Compression Ratio

decoupe

decoupe

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Might be to general a question (given the number of models the M30 was used in) but can anyone tell me what the compression ratio is for 3.5 litre from an 80's 5 series ? Probably less than 9:1.
 
That depends on several factors:
1. US or Euro car?
2. E34 or E28?
3. Any idea of the specific year?

It ranges from 8:1 up to 9.3:1.
 
decoupe said:
3.5 litre Euro "L" block and 535i head. 93mm bore. That's about all I know.

Doug
Click to expand...

Ok, then there's a few possibilities.

If it is a B35 head, then the CR will be lower than if it had a B34 head, as I think the chamber volume increased from ~59ccs to 63ccs or something like that. There is a big page with that information over on firstfives. If it has the B34 head, then it should have the stock M90 CR.
 
Those pistons that are in that engine were made by Arias and they're flat top pistons. I do know the head was milled a bit, but I don't know how much. My guess is that the compression ratio is around 9:1 as others have suggested. Didn't I include the results of a compression test I'd done at one point in the paperwork? It's not completely accurate but I think you can take that number, divide by 14:7 and get a rough estimate of CR right?
 
Hi TJ - didn't see the calculation in the paper work but everything I've seen indicates 9:1 +/-. I've assemble most of the parts for a FI conversion I'm planning over the winter and there is a local company with a fuel and ignition management system I want to use.

http://sdsefi.com/

Thanks to all,

Doug
 
decoupe said:
Hi TJ - didn't see the calculation in the paper work but everything I've seen indicates 9:1 +/-. I've assemble most of the parts for a FI conversion I'm planning over the winter and there is a local company with a fuel and ignition management system I want to use.

http://sdsefi.com/

Thanks to all,

Doug
Click to expand...

Many, many people have had issues with that company and their system on Bimmerfourms. Why not go with a MegaSquirt system, or even a tuned Motronic?
 
Thanks for the warning - I've heard both good and bad and I'll check out Bimmerforums. One thing I will ask is an opportunity to talk to one of the 535i owners that has installed the system - they said they wold give me the contacts.

There isn't a distributor of Wolf products in Canada and SDS is located less than an hour from my house - which is a huge plus in the decisions. Mega Squirt is an option but my computer skills are pretty basic though that system is more user friendly now and I have friends that use it on their 02's.

Lot's of research to do but I'll have the time come June.

Doug
 
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