first off...what is it? is it good? when is it good? How can I get it/avoid it? I hear its good for turbos and bad for sc's...but i also hear its good for sc's...so i have no clue. thanks for any help.

 

u need back pressure for the engine to suck air into it i think....too much back pressure creates constrictive flow...too little back pressure no air being sucked into the engine....for turbos...i have no clue, i think its for spinning up the turbo...for s/c's....u dont really need too much since the air is being forced into the intake and not pulled...

then again i could be talking out my a$$..but thats how i thnk i goes

 

Backpressure is created when exhaust gases see restrictions trying to exit the engine. Can be because of poorly designed exhaust manifolds, extreme bends or kinks in exhaust tubing, too small of exhaust tubing, lots of cats, ect. A NA engine needs a little backpressure to effectively scanvenge each of cylinders of all vapors. On a turbo car, usually the less the better. Too much restriction on a turbo car will not allow the turbo to spool up quick enough or not to a high enough rpm to create ample boost. On top of having more air and fuel being pump in on a turbo or supercharged car, you need a efficent way to get it all back out. Scavenging isnt as much of a issue since you have fuel and air being pushed through instead of sucked through the cylinder heads.
Someone else chime in if I missed something or need to correct me.

 

so basically...if you have a supercharger with stock headers...and then get aftermarket headers, will it help or hurt performance?

 

The stock manifolds on our cars arent too bad for stock but I would put some longtubes on to take full advantage of the boost. Shorties are a improvement over stock but not to a real great extent.

 

ok. I just know a guy who(he's older but seems to not know what he's talkin about alot) said that givin long tubes loses 3 lbs of boost on a sc and I had no idea if it was true or not.

 

In a perfect world back pressure would be eliminated by just letting the exhaust out the exhaust port into the outside air.If you try to do this the power of your engine will be killed down low and come on quickly at high rpm's.An exhaust smooths things out by allowing gases to flow smoothly out of the engine and when working right,to pull intake charges into the cylinder.Air has mass,and therefore inertia.This causes the slug of exhaust gas to remain in motion after it leaves the cylinder.This creates a partial vacuum,and pulls more air into the cylinder.(and even pull some out past the exhaust valve)Now here's where the mis-named backpressure comes in.As the exhaust shoots down the tube it will eventually hit something.This will cause a Reversion Wave.This,if timed correctly,will cram some of the intake charge thats now in the exhaust back into the cylinder to be burned.(two stroke dirt bikes use this principal in their expansion chambers)Long tube headers allow the slug of gas to travel the longest distance before it hits something so they will generally give better power higher in the rpm range.So you see,zero backpressure would be best but since the laws of physics dictate otherwise we learn to make them work for us.