Single Exit Exhaust Noise Control

  • Intro

    So as many of you already know, having a single exit exhaust is LOUD. Almost too loud depending on where you live/work and if your gf/wife has sensitive hearing lol.

    Anyway, I have always liked the look of a single exit. It has a nice aggressive look to it when done right, and the weight savings are an added plus when you consider how heavy the OEM exhaust is.

    After running a single exit exhaust paired with the BHR midpipe for a while, my love for the tone was soon suppressed with the random looks and the comments from friends about how loud it really got when I stomped on it. Driving through the parking garage at work was also funny depending on how sensitive people had their car alarms set. So I tried a few things out

  • CC Inserts

    Source: Exhaust - CC Inserts - Car Chemistry, Inc.

    These things are nifty, and their price was really nice. I went ahead and ordered one of the 3" ones, and was actually caught a bit off guard when i felt it in my hand. The darn thing is pretty heavy for its size. I will weigh it when i get home and will get some exact measurements. I tried installing this two places. First, I installed it in the front section of the intermediate pipe (basically right after the midpipe). Didn't really do a darn thing for noise, but totally snuffed engine output a bit. Wasn't noticable at all during normal driving, but once you hit an on-ramp and really got on the throttle, you felt something "holding you back".

    The next thing I did was move it further back to the axle back portion of the single exit. No dice. Although it didn't really kill off the performance like the former test did, it also didn't really do anything for sound. There was a slight muffle, but nothing that really warrented the need to have something extra in my exhaust.

    This was ultimately removed.

  • Dynomax Race Bullet

    Source: Dynomax® Performance Exhaust | Mufflers | Race Bullet Mufflers

    Man these things are popular and it is thanks to its design. Essentially a straight through design, where the inside of the canister matches the size of your inlet and outlet diameter. The perforated interior with fiberglass packing is what aids in noise suppression.

    The design of the intermediate pipe of the single exit exhaust allowed me to mock up something which allowed me to place this muffler in my flow path. This will come as a shock to some, but probably not to those who have done exhaust design on these cars, but the bullet actually made the exhaust louder lol. What it did do, is remove the lows from the exhaust, but left the highs. This gave the impression of a louder exhaust. This was pretty much counterintuative to what I was looking for. Not to mention that you can expect the packing to become obliterated after some miles.

  • Auger Style Inserts

    Source: Dynatech Auger Style Muffler, 11 x 3 Inch - Speedway Motors, America's Oldest Speed Shop

    At first glance some of you will be able to recognize these inserts. They are very similar conceptally to some popular resonators. Now let me preface this review by saying this: This really isn't an alternative to a Moroso (and [I]others[/I]) style muffler. The reason being because inserts like this lack the one characteristic of the resonators that prevent it from harming performance, and that is the enlargement of the chamber. For example, a moroso style muffler spans out about an extra inch over the inlet/outlet diameter.

    Now with that out of the way, I was tempted to give this a shot. At the price, I figure 'why not'. Better than listening to speculation from those who haven't tried, and if anything, I would try/fail/educate.

    Once i recieved this thing, wow ... super light. Not going to lie, in my hand it felt similar in weight to the insert that was a quarter of its size lol.

    It isn't perfect though, and you NEED to have some time, a grinder, or some vice grips. The reason being that when it says it is 3" ... it is seriously 3". It just wont slide in without some finesse, or, if you want to drop it in to weld it, you surely need to grind down the edges a bit to allow for a smooth fit.

    I installed this at the axleback of the exhaust, right before the muffler. The reason being that A. Folks like BHR have gone to great lengths to strengthen their resonators against the heat of a rotary, you can tell by looking at the welds. Knowing that, I wanted this as far back as possible. Also, being far back, conceptualy, would present the least restrictions as the exhaust velocity would have tapered off a bit after going through my midpipe and right before hitting the muffler. I wouldn't recommend placing this insert any further upstream.

    Now, all that aside, first fire up, DAMN, a hell of a lot quieter. Now in my head I had the "been here before" feeling. So I took her for a drive. No more cabin drone, and no more super loudness under normal driving. Not done yet though as the true test is really throwing it on the highway and hammering it.

    On the drive to work today, completely different sounding exhaust, in a good way! Still had that nice deep roar of the single exit, without the booming loudness in the cabin. At WOT, no measurable drop in performance from the butt dyno (nothing like what i felt with the CC insert), while still maintaining that awesome rotary whine.

    Of course, time will tell, but hopefully this thing lasts. At the price it can't be beat.

    (not my pic, but exactly what mine looks like when viewed from the axleback inlet)

    Here is where the auger style insert was installed

  • Auger Style Video Clips

  • Auger DB Readings

    App Used: deciBel

    Test 1: 11ft from muffler exit, phone along exit axis

    Test 2: 1ft from muffler exit, phone along exit axis

    Test 3: In cabin, windows open, phone close to ear

    Test 4: In cabin, windows closed, phone close to ear

    *All photos taken during engine idle after 30 mins of driving.