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Like wtf bro, if you have a piston that's doing 12:1 compression ratio, that's a calculation based on volume. If you compress the air with a compressor, that pressure ratio is factored into the cylinder with the piston at BDC. Where is the calculation for the effective compression ratio where boost is added to the compression ratio at TDC? It doesn't exist, it's a conspiracy man. I mean what is the functional relationship? Is it additive? 14 psi of boost = 2:1 compression ratio, and an engine with a 10:1 geometric compression ratio now has an effective 12:1 geometric compression ratio? That can't be right, because then it would just be easier to use an 12:1 piston and save all the turbo plumbing. Is it multiplicative? 10x2=20? So a 10:1 CR piston with a 2:1 compression ratio from a compressor would effectively have 20:1 compression ratio? Or is it some other non-linear function that can only be gleamed through experimentation?

Like wtf bro, if you have a piston that's doing 12:1 compression ratio, that's a calculation based on volume. If you compress the air with a compressor, that pressure ratio is factored into the cylinder with the piston at BDC. Where is the calculation for the effective compression ratio where boost is added to the compression ratio at TDC? It doesn't exist, it's a conspiracy man. I mean what is the functional relationship? Is it additive? 14 psi of boost = 2:1 compression ratio, and an engine with a 10:1 geometric compression ratio now has an effective 12:1 geometric compression ratio? That can't be right, because then it would just be easier to use an 12:1 piston and save all the turbo plumbing. Is it multiplicative? 10x2=20? So a 10:1 CR piston with a 2:1 compression ratio from a compressor would effectively have 20:1 compression ratio? Or is it some other non-linear function that can only be gleamed through experimentation?

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[–] • 1 pt

Look I'm not going to argue with you. (I have 9 ASEs) You're right the VE calculation, it is the measurement of air actually in/compressed vs theoretical at sealevel 14.7 psi. However you are dead wrong on boost not affecting VE. On boosted engines VE can be over 100%. Air pressure affects VE as does RPM etc.

The short answer to your question about compression not being a constant is VE.

[–] • 0 pt (edited )

There's only 8 ASE certs, I got'em all. Boost affects density of air, not VE, because boost doesn't affect the mechanical volume of the piston and cylinder. VE relates to volume, not to density, it's in the name Volumetric Efficiency, how efficiently you can fill that volume. VE is affected because of boost because of the pressure ratio in the manifold vs the cylinder. When pressure ratios approach 2:1 IE at and above 10 psi of manifold pressure(24 psi absolute), you have to treat the airflow as a compressible fluid. Thus the geometry that worked so well at a lower pressure ratio will work differently at a higher one.

[–] • 0 pt

Wrong again my friend 8 for an ASE Master + an L1

[–] • 0 pt

L1 is gas station maintenance.