Cat Bypass Decision Help Needed
 

Should I just leave the cat in there as it is?

Or should I do a home-made bypass and take it out and bash its guts out?

Or keep it in a box and get a used bypass cheap form the parts forum?

Or just leave it alone and don't worry about it?

Or get a pre-muffler? If so, What kind would that be?

This is on a very stock 3.0 SC that still has CIS/WUR issues, but I was just thinking of a fun project, I guess.

After the cat bashing, or bypass installation, will it be louder? I am not wanting to get loud. But the biggest question is, will there be any noticable performance gain? Or if it gets louder will I just think Im going faster?

Anyone done any of this before?

scotricker,

I recently installed a euro cat bypass with a Bursch 1/1 (BX 1134) that I found on flea bay at a great price. Looked like crap in the pics, but was solid. A little naval jelly and wire brush and high temp paint made it look 10 times better.

Much much louder than stock at first, but now I've, and more importantly, my wife unit, have become accustomed to it.

Butt dyno says I've got more power, and the sound is fraking awesome.

I did notice upon removing my old cat that it failed the "daylight" test. Could not see a darn thing thru it when shining a light at one end.

Good luck!

"keep it in a box and get a used bypass cheap form the parts forum"

You can always go back to stock if need be.

I would leave the cat in. It's better for our air quality. Replace it with a modern high flow cat if need be.

You won't see much, if any HP gain unless your converter is plugged. A cat bypass or emptying the converter is a cheap alternative and it won't make the sound much louder than stock. The tone may change a bit, however but that's about it.

I have the factory pre-muffler with a Flo-Pro muffler and the sound is just right for me. Check this thread out for all sorts of combinations and opinions.http://forums.pelicanparts.com/porsche-911-technical-forum/332660-ultimate-exhaust-sound-clip-thread.html

I just installed a fabspeed pre muffler.

http://forums.pelicanparts.com/uploa...1268493833.jpg

Deeper sound, not any louder with the stock muffler, not that expensive either. Maybe a couple of ponies added, good upgrade.

Take care.

On my Club Sport, I installed a Fabspeed pre muff and a B & B sport muff. At he same time I removed the airbox in favor for a K & N and installed a Steve Wong chip. All were done at the same time and I noticed a "seat of the pants" improvement. A friend in CA with a CS did all 4 mods as well and has dyno sheets showing 238 hp.

On a 3.0 you will see slight improvement with the pre-muf and a sport muff but I doubt it would be something you'd feel. The pre-muff will reduce temps and that's a good thing and the sound if you do both, can be intoxicating :)

A cat bypass will give you a deeper and slightly louder sound. You will get rid of a lot of heat and save some weight where it counts. You will also pollute more. I would recommend saving the cat for future use if the smog laws change or if you sell the car to someone who needs it as they can be expensive to replace. The euro premuffler is supposed to add a little power as compared to just a straight pipe bypass.

I did the Dansk euro pre-muffler and have the cat if I ever need it. Didn't notice much sound difference and dyno numbers on another thread here showed a HP increase with pre-muffler as to no increase with the bypass.

http://forums.pelicanparts.com/uploa...1268636420.jpg

I've been considering the same. i'd say if your cat has collapsed, go for it. no use in wasting your money on a new cat when you can get a premuffler/bypass for a lot cheaper(or bash your cat out for FREE if it has collapsed and useless anyway) note, the only people worried about the environment are from CA. - i could say a million things wrong with that state, but everyone knows so i must refrain.

I installed a cat bypass and really didn't notice any sound difference. Straight thru flow seemed much better than thru my old cat, I still run it thru my regular muffler. Also, my 79 911 did not have an 02 sensor. Here in MI we have not had laws for car exhaust since the mid 1980's!

from milo 2361

That's just not true. To me it's very important and I can understand that you might get that impression in NE, but imagine every motor vehicle in the tri-state area or California without a cat. The air quality would be much worse.

I took my cat out because I take mass transport every day all year long to work, and I never take my car when I go to the city. I go for drives (away from the city) in the week ends and I probably release less CO2 in a year than anybody who puts 15K to 20K miles a year on a hybrid. But I still believe the environment is a very important modern issue, everybody is concerned.

Take care.