mufflers

Vincent Keene · **Posted:** Wed Nov 30, 2011 4:15 pm

DickRasmussen wrote:

For you guys where the glasspacks aren't quiet enough, even with two in series:

How old are they? Any "packing" type muffler gets louder as the packing goes away.

SuperTrapps, Coastfab, Burnsstainless, etc mufflers can be repacked.

Summit sells SuperTrapps and the packing in various lengths and diameters.

Dick

Dick, ours were brand new. I'm telling 'ya, adding a second one (in-line) made no difference at all.

DickRasmussen · **Posted:** Wed Nov 30, 2011 6:51 pm

Vincent Keene wrote:

DickRasmussen wrote:

For you guys where the glasspacks aren't quiet enough, even with two in series:

How old are they? Any "packing" type muffler gets louder as the packing goes away.

SuperTrapps, Coastfab, Burnsstainless, etc mufflers can be repacked.

Summit sells SuperTrapps and the packing in various lengths and diameters.

Dick

Dick, ours were brand new. I'm telling 'ya, adding a second one (in-line) made no difference at all.

I wasn't doubting you. :lol:

Just hoping the problem was tired glasspacks. Longer glasspacks are supposed to be more effective at reducing noise so I don't know why two in series isn't doing the job. A bigger OD versus the ID allows more packing. That might be a help.

DickRasmussen · **Posted:** Wed Nov 30, 2011 9:41 pm

The GRM Muffler comparison was December 2010 issue. The article doesn't appear to be on the web site.

SimonWright · **Posted:** Wed Nov 30, 2011 10:44 pm

RichardNuss wrote:

SimonWright wrote:

Does it need to be inspectable? Just had my rally car inspected at a racer friendly station and even they wanted to know where my cat was.

Simon

In that case, why not leave the cat shell in place with the guts removed from it?

Ah, good question - in fact that's what we had for the first couple of years after the engine work. But Rally America modified their rules requiring that the cat be verifiable visually. So rather than add an inspection bung in the exhaust we put the cat right at the end of the tail pipe.

Simon

Bernie Baake · **Posted:** Thu Dec 01, 2011 9:35 am

Cats don't work at the cool end of the exhaust....so whats the sense of having it????
If you place a gutted cat in its original position at least you get the benifit of lower back pressure!

Vincent Keene · **Posted:** Thu Dec 01, 2011 9:41 am

Bernie Baake wrote:

Cats don't work at the cool end of the exhaust....so whats the sense of having it????

The sanctioning bodies want to appear to be 'going green'. I'm sorry, but motorsports are the exact opposite of going green, and I'm OK with that.

SimonWright · **Posted:** Thu Dec 01, 2011 5:56 pm

Vincent Keene wrote:

Bernie Baake wrote:

Cats don't work at the cool end of the exhaust....so whats the sense of having it????

The sanctioning bodies want to appear to be 'going green'. I'm sorry, but motorsports are the exact opposite of going green, and I'm OK with that.

Ditto. I rue the day when the rally sanctioning bodies demand oem exhaust. Hopefully we'll all be rallying electric cars by then. :roll:

Cash Davidson · **Posted:** Wed Dec 21, 2011 9:09 am

Cash Davidson wrote:

I'm working on the same thing for my V6 Mazda. I was thinking about coming from the headers into a single 2.5", then a muffler and a turn down. Maybe I should do an H-pipe, two mufflers and two turn-downs. Wadaya think? I have two of the "big manly" cherry bombs in the shed that were on the Firebird at one time - obviously, I never throw anything away.

OK . . . I'll take your collective silence as approval.

I'll start with the cheapest and easiest route: Gut the cats and leave the shells. Keep the y-pipe and replace the resonator with a single glasspack. Then add a 90 and exit the side of the car. We'll see how loud it is. :mrgreen:

TomFreeman · **Posted:** Fri Dec 23, 2011 11:48 am

I am NOT a "real" engineer, nor do I play one on TV...but I was thinking about the H-pipe and duals setup you were describing Cash. My only concern if you did choose to go the harder route is that with a stockish motor, you might not need all that pipe volume. Summarily, you might end up with not enough velocity and scavenging and make less power.

I'm certain there are calculations to see how much air the engine will move at X000 RPM, and what kind of piping diameter you'll need to support it...but I have no idea what they are.

Vincent Keene · **Posted:** Fri Dec 23, 2011 12:00 pm

FWIW, our team has decided to punt, take the car to the exhaust shop, and have a stock-ish one put back in place.

I guess we're all too old because it's just too damn loud.

Cash Davidson · **Posted:** Sun Jan 01, 2012 4:57 pm

Well, here's what I ended up with: I gutted the cats and kept the y-pipe and resonator. I added a small bullet muffler I had in the shed and a 30" chamber tube after that. Finished it with a chrome tip of course. All the pipe is 2.5" The stock 2-1-2 pie was 2.25. I'm hoping to fire it up tomorrow to see how it sounds.

JohnByers · **Posted:** Sun Jan 01, 2012 5:09 pm

I like that alot!

Jordan Normark · **Posted:** Thu Jan 19, 2012 9:48 pm

You may have already built your exhaust by now, but if not, I have some experience on the subject. I have been through several exhaust systems on various Miatas. On my street car I had a gutted cat with an aftermarket cat back, the gutted cat sounded terrible (hollow and tinny), so I welded a pipe through the middle of it.

On my spec miata I started with a staight pipe, much to the chagrin of fellow autocrossers. After that, I added a "cherry bomb"/glasspack to the end, but the exhaust was still straight, no turn down. This brought me under the legal sound limit at VIR, but just barely. It was nice to be able to hear my engine over the other guys I was racing.

Recently on my street/autocross miata I built a 2.5" exhaust with a Magnaflow muffler. The sound is nice, growly and deep and it is not as loud as a glasspack, but it could use a resonator since sometimes at certain rpm's it has a tinny resonance.

I will be at the test-n-tune in Feb if you want to take a look.

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