Muffler thoughts

[Dat Lurka]

I'm running straight pipe to front of rear tire with a 13" glasspack from Summit. The fat tip is what makes the sound though.

[ggzilla]

I'm running large-tube headers, 2.5 pipe to a huge V8 turbo muffler and 2.5 pipe to a stainless glass-pack at the back.

 

It's not quiet, but it's not loud either. Probably loosing some HP with the big downpipe, but the A14 runs well.

[high winder]

i run a 26" cherry bomb with straight pipe out the back..not loud at all and at idle it almost tries to have a cam sound..it might be hearing my 67' camaro run and it gets jealous

[banzai510(hainz)]

pineclone

I would had a rsonator in front of the muffler if you gog the room.

 

I gave Datto510 a Cheerybomb turbo muffler the smallest case they had (Think 13 inch) 2inch in/out

 

he had a resonator and this muffler and was perfect. He had dual 40mm Webers also. Was perfect for the long drives he was doing.

 

depending on How low your car is the size of the resonator

[JAS]

I have a stock system, except for a 2" conversion out of the muffler to the rear. No resonator, sounds real throaty, but i do run a shaved H89 head with matched manifolds for it.. the high compression just pops out the exhaust....

[datzenmike]

A 2 1/2" pipe (even though it is only 3/4" larger) will flow two times what a 1 3/4" diameter pipe will. Unless you are flowing a 4 liter motor through it what's the point????? Lets say the Nissan ran a slightly smaller pipe than needed because its...

 

a/ no one drives at 5K-6K anyway, the differences are hardly noticed.

b/ it's over all quieter.

c/ cheaper less metal used.

 

Lets say you have added a weber, maybe a mild cam and actually have a small increase in exhaust volume you want to need to get rid of. Going from a 1 3/4" pipe to a 2" (1/4") is an increase in cross section area of 30%!!! For Christ sakes just how much power do you think you're making???? Because I doubt its a 1/3 increase over stock.

 

You want the gas speed inside the pipe to be as high as you can make it. So use as small a pipe as you can without it being restrictive.

 

A muffler's job it to take one big bang (in a long series of bangs) and release it over a longer time. Sort of like letting air out of a tire vs. it exploding. One way is with a series of small holes and baffles so it takes time for all the exhaust to find it's way out. Instead of a single loud sharp POP it becomes a longer THUD sound. Fiberglass packing can also be used to absorb this pulse of sound.

 

Internal chambers and baffles can reflect waves that cancel other waves but this 'tuned cavity' will only work at set speeds and does little over a broad range of RPMs. These are known as resonators and they can be designed to soften and eliminate a problem sound area such as your cruise speed. The good thing is they are low restriction and (more or less) straight through. A factory muffler may have a tuned cavity in it designed for a certain motor.... replacing it with a generic muffler may make it louder or change where the loudness is..

 

Even the bends in the exhaust pipe will help homogenize the sound. Even catalytic converters muffle the sound.

[ggzilla]

Mike, your theory is sound but ignores real-world factors.

 

what's the point?????

Glad you asked. It was on the Datsun when I bought it. Instead of buying all new properly sized exhaust, I've been running it for the last 5 years. Got plenty of power, and yes, I know it would have more with the right size pipe (as I said). Even 2" piping is too large for optimal HP with a 1.4 liter even a "built" 1.4.

 

a/ no one drives at 5K-6K anyway

I do, for hours at a time at 5000 RPM. It's only 1.4 liters. Keep it in the power band.

 

Max fuel economy, driveability: Use 1.5" pipe

Max power with a modified A14: 1.75" for anything under 6400 RPM