Making an Exhaust Silencer - Advice Appreciated

[Chuck1986]

First a little background info:
My Eclipse has several aftermarket performance parts: Headers, 2.5" Borla exhaust, downpipe, intake. I was very pleased with the incresed acceleration and improve fuel economy I got, but I'm very disappointed with the noise these parts make. It's nothing loud enough for the cops to stop me, but it can be annoying at times.

With that in mind, I bought a silener that is inserted into the muffler to baffle the noise a bit. I like its effect so far, but I was just wondering, would it be beneficial to drill 8 holes in it? (See picture.) I'd like to drill the holes because I think the silencer's tiny opening coupled with my exhaust's thick, 2.5" piping is causing MASSIVE amounts of backpressure. My question is, will drilling those eight holes FURTHER aid in its job of decreasing sound output? (Since the airflow will have extra surface area to escape.) Any advice/opinions are very welcome and thank you very much in advance!!

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[Gary Allan]

I don't have a clue ..but I envision it "fluttering" (phhhhhffftttt_). The noise that is not unlike some plugged exhaust with a few holes in it. I could surely be wrong.

How about just extending it to just shy of looking strange, open it up to the former opening, and installing some additional sound deadening material?

 

[Quest]

You'll have to experiment a bit in order to find out.

Lowering back pressure is mood (IMHO) if you don't get the resonance frequency right, for max. exhaust scavenging (max. pwr output per intended design) could only happen at the peak of the resonance frequency of your exhaust system (for N/A engines, turbo/supercharged is a different beast).

 

[MrCritical]

Get the longest free flowing muffler you can.

 

[Drew99GT]

Do you have a Borla catback, or a custom system with a Borla muffler?

My advice would be to get the biggest Magnaflow resonator you can get if you ditched the factory resonator. That will cut out the raspiness and interior resonance and give it a much more mellow tone, without sacrificing any performance (it's straight through perforated core)

 

[Drew99GT]

http://www.borla.com/applications/lookup...k_System/14906/

Is that what you have?

 

[NYEngineer]

You could add a Supertrapp muffler right on the end of the tailpipe. It uses diffuser discs to send the noise 360 degrees out the end of the pipe instead of straight back. More discs equals more flow and a louder note, but since it would be the second muffler in the system, you could probably use quite a few.

 

[Chuck1986]

Originally Posted By: Drew99GT
http://www.borla.com/applications/lookup.aspx/2001/Mitsubishi/Eclipse/GTStainless_Steel_Cat-Back_System/14906/

Is that what you have?


Yes, that's exactly what I have.
I paid $500 for increased fuel economy, better top end power, and tons and tons of noise unfortunately. Bad deal.

 

[Chuck1986]

Guys, I appreciate the advice very much!
But I'm not looking to spend the $$ to get change out the muffler. (I'd also have to factor in the installation cost.) I've already spent more than I can afford on modifying this car and I just want an easy, do-it-yourself fix...so first I'd just like to know if I drilling the holes in the silencer will help any.

 

[5cylinders]

Drilling holes will make it louder.

 

[XS650]

Originally Posted By: 5cylinders
Drilling holes will make it louder.


Bingo, and sticking a restriction in the end of the pipe to make it quieter will make power worse than the stock muffler.

 

[5cylinders]

probably the cheapest and easiest way to make it more quiet, is to add a cheap - straight through glasspack style muffler to the exhaust system. These are not expensive, and if you don't do it yourself, it shouldn't be expensive to have it done. I assume, for a variety of reasons, it is a turbo car?
Anywhere after the cat converter you can add the glasspack.
3 basic ways to kill noise - baffles, restrictions, and / or sound deadening material. Baffles, and restrictions hurt the performance of an engine.

 

[Chuck1986]

Originally Posted By: 5cylinders
probably the cheapest and easiest way to make it more quiet, is to add a cheap - straight through glasspack style muffler to the exhaust system. These are not expensive, and if you don't do it yourself, it shouldn't be expensive to have it done. I assume, for a variety of reasons, it is a turbo car?
Anywhere after the cat converter you can add the glasspack.
3 basic ways to kill noise - baffles, restrictions, and / or sound deadening material. Baffles, and restrictions hurt the performance of an engine.


I was thinking about splicing in a glasspack after the cat (they sure are cheap.) It does a good job reducing noise eh? I've always thought they were basically straight-thru "mufflers" that hot-rodders use, which are known for noise.

 

[5cylinders]

Well, I wouldn't say it does a "good job", but you spent a lot of money on a nice exhaust, and you don't want to loose the performance you just paid for - That pretty much only leaves one option that I'm aware of. I'm no expert, but I've done a lot of reading on the subject. If I were in your shoes, certainly that would be my next step. Measure the longest straight piece of exhaust pipe, and buy the longest glass pack that you can splice into the system. Is the muffler you have now at the very back of the exhaust system?

 

[BuickGN]

We did that on one of the turbo cars that droned a little. It had a test pipe in place of the cat. Measured the test pipe and ordered a straight through muffler of the same length and the drone was gone. Very effective and doesn't hurt performance.

 

[Drew99GT]

It already has a huge resonator though with the Borla catback. I'd look more at the muffler. Magnaflow makes some larger muffler that are polished stainless with integral tip that I know would quiet it down. Heck, I'd simply get a magnaflow resonator and muffler in place of the Borlas; Borla has always been known to be a bit on the louder side.

 

[Steve S]

The holes will increase the noise.I had something close to it on the headers of my last boat.