerful tuned engines on the planet, are actually commercial/diesel based, but that sure as shit don't make them all suitable! Most big OEM commercial/diesel turbos will have far too big a turbine housing to be much good for the fairly small engines we tune, so a random purchase just because it's called a HX35 or whatever could well be a total waste of money unless you know what you're buying.

For somewhere between 400 and 600 you can often get brand new GOOD/CORRECT spec Holset or BorgWarner turbos from a specialist who knows about these turbos. Personally, for my budget and needs, this is what I go for, and what I feel is the best value for money.
Are they the very best turbos on the planet? No, of course not,  if money was no object I'd have some swanky as fuck £1500 Precision or GTX or EFR or whatever. But for 99% of us money is an object, and from experience, comparable size for size on wheels and housings, both either twin or single scroll, the performance difference between a decent Holset or Borg and a swanky one for 2 to 3 times the price, is pretty minimal.
More importantly however, and the money saved on the turbo can be spent elsewhere (better manifolds, exhaust, cams, mapping, whatever) to make the performance better than any turbo alone will.
If you have the cash to make everything on the car perfect, and can afford spending big bucks possibly yearly when you need to replace a broken turbo, fuck yeah I'd get the expensive one as it's a little bit better, but spending loads on a turbo but then having pretty average/crap spec other bits as you've not got the budget for it all, is fucking stupid IMO.

And now, top dollar turbos. Yes, they are the best, defo, but they're also expensive to buy and fix, often most of the cost of buying a new one, so you need to be able to afford it short and long term. Top dollar turbos tend to not be no more reliable, arguably less sometimes- What you're paying for is performance rather than longevity, so make sure you can afford the upkeep.

You can't read anything, from Wikipedia to 'respected' car publications without them mentioning the “fact” that the insane Porsche 917/30 CanAm cars had '1580bhp' or '1580bhp in qualifying trim' or similar. But personally, I don't think that's true at all.

​The 5.4ltr twin turbo engine was INSANELY fast, zero doubt there, and the claims of 1000bhp+ in qualifying trim I certainly do believe. The fact the car weighed under 900kg was also was a big part of why the cars were really mind blowingly quick- Especially bearing in mind this was 1973, long before most of us were even born!

​BUT do I think the CanAm versions ever made this so called 1580bhp so many quote these days? No.
I think this is yet another case of half-truths from a long lost past getting mixed up, and now being talked about like reality. And after speaking to others who are some of the few people that I do trust what they say when it comes to things like this, they agree.

​But ONE 917/30 DID run at this power, I’m 100% sure of that, but never in CanAm!

​The CanAm series was cancelled after a season of the 917/30 obliterating the opposition, leaving some incredible cars with no series to race in, so Porsche decided to use it to go for the world speed record for a closed circuit, at Talladega Speedway.

​6 months of development later, and the car had one big change that made it unlike all the other 917s- It now had INTERCOOLERS.

Look at all other pics of the Porsche 917/30s, old pics or even the cars today- They didn't run intercoolers at all! Pure hot air.
BUT for this speed record attempt they wanted more power and performance than ever before, and a big part of that came from two large alloy intercoolers at the rear of the car...

THIS is where this '1580bhp' story comes from IMO. But the CanAm race cars? With no intercooling at all? No, they wasn't as powerful as this, even in qualifying. Hundreds of bhp less in fact, same as  comparing any engine at significant boost levels with and without intercooling.

​For what it's worth, the car did brake the record, averaging over 221mph through the whole lap, going well over 230mph at times, and that's STILL a record at Talladega to this very day.

​So yeah, next time you see or read about 917/30 CanAm cars having a supposed 1580bhp, well, you know a bit more about the reality of it now.

​Here's a couple more pics of the intercoolers on this one-off spec car for you too...

A fairly short one this time, but a good bit of mythbusting and something very cool most of you have probably never seen.

​Hope you enjoyed this one, and as ever, stay tuned with more coming on here, the Facebook Page, and the YouTube channel.

​And please, if you enjoy what you see and want this to carry on and hopefully grow, please become a Patron of StavTech and receive exclusive bonuses for doing so too!

Cheers
​Stav

You may think the title of this feature is a big claim, but I'd say it's fact, and in fact this car is FAR crazier than what 99% of people who know this car even think it is!

​As you may have seen on THIS recent post on the Stav-Tech Facebook page, I personally think, especially from an engine tuning point of view, 80s and early 90s Rallycross is THE most insane motorsport there ever has been, even more than Group B rallying.

​BUT the thing is, it's all pretty unknown to most current tuning fans, and there's VERY little detail out there that explains how crazy the cars were- Even most retro rallycross fans know very little about the cars back then. I've asked these 'fans' many times what engines were in certain cars etc, nothing complex, but people rarely even know that much!
​I’m sure that if only people today realised how insane these cars were, they'd be more legendary than even Group B cars are, and I'm determined to find out the details for YOU guys.
While they're pretty unknown to most, their specs and their performance are exactly the kinds of things you love, and totally relevant to your own tuned cars of today.

​Anyhow, the first car I've managed to source the long-lost info of is a car that's always been my favourite rallycross car, despite even myself not knowing that much detail about it, and it's this- Arild Martinsen's E30 BMW M3...

I'm not a massive E30 M3 fan normally if I'm honest. I've driven a few, standard and modified, and while I think they're cool cars, they've never been a car I've wanted to own, but this one, well shit the bed, this one is literally my DREAM CAR.
​
​Well why? Well, before I give you all the details, I'll let this absolutely incredible video (From 30 years ago!) below do the talking, check it out...​

Watched it yet? Did you say "Holy shit!" and "Fuck me!" loads of times while seeing that 700bhp four wheel drive E30 M3 fly around the track, sideways everywhere, accelerating like a rocket, and chucking flames out the side exit exhaust? Well yes, that's the pretty normal reaction, as that thing is flippin' bonkers.

​Funnily enough though, that's one of the VERY few videos out there of this car, as it actually wasn't hugely successful in rallycross, as while it was insanely fast and generally awesome, it just didn't have the traction to match. But it's performances have made it a favourite with many to this day- Including me!

​The thing is though, that video is pretty much as far as most people's knowledge of this car goes, and it was only relatively recently I'd even seen an engine bay pic of the thing myself.
But as I love the thing, and I knew you lot would too, I decided to do some serious research (Not just Googling, as there's fook all on the net about it- Believe me, I've looked!), which has enabled me to do this feature you're checking out right now.

​Starting with the engine under the lightweight Kevlar bonnet, the common story is it's a modified E30 M3 engine, ie the S14B23 2.3ltr 4cyl lump, fitted with a turbo off a BMW Formula One car.
​Well, that's NOT true, in fact it's WAY wilder than that!

​The engine is in fact the BMW M12 race engine, ie an engine that's never been in any production car, and has been used in it's various forms and capacities, in Touring Car Racing, Formula 2, and was also the legendary 1.5ltr turbo BMW Formula One engine from the 1980s that was alleged to produce as much as 1400bhp in qualifying form.

​This particular version isn't the 1.5ltr F1 lump, but is a modified version of the 2ltr turbocharged lump used in IMSA racing in the USA, used first used in the late 70s BMW 320 Turbo IMSA race car, making 650bhp at 9000rpm, then used in 1985 and 1986 in the BMW/March IMSA GTP race car, making 800bhp at 9000rpm.

​Here's some pics from the engine in an original BMW 320 Turbo IMSA car...

Clear pictures of the later IMSA GTP engine are harder to find, especially as the engine was hidden under bodywork at the rear, but here's the car and some spec...​

After the GTP car stopped racing in 1986, Arlid Martinsen, with the help of BMW Norway, managed to source one to use in his insane new rallycross build for 1987, and here it is...

Looks like it was made to be there eh! Fits lovely. Here's some closer up shots...

What we have here is, as said, an M14 IMSA GTP lump, 2ltr, heavily turbocharged of course, and in the spec in Arild's E30, it made 650bhp at 2bar boost, and was capable of 2.5bar boost if he wished, which although never measured, was without doubt going to be 700bhp+..
​Internal spec was pretty typical as you'd expect for a full-on race engine, though one particular thing to note was Titanium conrods- Now that's flashy.
​In 1987 the engine was 2ltr built by a famous Norwegian engine builder, but word is (from a good source too) in later years a 2.3ltr version was built for him by a Swiss engine builder.

As the pics show, it featured a big air-to-air intercooler, carbon fibre inlet plenum, twin scroll tubular exhaust manifold (everyone ran twin scroll back then- Madness not to as it really helps spool), HUGE single external wastegate (same one they used on the F1 etc engines), and a BIG single Schwitzer turbocharger (Schwitzer are now what's called BorgWarner Turbochargers, and they actually invented the ETT Extended Tip Technology compressor wheels before they became BorgWarner- In fact the entire BorgWarner S-Series of turbochargers, and therefore the majority of parts in SX, SXE, and EFR turbos too, use what was originally Schwitzer turbo parts).

Yep, Jubilee clips and rubber hose at 2.5bar boost... ;)

Perhaps what's MOST INTERESTING, and different, in fact pretty much unknown to most people these days, is this car ran FIVE throttles! In fact, so did the insane 1400bhp Formula One version of this engine too.
​So yes, I can hear most of you already... "Five throttles? What the fuck are you on about? It's only got four cylinders". Well, do you want to play "Spot the throttles" on the next pic? Check it out...

Spotted them all? Well, it's not easy, but they're there! The first four are in the typical place for a race engine- Ie it's running individual throttle bodies, one per cylinder, right at the inlet ports of the head. So where's the 5th one? Well, look at the throttle cable, it comes over the strut brace, to the ITBs, then continues forward somewhere and disappears. But to where? Well look at the bottom right. As well as a big cone filter, what's that in front of the turbo? Yep, throttle number five!

​Confused? Well I better explain then eh, that's what Stav-Tech is all about after all.
Well, it's a form of anti-lag that was used before anti-lag as we know it existed. And while it's not as effective as what modern ALS can potentially be (ie full boost all the time), and has issues (unless you have a specially modified turbo, you'll be sucking oil in to the compressor side badly when off the throttle, filling the entire inlet system with oil and making the exhaust smoke badly for a start), but done right it really is very effective- It was used in Formula One after all.

​How does it work? Well, in essence it's the same as when you put your hand over the inlet on a vacuum cleaner, blocking the airflow. What happens? You can very audibly hear the motor speed up as it's doing less work, that's what.
​On a turbo, the compressor side is the equivalent of the suction fan on your vacuum, and the turbine side is the equivalent of your vacuums electric motor.
​With no airflow the fan/wheel has nothing to do, it's literally spinning in a vacuum doing no work at all, no air to push, and therefore the motor/turbine can turn far faster for any given power input to it (ie the electricity on the vac, or the exhaust gas on the turbine).
​On a vac it serves no purpose, BUT on a turbo, if it's spinning far faster when off throttle, it also gets up to speed far quicker when you're back on the throttle; in fact potentially it's already at the required speed!
​This is exactly what modern anti-lag does, ie keeps turbine rpm as high as possible even when off throttle, just done in a totally different way.

​In related news, I want to test this setup for StavTech, as while it's got issues, A- I think I may have a solution to that, and B- I want to see, and show YOU, how effective it is!

Anyhow, back to the car...

While as I mentioned previously, details on these Rallycross monsters is scarce, but thanks to one of the top motorsport photographers from back then, the legend that is Eddi Laumanns (who took many of the pictures in this feature too!), I got hold of a feature on this car from a German car magazine when it was first built in 1987, and it has some VERY interesting details, in fact some of them can only really be described as pretty fucking insane.

The car was tested in the feature by Jochi Kleint, works rally driver for Opel, Ford, VW, and others in his career, and driver of the Golf Bi-Motor, the twin engine Mk2 Golf that VW entered in the Pikes Peak hillclimb in 1985, 1986, and 1987, with as much as 650bhp!

​In the feature Jochi not only says the car feels at least as fast in a straight line as the Golf Pikes Peak monster, but he says it's very tractable, no need for 1st gear even in tight hairpins, and FULL BOOST is by just 4000rpm! A ~700bhp 2ltr turbo engine, making peak power at 9000rpm, but full boost by 4k! That's a 5000rpm+ power band, ie HUGE, far far more than 99% of cars even today, and this was 1987.
​Like I've said before​ you can have all the new technology you like, but a correctly specced and set up engine even with very old spec parts will still wildly out-perform most stuff.

We've pretty much covered engine performance, so to finish this section off, and to go nicely on to the next bit, here's a great pic of the underside of the car, showing the big intercooler and 4inch exhaust system...

 Anyhow, as bonkers as the engine is, the TRANSMISSION is probably at least as wild!
​For a start, the gearbox is by possibly the best known brand from rallycross- Xtrac. What makes this special, especially for 1987, is not only are they ridiculously strong and capable of handling huge power and abuse, but they had in-car adjustable front to rear torque split, which on this car was meant to be between 28F-72R, right down to 50F-50R.
​In the magazine testing Jochi stated he felt the car was fastest at 40F-60R.

​The transmission had another setting too, again selectable from one of the buttons within reach of the driver, and I don't know if this was a 1-off for this car or a feature of other Xtrac transmissions of the time, but it's deffo the first time I've ever heard of it- It had a BOOST OPERATED four wheel drive!
​Yes, you read that right. One of the settings this car had made the car 100% RWD until boost pressure hit 3psi (0.2bar), and then the 4wd would kick in! Clever as hell, especially 30 years ago!
​In theory I can imagine an advantage on turn-in off throttle to eliminate understeer, as chances are this car had a pretty serious plated LSD front diff, but according to Jochi in the magazine feature, he felt it was faster when in permanent 4WD mode.

​Away from all that madness, the clutch was a Sachs triple plate item, the front diff was based on the E30 325iX setup, the rare factory 4wd version, and the rear end and diff was full Group A E30 M3 setup. This is a pic of the rear end actually...

And here's the front suspension setup..

The interior of the car was pretty sparse as you'd expect from a race car, but notice the bank of switches, most of which within reach of the driver to adjust the trick 4wd system settings, not to mention the all important boost pressure.

For cooling, the car had what has become a bit of a trend for drift cars and even some Time Attack cars in recent years, and that's a rear mount radiator, and you can see the holes and ducting for it in these pics...

As well as the radiator, there was two other things in the boot of this car, two VERY unusual things, something to mental that if it wasn't for me reading the words in this very sensible and technical German magazine who tested and reviewed the car when it was brand new, I'd be 100% they were joking...

​It had the alternator and A MOPED ENGINE in the boot! Seriously! It really says that! It says it has a small moped engine mounted in the boot that has the sole job of spinning the alternator, which in turn gives the electricity for all the trick parts this car runs. Crazy!​

So, I've already mentioned that, despite it being absolutely incredible and hugely spectacular, this car wasn't actually very successful in rallycross.
​
According to Jochi Kleint in the feature, the car was almost undrivable as it simply had TOO MUCH POWER for the tyres and suspension to handle, even with the trick 4WD system, and he felt on loose surfaces a well-sorted 200bhp FWD Golf would be as fast if not faster.

​The feature also says the owner/driver, Arild, was having to change tyres after every race, which wasn't normal for rallycross, and was due to the combination of massive power and running hugely soft tyres in an attempt to get decent traction.

​There's another alleged issue too, which does tally up with the fact the car always seems incredibly tail happy, and it's said in recent years his son has talked about the car and stated the 4WD system or the front diff at least wasn't actually working like it should, making the car far more rear-bias than it was meant to be.

​Either way, win or not, the car has become a bit of a legend and deffo my fave car, and even Arild himself is said to be incredibly surprised people now, 30 years later, still talk about the car. He will probably be a lot more surprised if he sees this feature!

.ANYHOW, that's about it for this feature on this insane and amazingly interesting car, and I hope you've liked reading it as much as I loved writing and finding out about it.

​There's a LOT more incredible cars from this era of rallycross, and as long as you guys want to hear about them, and as long as I can find out the long-lost info about them, you'll be seeing more features like this in the future!

Also, please, if you liked what you see, and want to see a lot more, want to see and read exclusive content and even get help on your own project, help Stav-Tech grow to bigger and better things by becoming a patron of the brand, giving whatever you feel it's worth to you, simply by following this link- ​www.patreon.com/stavtech.

Of course, don't forget to check out the StavTech Facebook and YouTube channels too, as I regularly post great stuff on both channels, so don't miss it!

Cheers!
​Stav

Since I created the StavTech YouTube Channel (Click here!) I planned to put everything on there from now on, as unlike here, there's money to be made, and I need to make a living after all, BUT some things just work better as words, so I've decided some things will be on the website regardless (plus Facebook and Instagram), so here we go...

A few weeks ago I saw a post where a bunch of retro-rallycross fans were confused about the strange 'loop the loop' inlet manifold in the above picture (by rallycross photography legend Eddi Laumanns), and were discussing what the hell it was all about.
I replied and explained exactly what it was, but I got the feeling they didn't really believe me. It was only once someone posted a clearer pic that proved I wasn't talking out of my arse that they finally seemed to accept it.
BUT the whole situation made me think it's ideal as a cool bit of tech for you lot, so here it is!

​This funky looking inlet manifold is used only on certain variations of one engine, the XU8T, which is the 16 valve turbo race engine version of the PSA (ie Peugeot + Citroen) XU series of engines that are found in countless production cars, and was first used (unless very late spec 205 T16 Evo2 Group B engines used the same? If so I've never seen one!) on the 1987 Pikes Peak 205 T16, ie this one...

It was then used the year after in the 1988 Pikes Peak winning Peugeot 405 T16, the world famous car driven by Ari Vatenen which starred in the famous 'Climb Dance' video.

In fact, here's a few pics of this inlet as fitted to the 405 T16 Pikes Peak winner...

The next time this inlet was seen on a car was in Matti Alamäki's 205 T16 E2 rallycross monster in 1989, which made well over 550bhp from it's 1760cc (I understand? Slightly less than the GrpB versions for some reason?) engine...

Soon after this it also found it's way in to Jean Luc Pailler's Citroen BX4TC rallycross monster...

And after a good few years Jean Luc Pailler pretty much swapped the engine and running gear in to the BXs replacement in the production car world too, the Xantia, where it was used for the number of years in the 1990s...

ANYHOW! Enough of the history lesson... What the FUCK is that crazy looping inlet all about then?
​Well, it's actually a lot more 'normal' than you might think...!
As crazy as it looks, all this inlet really is, is a variable length inlet manifold like a lot of production cars have these days, albeit a super trick one running two sets of individual throttle bodies, really long runners (which should have a far greater effect than typical ones), and a boost-operated (rather than rpm) switchover point.

Variable length inlet manifolds are quite common these days, used on everything from MX5s to Ferraris. As you probably know, in conventional inlet designs, longer inlet runners tend to improve low rpm performance at the expense of high rpm performance, short runners improve high rpm at the expense of low rpm performance, but a good variable length inlet should be the best of both worlds.

The common myth is that inlet length makes no difference to turbo engines, hence why it's rare to see factory turbo cars with them, but in reality it makes a difference no matter what; it's just turbos are so good at making a wide powerband, and masking flaws in an engines powerband, that they're rarely used on boosted engines.

​Rarely used or not, it doesn't take Sherlock Holmes to work out that if Peugeot, who were one of the world leaders in turbocharged motorsport at the time, used it on multiple Pikes Peak cars, including an outright winner, and then it was used for about another decade in high end rallycross, it's fair to say it had a very worthwhile effect- They didn't fit stuff for fun or just guessed at that level, that's the stupid shit road car tuners do, not them!

The main reason they fitted this inlet to these engines was to improve low rpm performance via the long runners, which has the positive side-effect of spooling the turbo faster, while also having the switch-over to short runners, shorter than most typical non adjustable inlets, for maximum high boost high rpm power.

The engines this inlet was used on were as small as 1760cc and up to only about 2.1ltr, but all made somewhere between 550 and 800bhp depending on the application; we're talking really big turbos that needed all the help they could get to spool, especially for the tight and twisty rallycross and Pikes Peak events they were used in.

So, what are we actually looking at here? Well the top-down shot of it mounted in the Citroen BX is a good one to check out... Follow the boost pipes!

The air comes from the filter (bottom right), through the Kevlar inlet pipe, and in to the turbo compressor housing (top centre). It then leaves there and enters the chargecooler (top right), then heads down to a centrally mounted plenum as part of the inlet manifold this feature is about (middle right).
​Just to the left of the central plenum are 4x individual throttles, one per cyl, but these aren't the engines main throttles, these are simply to block the short inlet runners, forcing the air to go around the long looping runners you see exiting the right hand side of the centre plenum.
​The aforementioned throttles are opened at a set boost pressure via the turbo wastegate style actuator you can see painted black on the right hand side of the inlet, near the air filter outlet.
​The engine itself also has 4x conventional throttles, one per cyl, but they're mounted VERY close to the inlet ports, and are pretty much invisible in the above shot, but you can see the the springs and rods that operate them on cam cover.

​For a MUCH clearer view of both sets of throttles, which will also easily show you how the inlet works, check this pic out...

This style of inlet isn't seen in modern motorsport anymore, mostly as modern anti-lag systems are so effective at spooling turbos, which makes setups like this a bit redundant for most race works race engines which have pretty unlimited budgets.
​
​Having said that, this style of inlet makes no noise, adds no engine stress or heat, and is purely mechanical, so for us road car based people, indeed for race car people without a works race team budget, variable length inlets do potentially have a worthwhile use on turbo cars, despite what many people think...!

Or do you (think you!) know better than Pikes Peak winners...? (Hint- You don't!)