cncfan

Recently I decided to take the plunge and upgrade my 2005 V6 Mustang to dual exhaust with GT Takeoffs. I've had a single GT Takeoff on my car for quite some time now and was always satisfied with it. So I eventually went to my shop and they insisted on fabricating me a catback system. Here's a photo of what they did underneath my car:



As a result of this system, my car produces more drone than I ever imagined a dual exhaust system with GT Takeoffs would ever do. That's the whole reason why I chose GT Takeoffs in the first place. Another problem is that my car idles in the most unattractive manner I've ever seen a car do. It has this mellow popping and shaking sound that I have no idea what I need to do to get rid of. Any advice on what I need to do would be greatly appreciated. I want to get these problems fixed as soon as possible. I believe the issue has to do with the piping.

aaquib1992

Okay so the number one thing that sticks out here is that you have no cross-over pipe. Straights do not sound good on a V6, you need a cross over like an X or H pipe after the cats, which is probably a huge part of the problem.

Second it looks like you still have your cats (pic is blurry) but there could be an exhaust leak somewhere, is the shop pretty good? Because I would have them go back over all their welds with a fine tooth comb.

cncfan

Thanks for your response. We checked out all the welds and that didn't seem to be the problem. Yes, the cats are still there. I'm considering to go down there and tell them to weld a pipe connecting the 2 together to create and H. Hopefully that'll be the solution.

rls82959

The popping/spitting sound is because you don't
have an X or H pipe.
An increased idle rpm (825) can get rid of that, or of course
get an X or H.

For the drone, check where the drivers side pipe goes
over the rear axle. Is it rubbing or really close to the under belly
of the car? Is that driver side pipe rubbing anywhere?
That might be your drone.

cncfan

Is there a chance that getting an H pipe alone might fix the drone?

aaquib1992

No problem! Okay so exhaust leak seems to be out, so it's just the fact that you don't have a crossover pipe.

I am not 100% positive if that will fix all your problems but if memory serves me correctly (it's been a long time since I read this) the 4.0 is an even firing engine so without that cross over the separated exhaust can sound very funky.

IMO it should take care of the drone, because if there are no leaks, stock cats, and you have a cross over, then it should be just like any other 4.0 with GT take off duals, and mine does not drone very much at all.

Also, take a look at your driver side muffler and check out how they secured that to the car. If they used some crappy exhaust hangers that could also be a factor in the drone/rattling or any other noise/vibration problems you have.

cncfan

Today we put a crossover pipe on (H) and took care of some hangers that were badly put on. One problem was fixed whereas the other persists and is practically worse. The idle is fine now, sounds great, but the drone for whatever reason is a lot worse. At this point I'm done with going to exhaust shops. The shop I went to to get the H pipe and hangers taken care of was a Midas. Is there anything else I can do to get rid of the drone?

tx_zstang

I'd of told you the H wasn't going to help. I ran w/o any crossover (on purpose) for several years. The mufflers may have a little drone, but not that bad.

As far as the idling, you probably need to just give the car time to relearn itself, or force the relearn by "clearing dtcs" or disconnecting the battery for 20 minutes. The change in exhaust flow may be fooling the engine on there being a problem, and is at a minimum different breathing characteristics.

aaquib1992

I get a very little amount of drone around 2-3K RPM but that's it. And it looks like we have roughly the same setup.

Does it drone at all RPMs or just a specific range? Could just be that you got unlucky and are matching a resonant frequency somewhere.

cncfan

It drones at the 2-3k RPM range. It's pretty annoying, but I guess I'll have to deal with it. Some people told me as the mufflers break in the drone will not be as potent, but I don't know if that's true.