With my car less than 24 hours old, I bit the bullet and had a cat-back custom exhaust made for it. For those who are interested in what exactly I did, read on...

Standing under the car while it is on a lift, you will see that two exhaust pipes come back from the cat individually. They then form an "x" type crossover before continuing back to a large suitcase style muffler. After the suitcase, they continue separately back to a sport where each has an additional individual muffler sandwiched into the void in the rear quarter before terminating in an exhaust tip.

The torch went to the suitcase muffler first and individual Flowmaster mufflers were fitted onto each tube, in line and in place of the large single muffler. The choice of Flowmasters was mainly due to availability and the near perfect fit into the space at hand, without coming into contact with the drive shaft. You may be able to experiment with other mufflers (Borla, etc.) and get the same results. After fitting the Flowmasters, the second set of mufflers were removed completely. New tips were fitted to a couple of inches of custom bent pipe and fitted into the stock location. All of the work was expertly welded and the stock hangers were retained (as well as the rubber insulating bushings). The tips are slash cut similar to stock but about 1" larger in diameter.

The total cost of this adventure including parts and labor? $330 at a local muffler shop! The sound of the Magnum R/T uncorked? As they say in the Visa ads, priceless!

I know I am going to be asked how they sound and I'll do my level best to address that here. At start and idle, they are aggressive but not overbearing with a very pleasing muted exhaust note. Under acceleration, they open up quite a bit. Not for the faint of heart. If you want it to sound like those Hemi powered Dodge trucks you hear, this is the mod for you. I must note at this point that the WAF/GAF (wife or girlfriend acceptance factor) may suffer a bit here. I am fortunate enough to have a girlfriend who appreciated the sound and didn't mind the droning at highway speeds. Speaking of which, the droning is occasional and tolerable at all cruising speeds below 80mph when not under load. You will certainly be aware of it but it is nothing that 6 Boston Acoustics speakers can't cure. At other times under load the droning can get a bit louder but only momentarily. Overall, I can't tell you how good this thing sounds! I am extremely happy with the results.

As to the performance question, I can tell you that the performance has certainly not been hampered by this mod in any way. My unsubstantiated "seat of the pants" evaluation is that I have gained a bit more power but this, again, is just my impression. I still look forward to an intake and some upgraded programming as well as a set of gears to give it some low-end launch.

Thanks for reading and let me know if anyone hears of the availability of the other mods I mention.

 

for one thing...it might be hard for a speed shop to upgrade tour trans or computer...Mercedes did a good job with the comp, and it is all located in one main moduel with 6 can/bus lines going to the sensors around the car. As for the gearing, I would say something to the effect of transfer gears, but thats not going to be the case..you probobly have to change a few sun gears and hook the second reverse gear to run an overdrive 6th gear maybe

 

I agree the gearing and comp issues may be a bit tricky but I am sure that someone (much smarter than me) will come up with some solutions once they begin to hit the street in mass. Thanks for your input.

 

What series flows did you use?

 

Nick,
I bought my RT on 5/27 (first one around).
My car should be on the cover of Hot Rod Magazine or Mopar Muscle next month. Geoff Stunkard did a photoshoot with a 65 HEMI wagon....What a rush.
Anyway. I am very interested in the exhaust changeout. Sounds like a good no warranty refusale type changeout. My main question is...Is the exhaust overwhelming or moderate. I can deal with moderate. Also, did you replace the large mufflers at the very rear? Or, just where the pipes come together to the "SUITCASE"? I am thinking of the same mod with maybe a set of mufflers that are not so invasive to the ears. But hopefully can still free up some airflow.

I own a Stainless Fab shop and can fab up the tips. I was thinking of something similar to the old mustang GTs.

Anyway, good luck and enjoy the ride.

-Mel

 

I'm not sure (I was afraid someone was going to ask that). The shop had several in stock and I just went with the ones with the best fit.

 

Mel,
That's a tough on to answer. I would say they are not overwhelming but the term moderate may be a bit low on the scale. At idle I would say moderate with no hesitation but they get pretty loud under load. I did remove the large mufflers at the rear. A good bet for you would be to find mufflers you like and hack the suitcase off and replace it with them. Leave the 2 at the rear in place. If you like it like that you are all set and if you decide you want it louder, just finish the job by removing the rears. I did have them fire it up with the new mufflers replacing the suitcase muffler but with the rears still intact. You certainly get a bit more sound with just that mod alone. BTW, I kept all of my old parts just in case...
Nick

 

From your discription of the sound in previous posts, 40 series is a good bet...Thanks,Don.

 

Sounds like it has the 'one into two' system where it only uses one catalytic converter?

If you could use two converters, back pressure would drop 'on the square' and it wouldn't really be any noisier either. Back in the '70s Dodge was the only maker who used two cat cons, while GM, even with 'dual exhaust' cars like the Trans Am used the 'one into' two, mostly because the converter has expensive elements in it like platinum, and it was cost prohibitive to the General.

Also I see the base model uses a 3.92:1 rear gear and the 3.5 V-6 has something in the middle three range 3.55:1 maybe. Can you make a direct swap? More importantly, is the ring tough enough to take the extra multiplication without failing? R/T only has the 2.82:1 but I suppose the 5 speed auto has a lower 1st to compensate.

Finding some lower profile wheels/tires has the same affect as a gear swap - maybe that would be a something to try before switching rings - plus that' got to void the warranty, not just on the axle but they'd probably claim the engine and tranny weren't designed for stump pulling ring and pinion. You might also run into that bugabear of low geared 1960s musclecars - wheel hop. I've heard the new GTO, with 3.46:1 axle has this problem.

I've heard horror stories about ring swaps where they keep failing or at the least, whine like crazy. I contemplated a ring swap once, and looked far and wide to find someone willing to do it - and this is in Chicago with 8 million people. Still, there's nothing that boosts response like low gears.

 

No, 2 cats then the pipes touch for about 4" then into one big muffler (may or may not be connected internally, 2 pipes go in) then individual pipes that go into yet 2 more seperate mufflers right at the tips.