Exhaust gases mave much more energy and can overcome obstructions much easier than the air coming into the engine. So in that sence, an engine needs more help getting air in than exhaust it out.

Actually, in an automotive situation, where the exhaust is carried from the front all the way to the back, the exhaust cools down as it gets to the end. The manufactuers design the exhaust systems to have a backpressure at the end, in order to create more heat in the pipes, so you would as a result have less dense air(read: lighter), which ELIMINATES backpressure when at operating temperatures.

So those ricers with huge mufflers actually lose horsepower.

Best is to have pipes coming out of your hood! But not too practical for the streets

I think that having something suck out exhaust gases would just increase engine power draw than put out more power.

In a two-stroke, the "valve overlap" is called scavenging, they use the supercharger to force out exhaust gases and unburnt gases, then fills the combustion chamber with clean cool air.

You mean four stroke?

No, I mean a two stroke naturally aspirated uses a supercharger to attain 14.7PSI, since it has no way of filling itself with enough air. And yes, equipped with a supercharger(gear driven), its still considered naturally aspirated. Unless of course you have turbos on there as well or something.

No intake valves, just exhaust valves. And Its just Squeeze, bang and air through. Compared to the four stroke'* suck, squeeze, bang, blow.

You're benefits are quicker accelerations, instead of two rotations of a crankshaft for one cylinder to fire, you get one bang out of each 360 degree rotation for each cylinder. More response.

ieatfeet: OT, but are those '91 Reatta wheels?

We discussed it a little bit in this thread in February of '05. Could be interesting. I wonder if anyone has really played with the idea?

i have no idea what your talking about and yes they are avtually it came with gold laces and i got rid of em quick

The old school muscle car blowers, 4-71, 6-71, etc..., were originally exhaust scavenging blowers for industrial diesels.

Yeah, those were the Detriot Diesel two-strokes, but the blowers weren't just for exhaust, it was also for intake, since the two strokes eliminate the intake and exhaust strokes, they use the blower to force exhaust air out and new intake air in, at the same time, at an airbox pressure of 14.7 PSI, it was considered naturally aspirated, because it never served for additional boost. And it was gear driven, so its not like you could swap a pully. But its still quicker than a 4 stroke when it comes to acceleration.

Ok sticking my nose in likely where i shouldnt.. but hasnt this recently been done by a company called STS ? its a turbo that uses exhaust gas pre muffler and feeds it back to the intake. the turbo was moved there cause like someone said the air by the end of the exhaust pipe is cooler rather then use a traditional turbo picking up hot air.