Compresion ratio Info

[Jose Luis]

I have just finished building my new evo vii engine (eagle rods, wiseco pistons, hks cams, motec, etc) and planning 27-28lbs of boost with avgas. What would be the the ideal compresion ratio, I´ve just measure it and 4 cilinders are showing me 200lbs wich I think is to much.

Thanks in advantage for any help

Jose L

[turbolarry]

Compression ratio is different from cylinder pressure.
That's a brand spank'n new motor. Once the motor has been around the block a couple of times you'll probaby see 175-180 psi across all cylinders, which is fine.
Since the motor is already built, I hope you have an extremely efficient turbo, or a compression ratio of 8.0:1 and definatley no higher than 8.5:1 for that much boost.

[Fourdoor]

Originally Posted by turbolarry

Compression ratio is different from cylinder pressure.
That's a brand spank'n new motor. Once the motor has been around the block a couple of times you'll probaby see 175-180 psi across all cylinders, which is fine.
Since the motor is already built, I hope you have an extremely efficient turbo, or a compression ratio of 8.0:1 and definatley no higher than 8.5:1 for that much boost.

Hey Larry,

He is talking about running avgas all the time (104 octane low lead) so he can do 8.8:1 or 9:1 without too much trouble.

Later,

Keith

[ldstang50]

My stock compression in the car was 182. I just put in pistons rods and a few other goodies. Once broken in I'll compression test my car and let you know what I have for psi. I put in eagle rods and ross 8.5:1 pistons