Mufflers, How Restricting Are They?

[jasont82]

hey guys

got a question about mufflers. when you buy one do they have a flo rating like hi flo cats do? my mate recons i'll get better performance if i change my muffler to a cannon. i didnt agree. i thought mufflers were all about sound not performance. you piping gives you the performance and you muffler keeps it quiet? the cat restricts air flow but what about your mufflers? do you buy them for athestics and sound or are there actually gains to be made from different mufflers?

[mad082]

what sort of muffler do you currently have? yes mufflers do restrict. for example, zoom magazine did a test where they got a stock xr6 turbo. they did pressure tests with the stock mufflers and found by removing the centre muffler they gained about 17kw. the restriction at 5500rpm with both mufflers was 0.414bar. when they removed the centre muffler it dropped to 0.207bar. so it halved. but these are stock mufflers which are more restrictive than aftermarket ones.

if you have a 3" system and it isn't a cannon but still is a straight through muffler, then don't bother changing it. the difference would be little.

[jasont82]

yeah i have a 3inch system not sure what style you would call my muffler its an aftermarket one got some brand on it cant remember what it is. think they call them oval mufflers same sort of shape as the stock one but with a big tip on the end.

[RANDY]

It depends on the internals of that muffler, as Mad082 is saying.

Most mufflers quieten the sound by rebounding the exhaust gas off things until the resonance cancels itself out.

A stock muffler is basically an empty can, with a few "U" shaped bits of metal at each end. The gasses bounce off one, back to the other end of the muffler, then bend again, then out the end-pipe.

A "straight-through" muffler will be louder, because they are basically a can, with a perforated tube from the inlet to the outlet. Some gasses can escape out the perforated tube and into the body of the muffler, but that's about all it does for quietening.

So as you can imagine, the less restrictive design is going to be the better flowing one... better flowing should equate to more power on a turbo'd car.

I beleive on a 4-banger, it will just reduce backpressure, which is what small motors rely on for making torque.

[mad082]

if it is an oval type muffler and a 3" it should be a straight through design, so the gain going to a cannon would be extremely small, if at all. the air has usually slowed down significantly by the time they exit the exhaust. the biggest restriction is the cat. changing your muffler won't do anything accept add more noise. tell your mate he's an idiot.

[jasont82]

thanks guys. yeah thats what i thought, u idiot. Thats like saying by putting a cannon muffler on your stock exhaust is gonna give you more power. i doubt it. probably about as much as i got from the 15kw SAU stickers!

[khunjeng]

yeah what they said...OEM mufflers are baffled to the shithouse to make them quite....