Ideal compression ratio?

[motormike40]

what is the ideal compression ratio for a ride with 14 psi to have it a daily driver? Or just to run 14 psi safely

[Polygon]

I would say anywhere between 8:1 and 9:1.

[454Casull]

The ideal compression ratio? As high as possible, of course.

[SaabJohan]

A little above 9:1 should be possible with a good engine.

[MustangRoadRacer]

as much as you can withou detonation

[Evil Result]

i would use a 8.0-.5:1 compression radio if i was running boost, at that you would be safe from detionation and leave some head romm for more boost later or if your low on money gas prices are high and you can't afford 92-97 octane drop the boost and run on 84 (does that idea work?)

[ToP cAt]

I have always read about or heard about this thing called a compression ration!! i really dont have any clue as to what it really means. Is there anyone out there who can help me???

[2turboimports]

it;s just the ratio of air that enters the cylinder for every stroke. 8.5:1 ,for every 1 stroke, 8.5 times the volume of the cylinder enters. at least this was my understanding.

then there's staitc and net compression. static is the compression of the piston and everything ONLY. When you add boost you up the compression b/c air is being forced in, forced induction. Pump gas and ample tuning is supposed to make somewhere around 12.5:1 the MAX static CR for an NA car. Although there are badasses out there who can run 15:1 and hjigher NA drag motors.

[ToP cAt]

Thanks alot man, you sure have helped me out alot on this topic.

[2turboimports]

ahh, shit i have spotted errors....while that's the general jist...the compression ration of a piston means that for every 1 stroke it COMPRESSES 8.5 or whatever the amount of air that many times. So 12:5:1 is extremely high to be running around with.

[454Casull]

Compression ratio is the volume of the cylinder when the piston is at the bottom divided by the volume of the cylinder when the piston is at the top.

[jdrumstik]

how high until you breach 91 octane?

[boosted331]

Originally Posted by jdrumstik

how high until you breach 91 octane?

Theres about a thousand variables that effect this, so you really can't answer this. From simple ones such as inlet air temps and the compression ratio of your motor, to bore size, quench area, spark plug position, cam specs, etc, etc, etc, they all effect how much boost you can run.

[RocketDSM]

Compression ratio shown so everyone can see it without question -

Volume of Cylinder with piston at bottom = 100ci

Volume of Cylinder with piston at top = 10ci

Copmression Ratio = 10:1

As for what compression to run with a particular boost - too many variables to reasonable answer this. I'm one that like high compression engines for the broader torque curve. I run 9:1 at 12psi on 91oct. With better gas I can handle 15psi without detonation problems. If you have a really good engine management system onboard, you can push 9:1 at 14psi on 91oct with no worries. You would need a full standalone and lots of tuning time, but it could be done safely. If you are on a stock ECU, keep it to 8.5:1 or even lower. My examples use 91oct because that is all I have in my area so that is all I can honestly do comparisons with.

[Kurtdg19]

Pretty much as what they all said. Compression ratio determines how much air-fuel mixture is pressurized. A ratio of 9:1 would mean that the maximum cylinder volume is nine times the amount as the minimum cylinder volume. When you have a power adder such as a turbo or supercharger, lower compression allows more fuel charge into the cylinders..