Old Back Pressure Arguement

[Ft. Campbell Busa]

I know what you all may have be thinking but hear me out, lol. My question on this is how necessary is back pressures on any motor? Seems like I read about it on bike sites more than anything. Are they behind the times, or are there certain types of engines where this is more necessary than others? Example is on a very popular bike exhaust. Stock motors will always make less power on the Dyno with this pipe except on Nitrous use. The manufacture also recommends installing a baffle on stock motors to create back pressure and not hamper power.

[my63]

On a stock motor, if all of the other supporting pieces are not improved to take advantage of a freer exhaust, then it will loose power.

Remember, to get air in, you must be able to get air out and vice versa.

How much difference will open air filter elements make power wise if you can not get the spent gasses out?

The only engine I can think of where exhaust back pressure is a critical design element os a 2 stroke engine!

[jayh]

Im thinking you need to have some type of velocity to develop a scavaging/syphoning effect, as much as some people hate the word "velocity" if the air gets too lazy/stagnant, I cant see it being a good thing?

[my63]

There has to be some sense utilized here.

A 5" straight through exhaust on a 1000CC engine with a stock air box and filter isn't going to work here.

[Ft. Campbell Busa]

There has to be some sense utilized here.

A 5" straight through exhaust on a 1000CC engine with a stock air box and filter isn't going to work here.

Right, but I see this "back pressure" word thrown around over on bike sites now like it was on the Corral and Stangnet years ago. You know the 3" exhaust is way to big unless you are making 1000HP because you lose backpressure. The 2 stroke information is enlightening. Thanks

[TooNuts]

want to say motorcycles need it, not so sure about cars.

[65mustang393]

It seems like cars always run faster with the exhaust dropped & open headers.

Does backpressure ever do anything other than create a pumping loss and restrict the engine from revving as freely as it could?  I would think the answer is no, but I'm not sure.