low compression for blown motors

[BurnTire]

Lower to run more boost.

[WildBill]

Lower to run more boost.

Not with a centrifugal style blower

[BurnTire]

You take a motor with a lower Static CR and one with a Higher Static CR then adjust boost on each motor so they the same Effective CR. Which car will make the most power?????

I guess the ultimate question is how much boost does he want to run. If he wants to crank it up by no means does he want to increase the static cr.

[WildBill]

You take a motor with a lower Static CR and one with a Higher Static CR then adjust boost on each motor so they the same Effective CR. Which car will make the most power?????

I guess the ultimate question is how much boost does he want to run. If he wants to crank it up by no means does he want to increase the static cr.

You're missing the point. A centrifugal style blower needs and can use more compression.It needs the higher compression for the low boost bottom end with that style of blower. With a roots or twin screw, higher than stock compression is not needed due to the boost being made in the low rpms. This is common and well accepted practices. At the very least he should keep the stock compression ratio, NOT lower than stock.

[BurnTire]

You're missing the point. A centrifugal style blower needs and can use more compression.It needs the higher compression for the low boost bottom end with that style of blower. With a roots or twin screw, higher than stock compression is not needed due to the boost being made in the low rpms. This is common and well accepted practices. At the very least he should keep the stock compression ratio, NOT lower than stock.

Again it depends on how much BOOST he wants to run. High Boost + High CR = Boom. I believe his car has about 9:5 to 1 so it by no means is high compression, but I wouldn't run that in a higher boost application.
I see you bypassed the question I asked above

[Stanger00]

I would keep stock compression and keep boost below 20...Ideally 15-18 on street tune...anything more and the power is semi useless below 50 MPH. This is just me though. I doubt that P1-SC can even be spun to 15 psi and make power. The V2-SQ blowers fall on their face around 16 psi with stock compression, heads and cams. That much boost still makes 500-525 to the wheels though. These 2 valves kind suck at the making power thing..but with the right build its possible to make more. We have the little blowers so they lose steam before the motors do. Upgrade the blower then we have FUEL issues.

[WildBill]

Again it depends on how much BOOST he wants to run. High Boost + High CR = Boom. I believe his car has about 9:5 to 1 so it by no means is high compression, but I wouldn't run that in a higher boost application.
I see you bypassed the question I asked above

I didn't address the question above to refrain from making you look less credible.
The higher compression engine with lower boost will make more power over the curve and more peak HP than the lower compression and higher boost combo. Parasitic losses will be more with the higher boost combo as well losses due to higher inlet air temps.

I would keep stock compression and keep boost below 20...Ideally 15-18 on street tune...anything more and the power is semi useless below 50 MPH. This is just me though. I doubt that P1-SC can even be spun to 15 psi and make power. The V2-SQ blowers fall on their face around 16 psi with stock compression, heads and cams. That much boost still makes 500-525 to the wheels though. These 2 valves kind suck at the making power thing..but with the right build its possible to make more. We have the little blowers so they lose steam before the motors do. Upgrade the blower then we have FUEL issues.

You are correct on all points, hence my recommendations to the OP.

[Bandit]

[WildBill]

[BurnTire]

I didn't address the question above to refrain from making you look less credible.
The higher compression engine with lower boost will make more power over the curve and more peak HP than the lower compression and higher boost combo. Parasitic losses will be more with the higher boost combo as well losses due to higher inlet air temps.


You are correct on all points, hence my recommendations to the OP.

Bill with all due respect you have those backwards.

For example my car has 8.5:1 at 20 PSI that is an Effective CR of 19.8

If my car was 9.5:1 it would take 16 psi to have an Effective CR of 19.8

The 8:5 20 PSI combo will produce more power across the curve and more peak HP.

Worry about your credibility not mine