Adding Resonators to RPI GT catless system

[Raptor251]

As of right now I have the full RPI GT catless system on my car and it sounds really bad. I have the ringing/pinging and drone that everyone talks about. I know the new "GTM" mufflers are designed to eliminate the problems but I have heard it still drones.

I really love the power gain however! The RPI system makes great power and I'm totally sold. My gripe is the sound quality and honestly its a little bit too loud. I purchased another RPI GT front/x-pipe used for a good price with intentions of a mod.

My question is if I add resonators to either the down pipes or x pipe will it solve my sound issues? Do I have to replace the mufflers? Any thoughts or input? I called RPI today and am waiting on a call back but figured I'd pick the brains of everyone on here too! lol

Thanks

ps- I kinda have a thing for the cat-less smell Im sick I know

[pbonsalb]

Add 2.5 inch resonators either before or after the X section, or both (after like Challenge and both before and after like Dinan and Borla). Try Pypes M80 or other aftermarket mufflers. You could also fit an oval muffler where the primary cats would go, but I would put them later (like Challenge, Dinan, Borla).

[Raptor251]

Has anyone actually done this? Im really curious if it will clean up the sound and make it sound like it should!

[THE TECH]

Since any drone would have to do with their mufflers, I cannot clearly see why adding additional resonators/mufflers would change this fact. I can see that by adding additional restrictions inline that the flow downstream might change and the resulting exhaust coming through the rear mufflers would then change.

[pbonsalb]

Originally Posted by Raptor251

Has anyone actually done this? Im really curious if it will clean up the sound and make it sound like it should!

I am going to add 2 or 4 resonators once I receive the track pipe that I ordered. You will have to wait a couple of months because this is not a priority job for me and I have some other fabrication work to do first. In the meantime, ask Dinan and Borla owners whether they are happy with their well resonated track pipes, and what rear exhausts they are using.

A subsequent post notes that a lot of exhaust sound is attributable to the rear exhaust. I have found this to be true. With the same headers and trackpipe, I had a really loud exhaust with a B&B rear section and a very civilized exhaust with a replica Supersprint rear section.

In contrast to the subsequent post, however, I think you can reduce the noise that is going to your rear exhaust by adding resonators. The rear exhaust will then be muffling noise that is quieter to start with.

But I am not sure anything will make a really loud rear exhaust quiet. Quieter maybe.

[Dave07997S]

I had a Riss Racing xpipe with no resonators and I added 2 magnaflow 2.5" resonators. It really cleaned up the sound nicely, otherwise you will have to run a muffler that is designed to balance out the sound.

Dave

[Raptor251]

Anybody have any 2.5" resonators? I think I have a little exhaust project on my hands! lol

[Dave07997S]

Originally Posted by Raptor251

Anybody have any 2.5" resonators? I think I have a little exhaust project on my hands! lol

This is what I used for resonators..

[pbonsalb]

I would prefer something with a longer body if it will fit. A 6 inch body muffler is pretty small. I was looking at the Pypes MVR200S for $42 each from Summit or Jegs. I think the body is more like 9-10 inches.

[Dave07997S]

Originally Posted by pbonsalb

I would prefer something with a longer body if it will fit. A 6 inch body muffler is pretty small. I was looking at the Pypes MVR200S for $42 each from Summit or Jegs. I think the body is more like 9-10 inches.

Actually you want to keep it as small as possible, there is not as much room as you think. Also this is to act as a resonator not as a primary muffler.

Dave

[Raptor251]

I really love the dimensions of the OEM resonators. I think I could fit those in to the RPI system nicely. Anyone have an xtra set by chance??? Please!!!

[pbonsalb]

Originally Posted by Dave07997S

Actually you want to keep it as small as possible, there is not as much room as you think. Also this is to act as a resonator not as a primary muffler.

Dave

I disagree with the second sentence. The cats that are being removed are like mufflers. If you want the car to be quiet, you need to replace those muffling devices you removed. I will measure the track pipe before ordering the resonators; that may be the limiting factor.

[Dave07997S]

Originally Posted by pbonsalb

I disagree with the second sentence. The cats that are being removed are like mufflers. If you want the car to be quiet, you need to replace those muffling devices you removed. I will measure the track pipe before ordering the resonators; that may be the limiting factor.

Im just giving you my experience, to get it to fit under the car in the tranny tunnel is not as much room as you think. The secondary cats do act as a sound reducer for sure, but not as much as you think.

Dave

[per]

I have rebuild my rpi midpipes, with 2 mufflers and an x-pipe to get rid of the droning at 2000rpm.
I have milltek mufflers and are very pleased with the result, no droning, only a deep rumbling sound

[Raptor251]

Has anyone ever heard the GT system with any other resonated x-pipes? I'm trying to decide if I should attempt to add resonators to my x pipe

[Raptor251]

So I bought some resonators and did a little chop, cut, rebuilt on my extra RPI GT system. Im gonna do the install tomorrow when I have some more free time. I also swapped out the mufflers for the Fabspeed Maxflo axle back and couldn't be happier. There is no more ringing sound and very little rasp. Im hoping my custom x pipe will finish everything off. Dinan flash should be here Wednesday too!

[pbonsalb]

What resonators did you buy? I just ordered a pair of Vibrant 1792, which are 2.5 inlet/outlet with 12 inch total length. $48 each and I will probably pay $20-25 each for the tig welding since I have a mig.

[Raptor251]

UPDATE 11/15/11- I installed the new x pipe with resonators and the modified front pipes. The car sounds amazing. Almost no rasp at all, very, very little drone (only up a long steep hill on the fwy) and over all its not too loud for a full cat-less exhaust. This worked out really nicely and didn't cost an arm and a leg because I did all the work myself. I purchased the resonators from Lyons Muffler in San Marcos, CA. I honestly don't even know who makes them I just explained my project to Jim the owner and this is what he ordered me. As usual Jim was spot on, perfect fitment, amazing sound and looks really clean from the underside! I love Lyons!

On a similar note I have another complete RPI GT Header back with the X pipe and if some one is interested in having me set it up with resonators I would do it and let it go at a decent price. PM me about that, thanks for looking guys

[Tkiss]

so its a small mufflers installed or resonators?

[pbonsalb]

Yes. They come in 12, 14, 16, 18 and 20 inch lengths, depending on which company. That is the length from the end of the pipe to the end of the pipe -- the pipe any total as much as 6 inches so the muffler body is short. They are also small diameter, from 3.5 to 5 inches diameter depending on what kind you buy. For clearance to the car body and the ground, 4 inch diameter is fine.

[Tkiss]

and what about gains? does addition mufflers are bad for gains of the exhaust?

[pbonsalb]

Just about anything that is put in the path of the exhaust to reduce noise will take away some power. A straight through design muffler or resonator takes away the least power (and is probably the only kind of muffler or resonator that will fit in the x-pipe).