Internal engine geometry

Competition engines and ancillaries - general discussion
trickymex
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Re: Internal engine geometry

Post by trickymex »

Rich Ellingham wrote:Better look at the LMA instead.....Saloon and sports car series. Hows an S2000 a sports car and a Audi TT not?- Did the TT have rear seats as a road car? as I know one of those raced last year in the DMN. I'd ask Rod Birley at BARC SE (Assuming that's not who you spoke to already).

rich

I have not spoken to Rod Birley but i may as i have a fair few questions to ask now and it would be nice to do them all at the same time rather then when i think of them

LMA could be a choice but i know a few people running in the DMN series and its always nice to have a few familier people around to help

I am not familier with that TT you mention but was it a convertible version or tin top?? Maybe this is the distinction that outlaws the S2000?

Thanks again

Ricky
Boyracer
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Re: Internal engine geometry

Post by Boyracer »

Hi again!
trickymex wrote:The fact that the head has hydraulic lifters adds to the extra work needed to get this head competative and also i cannot seem to find any really wild race cams(maybe you can help with this?)
There are aftermarket cams available for M42 that go up to and beyond duration/lift of cams BMW Motorsport used in factory S42's. I'm not sure if we are allowed to mention manufacturers but send me an e-mail and I can point you to them.

I think solid lifter conversion with VW parts (16 lifters and alsh caps) can be had for about 300€ without taxes. That lifter + lash cap combination weights about 55 gr. Stock S14 lifter + shim weight around 80 gr and you have the risk of losing the shim with aggressive cam profiles and high revs.
trickymex wrote:For the sort of power i am aiming for i am reluctant to put to much faith in any O/E crank, rod or piston, of course the rods and pistons will be changed for aftermarket forged items but for peice of mind i would bite the bullit and go with an aftermarket crank as well, but the problem with the M42 is once i get the engine up to the 2000cc capacity limit for this class i would end up with an engine that has had huge sums of money thrown at it but will have a rather dissaponting rod ratio when compared to a short stroke S14 engine
I cannot give you any firm information about M42 crankshaft durability but atleast I haven't heard any inherent problems. M42 engines are often turbo/supercharged to around 300 hp without problems but of course stresses from that are different compared to high rev naturally aspirated use. Also, alternative M47 crankshafts are meant for diesel use so they are quite durable as well. If all else fail, you can still get factory new S42 cranks (and other parts) from BMW Motorsport.
trickymex wrote:But what i gain with the S14 over the M42 is a better bore to stroke ratio and a better rod ratio plus many proven cam profiles to choose from and many other aftermarket parts that i will not have to get custom made like i will on the M42

All in all i think the S14 will be easier to tune to the levels i want and its much more proven for this sort of thing, the M42 is going to be more of an experiment with unproven results, if it was a road car then i would go the M42 route but because its for a race car and i want to be competative i think it may be best to go for the proven method and be done with it
BMW actually used 2 liter S14 in 1992 and 1993 in their ClassII / Supertouring cars. I have gathered that it was not ideal to touring car use because of internal engine geometry. Because of S14's large bore, stroke had to kept short which was not good for torque which heavy saloon required to get out of the corners and in traffic. Also, advantage of short stroke and large bore allowing high rpm's was negated by rules that limited revs to 8500.

Maybe it can be different on your series and you can go as high revs as you can. Then S14 should have advantage due better breathing.
Boyracer
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Re: Internal engine geometry

Post by Boyracer »

Something I just noticed elsewhere on this great board that might have relevance to this discussion.

Guy said while describing Peugeot 1600 head job:
A 2 liter Vauxhall XE in full spec might have 48 x 26 and say, 26mm thru the splitter and flow over 150cfm.
I just measured M42 standard intake port in cylinder head face to be 50 x 27 mm. So if I understood correctly, M42 has larger intake port as stock than well ported XE that will produce high horsepower (maybe saround 280hp)?

Unfortunately I do not have measurements of valve seat and throat with me right now...

EDIT: 1995 season S42 with 285 hp has intake port measurements of 52 x 29,7 mm
trickymex
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Re: Internal engine geometry

Post by trickymex »

Thanks again Boyracer,

I will e-mail you with a few questions that are best kept off the site

Also you seem to have quite a bit of info and knowledge with regard to these specific engines so I may 'pick your brain' when I decide what way to go?

E-mail on its way

Regards

Ricky
nyssa7
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Re: Internal engine geometry

Post by nyssa7 »

Rich Ellingham wrote:
Better look at the LMA instead.....Saloon and sports car series. Hows an S2000 a sports car and a Audi TT not?- Did the TT have rear seats as a road car? as I know one of those raced last year in the DMN. I'd ask Rod Birley at BARC SE (Assuming that's not who you spoke to already).

rich
TT in the DMN is a Coupe, they have rear seats as standard if not particularly habitable ones

Rich is right, S2000 would be welcome within the LMA series and would sit in Class E up against Clios, MG ZR and a certain blue Fiat Tipo if it comes out to play again :-)
Guy Croft
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Re: Internal engine geometry

Post by Guy Croft »

I am impressed by the calibre of this thread, well done all contributors.

GC
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