I went to 2 muffler shops, told them I was installing a header and I wanted a Hi-Flow Cat, Resonator and Muffler. Both told me that the cat was already a Hi-Flow and it did not need to be replaced.
when you need to use a transition to get pipe diameter to match something smaller, you lose the "hi flow" part.
unless your car has an aftermarket exhaust on it already.
the pipe diameter of the cat should match the pipe diameter of the entire exhaust system.
definatly replace it. i was so impressed with the gain i got from my thunderbolt cat. my buddy also bought a highflow magna flow cat and his car got a huge gain from. also a z24
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i'm running a magnaflow hi flo cat its great wouldn't buy anything other
JBO since July 30, 2001
DaFlyinSkwir(LS61) /PJ/ OEM+ wrote:when you need to use a transition to get pipe diameter to match something smaller, you lose the "hi flow" part.
unless your car has an aftermarket exhaust on it already.
the pipe diameter of the cat should match the pipe diameter of the entire exhaust system.
If you're running a header, an additional rule to apply is one used in designing a exhaust pulse-wave isolation chamber. This is a device that goes on the end of the collector that's used to isolate the exhast pulses from the rest of the system so downstream exhaust design has less of an effect on the engine's power production. Basically, it makes the exhaust think that it's seen the end of the system & helps scavenging, which helps make power. A catalytic-convertor can be used to act as one. The guideline is that it should have an area equal to the displacement of one cylinder (in cubic-inches) multiplied by the total numbers of cylinders the pipe (Or header in this case) will see the operation of (in this case: 134ci). It's one of the many guidelines presented by David Vizard (One of the guys whom had a hand in the design of the original Flowmaster muffler) in a article he authored for Popular Hot-Rodding. He's been at building engine performance & exhaust systems for years (MAybe even longer than your father has been around) so he knows what he's talking about.
Go beyond the "bolt-on".
^^sounds like it could make sense in theory, but ive never seen anything like that.
1997 Cavalier Z24
Bomz Short Ram Intake
Vibrant Cat-Back
KYB GR2 Struts
Goldline 1.75" Springs
RK Sport Upper Insert
RK Sport Lower Dogbone
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15.647 @ 88.02 MPH
Mr. Vizard has yet to lead me wrong!
Go beyond the "bolt-on".
but flowmasters suck and are among some of the worst flowing mufflers made actually. id say any cat will work. people say the high flows are no different than stock.
Vincent Morris wrote:but flowmasters suck and are among some of the worst flowing mufflers made actually. id say any cat will work. people say the high flows are no different than stock.
It depends on the design of it. A higher cell count per inch to the monolithic ceramic bricks inside a conventional catalytic converter equate to higher flow. Metal-substrate units, on the other hand, easily out-flow ceramic-brick units by 50%.
As for Flowmasters, I meant the original design jobs (2-chamber & 3-chamber). David Vizard has since moved-on from there. Too-bad Flowmaster has just simply become the Pep-Boys common-stock part, like Warlock & Cherrybomb.
Go beyond the "bolt-on".
