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Catalytic converters and exhaust flow

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The guts of my cat broke apart and have now been removed (empty cat is still there).

I am barely failing the emissions section of inspection.

1. Does a catalytic converter hurt performance and fuel economy? If so, will an unskilled driver notice the performance?

2. How important is the back pressure caused by the cat?

3. Any suggestions to what cat to buy and where to get it should I decide to get a new one?


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will notice little better turbo response

and little louder with no cat

here are couple universals on ebay

I had great experience with magnaflow

products in past, but they both look the same

two welds, it shouldn't be more than $60 to put on

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a lot depends on your cam, I do not know lotus cam setup at all, but in the performance cars, and race cars, a really agressive cam can have a bit of overlap between the exhaust and the intake lobes, if you have no back pressure at all, you can actually lose fuel air mixture, doubt this happens in the 2.2 . . . but I have seen it happen on chevy V8's with major modifications . . including turbo. Have a callaway twin turbo vette from the 80's, saw the decrease on the dyno with super agressive camshaft . . . so cats are generally performance robbers . . . but a wide open exhaust on a car that was designed to have some backpressure can cause issues as well . . .

having no cat at all can cause your O2 sensor to read too lean as well . . . because the exhaust gases get away too quickly . . . but with the turbo I doubt this happens at low RPM's either . . .

Edited by CBrownstead
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On my STI, with the 2.5 liter with no cats, i shoot flames :D because the downpipe that connects from the turbo to the catback on the sti has no cats. so on sti's turbo spool depends on the downpipe and not the turbo cat back, however, without proper Engine Management, you get boost creeps. I dont know if that helps you or not but no cats = faster turbo spool. Where I live in Wisconsin, I know for sure my STI wouldnt pass emissions. I have 850cc injectors, blow off valve, no cats on any pipes, a free flowing headers, 250lp walboro fuel pump, Access Port II for my Engine Management system. gas burner..LOL. Ill gladly trade it for a v8 Esprit, anyone?

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