View Full Version : Muffler/sound control

05-28-2002, 10:21 PM
Well, I tried to search the archives, but to no avail, so sorry to repeat this if it's been covered before.

OK...Does anyone have a good solution for the loud obnoxious noise problem when running the race car in the shop and around the house?

My car has the usual header, and a twin primary system going under the axle , then into a 3" collector and finally into a Walker Dynomax stainless steel straight thru "muffler", exiting just under the bumper. As you can imagine, starting it up (and the requisite revving to warm it up enough to idle) immediately pisses off the neighbors, especially in the early AM when it's load up time!

So...has anybody had good results with a particular muffler? I'd be OK with either bolting it into the Dynomax position for non track use, or as an add on behind the Dynomax, bolted across the valance , or....??? Preferably quick and cheap!


Jake Gulick
ITA 57 RX-7

C. Ludwig
05-28-2002, 10:53 PM
I got a Supertrapp cap from Summit to run on my car at some autox events where there are sound regs. It worked great and was simple to install. It is just an adapter piece that welds to the end of the Dynomax (I got the same setup you do). You can bolt the discs to that piece. I'm running with all the discs for more flow though you can take some out to quite it down for moving the car around the house. For track use you remove the six bolts that hold the discs in place and you're wide open again. It was less than $100. Think it was link $60-70 but don't quote me on that. The only problem was that the discs directed the exhaust out toward the plastic bumper and melted a good 2" of it all around the Supertrapp!! http://Forums.ImprovedTouring.com/it/smile.gif


05-28-2002, 11:56 PM
Sounds good....I vaguely wondered about Supertrapp....but had forgoten about the unit you referred to. I wonder how quiet it can get....

And...the melting problem....do you think a fabricated sheild of some sort that would bolt on/off with the "cap" might be effective at controlling the problem? Was it from the radiated heat or from the actual hot exhaust gasses ? (Sounds like it's the gasses>>>)


05-29-2002, 01:39 AM
For moving it around, loading/unloading the supertrap disc only setup is great. Not good for racing!! I tried it as a quick, low dollar supplement to my regular exhaust system to meet the strict 92dB limit at Laguna. By the time I removed enough discs to meet sound control requirements it was so restricted it wouldn't rev past 6000!!

Ever driven a car with a plugged cat?

How quiet? Put two or three discs on it an I would bet it won't be louder than a stock exhaust. Probably won't rev over 3000rpm either. But would be plenty good for loading/unloading.

C. Ludwig
05-29-2002, 08:30 PM
Quickshoe's got it nailed. I left it on during the first practice session just for grins this past weekend. With all the discs it is significantly quieter and seemed to move the power peak down a bit which helped the car on the autox course. It killed the car on the road course though. Knocked a good 1000 rpm off the powerband.

The heat looks like it's the exhaust gasses being pushed out through the discs at a right angle to the normal flow. The end of my Dynomax is tucked in a couple inches behind the rear bumber cover. With the Supertrapp it just pushes the hot gasses right into it. If you were to fab an extension that moved the Supertrapp back behind the cover you'd be OK. And if you're just moving the car around the house you probably won't make enough heat to melt anything anyway.


Chris Ludwig
08 ITS RX7 CenDiv