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Old 05-20-2009, 04:48 PM   #17
Scooby Newbie
Member#: 182253
Join Date: Jun 2008
Location: North Georgia
2002 Impreza OBS


Originally Posted by Da-Risin-Smoke View Post
Really though, I think hfc are a waste of money.

Expensive HP with the risk of a P0420 code.
Since mention of the P0420 code was made in this thread, I thought I would throw in a quick summary of experience with my OEM converter.

My car threw the P0420 code with stock configuration, and Subaru replaced the catalytic converter under emission system warrantee. This happened with about 65k-70k miles on the odometer. I also requested new O2 sensors with the cat replacment - but I had to foot the bill for these; couldn't get them covered under the warrantee bill.

I got the new cat, then bought a Borla header and Stromung CBE. Got the Borla coated - with ceramic-type stuff - hoping to keep the heat in the exhaust and avoid the CEL-P0420. Removed the entire system, then added the new pipes and kept the new OEM cat in service as well. The new exhaust worked great for about 10k miles, then I got another P0420 code.

The current code/CEL has come and gone (many times) over several hundred miles, and now has been off for a couple thousand miles. I haven't checked to see if the code is still stored, but I fully expect it to be there, and I also expect that it will return - eventually - after clearing. It seems that the OEM design won't last without killing either the converter or the O2 sensors, at least with my car.

Why shouldn't I now go ahead and try a high flow converter - can't be any more problematic than keeping the stock exhaust system?

Related question - does the rich-running nature of these cars cause any problem with catalytic converters? Can the excess fuel (with periodic afterfire) destroy the element? If so, then it's likely to happen with a HFC also - right? Does that make the track pipe a longer-lived solution?

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