just installed an uppipe in my car, downpipe is stock and running STi catback. Dynoed and my AFR was ridicilously rich, 10.0:1, i think it even dropped below that. Was wondering if the resistor mod for the EGT with helo lean out my car a little . I did not receive any CEL and have been running it on the car for about a month now. just dont like how rich i am running, i know theres more power hidden there. any opinions ??

 

I dont understand how an upipe could make a WRX run rich. I would think if anything it could only make it run more lean since you are increasing air flow. Do you have any other mods like a bov? I dont know a lot about this stuff but logic tells me it is something else unless it is tricking the ecu to add too much fuel but I wouldnt think that would happen.

 

only mods are intake, intercooler hoses, sti catback

i dont know why it runs so rich, and i was told that 03's run leaner than the 02's

 

Thats odd I dont see how any of those mods would cause the car to run rich. Are you the first owner of the car or did you buy it used?

 

original... i was also lookin at plug gap....

 

Checking the plug gap isnt a bad Idea you will also see if they are all fouled up and if they are not the test may have been wrong (I dought it). I dont know that this will help but you may want to reset the ecu and see if that helps. Here is a thread that has a quick learning trick for the ecu (for remapped ecus) so I dont know if it will work on factory map: https://www.i-club.com/forums/showth...threadid=6413. You can also just disconnect the - battery cable and hold the break for a few seconds then reconnect it . The only other thing I can think of is to put the factory airbox back in and see if that does it. If you read some of the threads here you will see that an aftermarket intake can mess up maf reading but it usually causes the car to run lean.

 

Another thing to look at is the Maf. It may be dirty from filter oil and that could cause a problem.

 

When you say you have modded the intake, what do you mean? I thought one of the major bad mods to do to a stock WRX early on is a CAI.

 

CAI may be a major mod on a Honda, but not a WRX. See 'sticky' thread on intake debate near top of list on this forum. Stock intake is adequate for anything short of large upgraded turbo (larger than VF30/VF34).

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adding a catless upipe will make your afr read more rich when you dyno it. when they dyno your car, the afr is measured at the tailpipe. with the addition of the uppipe you are removing a catalytic convertor. canalytic convertors help complete the combustion process. so that with one less cat, that extra fuel isn't being completly burned do to the one less cat.

make sense?

 

its a graham goode short ram....

wrx ish :
makes plenty sense but i thought the computer would try to compensate for the richness as much as possible.

 

Im not sure but I think what WRX ish is saying is that when they are taking a reading from the tailpipe it is showing a rich mixture coming out of the exhaust since the extra fuel isnt being burnt by the cat in the upipe and the actual a/f ratio may be ok at the cylinders.

WRX ish.

What you said makes sence but I thought the upipe cat was only used for cold start emmisions and it wouldnt have a negative effect on emmisions once the car was warmed up since there are 2 more cats down stream. I dont know this to be a fact but that is what I was told here at I-club.

Thanks.

 

it is there for cold start emissions, but its still in line from the exhaust manifold to the muffler and it will have an affect on it

 

Thanks for the quick answer. Did I understand your explination about the a/f ratio correctly or do you think he may be running rich at the cylinders also? The reason I ask is because I plan on installing an upipe and I want to know what to expect.

Thanks.

 

i understand the concept of being rich in exhaustbut not in cylinder, but at the same time i am not 100% aggreeing with you.

my friend who is totally catless run more lean than i do and we dynoed on the same day under same comditions.