Anyone made their own pre-muffler out of a cat bypass pipe?

[mr.bch]

I have my SC cat bypass pipe in at work today so I can weld on an M18x1.5 nut for my O2 sensor... and it sure looks like it would be easy to add a small resonance chamber in where the long, straight section is.

The opinion as I have read in past threads is that Euro pre-mufflers sound better, make more hp than a straight bypass pipe and are generally more desireable (more $$, too).

Anyone had a euro premuffler apart to look at the innerds?

[Eugene at Pelican Parts]

I think there are at least two different kinds of factory euro pre-mufflers. Mine is skinny and is pass-through with a resonance chamber. Maybe you could just chop your test pipe and weld the ends onto some big old Harley muffler. Add a little American badass to your fine German machine.

[Kurt B]

Maybe you could just chop your test pipe and weld the ends onto some big old Harley muffler. Add a little American badass to your fine German machine.



HAHAHAHAHHA Classic

[mr.bch]

OK... here it is. Don't laugh at me. Everyone here seems to poke fun at the stuff I do to my 911..... but hey, it's mine. The concensus of this board iss the cat-bypass pipe provides too muc audible assault, so I did this.....

I bought a cat by-pass pipe off a user in this forum. It looked well-used but did a good job blasting it. Very porous steel.

I looked around and decided to buy a Moroso spiral racing bullet muffler. It doesn't have any packing in it, so it isn't like a glass pack. It has what looks to be like a couple of impellers welded into it. These are supposed to baffle the sound quite a bit. My friend just welded up 2 dynomax bullets on his C5 and it sounds like a nascar (too loud). They were the perforated tube in a tube. I chose this one. Minimal backpressure as the tube through the center is 1 3/4"

I stuck an M18-1.5 hex nut in the lathe and turned it down 6mm to match the thickness of the stock O2 bung. Then I TIG'd it on in a location where I thought it would work.

I also powder coated it in 1000 degree silver. I didn't clear coat it, so it doesn't look very shiney. It just looks silver. You can also see a bar end for my GSXR1000 that I podwer coated in the first pic. (these were forom my C5 friend's totalperformaceracing.com's business... shameless plug).

So tomorrow I mount it up. I made a jig to the original cat. It should fit better than it did before I hacked it up.

I also have 2 extra flanges that I lasered up if anyone needs them for whatever reason. The flange (muffler end) that I cut off was only .200" and was severely warped from weld. I suspect most are like this.

Let me here your your honest feedback on this.

Also stay tuned for other projects of mine... I have a lot cooking right now....

[Bob's Flat-Six]

Nice work! I'm about to replace my cat too and am trying to figure out the premufflers that are out there ?
Let us know how she sounds

[mr.bch]

OK, all mounted up and drove it all around this weekend. Sounds nice. I really thought it would be louder, but it isn't. Marginally lower tone that the cat, a little bit more db's when fully into it.

I think I might work on ditching the stock muffler now and fab up something small and light weight. Who would have thought exhaust work could be this much fun.

Also, the high temp powder coat is working out well. I think it is on there life.

[Kemo]

Hey! that looks pretty good! Nice to see you got some pride in your work. Post some more pics of the install.