Quiet down exhaust and eliminate drone - E30 LS1

[kristov]

Hi,

I need some input on how to quiet down my exhaust and eliminate the terrible drone between 1500-2000 rpm cruising.

The one I have now is a straight through from Scorpion for an E36 M3. Up front only an x-pipe and two small cherry bomb resonators.

Do I need bigger resonators, mid muffler or bigger rear muffler?

I do have an oem E36 M3 rear muffler I am thinking about trying although it might be too restrictive.

[kristov]

Any input here?

How much sound does catalytic converters suppress?

[NotaHybrid]

Stagger your resonators if they are not staggered to eliminate some drone. You could mid mount some borla stinger mufflers also, and stagger them. The stingers are a straight through muffler.

http://www.borla.com/products/stype_...t__40842s.html

[Liquidity]

Those cherry bombs look really small. You probably need something longer.

[kristov]

Stagger your resonators if they are not staggered to eliminate some drone. You could mid mount some borla stinger mufflers also, and stagger them. The stingers are a straight through muffler.

http://www.borla.com/products/stype_...t__40842s.html

How would staggering help?

[1990m3]

get larger resonators. They will have virtually no effect on your power output and quiet it down significantly.

Look at LS exhaust systems from camaros and corvettes.

[SmokeE30]

My buddy's ls swap with straight pipes and a x pipe has no 1500-2000 rpm drone it's actually quite civil sounding down there for straight pipe. What headers are you using?

[Madhatter]

longer resonators + a bigger muffler. If you can find a 2 in 2 out muffler in the right diameter, one trick is to size it one inch bigger than what your actual pipe diameter is. Much like resonators, longer and bigger and you'll dampen down the sound.

[Gertech]

My exhaust goes into a Y to 3" cat where you have your x-pipe. It's 3" out from there with a Pypes M-80 glasspack out back. It's very civilized with absolutely no drone at highway speed. That being said, it makes a hell of a racket when you step on it!

[kristov]

My exhaust goes into a Y to 3" cat where you have your x-pipe. It's 3" out from there with a Pypes M-80 glasspack out back. It's very civilized with absolutely no drone at highway speed. That being said, it makes a hell of a racket when you step on it!

Do you happen to have a picture of it?

[NotaHybrid]

How would staggering help?

The drone comes from the "clashing" of sound waves with similar frequencies. Staggering or disrupting the sound waves through other methods reduces/eliminates it. Think of the pipes as a giant tuning fork. If they were perfectly symmetrical, then it would cause drone just like a tuning fork generates a tone when you hit it against a surface.
This is the reason why the factory 5.0 resonators are flattened in different areas on each side. Because of that design, the similar sound frequencies won't bounce off each other because they are going in different directions.

This was copied from a mustang forum I'm on.

[lemansguy]

i had a LS1 camaro with headers, no cats and flowmaster muffler. i had zero drone, and i beleive it was because of my slightly bigger (some say more restrictive) muffler. the daily driveability was worth the MAYBE 5hp i lost. i also had zero "rasp" that a lot of non catted LS1s are prone to. my exahstu was great for daily driving, throaty and deep under when your fit was out of it, but screemed when you wanted it to.

[The Dark Side of Will]

How would staggering help?

Like an organ pipe, the frequency at which the exhaust pipe resonates is related to its length. If you have two pipes the same length, they'll resonate at the same frequency and make a loud drone. If they're (significantly... 15%) different lengths, then they'll resonate at different frequencies. This will make any droning less loud, but over a wider range of RPM.

[kristov]

Replaced the rear muffler with a stock E36 M3 muffler and it got a lot better.