Oh no a 3" vs 2.5" exhaust question on vr4.org

[Brunoboy]

the dynomax have many mixed reviews and a lot have said it makes a rattling sound because the valve gets loose. This is a setup I would be interested in if i knew I wouldnt have that problem.
-Shane

 

[trunks]

I've read to add some extra welds onto the body and then they should hold up.

There's lots of conflicting information, but it seems 3" high flow cats will only flow around 570 cfm. So the fact that I have one on already makes me think my 3" exhaust is limited anways.

My latest super genius idea is to keep my 3" downpipe with cat in it, then reduce to 2.5" with a very long resonator. Then at the rear go back up to 3" so that I can put a dynomax 17769 super turbo hemi muffler on there with the 20" body. Since the pipe, cat, and muffler are all testing around 560 cfm range it should be the quietest set up with the least loss in hp. I like welding so no biggie there. I'm even considering a resonated tip to finish it off.

 

[RayH]

The Dynomax Ultraflos with the oval cross section are the quiet ones. The cylindrical ones drone a bit especially at highway speeds. At least this seemed to be the case with a 2.5" exhaust.

 

[KiNgMaRtY]

If you are going with the 3" DP and still keeping a 3" Muffler, than just keep the 3" midpipe. I don't think going with the 2.5 in that section will make much of a difference if any

 

[trunks]

So I went ahead with my plans but kept it 2.5 all the way until the muffler where I increased it to 3" to maximize the flow of the chambered dynomax super turbo muffler which is huge and barely fit. Here's a pic after welding the biggest resonators I could fit along with a 100 cell high flow cat. I'm waiting for the clear coat to dry but will report back on the noise levels.

 

[trunks]

So I haven't been able to drive it much since f*ing around with the suspension. It's a lot quieter for sure but you do still hear it when you get on it. I can't even tell if it's idling inside the car when I come to a stop. The only problem is I can now hear other sounds that were previously over powered - fuel pump and differential. I forget to rev it from a stop and the thing just rumbles to no end like a semi trunk until the rpms get over 2k.