Has anyone ever figured out a rule of thumb or something similar for the power loss you get when you drop the compression ratio? Does it work proportionnaly for boost too?

For example, I have a B16 with 9.0:1 compression, down from 10.2:1 stock. Bore is the same. Assuming it makes ~140whp stock, how much do you think it would make now, and can you assume a similar reduction percentage when boosted from what it would do if it had stock compression still?

I hope it makes sense! Thanks!

 

you'll get pretty close if you do the ratios between the two multiplied by the original. so (9.0/10.2)*140 = 123whp

 

Plus the extra 5psi you can run on pump gas now is 127+5*18=217..

 

you will be down about 2.9 % hp

 

lol wtf?!

 

Was that @ me? If so what I mean is the small amount of power you will lose by droping compression will more than make up with the higher boost you can run..

 

No that was for b18c1boosted. The intent of this thread was to get an idea as to what kind of difference you will observe on 2 similarly boosted set-ups @ the same psi with the only difference being a compression drop. I know I can crank that sucker up.

 

If you're going to leave the boost at the same place, then why would you lower the compression?

 

Pick up the new drag sport mag. it talks about forged pistons. it has a chart and i baisically says if your original comp was 10:1 and you drop it to 9:1 you will lose 2.8% at the some boost level but you get a larger margine in tuneing error.

 

exactly

 

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Argggh! I was curious that's all, that was an example, I just wanted to have an idea of what kind of power reduction per point of compression drop you'll typically see.

b18c1boosted, that's exactly what I was looking for, thanks I'll look up the mag.