# a couple of things..

Posted by Matt (93SE) on September 08, 2004 at 10:13:23: In Reply to: ok providing that.. posted by Alex on September 08, 2004 at 10:02:30: Just having the pipe on the car causes the ECU to compensate- it'll change the entire fuel map slightly to gain the benefits of the pipe. that includes while at idle. (which is NOT where emissions tests are done here in TX. they're done at 15 and 25mph, and are supposed to be between 1500 and 2500rpm, IIRC)... So this will cause the emissions to change slightly just from that. ASSUMING that everything else on the car is working properly, O2 sensor, TPS, MAF, EGR, cat, etc... then emissions will pass fine. BUT, if you have a borderline component in there somewhere, incorrect TPS, failing/lagging O2 sensor, failing cat, etc... then you're going to have problems... you're going to have problems anyway, but the fact the Y pipe is there will cause more. The pipe is also larger diameter and thinner walled, so there is lower exhaust gas velocity and lower exhaust temperature due to radiation.. that causes the cat to run cooler and hydrocarbons to go up.. so again, if the system is working at 100% before the Y pipe, you'll be fine. if the system is borderline before the Y, then you'll likely fail. last year's emissions test, I was well under the maximum on HC.. this year, max was 124 and I passed with a 124. the only change in the system since now and last year is the Y pipe. before going in for the test, I did the same ritual as I did last year. clean air filter, replace spark plugs, plugs, test EGR for proper function, retard timing to stock base timing, fill with 91 octane, and burned off a tank of gas. the only change in the emissions was a higher HC content. all other tests passed with flying colors.. of course there are many other minor things that could be wrong with the car causing the high HC, but for overall performance and running condition, the engine is the same as it was last year. Replys: what about your o2 sensor? Alex (90 300zx) 10:18:01 9/08/2004 (2) it's working per the FSM, but that doesn't mean it's lagging. replaced 1.5 yrs ago. nm Matt (93SE) 11:12:02 9/08/2004 (1) I dont know how old my O2 is, but its from Jeffys old car ;) MrGone (92se) 12:06:19 9/08/2004 (0)

Name: |
E-Mail |
Car: |
Subject |
Message:
: Just having the pipe on the car causes the ECU to compensate- it'll change the entire fuel map slightly to gain the benefits of the pipe. that includes while at idle. (which is NOT where emissions tests are done here in TX. they're done at 15 and 25mph, and are supposed to be between 1500 and 2500rpm, IIRC)... : So this will cause the emissions to change slightly just from that. ASSUMING that everything else on the car is working properly, O2 sensor, TPS, MAF, EGR, cat, etc... then emissions will pass fine. : BUT, if you have a borderline component in there somewhere, incorrect TPS, failing/lagging O2 sensor, failing cat, etc... then you're going to have problems... : you're going to have problems anyway, but the fact the Y pipe is there will cause more. : The pipe is also larger diameter and thinner walled, so there is lower exhaust gas velocity and lower exhaust temperature due to radiation.. that causes the cat to run cooler and hydrocarbons to go up.. : so again, if the system is working at 100% before the Y pipe, you'll be fine. if the system is borderline before the Y, then you'll likely fail. : last year's emissions test, I was well under the maximum on HC.. this year, max was 124 and I passed with a 124. the only change in the system since now and last year is the Y pipe. : before going in for the test, I did the same ritual as I did last year. clean air filter, replace spark plugs, plugs, test EGR for proper function, retard timing to stock base timing, fill with 91 octane, and burned off a tank of gas. : the only change in the emissions was a higher HC content. all other tests passed with flying colors.. : of course there are many other minor things that could be wrong with the car causing the high HC, but for overall performance and running condition, the engine is the same as it was last year.