I am running a 3in dp, Ultimate racing cat with a stock exhaust and it's still pretty loud when it idles....

 

I was running the stock catback on an HFC and megan dp. It was very quiet. With just a downpipe and drop in filter the car made 290hp/320tq at 25psi. This was with the stock cat. There was 0 top end though.

 

Look into the Corsa RSC noise cancelling mufflers. APR uses them on their GTI cat-back kits, pretty cool technology. Magnaflow also has the TurboXL baffled 3 chamber muffler that's supposed to be really quiet. Combine that in the largest size you can fit with a resonator and metal substrate cat, and it should come pretty close to stock sound level.

 

I saw a fully built 37R car make 400 whp on a low reading Mustang dyno through the stock catback (on pump gas), which is enough to trap over 120 mph. Of course when he opened the cutout it picked up something like 75 whp!

 

i would like to know this information as well because then it seems really stealth

 

http://www.maperformance.com/works-e...ffler-evo.html

 

I'm curious if it was the stock catalytic as the culprit for the 0 top end?

How was it during driving? Besides exterior noises how was the sound level inside the cabin with the windows up?

Interesting... But thats a pretty big turbo if I'm not mistaken. I'd assume that with something smaller like the IX turbo, green or red the HP difference would probably be less. Unless your pushing really high psi.

I would try that but its just too expensive for a stock exhaust.

 

I haven't dynoed since but i can tell you the HFC seemed to improve via the butt dyno. I could run more boost up top so it definitely helped.

 

Ok did some more searching this is what I found. I'm going to try and use this thread as an ultimate stock cat-back power info so that if some one searched it, they would find most their answers here.

https://www.evolutionm.net/forums/sh...d.php?t=235538
Video:
http://ru.youtube.com/watch?v=DQsMC_DyC_M

 

Any one know anything about this?

http://www.stainlessworks.net/cart/p...c94f03a15aca26

Stainless steel chambered muffler...

 

Ok listen up I got an idea.

Since the stock exhaust is only 2.25-2.5 inches in diameter. I figured why use a small diameter exhaust pipe and muffler with chambers when I can get a 3" one.

I'm going to put my Cobb exhaust back on my car and most likely order the 3" stainless steel chambered muffler from this site . http://www.stainlessworks.net/cart/p...c94f03a15aca26

Here is an image:

 

Any muffler experts out there?

Which would do a better job silencing from looking at the design. The top picture or this:

 

How about modifying the stock cat back (works stealth?).

I currently use HKS Silent Hi-Power w/t test pipe and modified stock airbox w/t works drop in. as far as noise, it isnt that bad but I would NOT want it any louder. You can definitely hear my exhaust from inside the car

 

Straight through designs (like Borla) generally will outflow chambered designs (like Flowmaster).

 

I'm in the same boat. LMAO! I've been through the RSR EX-Mag (Big Muffler) and have recently just removed the RRE Stealth-back from my car because of the f#$king noise. I now run my 3" downpipe with RRE Rallycat with stock catback and love the quietness, but despise the loss in topend power and turbo spool. I'm looking to re-install my 3" RRE piping but I need a muffler drum that's big as h3ll to mute the "rice." The RRE exhaust is probably one of the best Evo exhaust I've ever heard as far as having a muscular note without being too loud and making good power. But unfortunately, I DON'T want to hear it 80% of the time. I even went as far as installing a modified QTP electronic valve inline with the exhaust (sort of like the exup valve on most sport-motorcycles today), but the motor on the valve failed and I had to remove it. The system in that configuration was still too loud for regular cruising. I guess I'm getting old too. So BlueEvoIX, please keep me updated. If I find a solution on my own, I'll pm you.