Killing 'drone'

[mullett]

I've just fabricated an exhaust for my daily (2.0 NA hatch). At the moment it's 2.5 all the way through (turbo might come later, so I didn't want to have to do it again) with a straight thru 350mm glasspack muffler, and a single 300mm long 2.5 resonator. I'm happy with the 3000rpm+ noise level, it's very quiet and refined, but under 3k it's very droney, what's the best option? I've got room for another (small) muffler, or quite a lot of room for more resonators, but I want to cut the drone out without killing the sound 3000rpm+...Any ideas? Also, does the position of the resonators versus the muffler make any difference? At the moment the resonator is before the muffler, but I could put an identical one post-muffler.

-RM.

[willwal98]

If you add more resonators / cats / mufflers etc you will probably change the 3000rpm note. How about a valve triggered by rpm? AFAIK as long as it meets noise regulations when fully open it is legal.

[oldcorollas]

which is first in the path? should be the resonator....

glasspacks are shit and should not be sold

what is th einternals of your resonator like? if it is louvred, it might not be doing anythign useful.

[madmont]

I find that when I end the exhaust before the end of the bodywork it reflects noise back into the cabin. Does your exhaust extend past the bodywork or end before it?

[Aust162]

I find that when I end the exhaust before the end of the bodywork it reflects noise back into the cabin. Does your exhaust extend past the bodywork or end before it?

+1. especially in a hatchback, as the cabin is all one space.

My friends car had this problem and he got the muffler positioned 2" further back (clearing the rear bar) and it made a hell of a difference. Im guessing now the sound doesnt get trapped under the body of the car and resonate into the cabin.

[mullett]

which is first in the path? should be the resonator....

glasspacks are shit and should not be sold

what is th einternals of your resonator like? if it is louvred, it might not be doing anythign useful.

I think I agree with you about the glasspacks. First in line was the resonator, then muffler, then a dump just behind the rear axle. That was extremely droney, I've since put another resonator right at the back, and run a straight pipe out to the rear bar, it's perfect now. A little quiet at high-RPM, but I can't complain.

The internals of the resonator are like a series of dimples punched inwards...

-RM.