history and reference Calling C.d.iesel, Pat Allen, Byron- Preyupy: Info On Turbo Piston Specs

[chrisrouse]

Hey c.d.iesel, Pat, Byron

 

You're the master(s) of esoteric BMW technical info. Do you have any information on the piston crown volume for '74 turbo pistons? I'm starting assembly on the motor for my pal Stan's Turbo (vin 4290767) and I'm in the process of calculating necessary head gasket thickness for the proper compression ratio. My blue service manual doesn't have any of the addendum for the turbo models. The pistons are new Mahle 89.47 dish top pistons. Got a spec on the volume of the dish?

 

Thanks,

Chris 

Edited September 17, 2014 by chrisrouse

[M3M3]

cd doesn't come here anymore.....

 

bunch of threads pop up with tech details from a forum google search on "turbo piston volume"

[jrkoupe]

wonder why thats so?...

CD going gone I mean.......?

[Guest_anonymous]

try contact Pat Allen

[TobyB]

...or Byron- Preyupy- here... he knows more about these engines than BMW did...

 

t

[chrisrouse]

Hmm, no more C.D., eh? I tried the google searching and forum searching, and found the depth of the dish but not the volume. I suppose I could get out the calculus textbooks and try and figure it out, but I don't know if the dish is hemispherical or a complex curve. I could also try to measure the volume physically, but I was hoping it wouldn't come to that. Thanks for the input.

[adawil2002]

C.D.'s computer allegedly didn't play well with the new forum layout.

[chrisrouse]

Sounds like we all need to pool some money to get c.d. a new computer!

 

Start a new Sticky! Buy C.D. a PC!

[chrisrouse]

Well, the answer is 10mLs +-.5mLs. I dug out the graduated syringe, low viscosity oil, and leveled the block. 10mLs.

[Preyupy]

Sorry I'm in between races at Road America and Mid Ohio. I have the info on my computer at the shop. Sounds like you did it the old school way. Good luck

[felix_666]

Well, the answer is 10mLs +-.5mLs. I dug out the graduated syringe, low viscosity oil, and leveled the block. 10mLs.

 

This is more fun than a text book if you ask me and comes with a deeper understanding.

Edited September 18, 2014 by felix_666

[PatAllen]

well, i dont have that info specifically, but assuming you use a e12 head, with flat tops it makes 8:1, head is 61cc

turbo pistons/engine is 6.9:1 cr, so a rule of thumb makes it at 70cc, or ±9cc more into the dish of the piston.

cant tell if thats accurate or not but thats my first guess.

hth

 

fwiw CD sold his 02 a while ago, and probably became bored as 50% of the people didnt agreed with him....that means 50% also did agree....

Edited September 18, 2014 by PatAllen

[Preyupy]

The cylinder head combustion chamber is modified and has a larger combustion chamber volume than the standard E12 head. Again I don't remember the exact dimensions off the top of my head. I think it is close to 68cc.

[PatAllen]

The cylinder head combustion chamber is modified and has a larger combustion chamber volume than the standard E12 head. Again I don't remember the exact dimensions off the top of my head. I think it is close to 68cc.

 

are you sure of that ? 68cc + 10cc into the piston makes a extremely low CR, lower than 6.9:1. Where did they digged that 10cc?

i never bougth that idea, furthemore the literature mention something extremely similar if not exactly as is"The cylinder head combustion chamber is modified and has a larger combustion chamber volume" (than a 121 or E12?? they dont tell this detail) but i think its a huge miss understanding at that time i think they where just trying to explain they  moved from the initial 121 head to a plain e12. i might be completely wrong but would like to see a scientifc answer to that.

[Preyupy]

Yes I am sure they modified the E12 combustion chamber on the Turbo heads. I don't have access to my measurements right now but if you can find the pictures BMW put in the original sales brochure you can see the combustion chamber very clearly. I just don't remember the exact measurements of the combustion chamber and piston dish but do remember with the 0.006" I took off my head, 0.5mm overbore and stock headgasket thickness I am at 6.95:1. P