This weekend I am cutting out my Cat. And also am considering cutting out my exhaust to and just going straight pipe all the way back. However, I was wondering what would be the best to do, wehter or not i should leave the muffler. As far as sound, and a little extra power what do you guys suggest??
It's an 86 iroc-z tpi 305.

 

Most people, and myself would say definetly leave a muffler. If your taking your cat off it should be loud enough for you even with a muffler on plus 100x better sound. For a 305 the power different with a muffler is irrelivant. If you still have the stock muffler on there rip that off and put someone on that is any single in/ single out and just keep 1 tailpipe or just dump it right off the muffler, power loss really wont be an issue so just choose by whicher sounds best for you.

 

I have a 305 TPI also with headers and switched from Dynomax muffler to flowmaster 30 series, but between having them installed I went a day without a muffler. Just had the headers into single cat into straight pipe and dump over the axle. Let me tell you, it sounded like ***, and was way too loud for the street. No power gain. I'm so glad I have the muffler on now.

 

Alright thanks both of you, Im cutting the cat out his weekend and them I'll probably decide from there what to do. Cali Z, you seem to know some what about mufflers, could you explain to me what # series means what... as in the higher the number the louder or what?

 

Not necassarily the case. The series # doesn't follow a pattern for sound level, so it varies for each one. To keep the stock exhuast (dual outlet) design, you would use the 80 series flowmaster. If you wanted a louder flow, you could get the 40 series, Super 40 or the delta flow 40. I believe those are single inlet/outlet so you'd have to dump it after the muffler and couldn't retain the stock exhuast exit location (dual outlets). If you wanted something quieter than the 80 series, then the 30 series (what I have) would have the same setup for installation as the 40 series models. My 30 series is louder than the dynomax, which was almost no louder than stock.

To sum it up:

Louder: 40 series (single exit)
In between: 80 series (stock dual outlet)
Quieter: 30 series (single exit)

And then of course there are the race mufflers, but I was just reffering to street combos.

 

Those are just flowmaster numbers too, btw.

Alot of companies have different ways of organizing their mufflers, so you'll need to do some research.

As far as cutting off your exhaust - don't. If you gut the cat and get a good muffler you'll be happy with the sound. If you REALLY want it loud, then get either a cutout or you can go custom with a bullet muffler setup.

 

about a month ago i welded a glasspack to my stock y-pipe, and dumped it in front of the rear tire, noticed a bit of power gain (minimal), then i was bored, waiting for my order from summit, so i put a single three inch pipe replacing the glasspack. Definatley a fun novelty thing. dont go driving at night... i have a radar detector so i know when to let of the throttle, but... u sound like a half ton ******* who just hacksawed his truck. Definately turn heads, and get phonecalls from your neighbours. oh yeah and ull love underpasses. just pin it going under there with t-tops/windows off/down... its music to my ears. Oh yeah the most important part: it owns ur compression... like i mean owned. u go very noticably slower. like mustangs are competition to you, slower. its so sad... thats why its novelty.

 

take a blow torch to ur cat and muffler till they trun red take a rubber melit beat them a little to break the stuff in side and wa la stright pipe cop pulls u over and sees its not stright ur good to go

 

i ran a straight pipe for 2 days with the cat on.. and it was ridiculously loud and annoying.. the sound wasnt good

i had the 80 series 3inch catback and power increase was good.. added torque but some hp as well. i like that sound

that system and no cat will sound good.

now i have a chambered tube and its great flowing.. straight thru design. but its like the flowmaster at idle and small rpms.. but the tone is a tad different. but once u get on it, it is a beast. a good bit louder than the flow on the outside of the car. inside noise has increased abit but not too much. great sound

i'd recommend a chambered tube in place of the cat that u cut off