I need to know why low compression is better for supercharging..I have 10.4:1 compression right now..

Also how would this cam fair?
114 LS .510//510 I/E@.050 220/230 duration

Daz
87 IROC
Superram
TFS G1 fully portead heads
SCAT crank,ARPed rods,11:1 Hyepreutectics

 

Think of it like this: A supercharger crams more air in the cylinder. This effectively increases the displacement of the engine and raises the compression ratio because this greater volume of air will be compressed into the same space. Some numbers might help. If you have a 10.0:1 CR without the supercharger and the supercharger crams in 50% more air, you will now effectively have a 15.0:1 CR. So if you start with a lower CR you can add more boost without getting to high of an effective CR.

 

DAZ,

When supercharging a engine you are not raising the compression ratio, but you are indeed stuffing more air into the cylinder,and raising the cylinder pressure, as you compress air, it heats up, you add fuel and a spark and BANG!!!
Now you stuff more air into the cylinder with the supercharger or turbo...and start to compress it, the air/fuel mixture heats up sooner and to a high enough temp to ignite,BOOM!!!(no need for spark)...and you have preignition, i.e., detentation, a blown piston!!!
hope this helps
later,

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MÅN¡ÅÇ ©
88 IROC 5.7L,edelbrock TES,random tech cat,borla exhaust,chip,sfc,accel wires,airfoil,k&n's,ETC..
and soon to be supercharged
http://maniac.megamania.com

 

yea... that means you have to lower it so you dont get dotonation, also so you dont have to run race gas

 

As I said the supercharger will raise your effective compression ratio. The static compression ratio will not be changed. When your engine is running, the effective or dynamic compression ratio will never be the same as the static compression ratio except when the engine is operating at exactly 100% volumetric efficiency. 100% volumetric efficiency means you fill the cylinder completly with air at atmospheric conditions. A supercharger can raise volumeteric efficiency well above 100%. Most normally aspirated street engines don't get above 90% volumetric efficiency. To control detonation, the dynamic compression ratio must be controled. Static compression ratio and volumetric efficiency will determine the more important dynamic compression ratio.

 

Don't denotate with those hyperutetics. You will blow a hole in them with no problem without race gas and that compression ratio.

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'91 Formula
383CI Supercharged
5-speed
3.42
12.34@117.04
on Drag Radials