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if it is as you said 8:1 than its more than perfect for Turbo ....
However, i`m not that much sire about the compression ???

the m10 engines vary in compression from as low as 6.9:1 in the original 2.0 turbo but the flat tops where the next lowest compression so i think my figures are correct, i will get ben to find the table he downloaded for me

no wait i have found it

http://www.bmw2002faq.com/content/view/46/32/

cant believe i actually saved sumin

i am a little bit lost in all of this ... huuuhhh
The issue is that i have an E-30 injection head, and i wana swap an M10 B20 block ..... it might come with high piano pistons and i might come with flat pistons ..... don`t know .... still searching.
However, and because i already know that both M10 B18 & M10 B20 share the same pistons bore ... so even if i got a high piano pistons in the block which i wana purchase ... then i can use the flat pistons which i currently have in my damaged M10 B20 block ....

So the clear question would be ... (if i used the M10 flat pistons on E-30 Head) ... what would be the compression ratio ???

Jazziat

ok

the bmw e30 m10 compression is 9.3:1

I dont think there is a lot of difference in physical combstion chamber with that of a 2002 head. the valves are the same shape and size.

Im sure someone can help by doing it all correclty but i imagine with 2002 flat pistons, an e21 block and an e30 head will give you a compression ratio of about 8.4:1

only real way to find out is to build it and measure as you go

make sure you use a thick bmw headgasket as that will help lower the compression a little

From the data I've seen (I have not personally cc'd combustion chambers), the e21 2.0 head has a 60cc combustion chamber, and with flat top pistons this should yield an 8.1:1 compressrion ratio. The 1.8 head has a slightly larger 63-65cc combustion chamber, so I estimate the 2.0 flat top pistons coupled with the 1.8 head to yeild a slightly lower 7.9:1 to 8:1 compression ratio. The reason I say "estimate" rather than calculate is that the numbers don't jive based on measurements I HAVE taken. I've measured an 11cc dome on the US 8.8:1 CR 1.8L pistons. With a 1.8L, 63cc chamber and 11cc dome, I never get a correctly calculated compression ratio using the same head gasket thickness, etc. Read this thread for more info:

http://forums.bimmerforums.com/forum/sh ... p?t=482695

The good news is, if you couple flat top 2.0 pistons with ANY m10 head, you'll have a boost happy motor. I'm still not sure if your current flat top pistons will work, if you have a 1.8 with flat tops (not sure that was ever an option in other markets?), the compression hieght won't work with a 2.0 crank.

I have got and info that u can also use a flat top pistons from m30, they are the same size like in m10b18/b20 and it would be easyer to find

pozdro

i dont think the e30 ever came with flat top pistons, in fact im almost certain

m30 not e30

RetroBeemer wrote:m30 not e30

urrrrrgghhhh im such a dumb ass, please excuse my stupidity

My swap was done at last,

The M10B20 pistons were superflat .... and yes, the combustion chamber of the E-30 Head is larger than the Combustion chamber of the original M10B20 E-21 Head .... i didn`t measure both ,... but its clear with an eye look.

i got a very good head gasket ... i took some pictures ... go to my topic and see the result ( http://www.bmwe21.net/forum/viewtopic.php?f=3&t=12898 )

I hope i can get your idea`s about what Turbo charger i should use and the components and what HP i should focus to reach using the current setup and original internals.

Thanks
Jazziat

jrcook320 wrote: Tue Feb 16, 2010 4:28 pm ...i would recommend you mill the tii pistons to attain an 8.5:1 CR (or at least below 9:1) with a stock thickness head gasket. With the larger combustion chamber it won't take much. If you're set on the nitrous, then I recommend going with forged pistons. If you're going with forged pistons and megasquirt, you might as well just size the turbo to be able to make 300 hp (about 18-20 lbs of boost) on it's own and forgo the nitrous. It won't cost any more at that point. Also remember to file your ring gaps larger than stock for a purpose built power adder motor.

I'm desperately trying to find out what gap settings I'd need for an m10 2.0 turbo. Stock 2002 bottom end with flat top pistons im currently building. I'm Hoping for between 200 and 250 bhp. What kind of boost would it handle? I intend to put arp studs in everything. Is it worth it or is stock string enough?
Thanks so much in advance for your time guys