cottoneg

I would like to run the car at Lime Rock. But track has an 86 db sound limit (basically a muffled car).

I have sidepipe headers. The car runs best with the Max Flows inserts. The quiet mufflers inserts were so restrictive and built so much pressure they sidepipes would separate from the headers under throttle.

I called Burns Stainless (http://www.burnsstainless.com/) and they can make a custom sidepipe. Bigger diameter and custom insert. But even they admit, getting to 86 db with low restriction is a challenge.

So I figured I just check here to see if anyone else ran across this issue and if they were able to solve it. The car has a 383 motor.

Thanks!

shakedown067

86db at a race track? Holy crap. I think even my ole '89 chevy truck has got to be louder than that. Well good luck, I'm sure someone here has to run at Lime Rock from time to time that'll have some good muffler advice.

cottoneg

Even the guys at Burns were surprised. But go to the Lime Rock website. It's there. That is why I usually run NJMS despite the long ride.

69autoXr

86 dB at what distance? This matters. It may not be as difficult as you think.

My local track has a 75 dB limit at their property line, which is behind a sound wall along the main straight, and about 50' from the track. To get by I use side pipes that turn under the car, then I run flex tubing from the outlets under the rear suspension to an exit point at the right rear corner of the car. My point is, you may have to get creative with a solution in order to meet sound.

I don't know the brand of muffler inserts in the pipes I use, but I can say that they're more quiet than my other pipes that use dynomax bullet mufflers (similar to a Max Flow internally, but shorter length). The unknown "quiet" pipes have an internal diameter that is similar to a Hooker reverse flow insert.

It may be worth going to a track day there and running as is to see where you're at, but have alternatives with you so you can attempt to reduce the noise if you have to.

MelWff

read all 3 pages of this thread, I believe they test it 50 feet behind the vehicle at 1,000 RPM below redline during tech. Additional tests from various points while on the track.

http://forums.evolutionm.net/motor-s...striction.html

2 GTOs

There were a bunch of guys saying that 09 forward z06 and zr1 completely stock were sometimes failing and they were wiring closed the NPP.

I heard it second hand, but given how many cars were flagged at an event i attended (no corvettes), I would suggest taking it seriously before spending good money on a solution that may not work, or just watch for one of the "unmuffled" HPDE days. I know SCDA has them, but sign up quickly, they fill up fast.

cottoneg

Burns was basically recommending a larger diameter side pipe to cutback on restriction. Not sure how they would do the internal muffler.

A good friend recommended altering the brackets or weld deflectors to my side pipes or cut and weld them so the sound is directed down. I wonder if that would help.

Wish there was a non permanent way to do this in case it doesn’t work.