toddk911

Is there any dfference in performance between a cat bypass and punching out the cat? <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

tecart

thge answer is no, the gains will be the same, i gutted my cat and had the b and b test pipe, both make the same power, they both make the car 15-20 db louder too for sure, both will yield about 10-12 rear wheel horse, if boost is up higher then more gains will be had, but dont tell me how one is better than the other in terms of power, they will do the excact same within 1-2 hp, also the gutted cat will get you through inspections easily

RJP 951

How do you "gut" the cat?

Thanks
Ron

951and944S

What I'm currently doing is removing a 951 cat, clearing way for a pipe to run through the cat's full length, leaving the appearance that it's still functional.

I'll post some pic's within the next week or so..

Cheers

Ski

To get the cat clean,,get a five pound shop hammer, 31" wrecking bar and start hammering. You should have most of it cleaned out in about an hour. You will then need to make a home made spiral spear if you will,,coat hangers; to get the steel wool out of it. Then shake it a couple of times and its clean.

Alan C.

I'll bet that's one mad cat.

Had to do it, can't beleive someone didn't beat me to it. <img src="graemlins/xyxwave.gif" border="0" alt="[bigbye]" />

Ski

Not bad Alan,,,LOL!!!!

Joe@Fabspeed

why ruin a stock Porsche 944Turbo cat that is less than 2.5" in diameter as its metric tubing not SAE. Emissions will eventually become and issue for everyone unless you live in Mexico.

Even then eventually even Mexico City will have smog rules.

The very best choice is a 3.0" T304SS catbypass pipe/ performance downtube. Adds .12BAR more boost that a 2.5" mild steel testpipe and most probably .17BAR more boost over a gutted stock 944T catalytic converter pipe that uses small metric tubing.

When you have a stock or modified 944Turbo a 3.0" exhaust is all that it really should have when your over 250HP. There is even a RACE CAT for emissions that you can slip on.

Stock 944Turbo cats sell used for over $600 ......its doesnt make sense to destroy/modify/Gut a 944Turbo catalytic converter to save money....... BUT in essence ultimately have less performance, not be able to comply with emissions at any later date.......WHEN a $500 3.0" catbypass pipe does all of the above better and faster and even supports a slip-on racecat.

Have a great day.

Fabspeed Motorsport USA<a href="http://www.fabspeed.com" target="_blank">Performance for the next millenium</a> <img src="graemlins/r.gif" border="0" alt="[king]" />

tecart

well nice try to say something that made no sense, im not being a ***** but my cat that i gutted does not lose horsepower at all, i make the same or more than the pipe you sell, also i can get through inspections in new york with it as it appears stock and with a testpipe they could easily tell i didnt have a converter ok... Also the stock converter was not ruined by me but improved by me for performance, now i dont get clogged converters, or loss in power, but a gain of 12 rear wheel horse, and wheni crank the boost to 24 about 20 rear wheel horse, the exact same id get wiht your 500 pipe, so do not assume that we will ruin anything by uncorking the cat, its for higher boost and free flowing exhaust, ill bet you my setup will outperform any cat/testpipe except the SFR 3 inch one and that would only yield me another 5 hp maybe. My comments are simple, the gutted cat is for more power, less restriction, higher boost, preventing the honeycome innards and mesh from melting and clogging it, and more power, not to ruin a good one for those who dont seek extra power... Again any gutted cat or testpipe will increase the decibels about 15-20 and create a loud idle, i guarantee it 100% but i didnt do it for any noise concerns only power and i got all of it by gutting the cat, no test pipe needed sorry you think so at fabspeed but your wrong on more than one point here

Ahmet

If you just 'gut' a cat you will create a lot of turbulance in the cat housing. If appearance is an issue (for regulations), I would suggest openning the cat housing, and welding a straight pipe inside. If appearance is NOT an issue then I would suggest cutting into the stock piping about a foot ahead of the cat with a larger diameter pipe.
Ahmet

tecart

i get no turbulance when im at full throttle and my turbo is pushing out 20 psi at 105 mph in 3rd gear ok, you do not understand how this pipe can work if the car is being driven hard, their is no hesitation, backfiring, loss of power at all, you might be thinking about perfect inlet airflow for an extra 1-2 hp, but the bigger openind that a gutted cat makes verses a straight pipe is hogwash, bring your car to new york and ill spank anyone who thinks otherwise, not to brang but my gutted cat helps me crush vipers, vipergts, c5 vetts, big blocks in the 12's, stangs w 150 hp shot of NOs, and a saleen s351 w a bigger supercharger then stock, dont tell me a straight pipe will be that big of an upgrade, just gut the cat and youll be happy, and if you want to take me up on a race ill be there any time any day, later, god people think they know it all sometimes

tecart

i had the 700 dollar b and b test pipe, a powerhaus special made t304 test pipe, and a custom made pipe and a gutted cat, all performed the same, and all were very loud at all speeds and at idle, believe me or i guess believe others who never spent the time, effort, testing, researching, verifying with dynos, the gutted cat is within 1-2 hp at 18 psi of boost and 3-5 hp at 24 psi at 4000 rpm's, not being a ***** here but i do not want a newbie to assume he needs to spend anymore than 40 bucks to get some nice gains ok over1g, sorry i lapped at you

Ahmet

[quote]Originally posted by tecart:
<strong>i had the 700 dollar b and b test pipe, a powerhaus special made t304 test pipe, and a custom made pipe and a gutted cat, all performed the same...</strong><hr></blockquote>

Tecart, I doubt you've measured the the backpressure after the turbo with a straight pipe and compared it to the exaust backpressure of the same set up with a gutted cat.

I'd be willing to put money that a straight pipe will perform better (Less backpressure @same boost level--&gt;cooler charge, less spool up time, and better response)than a simply gutted cat. Weather or not that difference is worth several $100, that's personal...

My car's got a 3 inch open exaust from the turbo back, but I did spend a little bit more than $40.
Ahmet

Russ Murphy

I think it's hardly a debate that a more open exhaust with smooth or NO size transitions is going to flow the most gas. Even we here at the Rennlist can't alter the universe.
The question is the timeless one, what's the value of a paticular gain for you personally. While I tend to go the tecart way mostly, I beginning to see the value of doing it right the first time as well. IMHO the right way is save your cat for later or sell it and by a nicely made cat replacement ( and Fabspeed's is certainly that), but one that matches your turbo downpipe, whatever size that might be.

Jerry

I think the cat cost too much money to reck it. I bought a test pipe for around $200. and if you put less than 5000 miles per year on your car you can get a epa excempt sticker.