Ls1 cats
Whats the go with factory ls1 cats.
was looking at mine before is there any point to cutting off the shitty press bent pipe, opening up the inlet and outlet too suit 2.5" pipe and using the cat? or is this just a waste of time, considering running cats any advice etc would be great thanks
have to have a cat in a vehicle made after a certain year due to emissions legislation or some such thing. get rid of the factory exhaust system,get a decent 2 & half or 3 inch exhaust with high flow cats intstalled. decent extractors would be a good thing as well.
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i understand the legislation.
just threw a 2.5" twin redback system on it, and it has hsv gts 300 headers on it.
the real bottle neck in the system is these cats, just wondering how bad the actual cat flows or if its just the small diameter pressbent pipe work on them
factory cats dont flow to bad but they are a little restrictive. the simplest way to put it is-the more fuel/air your engine gets & the quicker it gets out the more grunt you have. a standard cat has like a honeycomb filling inside them,damn solid as hell & full of tiny as holes for the exhaust emissions to escape. a high performance cat is not so restrictive so the exhaust emissions escape quicker. also the smaller the pipe the less exhaust emissions get through,make it bigger they escape quicker. hope this explains it a bit better & is more helpfull
A pessimist is a man who thinks all woman are bad. An optimist is a man who hopes they are
well standard cats flow @ 400 CSPIOriginally Posted by cracker
were as i decent highflo cat is 100 - 200
explains it self standard cats are crap
Cammed 8t-body stroker
Opening up the standard cats like you have explained is fine 2.5" in and out has supported over 300rwkws with no problems as ive seen on other peoples cars.
i understand the concept of cats and exhaust flow vs diameter quite well.
its only a daily so just trying to open it up abit, hsv extractors and opened up cats with a 2.5" twin, look too me that it should perform quite well.
thanks for the input
Dont know if this will help you much unless you can buy the cats separate perhaps but this is a descent deal for 1k assuming there a descent quality.
VT/VX/VU/VY/VZ LS1/LS2/L76 1 58 Headers/Extractors/Cats - eBay Extractors, Exhausts, Car Parts, Accessories, Cars, Bikes, Boats. (end time 31-Aug-10 15:57:36 AEST)
I to would like to know how restrictive the standard cats are as well as ill be getting some headers soon most likely 4>1 and was going to do cats at the same time but if people think just welding on some 2.5" pipes are a better idea than changing to a aftermarket cat then thats what ill do.
IN THEORY
the best $ to performance ratio would be 2.5" pipe, through the guts and the rest done in 2.5"
pretty hard too out flow a straight piece of pipe, still have the look off a cat, still have the sound if tapped, and no pressure drop across a large area(such as a gutted cat)
if you happen to get epa'd throw a standard set back in, not that you ever would...once again in theory
The stock cats with 2.5inch pipe are ok on a daily driver undless your going turbos, massive cams etc.
Straight pipe would work best, but it is illegal and you can get huge fines for it; not that I actually know of anyone ever being busted.
I went 3inch metal high flow cats; 3inch to match the extractors. The main reason by the time I paid for the stock cat to be mod it helped bridge the gap. Also with the extractors the cats hang a little bit lower, and metal ones wont crumble if you hit them on a speed bump. Higher flow cats also change the sound.
QldKev
Exhaust Guru
Cats don't flow at CPSI....it stands for cells per square inch and means how small the actual honeycomb holes are in the catalyst. The standard cat actually flows quite well, they are good for over 300 kW as stated. If an exhaust system is restrictive then it is usually another component that is causing it and not the cats. When people replace cats and get an increase in performance, you will find that the pipe work in behind the cat with the press in it is replaced at the same time.
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