Compression Ratio Calculator

[89gte]

Hello all,

I'm looking for an accurate compression ratio calculator for our engines. Going to be going with a cometic hg, probe pistons, and eagle rods. Not sure about what bore is needed yet, but everythings at the machine shop now so I'm looking for the calculator. I searched this forum and the engine mechanics tech and only came up with this: http://www.bgsoflex.com/cr.html. Is that one that should be used? Also, stock CR is 8:4:1 right, I'm looking for a hpw goal between 400-500 eventually depending on the turbo selection. Going to be a DD street car running 93 with reliability. I'm thinking to maintain as close to stock as possible, which should allow me to run more boost compared to a higher CR right? One last question, does anybody know the exact amount to add for each additional PSI to the compression? Or does it variably change depending on the turbo size? Thanks in advance for answers.

 

[hvyman]

You can run higher than stock compression reliably. If you start running over like 9 then you need to make the fuel and tuning is there.

That calculator is fine.

Idk what you mean by the last question.

 

[89gte]

One last question, does anybody know the exact amount to add for each additional PSI to the compression? Or does it variably change depending on the turbo size?

Is the question you mentioned in your post? I worded that badly. I read that the dynamic compression is affected by the amount of forced induction. I thought there might be a number for each psi added to boost that changes the dynamic compression. Appreciate the quick reply. Will be using the MAFTPRO for tuning purposes should be able to get a good tune.