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...
Rear mount turbos are pretty new to the tuning scene as 'tuning' goes, having only becoming well known in the last decade or so, and even now are relatively unheard of in the UK. Therefore almost every time they're spotted they're always treated with amazement, both in good and bad ways...
The problem is, people's opinions of them tend to be polar opposites of each other.
MOST people, due to it being totally against everything they know, instantly say it will be laggy as fuck, won't spool, will be shit, and so on and so forth.
They're wrong if it's done right.
On the other hand, you got people, again have no actual experience of it, but love the idea and have seen a few on the internet, who tell you rear mounts are amazing, the best way to turbo, as good as a front mount, and so on.
They're also wrong.
Basically, rear mounts are neither shit or amazing, though they're perfectly possible to be shit if done incorrectly, just like a front mount turbo can be. What they are is simply another option if a front mount isn't viable for some reason, and done right can work fantastically well, often far better than most front mount setups, which are often sub-optimal, even when a 'pro' has designed them...
If ALL ELSE WAS EQUAL, a front mounted turbocharger IS BETTER, no iff's or but's, it is. But things never are equal with turbocharging, and there's a multitude of reasons a rear mount setup is useful in some applications, and if done right, they can perform as good or better than a typical front mount setup.
The E55 AMG rear mount I helped build for Compressor Racing was a perfect example of the above. Just like a whole lot of cars, there's next to no room in the bay for a turbo or two, so even IF it's possible, you'll likely be spending a few grand on custom manifolds, even before anything else. And then you've still got to find room for the intercooler, and then deal with the heat management issues for all of that too.
The only other option for the E55 is a supercharger conversion, that costs at least £7000 plus fitting, and makes about 500bhp at 9psi boost, about the limit of the stock (albeit modified) ECU, as we found ourselves.
The E55 rear mount turbo we built was on full boost by 3000rpm (despite a turbo capable of 1000bhp!), and the only time we put it on the dyno it made 465lb/ft at just 4.5psi and due to boost control issues we were only at 2psi by peak power but it still made 440bhp- About 90bhp more than standard.
In the end we sorted out the fuel and boost control issues and got it safely at 9psi. It was never dyno'd at this level, but it WAS timed with Racelogic timing equipment, the proper pro stuff magazines and companies use, not some crappy app or a stopwatch, and the results, despite horrendous wheelspin, were pretty impressive to say the least...
60-100mph time was 4.4seconds at best (backed up by a number of 4.5s runs).
To put that in to perspective, the later, best part of 500bhp, factory supercharged version of the E55 AMG does 60-100mph in 5.5seconds, over a second slower, and even a supercar like the Ferrari F360 is 4.6sec!
And it even made a pretty fun drift car, despite being a huge, heavy, rusty old boat, as these pics show...
And how much did the full rear mount conversion on the E55 cost to do, inc all the non-turbo related bits, such as the uprated fueling parts and so on? Under £2500.
You'd not even get a pair of custom manifolds made for a front mounted turbo setup on the same car made for that, and even if you did, will be spool a 1000bhp capable turbo much sooner than 3000rpm? Would you even want it to? Probably not for both accounts, and it'd be highly unlikely to make much more power at the same boost either.
While it's MOSTLY pure lack of room that makes a rear mount particularly tempting, it's also been done, even with very high end race cars, for weight distribution reasons, and the simple fact that, done right, it isn't a big disadvantage...
So does this mean we should ALL have rear mount turbo cars? FUCK NO! If you've the room to easily do a front mount turbo setup that's not a complete fucking bodge or cost an absolute fortune, you may as well just do that. As said already, if all things are equal, it will spool faster and make more power than a rear mount. It might not spool loads faster and make loads more power, but still, really no point for a rear mount unless it makes things a lot easier for whatever reason.
BUT as it often does make life easier, I'm sure most are you are thinking "Ok, but say if I do want to go rear mount, how the FUCK do I do it so it's not the laggy mess the naysayers say? How DO I make it as close to as good as a front mount as possible?"
Well, I better tell you what I know and have experienced...
MANIFOLDS- Use standard cast log ones, or short runner tubular ones at very most. For fastest spool you want to minimise exhaust length and maximise heat retention, and regardless of turbo position, long runner exhaust manifolds have very little effect on peak power on turbo cars anyhow.
PRE-TURBO EXHAUST DIAMETER- This is one so many people get massively wrong, and hugely over-do. Treat all your pre-turbo exhaust like you would your manifold on a front mount system, so with a T3 flange and even 600bhp+ a single 2.5in pipe is more than enough, and a single 2in or 2.25in is plenty for lesser power cars. Even with big V8s running over 140mph in the quarter mile, a single 2.5in pipe leading to a T4 flange turbo is well proven. Overly big exhaust diameter will drastically slow spool, and is the biggest killer of performance on rear mount setups.
PRE-TURBO EXHAUST LENGTH- To minimise heat loss, shorter is better, so if you can actually have a mid-mount turbo rather than rear, even better. Just behind the front seats? Instead of passenger seat? It's all been done...
PRE-TURBO CATS- I've not experienced this one first hand, but while basic theory says they'd be bad for power and spool, they're fitted to a great number of very powerful but emissions legal rear mount cars. It's possible the reason they're not the spool killer you might imagine is because post-cat exhaust temp is incredibly high (it's part of their job), which will help maximise exhaust energy and heat at the turbine. But I've never tested this so that's speculation...
BOOST PIPE LENGTH- As discussed in THIS feature, boost pipe length isn't actually a big deal at all. Don't make it longer than it needs to be, but of all the things to fuck up spool on a rear mount, this is a minor one.
One thing you might want to take in to account, though on smaller engine applications (or just using bigger boost pipes) it's likely not an issue, is the instant off-boost punch at very low rpm or just as you open the throttle. On small capacity cars there's not a lot unless there's boost anyhow, but on the AMG it had a huge V8, and once it was rear mount turbo, sucking through inlet pipes 10 times as long but about half the diameter of standard, it lost a little of this punch. You'd not notice unless you drove it back to back, and even then I only really noticed as I wanted maximum punch for drifting, but it was there.
I had a solution though, I fitted this flapper valve taken from a Volvo boat engine, allowing the engine an alternative way to breath in N/A mode...
INTERCOOLING- Yes, compressor outlet temp is lower in a rear mount. Yes, the long boost piping allows for more heat loss. But regardless, the inlet temps aren't that much lower, so if you've got room at all, you'd be mad not to fit an intercooler or chargecooler.
POST TURBO EXHAUST- As explained in THIS feature, bigger is better, and with rear mounts needing all the help they can get, as big, and as short, a post turbine exhaust, the better. Even with a 2.5in pre-turbo exhaust, noticeably faster spool has been achieved by going from a 3in to 4in post-turbo exhaust. As a rule of thumb, your exhaust diameter should be AT LEAST 1.5 times your turbine wheel exducer diameter for best spool...
HEAT RETENTION- This is a big part of spool for any turbo, and a HUGE issue on rear mounts. Basically, the hotter the exhaust gas is by the time it gets to the turbo, the better your spool is. So heat wrap ALL of the exhaust, front to rear, double layered if you can, and of course, put a turbine blanket around the turbo too. The difference between heat wrapped and not is very noticeable.
TURBO POSITION- Under the car is most common, and nothing wrong with that at all, as long as ground clearance isn't an issue. On the Merc we went boot mounted, which personally I prefer for packaging reasons. When we did so we got no fucking end of people saying how can it breath in there, we need to cut holes to let air in, etc etc etc.
Nah, not really.
Boots are FAR from air tight, thousands of small holes and gaps which overall make up to far bigger than a typical 3-4in inlet of an airbox, and the boot itself works as a giant airbox.
No matter how many times we said this, people still said it, so in the end we drilled some holes in the boot to see if it made any difference at all.
Nope, not a fucking sausage, exactly as expected.
WASTEGATE POSITION- The "Normal" rear mount position is right by the turbine inlet, but IMO they've decided that with zero testing and just their guess. IMO it's wrong. For me, the closer to the engine the better. The WW2 planes and the top drag cars have the wastegates just after the manifold collector. And I'd be more inclined to listen to war winning aircraft and cars that run 190mph in the quarter than some random other person who's probably not tested either way.
OIL FEED AND RETURN- While you certainly can have a stand-alone oil system for a rear mount turbo, it seemed like added complication for little benefit to me, so on the ones I've had dealings with, we've always just fed the engine oil the traditional way- An oil feed pipe direct from the engine.
Oil return is a bit different though. You NEED an electric scavenge pump so suck and pump the oil back to the engine, it won't go on it's own, you'll just end up with a smokey fucked mess. One bonus is, you don't have to return to the sump like on a conventional gravity oil return, anywhere will do- On the E55 we returned to one of the cam covers!
TURBO SPEC- This is the biggie. Compressor side, well, it should be the same as you'd choose front mounted for the power you want. Turbine, well, smaller improves spool, but also increases backpressure which kills power, and personally I'd not be going much smaller than I would front mounted, maybe not any, and just concentrate on optimising the setup as per above. Just be conservative on turbine size, sensible, as you can't get away with overkill as easy as front, but the exhaust gas still needs to come out, and having a tiny turbine to try and get good spool is why so many rear mounts make shit power for their boost level.
Of course, there's OTHER options to allow a massive turbo without the risk of killing spool.
On the E55 AMG we did for Compressor Racing we used a variable geometry turbine turbo, a Holset HX55V VGT unit in fact, a flippin' huge 1000bhp capable beast. VGT turbos, while not the magic solution to all our woes, have the ability to spool like a small turbine, and flow like a large turbine, so are very useful for rear mounts.
The issue is big VGT turbos are rare as hell in the UK in good condition, and the poxy little ones used on diesel cars are useless, so it's not an easy solution.
Another idea is twin rear mount turbos, compound style, one small for spool, one big for power. I'm currently building a rear mount setup like this now.
Finally, and one I've never seen tested, but I'd like to try one day, is the effectiveness of twin scroll. I don't think it will be a magic solution, but for cars with a very easily done twin scroll setup, mostly inline sixes and twin rotors, I'd be inclined to run two small pipes to the turbo, one to each scroll...
AND THAT'S THE BASICS FOR YOU...
There's a whole lot of bullshit, incorrect 'facts', guesses, and downright lies about rear mounts, but hopefully what I've told you will set a few things straight, and to be honest is plenty enough, if you choose to follow my advice, for a pretty well performing rear mount setup.
BUT DON'T FORGET! Don't do it if there's no good reason to...
OH! Forgot to mention something that's actually a BIG plus point, as childish as it may be... IT SOUNDS FUCKING MENTAL. All you can hear is turbo spooling up and down, super loud chatter and spool and everything else. Sounds like your car has a jet engine rather than a normal engine, which is amusing. Click HERE to see a short vid of the AMG, inside and out, to see what I mean...
And of course, it looks cool too...
I've known Thomas Zurawski for years, right from when he operated from a tiny little workshop in central Gloucester, in fact we now live 5min down the road from each other, but he has nooo fucking idea I'm writing this (TBF I only decided it'd be an interesting feature earlier today), so this will be a surprise to him to say the least.
One thing's for sure, I'm glad I know him, in fact I think all of his customers are, as he's the type of tuner I think we all expect/hope tuners to be in our heads, but in fact are rare, and that's someone who can basically create pretty much anything you can dream up.
No matter how unusual or one-off, he finds a way to do it.
I've worked with and for tuners constantly for the last 15 years, and I've seen it all. From amazing unsung geniuses, to appallingly bad and shouldn't be in business. From basic hot hatches to Formula 1 and WRC cars. From backyard tuners to enormous warehouse sized places.
Ignoring the bad and even the average tuners, and just talking about the great ones (I'll try and talk about some of them in future features), they generally do whatever they specialise in brilliantly, but most, totally understandably, stick to what they know, stay well within their comfort zone, and just do what they do best. If any requests come in for something very different, it's generally either discouraged/refused, or will be hugely expensive as any work they don't specialise in will be farmed out elsewhere.
When it comes to custom fabrication it's a similar situation too, as I know a lot of absolutely incredible fabricators, some of which would make a good feature on here too actually, but again, wisely enough, they stick to what they know best.
Because of the above, I've found over the years, and no doubt most of you have too, getting custom work made, unless you're very rich or can do it yourself, is very, very tricky.
But this is where Zurawski Motorsport is different, as Thomas is genuinely the only person I've ever met who I can go to with strange/crazy/one-off tuning ideas, and not only does he always say "Sure, we can do that", but he's not bullshitting either. He not only has the fabrication skills, but he genuinely understands tuning too, so what you have in mind, what you hope for, is what the end result actually is.
I first used him when he was fairly unknown, 6-7 years ago, to weld a few things for me. It was simple stuff, but I heard he was a shit hot welder, and was local, so it was ideal. From these basic jobs and talking to him, it became clear he knew what he was doing with tuning as well as fabricating, and as I had an idea in mind, and couldn't previously find anyone who'd do it, I went to him with a couple of bits of metal and what seemed to me like a good idea, and the rest is history.
What I wanted, but didn't exist, was a super short runner twin scroll turbo manifold for a 13B rotary engine. All manifolds available then were longer runner than I wanted, single scroll, or both, and was told what I wanted didn't exist as it wasn't possible.
I explained what I wanted and why, and within a few days he calls me and says it's done...
As time's gone on, Zurawski Motorsport has moved to a much bigger premesis in Ledbury, and the main things he now does are almost 'production' parts rather than 1-offs, albeit ones that didn't exist (or indeed were called impossible) until he designed them, such as the Toyota 1UZ V8 engine and manual gearbox conversion parts for 3-Series BMWs, big power twin scroll turbo setups for RHD inline 6 BMWs, and 1UZ V8 big single turbo conversions, all of which he sells to customers all over the world...
But why Thomas, and Zurawski Motorsport in general, has ended up with the large following and the respect they have, is because everything the company has done originally comes from an individual customers crazy idea/dream, and while others say they can't do it or expect horrendous money to do so, it's always the same "Sure, no problem" from them, and the result is mad shit like this...
Mid-engine SR20 Time Attack Silvia?
"Sure, no problem"
No, forget the SR20, fit a 1UZ Toyota V8 and a flippin' massive turbo in the same place.
"Sure, no problem"
Twin scroll tubular manifold on a tractor with a massive Holset turbo?
"Sure, no problem"
What about a BMW V8, in an E30, with twin turbos, massive intercooler, and a WRC style direct port anti-lag system?
"Sure, no problem"
Why not build a completely custom bike, and I mean REALLY fucking custom, even make the bloody frame and wheels yourself?
"Sure, no problem"
How about build a twin turbo setup with ITBs and insane custom plenum for some crazy off-road lightweight race truck?
"Sure, no problem"
Make a WRC/Rallycross style twin plenum equal flow intake for an RB20 and help it produce 470bhp (on stock head/cams) that has full boost by just 4000rpm (despite a 600bhp rated single scroll turbo!) that's still going strong after many years of hard use?
"Sure, no problem"
Massive single turbo setup for an E34 BMW 540i?
"Sure, no problem"
E36 BMW with a 1UZ V8 engine, massive turbo, and WRC anti-lag setup?
"Sure, no problem"
OK, OK, we get it, they can build some mental looking stuff...
But these things don't just look mental, the ARE mental. A big thing I like about Zurawski Motorsport, and why I've used them for so many of my stupid projects and ideas, is Thomas REALLY gets tuning, and works things out properly via a mix of sound tuning principles and his own experience. Steve Will's awesome E36 M3 turbo is a good example of this. It already was a 700bhp turbo monster with a fully forged engine, but he went to Zurawski Motorsport not looking for more power, but similar power but with a much improved powerband.
So off came the log manifold 99% of RHD turbo BMWs use, off came the stock inlet plenum, and what was fitted instead was the Zurawski twin scroll manifold and twin plenum equal flow inlet manifold, a setup Zurawski Motorsport now has available to any customer who requires it.
And, well, the difference in how the car performs, despite the same size turbo and not a single change to the engine internals, is nothing but incredible, as the dyno comparison below shows...
A big big reason why his stuff works is, unlike many (though they'd never admit it), he really does calculate and measure everything rather than make a best guess, and it's actually quite odd/bizarre when you see him do it, especially for someone like me that sucks at maths, as he does it mostly with a pencil and paper, like so...
It's also worth mentioning his shit is STRONG too! Unlike so many exhaust manifolds which crack all the time, his stuff is made from thick, and top quality, stainless steel, and welded not to look pretty in internet pics (though it does), but to be fucking bulletproof, even with hard anti-lag use and so on.
To the extent customers have had quite big crashes in their cars that bent chassis rails and so on, but did the manifold crack? Nope.
So yeah, it's not a big flashy company, but what Zurawski Motorsport does it pretty unlike anyone else I've found in all my years of pissing about with cars in the UK, and while I'm not easily impressed (there's only a handful of other tuners I can think of off the top of my head I'd like to write about), anyone who can so consistently produce such mental stuff as him, without the kind of WRC-style budgets and huge staff levels this kind of craziness normally comes from, gets my vote...
To see more, check out the Zurawski Motorsport Facebook page HERE, and there's a website HERE too.
This is the never ending myth that comes up almost every time someone asks about fitting big intercoolers on forums and so on. You can be assured a knowitall, who no doubt has zero experience of it or he'd not say it in the first place, will tell you long boost pipes and/or massive intercoolers will make your car laggy, especially if you have a small turbo.
Well, let me say, that's TOTAL BOLLOCKS.
In THEORY, and it is fucking basic, primary school, narrow minded, short sighted, theory, the longer the boost pipes, and the bigger the intercooler, the longer it takes the 'boost' to travel from the turbo to the engine, and the longer it takes the 'boost' to pressurise it all before it pressurised the engine.
In REALITY, airflow out the turbo travels at fucking HUNDREDS of miles per hour, and airflow in to the engine consists of HUNDREDS of litres per fucking second, so how in God's name do you really think adding even 10ft and 10litres (and that's massively unlikely) to the pre-throttle intake length/volume will make a car laggy is beyond me.
In reality, and I've tried it over the years with really bloody extreme examples, with poxy little turbos and ridiculously big intercoolers and pipe lengths, it never ever feels 'laggier' or 'less responsive' or 'slower boosting' or any other way people want to say it, and usually (Imprezas are a great example as they have insanely long intercooler pipe lengths and massive front mounts) they actually are noticeably MORE responsive and have MORE low down power than before, as low intake temps are far more effective for performance increases than any theoretical response improvements.
Almost all top mount setups, and most v-mount setups too, usually have pretty horrendous inlet temps compared to a decent front mount, and with no real response improvements, giving up lower inlet temps just to shorten boost piping is a terrible plan in reality, which brings me neatly on to this car...
What we have here is an MR2, with a mid mounted 2ltr (2.1 maybe, can't remember and it doesn't matter) 4cyl engine. But the turbo is REAR mounted, a good couple of feet from the engine. That alone is enough to make Pistonheads forum nobheads cry 'LAAAAAAG' in some dweeby middle class voice. BUT hang on, where's the intercooler? Well, it's at the FRONT! Yes, this mid engine car, with a rear mount turbo, has a front mounted intercooler, and at least twenty foot of boost pipes connecting it all up!
Seriously, I've literally NO doubt if this car was created by some random lad in this day and age, not only would it get fucking slaughtered on whatever forum he made the mistake of posting it on, but it'd end up going viral on Facebook etc etc as the hordes of internet 'experts' ripped the absolute shit out of it for being a ridiculous stupid idea, despite none of them having any experience at all with anything even close to it.
I can picture the unfunny memes about it now...
I'm sure, even now, even after everything I've wrote, a lot of people are looking at the pics above and thinking "Fuck me, that must be horribly laggy and useless".
Well, no, no it's not, in fact the above car won the GT300 JGTC (Ie Japanese Touring/GT championship) in 1999, vs RX7s, S15 Silvias, Porsche 911s, Imprezas, and more.
I'm not 100% as I've not found enough detail to be sure, but the same setup in different livery might have won the 1998 championship too (MR2s with the same drivers did), and I think the 2002 GT300 winning MR-S (below) looks like it might've been a similar setup too, but can't find enough pics to be 100% sure...
The title says it all really, and that's not opinion, that's cold, hard, fact.
They're not useless, in fact they're a handy guide if you have them, but the only tell a tiny part of the story when it comes to how useful a turbo is. For this reason, basing your turbo choice on what you see on a compressor map is ridiculous, and just shows that you, despite no doubt feeling smug that you understand how to read a compressor map, also shows you don't really know how engine tuning works...
I've actually seen a whoooole lot of people choose not to buy a turbo because there's no compressor map publicly available (or just doesn't exist). And considering pretty much no aftermarket turbo has a map available, and not even all OEMs publish theirs, this is pretty ridiculous.
The fact that the vast majority of the fastest and most powerful tuned turbo engines on this planet runs turbos with no compressor maps available for them is a hint at how "Think they're clever but in fact are stupid" (what's a good term for that, barring dickhead?) so many people are.
So what are compressor maps good for? Well, lots of things. They tell you the maximum (roughly, it's not gospel, most can do a bit more) airflow of a compressor. They tell you the maximum (roughly again, most can do more) pressure they can achieve. They also show you what sort of pressure and boost they're most efficient at, though if you're aiming for the most efficient point you'll be giving up both spool and power compared to a different spec turbo, which is a bit daft.
As the above sounds useful, why am I saying they're not that important? Well, while it's not as accurate as a compressor map, compressor wheel inducer and exducer sizes are a fairly good indicator of these things too. How much a compressor will flow is indicated by how big the inducer diameter is, and how much pressure it's happy to push is generally indicated by a bigger exducer diameter compared to inducer.
The another big reason you can't rely on them is because, as mentioned, the vast majority of the worlds best turbos simply don't have compressor maps available (Only some Garrett, some BorgWarner, and very very few from others), so you'd be likely hugely missing out on the best turbo for you if you went purely by maps.
Also, and this is a biggie, thanks to the wonders of the internet, plus the experts who create and sell these turbos, you're hugely unlikely to be venturing in to uncharted waters by using a turbo, and a bit of research can almost always find out how much they flow, how much boost they can produce, even without seeing any hint of a compressor map.
And this brings me on to the main reason Compressor maps aren't that important- ALL they show is the compressor side, HALF the turbo, and on most applications the less important side...
Compressor maps don't show, in any way, shape, or form, the number one question for 99% of people- How a turbo SPOOLS. Not only that, but it also doesn't show if the turbine side is far too small for the application; something that's often ignored, but is a HUGE factor on reliability and power.
An overly big turbine side won't spool well, or indeed at all- Compressor size has very little effect on spool.
An overly small turbine side not only can restrict power and usable rpm, but high-pre turbine backpressure causes huge reliability issues that wouldn't happen with a correctly sized turbine- What goes in has to come out! Check out my earlier feature HERE regarding backpressure for more info on this...
So to sum up...
Compressor maps = Useful yes, but vital, hell no.
Choosing a turbo via a compressor map = Stupid, as ignores all the main factors.
THE BMW M54B30 (AKA e46 330) ENGINE- GOOD, BUT WITH A HUGE, ENGINE SMASHING, WALLET DESTROYING, FLAW...
About a year ago I was in the market for a new daily driver and part time drift car, and thanks to E46 BMW prices being absolute rock bottom at the moment, an E46 330i Sport was the winner. The 330i is powered by the 3ltr M54B30 engine, and it was ok, but less revvy than I expected; feeling a bit dead beyond about 6000rpm. That turned out that was because the stock ECU is deliberately holding the engine back, partially closing the electronic throttle at high rpm. A remapped ECU totally wakes it up- Making it pull strongly to 7000rpm+ and feeling like a different, much better performing, engine.
I presumed BMW did this to make the M3 seem much more special, and maybe that's part of it, but there's another reason too- When you rev these things they explode in a fucking massive, engine wrecking, nothing worth salvaging, kind of way. Ever wondered why 325 and 328 engines are cheap and common and 330s cost so much more despite being so similar? It's because most of them are fucking broken!
My engine was running great, totally reliable and great, being both my hard used daily driver and used on drift days all over the UK with no problem. Then one day, at 6700rpm in 5th gear, the oil light came on, and stayed on, and it sounded like a bag of nails. I knew this meant game over for the engine, and seemed likely the oil pump failed. But I didn't know why. Well, it turns out it's because of this...
You know what that is? That's the nut that holds the oil pump pulley on! It turns out it's a VERY well known problem with 330i engines revved hard on track, and basically the harmonics of the 330i engine shakes it clean off, even though it's reverse threaded. The other, smaller, M54 engines don't suffer from this anywhere near as much; it's mostly a 330i thing.
So what happens? Well, the nut falls off, which then means the chain and pulley falls off, so the oil pump stops, meaning instant zero oil pressure, which as you can imagine, writes an engine off pretty instantly.
If you catch it super quick and at low rpm you'd likely get away with rebuilding the engine with new bearings etc, maybe a crank polish. That's debatable if it's worth doing over buying a good used engine, but mine fell off at 6750rpm and 3 figure speeds, and I likely didn't notice for at least 5 seconds, so it was deffo game over.
I limped it 5 miles home, and then thought 'fuck it, I'm not rebuilding it' so limped it as far as I could to my mates garage 10 miles away. Amazingly, it made it! Well, it got to about 200m away before it expired, and I coasted it the rest of the way.
What was the damage? Well, this...
Ever seen a cam worn down so much you can see inside it? No me neither, but it's pretty cool. That's a hole in the sump from a conrod in the 2nd pic. 3rd pic is the oil pump with the pulley that had fell off. 4th pic is the alternator bracket with a hole in as the conrod went flying through the block and that too. 5th pic is, among other things, a very bent and broken rod. And 6th is the remains of a cam bearing cap after being ran with zero oil for about 15 miles!
So what the hell fuck can you do about it? As it's mega common, and pretty flippin' disastrous lots of people have looked for a solution. There's a few expensive things that 'seem' to fix it, and a few cheaper things that seem to just delay the inevitable...
So, 'fixing' it. Well first up, BMW clearly knew of the problem, in fact to the extent they fitted a different nut to later engines (bottom right) which basically just seems to have thread lock on it. This supposedly helps, as it seems almost any M54B30 you take apart, even low milers in good nick, will have a loose nut, and earlier ones are worse regardless of miles, BUT it will still happen in the end, threadlock or not.
Another 'solution' is lockwiring the nut in place (top left). You can even buy kits for this, but again, it delays it, not fixes it. The entire pulley ends up shearing off.
Next up is almost the same solution and same 'in the end' fail, spot welding the nut in place, as the top right pic shows.
A better solution is a modified pump with a 4 bolt pulley, as per center bottom. Shame it costs about 750quid, which is nearly twice what a used engine costs.
Because it's crank harmonics that cause it, an ATI crank damper (bottom left) supposedly helps too, but again, it's big money, which turns most the appeal of a 330i in the UK (ie they're cheap as chips) down a little.
Best of all, but serious money that would certainly make you wonder why you didn't buy an M3 in the first place, would be a dry sump setup (top centre).
So what have I done on mine? Well, I picked up a low mile engine for £450, got the nut spot welded in place, which deffo isn't the full solution, BUT I hope it lasts a long time. Finally, partly as I wanted one anyhow for performance reasons, and partly as it's entirely possible it will change the damaging harmonics to a different RPM that it's no danger any more (but literally no way to know, it's SWAG- Scientific Wild Ass Guess, but a hopeful one) I've got a super lightweight flywheel to replace the fucking mental heavy dual mass setup they come with.
WILL IT LAST LONG? FUCK KNOWS! But the theory is fairly sound, I'll pray to He-Man that he can help it hold together, and one thing's for sure, I'll have fun until the time when it does happen again, if it happens.
If it does fail, I'll let you know!
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.