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The only problem with cats is the power they take out of a FI car. Ussually on a 600hp car taking them off will gain a easy 30-40rwhp.On a 800hp car we gained 80rwhp.
I have to ask: Are there any Dyno sheets to support this?
It just seems like a whole lot! I mean dang I would be throwing down 651 RWHP instead of my 591 just by unbolting the cats?????
Why?? If there are guys running in the 9's with factory cats, why not just leave them alone?
Good point, it will all depend on what my high flow cats look like now that the car is being taken apart for its new forged LS6 power plant.
It the high flow cats are clogged (off they go) if not, will probalby keep them on (but hate to think I am leaving up to at least 20rwhp on the table).
I don't know and I assuming my cats are not clogged, but I will be finding out for sure in the next week or two.
when cats are clogged you know it.I've seen a 300hp loss on a vette due to clogged cats.It won't pull at higher rpm.
As for graphs,yes I can get them but see no need to look them up again since I know they gain being gutted. Yes,you can make alot of hp with cats but I like the idea of taking out restrictions to make more power at the same boost level.
when cats are clogged you know it.I've seen a 300hp loss on a vette due to clogged cats.It won't pull at higher rpm.
As for graphs,yes I can get them but see no need to look them up again since I know they gain being gutted. Yes,you can make alot of hp with cats but I like the idea of taking out restrictions to make more power at the same boost level.
I'm pretty sure that is what my issue is..... I'm down about 60 rwhp from what the car did when it was built 6 k miles ago at the same boost level (11 lbs). It levels off at about 4,500 rpm....
Will keep everyone posted once I get the cats inspected.
I'm pretty sure that is what my issue is..... I'm down about 60 rwhp from what the car did when it was built 6 k miles ago at the same boost level (11 lbs). It levels off at about 4,500 rpm....
Will keep everyone posted once I get the cats inspected.
If you have a temperature gun (infrared or otherwise) get the car to operating temperature and measure the temperature just before the cats and just after the cats. If the temperature just AFTER the cats is not at least 100F HOTTER than before the cats, you likely have a problem with the cats.
My 3" hi flow cats work quite well with 640rwhp. 15# boost. course not often I get to see that kind of power on the street. But mine have been on for a bit over 14000 miles now.
I've read that hi flows are only loosing some 5 hp per cat over open pipes? Now that is NOT substanchated by dyno numbers at this time???? ZO6Bill....
I'm at a crossroads here. I have a LPE built motor and a Maggie. I'm pushing ~465 RWHP and got tired of the exhaust on the car that it had when I bought it. I bought a Corsa Extreme and X-Pipe, a tunnel plate, and I am about to do the install with the help of a local shop with a lift. What are the pros and cons of high flow cats replacing functioning stock cats?
I am not interested in going cattless, so it is either high flow, or stock.
I'm running 9lbs with kooks high flow cats. I don't have many miles with the procharger though. Maybe 1500 miles with it. Been running the cats for around 4000 miles.
There is a newer thread than this somewhere , here is a pic of mine after only a few thousand miles, 10 lbs or so on a 383, these were lg high flow cats that came with headers, my car was running too rich so maybe that caused it but many sc cars have had problems with them.
I only had like less than 4,k miles on a set of Kooks high flow with headers. Mine was worse than the pic,s above and also running 100% meth also. Like the guy with the pic,s said in his post when you F/I these cars it is going to run richer than a stock set up plus meth just going to heat them up melt the inside.
Then you are going to have worse problems if that stuff don't blow thur and then clog the flow up. So more than not run without them. You may are will at times get a little smell from time to time nothing really bad..Robert
I've had Magnaflow 59959 cats in my +600 hp C5 and no issues with melting the cats but I think the main reason is that I run >20 degrees of timing at WOT.
Without cats I get almost zero back pressure (with cats it's +5psi) on top end and that gives me room for taking ignition two degrees higher without knock. In dyno that showed about 30-40 hp increase in power at high rpm. I do not wan't to change pipes and tune for the sniffer test so I'm going with cats nowadays.
The problem I have/had with these Magnaflow cats is that the cell structure sometimes gets loose from the chamber and squeezes in the back cone resulting a bad cat in the long run. Not a very high quality item I think.
12-10-2007, 09:38 PM
get rid of them they will come apart eventually and clog your x-pipe & exhaust Guess how i know 
