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Location:
Sydney
Registered:
October 2003
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Performance of a high flow catalytic converter
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Mon, 18 April 2005 03:23
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OK, stupid question(s) time again.
Is there an emissions difference between a high flow catalytic converter and a regular catalytic converter?
Is there a difference between a cheap cat and an expensive cat?
If your car ran with a primary cat (on the dump) and secondary cat, could you get past an emissions test with a custom dump and single cat?
Cheers,
Dave
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Registered:
November 2002
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Re: Performance of a high flow catalytic converter
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Mon, 18 April 2005 13:54
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I will have a go at this question.....
There should be no emissions difference between a high-flow cat and a standard cat, each will convert the gases to the safer varieties, the high flow cat will (usually) do it while flowing more air at the same time.
Besides price, I would say no on the converting factor, but yes on the flow rate, usually.
Cats need heat to work, so the closer they are located to the exhaust manifold the better they will operate. I would hazard a guess that if the standard car used two cats, you will need two as well to pass any emissions test, but it all depends on who is doing the testing. The local test my be nowhere near as strigent as the factory spec's, especially if the car was made for markets all around the world, and Japan and California are very tough on emissions.
If I were you I would get my exhaust made in sections with flanges between them, so if you need to fit another cat you just bolt that in to a section, and then remove it and replace it with just a pipe for freer flowing exhaust gases when you are not being tested.
This way you have the best of both worlds, at little if any extra cost.
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Location:
Perth, WA
Registered:
December 2004
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Re: Performance of a high flow catalytic converter
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Mon, 18 April 2005 14:10
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best cat out there according to some test thingy, is the r#@ GTR stocker...
basically, as the exhaust flows through the cat, you want it to obstruct the least, which means converting gases to the bare minimum legal emissions...
so, the higher flowing cats you see out there, are actually worse at converting the gases, while still remaining legal...
also, its obviously better for your exhaust system if both inlet and outlet sides are bigger, less restrictive 
Eldar.O.
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Location:
Sydney
Registered:
October 2003
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Re: Performance of a high flow catalytic converter
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Mon, 18 April 2005 20:10
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Thanks guys, exactly what I was after and definitely logical.
Not too sure about getting it made in to any more sections though, I think my exhaust is going to go dump-flex-cat-muffler with no more than about 200mm of exhaust in between (mid mount engine without the snaking exhaust).
Might go for the performance option first and if I get picked up by the engineer, replace it after. Got my 3" dump in the mail yesterday and I'll think I'll pick up one of those $165 XForce 3" stainless high flow jobbies.
Thanks again for the help!
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Toymods member
I supported Toymods
Location:
Rydalmere, NSW
Registered:
May 2002
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Re: Performance of a high flow catalytic converter
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Mon, 18 April 2005 20:41
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| ra23celica wrote on Mon, 18 April 2005 23:54 |
If I were you I would get my exhaust made in sections with flanges between them, so if you need to fit another cat you just bolt that in to a section, and then remove it and replace it with just a pipe for freer flowing exhaust gases when you are not being tested.
This way you have the best of both worlds, at little if any extra cost.
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Exactly my thinking when I had mine done... subsequently mine is in 7 different sections all the way from the dump pipe to the canons.
I'll be looking at getting another hi-flow cat soon too as the one on there now is going to be utterly coated in soot from the last ECU making it run so rich, and the timing having a lot to do with that too. 
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Registered:
November 2002
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Re: Performance of a high flow catalytic converter
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Tue, 19 April 2005 01:25
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This really is the best approach if you need to make changes at any time for emissions, noise or track day reasons. The secret would be working out which single component you only need to change to pass emmissions (a cat), noise at home and neighbours (a resonator) or track day stuff (a free flowing pipe), to save you the hassle of changing all the components every time you you need to meet a certain target.
Sounds like a lot of hassle but I know a couple of people that live in the USA that do exactly this every few weeks as they seek to get maximum use out of their toys.....
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