Soooo, M50/M52 2.8 into E21 any ideas?

This thread www.trampdrift.co.uk/Forum/TD/showthread.php?t=51 any good to you?

www.e30zone.net/modules.php?name=Forums&file=viewforum&f=56 for a "how to" on fitting a M52 into a E30, E21 can't be that much different? You may have to join the forum to view.

www.endtuning.com/about.html can alter a M52 ECU to work in your car, cheaper then a Megasquirt and keeps all the M52 goodies, 2 O2 sensors, knock sensors and MAF etc.

www.rmeuropean.com/bmw-e30-m50-swap.aspx a quick overview.

www.e30dohc.com/wiki/index.php?title=DOHC_Swap_Basics as the title says.

Both a E30 gearbox and diff can stand up to a M52's power, unless you're going turbo!

I'm sticking a M52 into a Triumph 2000 MK1 at the mo' and I've found all these sites very helpful. I'm also using the M52 ECU, much better then a Megasquirt or any other aftermarket ECU. The only feature it lacks is the abilty to home tune via a laptop, which is very over-rated!

Speak to Rob0r on here !!

Why hello there ;D. As mentioned this is something I've heavily been involved with over the last few years, I have a suspicion I may have been the first to get an M5* engine mounted in a RHD E21 shell. I've only dealt with the iron block M50B25 non vanos engine but the swap is identical.

M5* engines use identical dimensioned bottom ends to the M20 engines (found in the 320/323i cars), but they are supposed to be laid at a flatter towards the driver's side. The result being you can use the E21 engine mounts that sit the M5* at the same angle as the M20 (more vertically), the beauty is that from the bell housing backwards it can be all standard E21 M20 parts (gearbox/prop). No custom gear linkages or custom length props ;D. The other win is that the engine now clears the brake servo perfectly. There are two downsides to this, 1) the M50 sump now hangs dangerously below the subframe (custom sump needed), 2) the standard inlet rubber elbow to the MAF won't clear the passenger wing (Samco 90 degree elbow or cut away the inner wing). I tried to mount the M50 at it's designed angle but I found it was impossible to get any sort of rear exhaust manifold to clear the steering linkage.

A quick recipe based on my own:
M50/M52 engine
M20 brown temp sender (for the gauge in the instrument cluster)
E34 M50 sump, modified, cut and winged to gain clearance
E21 M20 metal engine mounts (rubber ones of your choosing, I'm using hockey pucks)
E21 M20 subframe
E21 M20 gearbox
M20 flywheel of your choosing (E21 M20 is apparently the lightest OEM and what I recommend)
M20 clutch of your choosing
E21 M20 prop
E36 328i tubular exhaust manifolds (E36 323i might be the same), these need very slight modification
Front mounted electric fan
E36 328i radiator with custom mounts or Nas80 spec rally rad
Custom exhaust system (you could use a 323i system but don't, they are tiny and VERY heavy)

Nas80 is the guy to speak to about getting the sump modified as he has got a very good deal for this with an engineer he knows. He can also spec you a nice rally spec radiator for this conversion too, but I've found the E36 radiator as worked well enough. He is also able to do the whole conversion for you for a price!

The exhaust manifold clearance is still fairly tight, sometimes it binds against the steering linkage guibo. I'm swapping mine out for a straight linkage in the coming months.

You don't have to run the engine on megasquirt. My M50 non vanos is running the standard engine management. For M52s it is slightly more complicated. For a start they have EWS immobiliser security, if you retain all the EWS sensors and ECUs from the donor then it's no problem. But a lot of people get the ECU flashed to remove the EWS. The show stopper though is the M52 ECU needs a speed pulse signal from the ABS sensors, this limits the ECU to 4-5K RPM if it can't find this signal. But the reflashes available remove this feature too, as well as tuning it up a bit. Speak to Nas80 or Danthe on E30zone.

I'm running the pig iron M50 and it's not that front heavy at all. The M52 is alu blocked and should be significantly lighter than the original M20 engine. Not really something to be concerned about. If a cheap enough M52 2.8 came along, I'd snap it up just for the additional lightness. Access to the engine bay is not that bad and certainely nothing to be worried about. I will admit getting access to underneath the inlet manifold is a right b!tch. The only times I've needed to get under there though is anything related to the starter motor, air hoses/ICV, temp sender etc, so nothing you will need to touch on a track day.

Back axle... It really depends on what you want to do with the car. It's well known that people have exploded diffs and broken driveshaft CVs when running higher power, but I haven't heard of anyone for a while that's done this, apart from myself. I blew a driveshaft CV launching in first gear, very unsmoothly. I'm also running a welded diff, the other guy I knew (Murran) who blew more than one driveshaft was also running a welder. Me and a mate have a theory that the welded diff is more likely to break shafts than open/LSDs as there is obviously more stress on the drivetrain. I have spent a lot of time researching different rear axles and a fair amount of people have done this. You can buy off the shelf E12 diff conversions from Fritz Bitz (£££), or custom mount other stronger diffs into the original axle. Others have mounted complete E28 axles (5 stud) and I have looked into doing the E30 axle myself. E12 conversion use the E21 driveshafts, they IMO are the weakest link in the whole transmission! E28 axle swap increase the track massively and require bubble arches, you may find solid mounting is the easiest way. E30 axle will increase the track slightly, but the deal breaker for me was losing the original petrol tanks. I have actually mocked this up on a scrap shell. I'm also scared of screwing up the rear axle alignment if my measurements/cuts/welds are out causing dangerous handling.

I'm not happy with any of the axle solutions so I'm going to be using my car with the standard axle with the welder and take it easy at low speeds. If and when I have the money, I will custom mount an E30 medium case diff into my E21 rear subframe and then buy custom strong driveshafts to match, but this will be in the region of £700 for the driveshafts alone.

Brakes, use 323i stuff (vented front discs and rear discs) and if you feel they aren't adequate then upgrade. Suspension, the easiest thing to do is send off some 323i struts off to Gaz for £1000 (I think). My coilovers cost less than half of that but are strictly DIY. Also consider polybushing the whole car.

Any more questions then fire away... I'm sure MIB will chip in at any minute now, and Nas will likely have something to say also. The www.bmwe21.net/forum is also very good for information.

My 323i M50
retrorides.proboards.com/index.cgi?board=readersrides&action=display&thread=71185&page=1



Mine and Nas's M50'd E21s


Can be much tidier than this!

With all due respect to e21s & e30s, I want the link for the thread for that! Sweet!

Just to add, my E21 flywheel didn't need shaving and if possible I would stick with the E21 M20 gearbox if possible, anything else will be custom work.