What is the normal relationship, if any, between a motor's compression ratio and the indicated boost for a fixed supercharger?
IE, if I have a 10:1 CR motor and indicate 8 psi of boost at a specific RPM for a given blower, will how will going to an 8:1 CR affect my indicated boost?
I'm asking because I've got a forged 22R (Toyota) motor with a roots-type supercharger (new). According to the manufacturer (Atkins rotary) my current pulley configuration should be good for 8psi.
Unfortunately, they don't state at what RPM I should have 8psi or what kind of motor that 8psi is produced on. They have no data on such things and their main business is rotary engines.
My motor is 7.8:1 CR, forged pistons, ported head. I'm seeing 3psi off idle, 5psi by 3000 rpm, and 6.5 psi at 4500-4600 rpm. The 22r isn't really setup to turn major RPMS.. Maybe 5000 rpm or so peak.
Is it normal for a decrease in engine compression to result in a decrease in normal boost pressure?
Ideally, I'd like to be able to run this engine at enough boost to cause detonation and then back off by 2-3 psi or more. I'm guessing I can support at least 10psi.
If Atkins blower can't do it, I'll probably look into custom fabricating something to drop in an Eaton blower.. They have a more efficient design anyway...
Comments welcome!