Cutting a few dB off your exhaust

[Jackal]

Hi All. I've never been in a position where my exhaust may be too loud to run, and I'm looking for proven methods that you may have used to quiet it down a bit. This may be all for nothing as everything in my ride sounds loud and the car has very little in the way of sound deadening. I just don't want to get to an event an hour away and realize that I can't run after the first lap.

In a perfect world I'd like a quick way to quiet it down a few dB, but have it reversible.

My first thought is a sheet of tin rolled into an oval (the shape of my tip) held on with a hose clamp of some sort. The business end would have a metal grill or expanded metal over it, and I was thinking of steel wool to fill the makeshift canister.

Thoughts?

[Reijo]

Google "SuperTrapp" mufflers ... best solution ... quick to put on and you can take it off at the end of the day.  We used to use one for every event in San Diego (93db) when I lived in LA and it worked like a charm ... one bolt to screw on/off ... very quick ... 30 seconds.  Very slick.

You can see Shawn Bishop about one at rallysport.ca

[nnywg]

Also talk to Ryan - he's got the same motor in the mr-2/s and had to make some changes for noise that have worked well.

[JamesTCallaghan]

Steel wool and mesh to hold it in worked for me.

[MurrayPeterson]

I used a SuperTrapp on my S2000 and it killed my cabin drone (and the loud exhaust) beautifully.  And I had Cam whip up a quick release clamp so I could remove/install it in a few seconds.  Not the cheapest solution, but the most configurable and really is easy to take on/off.

[Jackal]

I used a SuperTrapp on my S2000 and it killed my cabin drone (and the loud exhaust) beautifully.  And I had Cam whip up a quick release clamp so I could remove/install it in a few seconds.  Not the cheapest solution, but the most configurable and really is easy to take on/off.

Do you have any shots of what your assembly looks like?

I'm looking for creative ideas as my exhaust is inside the car, and doesn't have anything exposed except for the tip. This limits me from using a clamp on pipe without dropping the whole rear pan/diffuser.

I'll be borrowing the decibel meter to make a few passes and see if its an essential mod for me or not.

Here's a pic of what I have to work with currently.

Untitled by Duane Jacka, on Flickr
 

[MurrayPeterson]

Sorry, but no pics I can find.  A T-clamp isn't going to work with your oval exhaust tip, but I am pretty sure that nothing else will work either.  Perhaps Cam has some suggestions.

[Ryan S]

If you have trouble with meeting sound, I can recommend some muffler replacements that have worked well on the MR2 with the same 2ZZ engine (albeit cammed and with some other goodies, but the recommendations should still be good ones).  I cannot comment on what the stock sound level will be for your car, but it is rare that a stock car is over our limit.  I just had issues as the original exhaust for the 1ZZ obviously would not work, and the tubular header and exhaust package I put in with the 2ZZ had a poorly selected muffler.

[Jackal]

If you have trouble with meeting sound, I can recommend some muffler replacements that have worked well on the MR2 with the same 2ZZ engine (albeit cammed and with some other goodies, but the recommendations should still be good ones).  I cannot comment on what the stock sound level will be for your car, but it is rare that a stock car is over our limit.  I just had issues as the original exhaust for the 1ZZ obviously would not work, and the tubular header and exhaust package I put in with the 2ZZ had a poorly selected muffler.

The exhaust I run isn't stock,  but came with the car as I got her.  The Exhaust is the Larini SC Sport for the supercharged Elise, this included the high flow cat.

[Ryan S]

It might be a case of seeing how loud it is when you get there.  If it is too loud, you can pull the connector for the VVTL lift solenoid, this will keep the engine on the 'small cam' with a rev limit of 7000 and you can at least run for the rest of the day (I had to do this several years ago, and yes it counts as a mechanical change and isn't harmful to the engine). 

If it is over, IMO the best solution would be going back to the OEM exhaust.  But I can recommend some mufflers that could be welded into what you have, depending on your available space.

[Rubicon]

I ran the Larini SC Track exhaust on my 2010 Elise SC and it consistently ran below 90 db - usually 85 -88 db

[Jackal]

I ran the Larini SC Track exhaust on my 2010 Elise SC and it consistently ran below 90 db - usually 85 -88 db

Given that it's all relative to what you've experienced, did it seem excessively loud in the drivers seat?

[Rubicon]

No. I previously had a Lotus Stage 2 exhaust which was terrible. The Larini was relatively quiet in the cabin with no droning on the highway.

[Jackal]

No. I previously had a Lotus Stage 2 exhaust which was terrible. The Larini was relatively quiet in the cabin with no droning on the highway.

I guess it's just me then.  My BMW was quiet to begin with,  but in the cockpit it was even more so.  Over the winter I've become used to the limo where I can't hear anything unless it's WOT (Even then it's really faint). I've been told not to worry about it, and it's just that the engine is 18 inches from my head.

I'll borrow the decibel meter this week and run some tests to see where I'm at and panic if I need to after that.

[Jackal]

Since sound was a topic this weekend,  and I have yet to show my setup off,  I thought I'd follow up here. 

I needed a way to cut some sound but allow the needed flow from my exhaust.  Here is my solution.  I added an external basket to the exhaust instead of stuffing it.  The reasoning was that stuffing an exhaust will create back pressure as the exhaust has nowhere to go but through the stuffing,  so an external basket would allow me to increase the span the exhaust can vacate from the exhaust tip while only incrementally adding to back pressure.

I made a double layer basket and sandwiched in the steel wool around the whole assembly.  This layer really doesn't need to be too thick,  and I have actually found that this alone got me where I needed to be sound wise. I can also fill the basket loosely to add to the sound diffusion. 

I safety wired the basket together and also wired the hose clamp to the basket,  so that it will stay on the exhaust as I want it to. Adding the basket or adding stuffing can be done in minutes between runs and allows for incremental changes as needed.

Bucket by Duane Jacka, on Flickr

Bucket by Duane Jacka, on Flickr

Bucket by Duane Jacka, on Flickr