IronFist

iTrader: (3)

In the book "Civic Duty" there's a pic of an exhaust that has a flap cover on it with holes in it to change the amount of back pressure as you change how much you press the gas. Has anyone ever seen one of these before? Is it legit or a gimmick?

IronFist

IDQcivic

iTrader: (6)

I think arospeed makes something like that, they call it an exhaust control system...check it out!

IronFist

iTrader: (3)

That appears to be more for sound control than performance and backpressure, but similiar idea I guess.

The valve I was talking about opens and closes on its own I assume. I don't think it's driver controlled like the one above.

Probably just a gimmick, tho, or else more people would use them I assume [IMG]i/expressions/face-icon-small-confused.gif[/IMG]

IronFist

4bangin

iTrader: (1)

there is an exhaust, or a muffler anyway, that i saw in an import mag that has rings or large washers that can be removed or added to change backpressure and sound, i believe. I dont know if that is what u r talking about or what. i thought it was kinda interesting tho.

PESTLNC

Domestics call it a butt-plug and I do too.

mwwhonda

iTrader: (3)

nissan uses a muffler like that...



mark

Grey

iTrader: (61)

Yeah, the Aerospeed one is only for muffling since it's not dynamic. One that changes the backpressure of the exhaust system with the engine rpm's is actually good for performance. I know that one other sport compact had a variable exhaust system, forget which one though. Toyota Corolla maybe? Anyway, the real deal is good for performance. If I could I would swap in one from another car. An aftermarket one that is... I'll have to do some research...

SMX

An engine is an air pump. An air pump makes more power by moving more air in and out of it. Moving air out of an engine means having an exhaust that flows well and maintains exhaust gas velocity at the valve. Anything that restricts that flow (backpressure) reduces power. What you want to control is exhaust gas velocity. Under some conditions (low rpm), a smaller exhaust header can maintain velocity better than a larger header and make more power at that particular RPM. It ain't backpressure, it's properly tuned exhaust at that RPM that makes the difference. The notion that backpressure is good at low RPM is BS.

Grey

iTrader: (61)

Yeah, exhaust gas velocity. At lower rpm's you want the exhaust system to be of a smaller diameter so that the exhaust gases don't get a chance to cool down and therefore slow down. I know about headers and the concept of shockwave tuning, but these variable exhaust systems only work within the muffler. I'm not exactly sure how they increase performance (backpressure was the wrong term to use; lord knows I've heard it way too often). I think I saw a commercial for a car with that kind of exhaust system and they showed a cut away. It looked like a valve controlled how much piping the exhaust gases went through within the muffler. Seems weird though 'cause I think this would only have an effect on reducing noise from the exhaust.

I guess a true variable exhaust system would have two pipes leading from the header on back with different diameters. The one with the smaller diameter would be open at lower rpm's and the one with the larger diameter would be open at higher rpm's. Seems kinda bulky though...

SMX

I think Yamaha had a variable exhaust a few years ago on their sportbikes. Can't remember what it was called but as I recall it was designed to maximize exhaust gas velocity at low rpms while opening up to support WOT rpms as well. Kinda like VTEC for your headers.

SMX

Now I remember - EXUP (i think)