BMW inline 6 cylinders.

[BRAAP]

I’m starting up this thread about BMW inline 6 cylinder engines as one of our members shared a wealth of BMW 6 cylinder information worthy of being its own thread.

[Gareth]

As requested by Braap, I'm submitting some info about the BMW engines as a possible alternative for Hybrid Z projects. This article only thoroughly describes the basic characteristics of the BMW six cylinders. For more details, I'd recommend browsing the Swedish websites – they are sometimes available in English, and the amount of knowledge available there is ASTONISHING. These guys did almost everything BMW-related that you could imagine...

 

1. Why BMW?

This is the most obvious question that comes to mind when thinking of an alternative to your tired L-gata engine. The BMW engines were usually designed in a very sophisticated way, and they were always up-to-date with the latest achievments in car technology. Although the inline sixes that I'm going to describe below are not the cheapest and most cost effective alternatives for your average L-gata, there are several reasons why you should swap in a Bimmer engine:

• Not many people have attempted this before.
  
• BMW engines have very few bugs to start with, which is a rarity among other potential swaps.
  
• Most BMW engines have big potential for making power, even when they have a lot from the factory (think M engines).
  
• Once tuned and maintaned properly, any BMW engine will last forever.

2. OK, so I chose to get a BMW engine. Which one should I get?

The vast range of BMW engines may be confusing at first, but as it happens with every reasonable car manufacturer, it is only a matter of time before you can easily find out what exactly you want.

 

The basic engines are designated with the letter „M”.

 

M20 series – Small 6 cylinders, displacement ranging from 2 to 2,7 liters, SOHC. It's a good engine in stock form, and many garage tuners choose it as their base for homemade turbo projects. It can make good HP numbers if tuned correctly, but currently it's being phased out by the newer M50 motors.

 

 

M30 series – Big displacement (up to 3,5 liter) 6 cylinders with a SOHC head. The M30 has much more competition history than the M20, and it formed the base for many future street performance and racing engines. With up to 3,5 liters of displacement, it is a cheap alternative for the later engines, but it's considerably heavier than the M20 and the newer M50 engines. Even so, many drifters swap M30 engines into lightweight E30 3-series bodies, and slide them with much success – it's only a matter of a well thought-out setup and a good driver to make the car handle well. Unfortunately, it will probably share the fate of the M20, and will be soon phased out by the newer engines. It's a good base for a modified NA project and for street turbocharging – because of its strong build, the M30 endures much strain when pressurized (there are many high-powered M30s in Europe).

 

 

M50 series – Newer generation, mid-sized 6 cylinder with two chain driven overhead cams, displacement ranging from 2 to 2,5 liters. This engine is steadily becoming more and more popular among BMW tuners and enthusiasts, as it's cheap, easy to maintain, tough as nails (the later aluminum-block M52 and M54 engines are not as strong) and not much more difficult to turbocharge than the earlier M20s and M30s. For up to 400 or 500 flywheel HP, this is probably the best choice that you can make (it can achieve this kind of power with a GT30-sized turbo, forged pistons, a metal HG and good head studs). Very good in terms of cost-to-effect ratio.

 

 

The diamonds in the BMW crown are the „S-code” engines that power the legendary ///M GmbH cars.

 

S50B30 and S52B32 – These engines are found in the European E36 M3. They offer power ratings from 280 up to 320 flywheel HP, which is very much for a stock NA engine. There are not many possibilities to tune it the naturally aspirated way – apart from a standalone ECU, radical cams and high compression pistons there's not much left to improve from the factory. It's a different story whn boosting. There are many aftermarket supercharger kits available, but turbo is slowly becoming more and more popular among M3 users. With a big wallet and a good shop, it is possible to build a scary fast M3. The factory block is very tough, and the crankshaft is absolutely bulletproof (it is proven to be good for power levels of over 1000HP). After changing the pistons and rods, dropping the compression ratio, getting rid of the VANOS variable cam timing system and designing a custom metal intake plenum (the stock plastic unit isn't strong enough for any kind of boost), this engine is the European 2JZ-GTE in terms of power making. It combines the advantages of two best Japanese engines – it has displacement as big (or even bigger) as the 2JZ (which translates to faster turbo spoolup), and has the response of the RB26 (because it was built as a NA engine with ITBs, COP ignition etc.). Additionally, the 6-speed Getrag transmission found in the later 3,2 liter model is bombproof – as far as I know, is similar to the V160 found in the Twin Turbo Supra. Please note that most of the RWD BMWs have Getrag-engineered transmissions – the fact that one particular tranny was made by Getrag doesn't mean that it's bulletproof. The 3 liter S50 shares the 5 speed ZF transmission with the lower range 323i, 325i and 328i (I think) models, but it's still tough enough to cope with as much as 600HP. The S50 and S52 are a good upgrade over the M50 engine. I'd say that for power levels between 300 and 800HP, the S50 is the best choice.

 

 

Warning: The S50B30US engines found in the USDM E36 M3s are NOT the same engines as the S50B30s from Europe. The US S50 is only a hotted-up version of the good old M50. Not the similarity of US S50 and M50 valve covers.

 

 

M88/3 – Sold in the E28 M5 and E34 M6 (M635CSi in Europe), the M88/3 is a younger brother of the M88/1 engine found in the street M1, which, in turn, is based on the older M49 engine (3 liter, DOHC, mechanically-injected straight six) from the E9 3,0CSL. As all ///M inline sixes, it utilises a cars-iron block with dry sleeves, aluminum alloy heads with twin overhead camshafts (which are driven by a single row chain) and a high performance fuel injection system, in this case a mechanical Kugelfischer unit with six individual throttle bodies (butterfly type). The block is the same as in the M30 (it has the same oil sump system and the same bomb-proof crankshaft), and because of that the M88/3 can be fitted with the weaker gearboxes from the regular M30s in place of the original Getrag five speed. The heads flow very well, but there is still much room for improvement. Frankly speaking, this engine may be a bit difficult to maintain because of its mechanical fuel injection. It's a whole different case with the later S38 engine, which was an evolution of the M88/3 design.

 

 

S38B35 – This is the refreshed M88/3 engine, fitted with twin timing chains (the so-called Duplex system), Bosch ML-Jetronic electronic fuel injection with ITBs, lowered compression ratio and catalytic converters for both the US and European market, hence the lower power output than the M88/3. Even though it has less power, it's a much better base to work on simply because of the electronic fuel injection, which is easier to maintain than the Kugelfischer unit, and still offers much room for improvement. In stock and close-to-stock form, the M88/3 and S38's 3,5 liter variant produce around 280 to 300 flywheel horsepower, depending on the level of tune. With heavier modifications, however, they are able to produce in excess of 350 NA HP, which would already be a respectable figure for a street Z car. For turbo applications, the later 3,6 liter variant should be better (read the paragraph below for details).

 

S38B36 and B38 – The 3,6 and 3,8 liter variants of the S38 are its final (and best) incarnations. Modernized with a more modern fuel injection system, bigger displacement and coil-on-plug ignition in place of the standard M30-derived distributor, these are the ultimate BMW inline six power-makers (remember that the fastest BMW in the world, V.S. Motor's E36 from Norway, is powered by the 3,6 liter variant and does 7s in the quarter mile). It's the same story as with the S50, S52 and S54 engines – with enough knowledge, skills, money and custom fabrication, these babies are capable of producing upwards of 1000HP – reliably!

 

 

The biggest difference between the 3,6 and 3,8 liter variants is the cylinder wall thickness, which is smaller in the 3,8 because of the larger bore (this makes the 3,6 block more appropriate for heavily boosted applications). Please note that S38 motors have „3,5” cast in the block, which was inherited after the M30. The fact that the block looks exactly like an M30 unit doesn't always mean that it was changed. Frankly speaking, apart from the lubrication system failure, I can't think of a single situation in which a S38 block could fail (except for a driver's mistake). It's a different story with the transmissions – the Getrag 250 tranny is said to be weaker than the later V160 found in the 3,2 liter M3. Unfortunately, the V160 bolt pattern doesn't match the M30 block, so the only solution for that would be either a custom bellhousing or a tranny adapter.

 

The S38 is the number one choice for professional drag racers or other people who need huge horsepower numbers while staying realiable. Being cheaper than the S50 and S52, it could also be a good alternative for power hungry NA engine enthusiasts, who are bored with their L-gata's performance. I'm unsure whether the amount of needed fabrication and expenses would justify the end result, but it's only your choice how to build your car...

 

3. Is it worth the money?

That's a difficult question. It's very relative, depending upon what you want from the car. I'm quite sure that the amount of work needed to get a BMW-engined Z to go would be similar to other inline six swaps, such as the RB26 and the 2JZ. I'm not a BMW specialist by any means, but I think that these engines could become a very nice alternative to the high-tech Japanese powerplants, provided you have enough force of will to buy one and swap it in.

 

4. What is the best alternative?

Having researched numerous alternatives for the L-gata engine, I think that the best competitor of the BMW engines is the 2JZ, both NA and turbo. The NA 2JZ is cheap to get, abundant, easy to find in your local junkyard, and is known to the last bolt by Internet-based Toyota gearheads, who ate their teeth while attempting to get the best out of the JZ engine. The BMW engines, on the other hand, are much better known in Europe, and after seeing many turbo BMW projects during the last year, I'm convinced that a BMW-powered Z could be as wicked as Z-Gad's, stony's, 1-fast-z's and, last but not least, mull's projects.

 

Even with my enthusiasm for BMW engines, I'm convinced that a BMW swap would only be affordable in Europe, where spare parts are not scarce, and the prices are just more realistic. On the other hand, you US guys have the LSx engines, which are probably the most versatile and the best in terms of cost-to-effect powerplants in the WORLD.

 

I'm sorry that this post being so long, but I hope I fulfilled Braap's expectations. Long live HybridZ.org!

 

P.S. - I'm sorry if there are any grammatical or spelling mistakes, point them out if you can!

[TrumpetRhapsody]

I love me some S38. I wish I could afford to go this route. Thanks for all the awesome info!

[BlackBeaut]

Nice write up Gareth, I'd definiteley consider a beemer engine, erm, if I get hold of a Zed again!

 

Can you answer a couple of questions on them? First would be what's the sump like on them, front or rear? Just thinking for ease of install a rear sump is preferable. Second would be the fun that is VANOS on the later M52 and M54 engines. Are there any aftermarket ecus that can control VANOS (I'm guessing it is controlled via the ecu!) If not then any install would require the oem ecu setup to run the engine, how possible is it to strip the ecu from the doner and get it running in much simpler surroundings?

 

Cheers,

Rob

[MatMan]

I have a 1976 3.0 Si, the first year of Bimmer injection. I have been tempted to swap the motor, which has been balanced and blueprinted, into the much lighter HLS30 chasis. Unfortunately, I am an auto-electrical moron, and I am MUCHO afraid of the German electronic engine control.

Anyone in CA want a vintage E-3?

[Gareth]

I'm so glad you like it guys, thanks!

 

First would be what's the sump like on them, front or rear?

 

In different engines mounted in different cars, pans can be either front or rear sump. The later M52 and M54 engines in the E46 are rear sump - today's BMW engines are mounted much further rearward than, say, 20 years ago.

 

Second would be the fun that is VANOS on the later M52 and M54 engines. Are there any aftermarket ecus that can control VANOS (I'm guessing it is controlled via the ecu!) If not then any install would require the oem ecu setup to run the engine, how possible is it to strip the ecu from the doner and get it running in much simpler surroundings?

 

I'm not much into ECUs, but a friend of mine, who has a turbo E36 M3, told me that the later models of Autronic and Motec ECUs can control variable valve timing. They're very expensive though, and I don't know any alternatives.

[BlackBeaut]

Cool, thanks Gareth. It would certainly make for an interesting swap. I love the idea of fitting an all alloy straight six in to a Zed.

 

I know the commonly available M52 2.8 has a restrictive intake on it and it's just a matter of tweaking the intake of a 2.5 and fitting that with a bigger throttle body and you can release a lot of ponies for very little money. Obviously still a long way short of the S series engines but then you're talking big money just to get them.

 

Cheers,

Rob

[slownrusty]

Good read. I am a big fan of European engines and this would make a neat conversion in a Z, but I really think a turbocharged BMW straight six would be sizzling hot.

 

Alos Mercedes Engines are the same price and similar power and same reliability, similar size, weights etc so that is another consideration. Mercedes build better V8s than BMW in my opinion.

 

And my three favorite letters are "AMG"...wink!

 

Yasin

[Gareth]

I know the commonly available M52 2.8 has a restrictive intake on it and it's just a matter of tweaking the intake of a 2.5 and fitting that with a bigger throttle body and you can release a lot of ponies for very little money. Obviously still a long way short of the S series engines but then you're talking big money just to get them.

 

 

That's true, the M52B28 intake is a lot more restrictive than the M50B25 intake, because BMW needed to limit the 2,8's horsepower rating to 193 horsepower (the insurance companies gave lower premiums for cars with less than 194HP, and many Volvo, BMW, Mercedes, Saab and other engines had this identical HP rating). The M50B25 intake conversion is very effective, especially when combined with a chip or a ECU remap. I've seen some flowbench data of the M52 and the M50 intake, and the M50 flows around 50% better in the whole rev range. Unfortunately, the plastic M50 intake has some supporting bars mounted elswhere, and the fuel rail mounting needs to be modified. These mods should be good for about 230-240HP on the flywheel. With a good exhaust manifold and some further tuning, it shouldn't be difficult to extract 250HP reliable horses from a nearly stock M52B28. The best thing about the M52 and the M54 though is the availability of aftermarket supercharger systems, which push the alloy-block 2,8 and 3,0 engines well over 300HP, which is more than just enough (at least for me ).

 

By the way, I checked some data about the Euro M3 3,0 transmissions: they were made by ZF, not Getrag, and they are the same unit as the tranny mounted in many E36 and E39 M50-powered cars, including the US M3. In case of a tranny failure, it shouldn't be difficult to source a used one.

 

Alos Mercedes Engines are the same price and similar power and same reliability, similar size, weights etc so that is another consideration. Mercedes build better V8s than BMW in my opinion.

 

Mercedes engines are in fact just as well built (if not even better) than the BMW engines. I remember seeing a W124 E-class with a 3,0 inline six and a whopping Schwitzer truck-sourced turbo, pumping out 500HP at a comfortable 1bar boost pressure (16psi IIRC... With a stock block.

 

About the V8s... Well, I don't have any knowledge about either, but it's well worth mentioning that Mercedes had some very nice alloy V8s with single overhead cams, sometimes with displacement of around 6 liters... A built Mercedes V8 could also be a killer engine.

[TrumpetRhapsody]

Sometimes I wish I lived in Europe. Well, Ok, more than sometimes

 

1 bar is normally accepted as 14.7psi IIRC. Just to be precise

[Gareth]

I think the same, but I'd like to live on the other side of the Pond... The grass is always greener behind the fence, eh?

 

Thanks for the correction.

 

By the way, BlackBeaut - don't you think that the TVR Speed Six would be a wonderful engine for the Zed?

[BlackBeaut]

By the way, BlackBeaut - don't you think that the TVR Speed Six would be a wonderful engine for the Zed?

 

As long as it had had a recent rebuild by one of the few engine shops appearing in the UK now that replace the dodgy parts made of cheese with proper new metal parts I think it would be a fantastic swap. However the 4.5 AJP V8 would still be the daddy of the TVR engines to get in, but we digress

 

On the topic of BMW V8s my daily driver is a '97 E38 735i, cracking little engine, the later ones with VANOS (post 98 I think) are supposed to be even better. If petrol wasn't so stupidly expensive here I'd quite happily go for a 740i with the 4.4 engine.

 

Cheers,

Rob

[DuoWing]

This is a great write up, oddly enough I've been pondering the thoughts of a BMW engine in a Z. As my friend recently got a 97 328is, I got to thinking, 2.8l inline-6 newer engine management, similar power, it just might be a good swap for the Zs.

[HB280ZT]

I also think a BMW motor in a Z would be great. However I am not sure if I would go with something like the motor from the twin turbo 3.0L US 335I or even better the twin turbo 3.0L diesel motor coming out in the 335D or the 535D, great fuel mileage (+35 or so) and lots of power and torque!

 

HB280ZT

[Gareth]

Yup, the new turbo motors are great! They were designed with a flat torque curve in mind for effotless cruising, high efficiency and low fuel consumption thanks to high torque available from the lowest revs.

 

As I'm searching for a daily driver now, I think I found the right car (a BMW of course)... While I won't tell you guys what model it is, I'll give you a hint - it has 3,5 liter engine and a long option list...

 

I thought that this thread would gather some more interest among HybridZ-ers... Guess it'll need to take some time.

[Accurate Injection]

We just picked up a 95 325is, and we are developing a bolt on "NO MAF" stock ECU ITB set-up for these motors! Working with the guys at MAF Translator to convert the car to Speed Density!

 

Stay Tunned!

 

Kevin

[alternativez2003]

Hey there, This is interesting. I've started a m30 from my '85 635 into my '70 240Z. It's a tough fit, but it will work. I've got a post here on one of the other sub forums from a while back. I've also got a '76 2002 with a '91 m42 very nearly done. BMW engines are great. Good job with this forum. Later, Jim

[Accurate Injection]

Well here's a little Update on the M50 2.5ltr motor conversion!! Plates are done, all measurements complete, now Tig weld up the Manifold and bolt it all together!

 

The Injectors are going to PICO's as this is just Mandatory on this motor! If the Oil Filter were in any other location injectors could be placed below the ITB's for a much straighter approach into the Ports! As it stands now the Head plate sits on the motor at 30 degrees to Horizontal and the ITB plate sits at 60 degrees to horizontal, not ideal.............. but will let the DYNO tells us what we need to do if anything different!

 

As it stands now the running length will be in the 6.5" Range, may need to add some to it to pick up the bottom end, but here again will wait and see what the DYNO says! Base line on this motor was 171/163 hp/tq at the wheels!

 

1 Correction to a previous post! WE WILL NOT BE WORKING WITH MAF TRANSLATOR!!!!!!!!!!!!!!!!!!!!!!!!!!! Split Second seems to be much easier and eager to build products for the BMW Crowd! We are still trying to pull this off without a MAF sensor, and using the PSC1 unit they have!

 

Kevin

 

 

[Evan Purple240zt]

^that is so badass^

[Accurate Injection]

What the ITB's or the Channel Locks Pinching the coolant line off, so as to not make a mess all over the Shop?

 

Thanks man for the kind words! Just wait till we are finished with all the other parts!

 

The Guys at "splitsec" seem to believe they can pull this "MAF to Density" off with excellent results! We will see!

 

Kevin