Suggest cheap+good means to quiet that E30 with the 3" exhaust?

The Monkey See E30 Chumpcar has a 3" pipe from the cross over all the way back to the rear bumper where it's at least turned down. That is delightfully obnoxious, and way over ChumpCar's noise rule, but when racing at a track that regularly hosts top fuel dragsters, these things are thankfully overlooked.

However, the next race is at Atlanta Motorsports Park, and from what I understand, they are not as friendly towards earsplitting uncorked e30's running wide berking open at seven grand. 92db, max, buddy, no excuses.

Suggest for me something to weld to the end(?) of this 3" pipe. Lets shoot for a <$80 budget. Adjustable would be cool, like a supertrap, but not really necessary. I would like to be able to hear my own exhaust note through my helmet over the noise of the cars around me (also presumably limited to 92db)

Cheap "turbo" muffler. I prefer Walker/Thrush/Dynomaax (same stuff, different name).

Like this http://www.summitracing.com/parts/sum-630130/overview/

Sounds like a job for a huge-ass cherrybomb...

http://www.jegs.com/p/Cherry-Bomb/Cherry-Bomb-Pro-Mufflers/772084/10002/-1

or a quieter option http://www.jegs.com/p/Cherry-Bomb/Cherry-Bomb-Turbo-Mufflers/769809/10002/-1

Was looking for their origional stuff, but looks like they have better options...

Might be cheaper stuff out there though.

Any sort of glasspack mounted in the middle with a chambered muffler mounted in the rear. I've had great luck with Super Turbo style mufflers as they are cheap and work really well at cutting noise. Other's have had good luck with Flowmasters as well.

You might also wander over to your local exhaust shop (the small mom/pop places) that work on diesel trucks and see if anyone has been in to upgrade their exhaust as there might be some take-off's you can scavenge to fit your car.

Of course a 3" exhaust seems a bit overkill on an non-turbo E30, but what do I know? It could be worse, you could be running a peripheral ported rotary. Those are notoriously difficult to keep quiet for long.

^^^ 3" exhaust was chosen based on material availability (was lying in the garage keeping the toolbox from sitting flush against the wall) rather than actual "need"

Cherybomb glass packs dont flow very well, you want the straight through, smooth perforated tube style, thrush is the cheapest most common one.

I was considering putting in a bid on these

http://www.ebay.com/itm/SUPERTRAP-3-ID-Race-Mufflers-w-Plates-/111174078511?pt=Motors_Car_Truck_Parts_Accessories&hash=item19e27dd02f&vxp=mtr&autorefresh=true

So I'd have one for the race car, and could make an identical exhaust for the "parts" car (formerly 16VCorey's daily)

But I hardly ever see Supertraps in Crapcan racing. Just the new cost? Would be kinda nice to be adjustable, so I can do something about it if I get a noise complaint.

The issue with supertraps is that once you get enough plates out to muffle well, you've really hurt the flow. I'd also recommend a super turbo style muffler with a fairly straight perforated pipe. We have an old borla muffler on our lemons Civic, and even on the vtec cam lobes at 6500 it keeps it fairly quiet, on a motor that can be quite loud.

The problem with supertrapps are that either they muffle effectively or they flow effectively. They don't' really do both too well. So expect to either make a bunch of power and noise or lose a bit of power and be quiet.

Stick a glasspack on there, about in the middle and expect to replace it after every race. It will kill the higher frequency noises.

Plop a chambered muffler behind it someplace and leave room for the tip to turn down and you should be fine and not lose too much power in process.

Get a Lobak and a chambered muffler

I've also read of putting a turn down, or even an "adjustable" tip on the exhaust so you can aim it away from the mic.

turboswede wrote: Stick a glasspack on there, about in the middle and expect to replace it after every race.

Wait, why is this? I was planning to use a perforated-tube glasspack for the resonator (and muffler) on my 'rolla.

+1 for turndowns though, that's a cheap and easy sound-killer with almost zero performance hit.

Glass packs tend to blow out the fiberglass packing in there, especially with lots of high temp, high flow use (ie. endurance racing). There are more robust designs, but they aren't as cheap. In the long run you'll be better off if you use a non-wearing muffler (not a glass pack).

Bryce

What about the glasspack-style mufflers that use stainless steel mesh in place of fiberglass that I was just researching in anticipation of such bad news?

The stainless steel mesh ones last a hell of a lot longer than fiberglass, but the stainless mesh does still wear away over time. Some of the decent ones that use packing material have a design that allows you to rebuild them. This is more common on motorcycles that have easier access.

Bryce

My suspicion is that louvered-core glasspacks are MUCH more prone to spewing their guts than perforated-core glasspacks. As much as i've heard stories about glasspacks losing their packing, i've never had one fail on me and i run them on turbo cars which ostensibly should be harder on anything due to heat cycling across a wider range (i would think). I've also only used perforated-core glasspacks, for flow reasons, but it also stands to reason that it'd be much harder for the packing to come out through the perforations than through the huge holes in a louvered core design.

Ive also run one each oval case and round case SS-mesh packed mufflers and i feel they also do a better job of sound reduction than a regular glasspack.

92db is really berkeleying quiet. For that you almost want a factory replacement muffler.

how about a $75 turbo...?

The other option for extreme noise-killing is to daisy-chain a E36 M3-ton of straight-through mufflers. There's a pic of Jeff Kiesel's Sprite running a ridiculous setup like this but I couldn't find it.

GameboyRMH wrote: The other option for extreme noise-killing is to daisy-chain a E36 M3-ton of straight-through mufflers. There's a pic of Jeff Kiesel's Sprite running a ridiculous setup like this but I couldn't find it.

I am also working feverishly to try and find that pic of the evo with what almost appears to have a freaking semi exhaust (with muffler) extension added to the back of it

What distance is the sound level measured from? Based on some calculators and very basic googling, apparently you drop 6db every time you double the distance. For example 116db at 3ft ends up being 92db at 50ft and 122db at 3ft ends up being 92db at 100ft.