meford4u,Nov 18 2004, 01:13 AM Wrote:From what I have found out about the under car cats for our car, they don't work. Why? Because they don't generate enough heat from the engine to make them efficient enough to work. That was the whole reasoning behind Ford putting the cat in front.
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I meant in the standard SVT location after the long header and before the flex, which I'm guessing is more below than in front of the engine. It is still in proximity to the heat of the engine but giving more length in the header for expressing of exhaust gases than a standard or shorty header.
If that location for the cat doesn't work then then there would be a few SVT owners that won't pass their first emissions test. :huh:
Mine allready passed its first emissions test with the lowest possible values. but what's kinda intresting me is the svt seems to run a bit rich, after a week my exhaust tip is always black. I know other svt owners say the same thing.
All hondas have the cat under the car and they seem to work fine. Vw's are the same, under the car.
So I dunno... I think its more myth then anything.
I always thought it was too close to the headers. because the main problem everybody has when changing their headers is too much heat and nuking the cat. so i'd think it would heat up fine in any other position. just not as fast.
the reason ford opted for a cat forward design over an undercar cat like used in pretty much all other cars is how QUICKLY the cat heats up.
the closer to the exhaust ports the faster it heats up, the quicker it gets to cleaning the exhaust gases.
i run an undercat cat right now and have the same emmission levels around a normal Focus even begin fiarly highly modified.
where the cat is placed has little do do with how well a cat works as a cat will work, although in a minimized capacity, when cold. they work best when HOT, which is why most good Automotive fix-it shops will tell you to keep your foot on the gas while in line waiting for emmissions testing to keep the cat hot and never to turn off the car.
the downside to a Catforward design is that in racing or extended spirited driving the cat can actually overheat and blowout... this will happen with a stock or a aftermarket high flow Cat replacement.
i believe ZX3Canuck has been through a couple of cats thanks to trackdays! ;)