Hey guys,

Like most, I have the GT500 axlebacks on my 2014 6MT GT; I also have the resonators deleted w/welded-in 3" pipe. Everything else is stock.

Seems like before the car is warmed up completely or the first few blasts through the gears, I'll get a higher-pitched "rasp" or "bark" out of them vs. when warm. Anyone else have this issue? Any thoughts on what's causing it (dunno...fibers in the muffler chambers/cats doing something funky)? Just don't like sounding like a civic at any time...

 

My '11 CS has the same exhaust setup and does not have that rasp you describe.

 

well, usually resonators are put in place to tune the sound and eliminate rasp or drone. If you've taken out the resonators, then it's not surprising that you're experiencing rasp.

What was the reason to take out the resonators? the new baffled resonator designs aren't very restrictive, unless the inner diameter is smaller than the rest of the piping.

or could it be what you hear is a rattle?

 

The GT500's do not come with resonators and the same axelback stock. I never had the issue you are describing on my 11GT500.

 

I'm so glad that when I owned my gt500 aclebacks for a year, I decided against deleting the resonators as most folks here did.

Hindsight, my borla catback setup now has no resonators lol. But then again, it was engineered to be like that and boy, does it sound gooooooooood.

 

I have the resonators deleted and GT500 axle backs. I've had my resonators deleted for almost two years and have never had the issue the op is describing. Nice deep rumble 100% of the time.

 

What year axle-backs, dual or quad tip?

 

They are the Ford Racing ones...not off an actual GT500. Part # M-5230-MGTCA1.

 

No! Cold Start tone comes from the Heavens, my friend. You may have a rattle somewhere.

 

The stock resonators choke the exhaust down to 2" in side , i replaced mine with some 3" race bullets to get maximum flow and still get the benefits of a resonator.

 

the rasp is because you removed the resonators.

The reason the Shelby owner didn’t hear the rasp is the 5.4 and 5.0 are completely different. So even though the mufflers are the same: Headers on the 5.0 manifolds on the 5.4, different cats, different exhaust pulses, different firing order etc. They are not comparable in the confines of the OP's question. This is why the GT500 did not require resonators to meet NVH requirements.

The GT resonators do not choke down to 2" they go down to 2.5"

 

Borla must have really done their homework then. Their full catback (xpipe and ota pipes) remove the resonators, but have no drone... Rasp, I guess depends on what you mean by rasp. It's a "GOOD" rasp if anything.

 

The Borla muffler and GT500 muffler are different so they have different characteristics.
Also is the Borla piping 3.0" vs. the stock 2.75 because that changes the tone too