Blower question

[Taylorman]

I know very little about superchargers and was wondering if you can run pump gas with them. What allows you to run pump gas with a blower but not on high compression engines. That being said, whats the difference between a high compression naturally asp. engine and a low compr. supercharged engine. Why can you run pump gas with a supercharger and not high compression. It seams to me that the supercharger creates high compression. Explain

[Jim B.]

Taylorman your right, you generally can run higher compression ratios when supercharging. Keep in mind, these are FINAL compression ratios. Static compression + blower boost = your final compression ratio. Higher compression ratios are possible when supercharging without causing detenotation because the FINAL compression ratio occurs at max. boost at high RPM where less engine loading occurs. The max. Final compression ratio you can run with pump gas is 12.5:1 but some prefer a little less. Check out some of popular blower builders websites (Blower Drive Service, Kuhl Superchargers, etc.). They have useful math formulas for figuring out comp. ratios,etc.

[Blown 472]

One other thing to consider is a blown motor when not under boost is nothing more than an over carbed low compression motor. I was told it is better to have low static and then adjust the boost as needed. A high comp na motor is set on kill all the time where as the blower motor is not, sept when you have your foot in it.

[UBFJ #454]

Not true about the high compression n/a motor always on "Kill": That's if it's built for hi-comp and right fuel is used with proper A/F mixture.

[Infomaniac]

My pump gas blown engines use 7.5:1 - 7.75:1
With an intercooler and conservative ignition timing 12 lbs of boost is no problem. Should be using 91 octane unleaded minimum. A little less boost with 87 - 89 octane.

[Blown 472]

BEAR_454PE:
Not true about the high compression n/a motor always on "Kill": That's if it's built for hi-comp and right fuel is used with proper A/F mixture. WHat I meant was a high comp motor is always going to be a high comp motor no matter what, a blown motor not under boost is a low comp motor.

[DogHouse]

Blown 472:
WHat I meant was a high comp motor is always going to be a high comp motor no matter what, a blown motor not under boost is a low comp motor. I know what ya meant... I have one of those "kill" n/a motors and it's a bit of a pain to live with, constant valve adjustment, short life on the springs, too much cam to idle reliably, etc. "Next time" (ha ha) it's going to be a bit more mellow but with some boost to get the hp up where it needs to be!

[Tee]

"Next time" (ha ha) it's going to be a bit more mellow but with some boost to get the hp up where it needs to be! [/QB]NEXT TIME? Damn Brian, You'll never get out of the "DOGHOUSE" If you build another one!!!!!!

[DogHouse]

I didn't say when "next time" will be now did I!
We all know that there is always a "next time"... wink
-Double_Dog_House