Steet vs Strip power under the curve

[Double"O"]

A centri is much more efficient, therefore at the same boost levels it will make more torque and more horsepower. And when using that extra power, it's all about the sweet spots of the power band. With a roots/pd you would be wanting to shift no higher then 6300-6500 to stay in the powerband. The centri, you would want to shift at 7000, staying in its powerband. We can use all the scientific formulas, but every car is different. And from my experience, the centri's seem to go faster. Look at the 03 Cobra, when it came out. Stock they put out about 10#'s of boost and will usually ran 12.90 at 110 in the quarter. When the 01's were the choice there was only centri blowers available. Bolt on an S-trim to that 01 with 10#'s of boost and the car would run 115-116mph in the quarter. Same boost level, yet quite a bit faster in the quarter. So, even though the 03 has a much flatter longer torque curve, which one goes faster?

you are aware that the 03 Cobra wieghs a good bit more than an 01 Cobra and has a lower CR as well.

 

[brkntrxn]

you are aware that the 03 Cobra wieghs a good bit more than an 01 Cobra and has a lower CR as well.

+1

 

[mlccar]

Efficiency

A centri is much more efficient, therefore at the same boost levels it will make more torque and more horsepower. And when using that extra power, it's all about the sweet spots of the power band. With a roots/pd you would be wanting to shift no higher then 6300-6500 to stay in the powerband. The centri, you would want to shift at 7000, staying in its powerband. We can use all the scientific formulas, but every car is different. And from my experience, the centri's seem to go faster. Look at the 03 Cobra, when it came out. Stock they put out about 10#'s of boost and will usually ran 12.90 at 110 in the quarter. When the 01's were the choice there was only centri blowers available. Bolt on an S-trim to that 01 with 10#'s of boost and the car would run 115-116mph in the quarter. Same boost level, yet quite a bit faster in the quarter. So, even though the 03 has a much flatter longer torque curve, which one goes faster?

You must be talking about a roots positive disp blower. The twin screw has a much broader and flatter torque curve and does not drop much at high rpms. A twin screw will also develop boost at a lower rpm than a roots. The twin screw has an internal compressiion ratio and approaches 95% at a few pounds and drops to 90% at 10 lbfs. A look at the Bell book shows a calculated power loss for a 10 lbf centri at 15 hp. The same boost for a twin screw is about 25hp. These differences are miniscule when compared to all the other variables in a 450 bhp car. The '03s are roots blowers. The KB is a twin screw.

 

[mlccar]

Lower Compression Ratio

you are aware that the 03 Cobra wieghs a good bit more than an 01 Cobra and has a lower CR as well.

Crap Mike. I got so caught up in my thermodynamics and physics I forgot about the CR. For a 2001 Cobra 9.8:1 CR + 10 lbfs of boost resulots in a much higher effective CR than 10 lbfs + 8.5:1 CR. Not the same beast at all. I am not surprised that a 2001 cobra with 10 lbfs of boost will beat an '03!

 

[SlwSVT]

03, lower compression but runs much more total timing (21-23). 01 can only run 17-18, so that offsets some of the compression factor. 03, has cams from the factory for a blower setup, 01 does not. Also, 03 is heavier stock. But, when you add in the blower package to the 01, you add 75-125 pounds to that car also.

 

[mlccar]

Heavier

Yup. I agree. I guess we are in agreement +-5% or so. From a standpoint of not having a built lower end I can tell you that I do not want to be shifting at 6800 rpms.

 

[Double"O"]

03, lower compression but runs much more total timing (21-23). 01 can only run 17-18, so that offsets some of the compression factor. 03, has cams from the factory for a blower setup, 01 does not. Also, 03 is heavier stock. But, when you add in the blower package to the 01, you add 75-125 pounds to that car also.

yes the 03/04 can run more timing because of the CR. Detonation can be better combated with a lower CR.

a car with higher compression can make equal power with less boost compared to a lower compression motor.


Bill the 01 Cobras' CR is 9.85

 

[Double"O"]

Yup. I agree. I guess we are in agreement +-5% or so. From a standpoint of not having a built lower end I can tell you that I do not want to be shifting at 6800 rpms.

Wuss....lol

honestly the power is dropping off their with our cars anyway bill, i shift mine at around 6500

 

[Wicked]

Wicked,

True, but as you and I know 12#'s from a roots or twin screw vs 12#'s from a Centrifugal would not have the same horspower or torque. In most cases on the same indentical car, the Centrifugal will walk away.

I was going to respond but looks liek everyone else has already argued the point.