E24 Racing History

[Bobo W]

From what I can gather most of the racing success with the E24 came mostly with the 635 CSI yet little success with the M-version - does anyone know why this was the case?

Thanks
Steve

[GazM3]

I'm not certain but I think it came down to group A homologation needing a certain quantity of cars produced to qualify. When they had group C here in Australia they used a 635 with an m88 making about 420bhp in 82/83. It was seriously quick but was handicapped with weight and other stuff so it wouldn't make a mess of the local product. I think the homologation quantity was 5000 cars. I guess to keep out the more exotic machinery so u don't see Porsches and Ferraris in group A.

Geez it's such a pity that they didn't homologate the m635. With an extra 150bhp more than the already successful racer it would have been more than a match for the early turbo cars.

Bmw went down the direction of homologating the m3 with 2/3's of the m88. Even tho it was a very successful racer wasn't a match for outright lap speed in the dry.

[Bobo W]

Requiring a certain number of cars makes sense, thanks

So does that mean the Group A 635 cars used a race version of the M30?

As a follow up to that and not being that technical, how did the M88 differ to the M30 in race spec?

[MrE]

There's a bit of info here:
viewtopic.php?f=10&t=26172

and here:
viewtopic.php?f=10&t=19209

Specifically check the posts by Rob Lord in those threads.

[Brucey]

IIRC they tested the M635 vs the E30 M3 and the latter was substantially quicker around typical circuits, mostly because it is lighter. It also has a better weight distribution, I think. The other thing is that the rule book allows you to do various things and this may allow you more scope for effective tuning depending on where you start from.

cheers

[Bobo W]

Thanks for the replies.

As the Group C 635 had an M88 was it essentially an M6 in all but name?

[GazM3]

Pretty well but in 1982 the m635 wasn't in production.

The good thing about the m88/3 is it is basically a 470bhp race engine substatially detuend for the road. If u ever refresh/rebuild it well u can warm it up from road car tune substantially.

The m30 used in groupA was warmed up to the max and was able to get just over 300bhp. The intake manifold being the biggest restriction but they had to keep it. In group2 in Europe they had the freedom to use throttle bodies which made lots more power c/350bhp or so.

[Brucey]

yeah, I've also seen some race-spec M30s (with lots of head work that would be illegal in most race series) that made about 350bhp on carbs too. Nowhere near street-able (of course) but the absolute business otherwise....

cheers

[Bobo W]

The nomenclature and lineage for BMW engines is somewhat confusing for laymen like myself especially when using wiki as a source of information. As such I seem to be going round in circles and while I don't want to be particularly anal about this it would still be interesting to understand how all these link together.

The Group A 635 CSi would have used an M90 engine - M88 block with M30 head upto 1982 and then the M30 engine - block and head

The Group C 635 CSi used the M88 block with M88 head albeit standard inlet manifold

The M635 CSI / M6 used the M88 which was derived from the M49 motorsport engine as used in the 3.0CSi and had an M30 block with M88 head

Many thanks for everything so far.