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Catback Exhaust


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Gentlemen (and Ladies)

So two weeks ago, my middle section decided that it no longer wanted to be attached to my back box. After a week of driving with what sounded like a bags of nails in my exhaust, I decided to go for a stainless catback system. My thought was, I would like a bit more noise, and it should be more efficient, due to reducing back pressure.

For the week before the mod (without the backbox attached), i seemed to get really good mpg, but on the first half a tank after the mod, the fuel gauge is dropping remarkably quickly.....and my driving style hasnt changed- if anything I'm being even more efficient so as not to get an ASBO (it's a lot louder than I thought it would be...gulp).

The new catback comes from after the  post cat o2 sensor follows the standard exhaust route, and then bends under the rear suspension before bending again into the new back box. I've removed the middle box, and the new backbox is not far off being the same size, only difference is the new pipework from after the cat is 1/4" diameter bigger. That'll slightly kill air velocity, i know, but surely not much.

Any ideas on why this mpg seems to have taken a nosedive? I know the celica fuel guage likes to play about a bit, but this is a little bit too much. I'm thinking of doing an ECU reset, my thinking being this could be to do with the air/fuel mixture. I'll maybe do a MAF sensor clean too, but I'd be surprised if that was it, i clean that every time i do a service. Is there a set procedure for resetting the ECU? On other cars i've owned, if you don't follow a set procedure you can end up messing up the BSI etc. (they were french).

Any help appreciated,


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