Compresion ratio Info

2518 Views 3 Replies 4 Participants Last post by ldstang50, Jul 21, 2005

Jose Luis

Discussion Starter · Jun 14, 2005

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

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turbolarry

· #2 · Jun 14, 2005

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.

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Fourdoor

· #3 · Jun 16, 2005

turbolarry said:
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

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ldstang50

· #4 · Jul 21, 2005

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

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