Exhaust Recommendation

[R31Nismoid]

just shove the biggest muffler or mufflers under it you can, 16-18" x 11-12" x 6-8" on the back with your existing middle muffler, if its not quiet enough make the middle muffler bigger, hotdogs don't do much in the way of noise reduction and your 5" rear muffler isn't what I would call a big muffler.

my 3" exhaust was legal (90db as tested by the rta and my engineer) and my 3.5" exhaust is just the same or quieter. the loudest thing when you put your foot down is the pod filter/Turbo.

Exactly.

My 3.5" on my GTS-R is 91-92dB @ 5100rpm, so it's just over legal - but close enough for it's size and the added RPM of a 26.

Has two custom made mufflers, big as possible - job done.

[R32Abuser]

To get rid of drone you would be best off tuning a Helmholtz chamber to cancel the unwanted exhaust frequency. Larger muffles will make the whole frequency range quieter but the chamber would target the frequency you want cancelled.

The maths behind reflective sound cancelling is quite complex so its best to make an adjustable length setup if you can. I doubt many muffler shops would help you with it though.

With regards to sizing, you would probably gain over 20kw going up to 3.5 inch at the moment, I gained 30kw but deleted the cat also.

My only concern with going a 3.5" exhaust system (cat back) was that it would make it louder. That being said, Im not that concerned with the power level of my car ATM anyway. The car is more traction limited more than anything and is plenty fast for the street.

just shove the biggest muffler or mufflers under it you can, 16-18" x 11-12" x 6-8" on the back with your existing middle muffler, if its not quiet enough make the middle muffler bigger, hotdogs don't do much in the way of noise reduction and your 5" rear muffler isn't what I would call a big muffler.

my 3" exhaust was legal (90db as tested by the rta and my engineer) and my 3.5" exhaust is just the same or quieter. the loudest thing when you put your foot down is the pod filter/Turbo.

I was thinking (pending packing/sizing restrictions) chucking the following on to replace the middle resonator:

http://www.magnaflow.com/02product/shopexd.asp?zone=main&id=10009

Then, Ill see how it is after that. For the sake of around $100-150 for it plus installation, Im hoping it will do the job.

Thoughts?

[sydking]

Might have to revise mt 3.5 cat back with signle hooker muffler

Is there anypoint having a cat back that is bigger then your dumps and front pipe, As they woul dbe the first point of flow.

[GTSBoy]

Yes, there is point. The less restriction in total, the better. But of course, best use of the large back end is to connect it to a large front end.

[TiTAN]

My only concern with going a 3.5" exhaust system (cat back) was that it would make it louder. That being said, Im not that concerned with the power level of my car ATM anyway. The car is more traction limited more than anything and is plenty fast for the street.

I was thinking (pending packing/sizing restrictions) chucking the following on to replace the middle resonator:

http://www.magnaflow...e=main&id=10009

Then, Ill see how it is after that. For the sake of around $100-150 for it plus installation, Im hoping it will do the job.

Thoughts?

you may find you run into space issues trying to fit a 22" long muffler under it, 18" is already taking it close to the axle/diff in mine.

[ClutchBurndout-:(]

got 3" to 3"cat, 3.5 straight no mufflers, is semi quiet, just a hotbog and cannon

Edited May 14, 2012 by ClutchBurndout-:(

[Rolls]

Two of the biggest mufflers you can fit under there, done.

[R32Abuser]

For any of those interested, I took some measurements under my 32 GTST for muffler sizing:

Rear Muffler (largest size possible without interference)

18X12X8

Middle Muffler

16X11X6 (CENTRE-OFFSET)

Keep in mind:

- Depth of each muffler will depend on how much ground clearance you need/want

- Main limitation with the centre muffler size is tailshaft clearance. Running a "centre-offset" muffler appears to allow largest muffler possible without creating an interference.

[butterfly effect]

My AES 3" , 7" diam. rear muffler with a resonator is quiet. I havn't db'd the combo but I expect it to be legal. I did some tests recently and found that the combination of a 3" perforated tube fitted to a 7" diam. housing is about as good as it gets. If the housing is ovalised so the crosssectional area is increased resulting in more packer nothing is achieved in the quietening department. If the length is increased it will become quieter but there is a limit.

[R32Abuser]

"My AES 3" , 7" diam. rear muffler with a resonator is quiet. I havn't db'd the combo but I expect it to be legal. I did some tests recently and found that the combination of a 3" perforated tube fitted to a 7" diam. housing is about as good as it gets. If the housing is ovalised so the crosssectional area is increased resulting in more packer nothing is achieved in the quietening department. If the length is increased it will become quieter but there is a limit."

If it does nothing for noise suppression, then what does increasing the cross-sectional area do?

I might sound sceptical, but I just don't see how having more material to absorb sound will not affect noise suppression...

Edited May 30, 2014 by R32Abuser

[butterfly effect]

Ok. I have a testing apparatus. I will put a pic on soon. What it comprises of is a large garbage can ( plastic} with a 7" diam muffler inside it surrounded by rockwool. Inside the muffler is a 6" diam speaker. The exit pipe from the muffler also exits the top of the garbage can. I then ( via a cd) excite the speaker with an exhaust noise sample relative to the vehicle the muffler is to be fitted to. The muffler to be tested is connected to the exit pipe coming out of the garbage can. I set my db meter to record the max reading. The reading I got for a 7" diam muffler was the same for a 7" deep but 9" wide ovalised version so it appears that the packer had maxed out initially. Actually I was surprised. They were identical length. I think the same thing will happen for a 3.5" bore muffler at 8" diam.

[butterfly effect]

Pic of absorbtion muffler tester.

[R32Abuser]

? Forget to upload?

Edited June 1, 2014 by R32Abuser

[butterfly effect]

Try again.

[Rolls]

Looks cool but I wonder how accurate it is, can never beat a proper db test on a car, a speaker just isn't going to create all the same highs and lows that you can't hear with our ears which get absorbed as well.

Edited June 4, 2014 by Rolls

[butterfly effect]

This technology to test absorbtion , non baffled mufflers , has been around since the 1950's. It speeds up the development process to find the optimum ingredients to suit the application. Obviously there could be a variation in the real world but it is surprisingly accurate. It works for me.

[Manuel Kasko]

Does it matter if the muffler intake and exit are offset?

I purchased the following from magnaflow before checking about that.

[Ben C34]

It's definitely not bad.

It means they are usually much easier to fit under a Skyline.

[GTSBoy]

All that happens there (assuming it's straight through) is that the pipe has two gentle bends so it goes between inlet and outlet. It's not like those other mufflers with lots of up and back triple pass bullshit. It's just a convenience thing for fitting it into a given space.

UNLESS you're talking about its muffling qualities...in which case it might be a bit different because one end of the internal pipe is much closer to one side wall than the other. But I wouldn't be worrying about it!

[R32Abuser]

Does it matter if the muffler intake and exit are offset?

I purchased the following from magnaflow before checking about that

I purchased a 16" X 8" X 5" magnaflow item for $200. 3in inlet and outlet and I can guarantee you its a straight through muffler. Pretty much looks like the above ^^^

My reasoning for going this muffler was that it was the largest middle muffler (cross sectional area and length) I could find without going custom. As per my post above, you can fit a slightly bigger item under the car but I was unable to find suitable off the shelf items without going custom. Custom = $$$...