You can also use a Y-pipe and small 5-inchers like NM does. Not easy with all of the bends, though.

http://www.nm-eng.com/260/0/0/2864/nm308860-nm-eng-cat-back-exhaust-system.html#popUp[products]/0/

 

The 10435 replaces the 2nd cat and resonator.

You're talking about replacing the rear muffler. I've now given you all of the options for doing so, but keep in mind that you're entering full custom territory (and I've spent way too much in that rear section only to fall back on an older design).

 

But don't all these installs in this thread remove the rear muffler? I took a peek under there and the stock muffler is huge. I'm not sure how else this would happen. I've been looking at single inlet, dual outlet mufflers which would require a lot of custom work, or single inlet/outlet mufflers into a Y or something. Not sure how else to do it.

 

What? No... We're talking about the resonator/cat removal. Nobody here's doing anything with the rear muffler.

 

I had a custom straight-piped section made for me (by a large vendor) to replace the rear muffler, and it wasn't cheap at all. It's also a one-off because it was such a pain in the ***. Sad part is, I don't even use it anymore.

 

So you guys are getting all this sound and popping from decelerating just from removing the second cat and resonator? Leaving the stock muffler alone?

 

Correct.

 

Well that's much easier. Is there better sound with replacing the resonator and cat with the magnaflow you linked me to earlier? Or is the delete alone enough?

 

I originated the resonator idea because I used a cutout before the muffler. It quieted down the exhaust while the cutout was open.

If you're keeping the muffler, just lose the cat and resonator and weld 2.25" stainless in there. That will give you the sound you're after.

 

When I had my Z28 I used a cutout with a flowmaster which gave it incredible sound. Now that you mention it, how was the sound with the cutout open?

 

Not too loud, actually. The resonator cut down a lot of sound (and drone), surprisingly. I believe I have videos floating around here somewhere... If you don't find them in my other thread I can post some here.

I gave it to another member (swapped systems and installed it to boot!) before trading in my last one.

Nowhere near as loud as what I have now, but that's a whole different animal.

 

Just got my cat and res removed. I love it. Still quiet when tooling around but when you get on it the sound is definitely there. Not to mention the awesome popping.

I had already done a new cone filter, so the intake sound coupled with the turbo blowoff and crackling exhaust is awesome.

 

Oh, and the guy said it's definitely illegal. If the cat came on the car, it stays with the car. Period.

Who knows.

 

Are you guys just sliding the new 2.25" ID pipe over the OEM pipe, after you cut out the bits?

 

Yep. I went to a custom exhaust shop. They cut out that roughly 2 foot section and just custom cut a new pipe to fit over them and welded it on.

 

I have a MCS 07 with a Catless DP and second cat removed.

The car is a lot louder and drones between 3100 to 3900 rpm with Windows up.

Just letting everyone know! =D

 

Just imagine putting a louder muffler and then it'll drone beyond belief lol. I have a little drone around the same RPM's but I can only imagine when I put a DP on what it'll sound like haha.

 

So to add to this discussion with another question....and maybe Theta knows the best answer /wink wink, which opens up the flow the most? Installing an axle back system, custom or aftermarket, or just removing the cat and resonator and leaving the OEM muffler?

And what does it sound like if you take out the cat, resonator AND get a new muffler?

Cheers!

 

Not nearly as much as it does when you remove the muffler completely. Learned that lesson a few times.

 

Flow rates will be limited to the most constricting part of the system. Largest flow deterrent is the stock DP / cat. The resonator is a straight-through. The 2nd cat is another 200cpi and limits flow even further.

The smallest diameter in the system is the effective diameter for the entire system (simple flow dynamics). The stock S/ALL4 system has two severe neck-downs before the res/cat area. Look at the bent pipe at the front for the DP connection - you will see 2-3 severe neck-downs, the smallest of which is down to 1 7/8". So, essentially, your exhaust system is 1 7/8" regardless of what you use from there back.

Now, that's still enough for these little engines, so don't let me discourage you. The two main factors before increasing pipe diameter are to remove/replace the two cats to maximize flow.

Axle backs do nothing except add/change the sound/loudness of your exhaust.

For the quickest sound bump, remove the 2cat/res, and straight pipe it with the OEM muffler. It's the most popular and cheapest mod that everyone agrees upon.

As for replacing the muffler, itself (not part of an axle-back system) - the only choice is the JCW OEM part. I've heard that combo before, quite nice. I'd point you to Kyle's videos, but he has much more work done, so the sound won't be a realistic expectation.

 

Thank you for the very thorough explanation. So if I were to cut out the res and 2nd cat I would use 2.25" pipe to bridge the gap? Or is there 2.18" that I can buy? And then once I got my pipe, should I weld it on or use clamps? Thanks again for answering. Cheers.

 

Of course!

The easiest method on the American market is to cut just before and just after the res/cat section, then replace the section with 2.25" stainless 18ga (if available - remember you can always order this before going to a shop that only uses aluminized). The 2.25" slips over nicely and requires only a small welding gap fill (I always use stainless sticks or TIG weld it, but you may be stuck with someone who only does wire-feed or MIG).

Clamps will not work in this case, as the dissimilar size is not standard (ie 2.0" -> 2.25") - it's best to have it welded, anyhow. Clamps that join two dissimilar sizes invariably leak, so even if you could use them, I'd discourage it.

 

Thanks again! My only issue is that my local shop said that they couldn't cut out the cat and that I had to do that. I can't imagine what THAT would sound like driving the 15 miles to the shop :/ So many ways to do this...thanks again Theta.

 

It's not too bad with the stock cat. It's MUCH worse with an open catless DP or even the Akrapovic (brain-jarring).

Quick advice for doing that - make the cuts and use band clamps (tight, of course) to put the section back on. Again, make sure the band clamps are on tightly before going on any public roadway. It doesn't sound pretty, but better than wide open. Costs all of $3.99 a piece at any AutoZone. You might even get lucky and find 2 1/8" band clamps.

I've seen this done before with success. Remember that if you drive with the section cut out, the ONLY thing holding the entire rear section on to the car are the two rubber exhaust hangers. Food for thought.

 

Man, I am sure that I would have found my muffler on the road had you not said something....and one more time, Thanks Theta!!