ok i am goin to the track and my evo it totaly stock. but i thought that mabye if i take out the cat so it is just the downpipe that it would be faster. but it was not soo. can anyone tell me why. is it cus the 02 sensor was throwing a code to the computer and was in a safe mode or somthing. i was told that mabye if i reset the computer with the cat out then drive the **** outa the car for like an hour that it will adjust. i thought that back pressure wasnt an issue on a turbo car. anyway please tell me if it does anything when i do that. or not. cus i put it back on but i want to go to the track on friday and if this makes me gain a lil hp then i will take it out agian cus it takes like 10 minutes to take out. thanks.

Derek

 

well anyone?

 

i think your safe mode theory was dead on.

 

so if i recet the ecu after i take out the cat. will it not go in to a safe mode. or do you think it will ?

 

When I had the Ultimate racing test pipe installeed ,
I felt a DIfference right away on the top end but didnt notice any performance lost at all. I have seen on pruven's site that installing test pipe and their axleback will actually MAKE you DROP your BOOST like 1 psi or 2psi and you'll need a Boost controller to dial up the boost agin to see the gain.

P.S. I always had a Boost coontroller from the begining so maybe thats why I never notice the lost.

 

The secondary o2 light should NOT put the car into limp mode. If it was in limp mode it would be waaay slower. Are you comparing previous passes with passes recently made w/o the cat? How different are the times? What were the weather conditions for each? Same track? Those are more likely culprits to the slower et's than the lack of a cat.

I've been running around for 2 weeks with a test pipe (Buschur 3" turbo back), and a CEL. The car is definately faster with the test pipe versus the 3" hi-flow cat. I picked up about 1.5psi of boost due to the decreased back pressure. It's real easy now to kick the rear end out when turning a corner.

 

o im talking about a bone stock evo with just the cat removed. that deletes the rest of the exhaust so it is just the "stock" dp and nothin else. would that make me slower. i have not gone ot the track yet with it out. but im wondering if it is worth it.. im want to go to the track friday so i need more info by then. do you think it is worth it or would it be faster stock.

 

to really tell if it helped or not you need to Dyno test it...
to find out on the track is to hard.. shifting slower, hotter day,clutch slipping,just a plain BAD driver.. it can feel slower. i think with a full exhaust and intake you will feel the most power out of removing the cat.. imo

 

I am a little confused, in the first post you said you ran it that way then in your last post you said you haven't ran it that way.
Seat of the pants will feel different with no exhaust past the downpipe. You probably are losing boost with no exhaust and are not able to raise it back up on stock. I don't know how much the boost control of the ECU can compensate for that.
You definitely want to reset the ECU with the exhaust off the car, there is a considerable difference between a learned map with an exhaust and without one. Aside from the potential impact on boost the car with no exhaust past the DP will defintely be quicker than stock.

 

ok well all along your engine has been working with some pressure against it..not that there is no cat and that its just free flow...and maybe the engine works better with some of that pressure against the engine..not sure though but ur o2 sensor idea might be right..but never really heard of that idea..

 

best idea would be to take ur car out 100% stock and get baseline numbers to work off of. When you begin hitting consistant times then u know thats pretty mkuch hwat the car runs... Remove your cats and what not then take it out again if you increase time then you've gained power, if your time stays the same but incdrease trap speed then you've gained power... Good luck