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View Full Version : 2007 modding season - exhaust



snowbird
09-15-2007, 09:14 AM
EXHAUST:

Two years ago, I installed a Kooks set-up (SS headers, mild steel X pipe and Magnaflows mufflers). Fine kit but the noise and cockpit drone level of the mufflers was way too much for my corporate taste. So I had tried 3 other different mufflers to no avail. My finished set-up were standard stock 2004 Mustang Cobra mufflers. I had thrown the towel in 2005 and was annoyed since.

This summer, the mufflers started to be noisier as they were slowly cooking off by the inside so I had to do something about it. The mild steel X pipe started to rust pretty bad and I needed some room in the trans tunnel for an aftermarket DS. Finally, the fact that there were still some 2 ¼” sections of piping was the final excuse for a rebuilt.

So I bought a used 2 ½” Mustang SS exhaust and some 304 SS tubing and started to redo the thing section by section since there’s no mandrel bent machine around where I live. A pretty long process as our rear suspension arms are different than Mustang’s and different from left to right.

I home made a shortened and spreaded X legs to clear the future DS and added some custom length 13” –17” overall Stainless Works smooth tube mufflers as resonator in the trans tunnel. Tight fit but the solution about drone, finally !! I then recycled some Super Turbo I had on a shelf and then completed with trued 2 ½” pipes all the way to the MEGS. The Megs were 3 bolts flanged for added noise reduction possibilities and I kept the front cats section for next year to let my welder cool off a bit as he was becoming nuts!.

The results are on par with my objectives: No more idle vibrations (the different sizes and thicknesses of SS seems to have cured that), almost 100% drone disappearance ( when you turn the head in the cockpit, the noise come clearly from the trunk) and full SS 2 ½” exhaust. The funny thing is that those “resonators” don’t cut the outside noise at the rear. They seems to perform only on the cabin noise.

Here’s a few pics.

sabtaj1
09-15-2007, 09:23 AM
Very Nice!!!!

Pat
09-15-2007, 11:54 PM
Cabin Drone. Some informed owners have used Meg's delete tips and extended the pipes out a couple of inches. Your post didn't mention this.

snowbird
09-16-2007, 04:17 AM
Pat,

I had tried the extended tip trick but the amount of gain was minimal for my taste. Remember, Kooks headers and 2 high flow cats really wake up the car on the noise level. The drone is just coming from under our feet and use the cabin as a sound box since our car have minimal sound insulation. I have tried 3 different mufflers and they all sounded quite a bit. I believe the answer is not in the mufflers or the tips (for my taste). I really wanted to get rid of the drone since the car naturally, with auto trans, is always in the 1800 - 2200 rpm range in traffic ==> on the drone spot !

The SS Smooth tube 3 1/2" from Stainless Works have a double core 2 1/2" so there are about 1/2" stainless wool packing. They don't age fast like others. They measure their stuff by the inner diameter (ID). It's doesn't look like much but there are also hundreds of tiny scoops about the size of a pencil eraser and the shape of a '55 Thunderbird hood scoop. The scoops are machined on a rotation basis, like screws fillet. The sound waves are forced in. That type of muffler is a lot more effective than tube with just spaguetti screeen holes and fiberglass, burning prone one's. I did my homework !!

When you install them, you have the choice of putting them against the flow for more silencing or within the flow (reversible). I went against for the biggest gain. The sound waves are forced in but the exhaust can still travel with minimal backpressure since the scoops are spaced about an inch apart.

They are sold as mufflers at 24" long (20 " core) but I had only room for 13" core in the DS tunnel since I wanted to use them as resonators, before the 2 - 3 chamber mufflers. So I ordered custom lenght 17" overall and cutted the 2 - 2" end tips at 1/4" before welding them in.

This is IMO the solution for drone with headers and such.