Welcome to my world, my world of turbos, tyre smoke, and tuning...
Tuning cars, driving cars, testing parts, and complaining about everything. It's my job, and a the majority of my non-work life too...
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...
You like cars, and car videos, but don't like clueless bullshit and channels where the only tuning is basically chucking a ton of money at an expert and then the channel taking the credit?
Want to see proper 'Built Not Bought' cars? Cars that, for the money spent on them, are actually FAST? Well, that's my channel.
The StavTech YouTube channel- www.youtube.com/c/StavTech
As long as you're not expecting big money BS and award winning cinematography, it should be right up your street.
And to make it easier to check out and keep up with, I've added a page on this website with all the videos on, HERE!!!!!!
It's still a pretty small channel in YouTube terms at the moment, but it's growing, and I'd flippin' LOVE for it to grow to a level where it's actually making me money, as then I can keep making better and better content for you lot too, so go bloody subscribe!
STAV'S TECH TIPS- THE HOLSET HE221W 360BHP+ CAPABLE AND FAST SPOOLING TURBO CAN BE EASILY FITTED TO STANDARD SUBARU, VOLVO, AND SAAB, EXHAUST MANIFOLDS AND DOWNPIPES! (AND MANY MORE CARS TOO!)
Fitting an uprated turbo to a cars standard exhaust manifold is often expensive and with a pretty average result at the end of it too, especially when you have a turbo setup with oddball turbine inlet and outlet flanges and don't want to change them to custom ones to suit the new turbo.
This is especially the case with Volvos, Saabs, and Subarus (And others! Read on for that), and the typical replacement hybrid/upgrade turbos from the stock TD04 turbos are both expensive and, well, a bit of a small improvement on the whole.
Well, while researching other things and thinking about upgrades to my Impreza, I had an idea that seemed like it would work, but seemingly had never been done, so I took the punt and bought a few bits to check, and I was right, and this is exactly what this feature is all about...
THE HOLSET HE221 TURBOCHARGER...
While I've already talked about the turbo (and countless others!) in THIS MASSIVE FEATURE, let's run through the basics of the Holset HE221W turbo again.
Holset is currently the single biggest turbo manufacturer on the planet at the moment, and while their sole sales plan revolves around OEM fitment turbochargers to commercial/military/seaborne/generator/etc applications rather than the comparatively tiny aftermarket (Though they've supplied turbos to Formula One and Indy Car winning vehicles!), plenty of people have realised how good many of their turbos are, so they've become hugely popular for tuned cars too.
The Holset HE221W is one of their smaller and more compact turbos, but also one of the most impressive, and while it normally comes with the T2/T25/T28 turbo flange and a 4bolt outlet flange, it's actually very easy to retrofit exhaust housings that are the OEM Subaru, Saab, and Volvo fitment.
Capable of up to 380bhp and 3bar boost (see above compressor map) as well as super fast spool and hugely wide compressor map with massive resistance to compressor surge, it is an awesome bit of kit.
Even with a tiny rally inlet restrictor that slows spool and can make many turbo designs absolutely useless, it still works fantastically, as the datalog graph below shows.
The graph above is on a Ford Sierra Cosworth rally car with the usual 34mm inlet restrictor, comparing a Mitsubishi Evo based turbo, a hybrid Garrett T3 turbo, and 2x Holset HE221Ws, one with a cast wheel, one with an aftermarket billet wheel.
As an example of restrictors ruining the performance of what's normally a good turbo, the Evo compressor was pretty useless with both power and boost.
The Garrett was a turbo well proven as a good choice with the rally restrictor made good boost, but hit full boost over 1000rpm slower than usual.
The HE221W though, despite being a OEM production unit, made more boost than the physically bigger hybrid Garrett, and spooled 750rpm faster too.
The above is what a HE221W normally looks like with the standard turbine housing (This is just pictures I stole off Compressor Racing as I couldn't be arsed to take even more pics of the one I bought for my car- THIS is the link to the sale if you wanna buy one), and it's about GT28 in physical size, with a 60mm compressor wheel, and has something only GTX turbos of this size tends to have- An anti-surge compressor housing.
"OK! SO HOW/WHY CAN THESE BE FITTED TO SUBARUS, SAABS, VOLVOS, AND SO ON?" I HEAR YOU ASK, WELL...
The answer to this is fairly simple when you think about it, but just like the OEM Subaru, Saab, and Volvo turbos, the HE221W is actually a Mitsubishi TD04 based unit, but the Holset version is far better than all of them, it's like a 'Super' TD04.
And yes, as many of you know, while there's loads of TD04 variations of both compressor and turbine wheel sizes, the HE221W turbine wheel is actually the same overall diameter (but a better flowing design) as the 'big' TD04HL turbine wheel as fitted to the TD04HL-15T on the Saab 9-3/9-5 Aero high performance B235R engines, the TD04HL-13T on the 2.4T 5cyl Volvo engines from the C/S/V70 and similar engines, the TD04HL-15G on the 2.3T fitted to the high performance versions of the Volvo 850, and in fact many older Volvos such as certain 940 turbos with TD04HL turbos.
There's no OEM Subaru turbocharger with the TD04HL turbine wheel, but Mamba and many others sell aftermarket Subaru fitment turbine housings to fit the TD04HL for very little money- HERE is the one I bought.
As well as these, the Porsche Cayenne turbo uses TD04HL turbos, as do many Mitsubishi engines and others too.
So yes, as you've probably guessed already, you can simply swap the turbine housing over from your TD04HL, on to the HE221W, it's just one clamp, super easy, and hey presto, you have a turbo proven capable of up to 380bhp, 3bar boost, mega spool, that fits to the stock exhaust manifold and downpipe, for very little money.
This is similar to what I did on the IHI turbo on my crazy little 660cc Mira if anyone remembers that, in that case I did the same, using the factory turbine housing and after a lot of research found a much newer model car with a far bigger compressor and turbine that bolted straight to the stock housing with no machining, and the result was incredible, about twice the original power, and actually faster spool than stock too.
SO HERE'S THE CAR BY CAR DETAILS...
Hi, I'm Stav...
You may or may not have heard of me, but I've spent the last 15 years working full-time in the tuning scene, and the last decade or so writing for various car magazines.