Does my compression calculation look alright?
Turbo Mini Forums

After a chat with my engine expert / machine man I am going to hold fire on the turbo for a couple of years until I can build a fully sorted one.

We came to the conclusion a fast n/a engine should produce the goods.

My problem is the volume in the piston dish is causing a bit of a problem with the comp ratio and I think I have managed to get the numbers up. Could someone please confirm if these figures are ok.

swept volume = 318.75cc
piston dish = 12cc (std turbo)
ring land volume (from yellow bible) 0.78cc
piston to deck volume = 0 (will flush pistons with the deck)
volume in head gasket = 2.8cc
combustion chamber volume = 18.0 (fair skim needed)

= 33.58

33.58+318.75/33.58 = 10.5

Does this sound alright.

Edited by minimole23 on 21st Mar, 2008.

My maths also makes it 10.5

If you want a bit more compression Pitstop have a head on ebay with 14.5cc chambers, would give you a CR of 11.5 ish

Cheers Rob. I will be asking Benross to cut me a head when I have finalised the spec.

http://www.afracing.com/CR.xls

Edited by AlexF2003 on 24th Mar, 2008.

AlexF

do a search on head gasket vol .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Robert.

I went by one of vegards posts for the volume of the BK450 gasket.

Hmm, got me thinking now.

450 gasket ,
cyl 1 73.08 along the block73.89 across the block,
cyl 2,,72.16/73.64 ,,cyl 3 ,,72.14/73.66 ,,cyl 4 ,73.36/73.82//
therefore cyl 1 averages out to 73.485 //
cyl 2,,72.9avg/cyl 3 72.9avg//cyl 4 73.59.
overall avg 73.21mm
gasket thickness of fire ring next to bore on used gasket .94mm,therfore volume avg is 3.95cc.

theres my calcs from the thread on it moley, i just did a search on 'head gasket volume ' and found it .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Thanks.