Ok, so in my continuing research into the mods I want to do to my 94 LTI, Im thinking about high flow cats.

I'll be honest from the start, while I know what the cat does, I dont know what the best cat I would need to satisfy UK laws, I would like high flows because of the engine mods Im hoping to do, If Im going with a hotcam and flowed heads and LTs, it would make sense to allow the exhaust to escape as easily as possible.

anyway, with that in mind these are the current requirements for cat testing in the UK, does anyone know what high flow cat will best meet these levels? (taken from the official testers manual)

"The first test consists of checking the emissions at ‟fast-idle speed‟ which involves
running the engine at a speed of 2500 - 3000 rpm. During this test the emissions of
CO and HC will be checked and a further check will be made on the lambda (1) value.
The second test consists of a check of emissions at „normal idle speed‟ in which the
engine will idle between 450 and 1500rpm, but in this case only the CO emissions
are assessed.

The emissions limits to be met are specified for both the fast and normal idle tests.
At fast idle, CO must be at or less than 0.2%, HC at or less than 200 parts per million
(ppm), and the lambda value(1) must be between 0.97 and 1.03. At normal idle, CO
must be at or less than 0.3%"

Hope that makes sense to someone!

 

I see you are going with long tube headers. You will have to change cats, stock units won't work with LT's. Dynatech PowerCats and a really good tune passed Missouri emissions testing on my 94. Not sure how our standards compare to the UK.

 

thanks STL, I'll look into the dynatech stuff, on my last yearly test, the emissions failed on the stock cats, even though its got new O2 sensors, 60K something miles, whether that had something to do with the occasional backfire I used to get with the Eliminators it was fitted with I dont know, I was always led to believe a backfire through cats will damage them,( which I dont get with the corsas) but luckily the tester was kinda sympathetic and managed to "adjust" the results..as he said, it was very close, and if a car appears to be well looked after then he see's no reason to fail it..

 

Old cats will fail. Best bet is to replace the cat. MagnaFlo is another mfgr of hi-flo cats.
Not the cheapest resolution, but you most likely pass if you were previously on the fence.
Of course it's always best to determine and repair the problem first.
Try adding some (1 pint or 500ml) denatured alcohol to the fuel, less than 1/4 tank.