can someone clear up these tuning issues...?
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
can someone clear up these tuning issues...? ok here is the deal. i have ported MAF ends and i just wanna make sure my tune is ok. i asked diablo to double check the different tables in the tune and make sure they were all right but here is the deal. my LTFT's are 0% at WOT. at WOT my o2's seem pretty consistent but every once in a while i get some KR. i think its just when the car is colder on its first WOT run. so anyway the o2's seem to stay consistent from 3000+ but lower rpm they seem to be 890 or so and then end up at 945 top end. im thinking its jsut delay in the o2's cause in 4th gear they seem to be the same all the way up. timing is all set right also. the problem is my MAF flow is in the low .9's lbs/min after it idle for a while. shouldnt these numbers be lower like in the 8's? im not sure what this means but i wanna make sure i have my car all set up right and i dont nkow what this effects. what else would make o2 readings to alter at high rpms? could flase knock cause a drop in the o2's? cause i cant hear it detonate but it shows knock and the o2s go down. i have header brackets hittin so i wanna make sure this false knock would cause a drop. i just need to make sure its all ok so i can get the car running right. sometimes it doesnt feel as good. anything else i should look at?
Any kind of KR will cause a small jump in the a/f ratio, whether it be false knock or real . The sudden reduction in timing will make your O2's quickly percieve a rich condition.
Additionally, percieved a/f will alter according to the load on the engine. Light loads (ie 1st and 2nd gear) will generate different O2 readings than heavy loads (ie 3rd and 4th gear) give the same fueling. Our cars are programmed to compensate for this, but messing with the MAF / programming throws this correction out the window.
FYI, O2 readings at WOT are pretty much junk, especially on a modified exhaust. If you want to check your tune properly, get a wideband strapped on, or take it to a shop with a wideband.
Additionally, percieved a/f will alter according to the load on the engine. Light loads (ie 1st and 2nd gear) will generate different O2 readings than heavy loads (ie 3rd and 4th gear) give the same fueling. Our cars are programmed to compensate for this, but messing with the MAF / programming throws this correction out the window.
FYI, O2 readings at WOT are pretty much junk, especially on a modified exhaust. If you want to check your tune properly, get a wideband strapped on, or take it to a shop with a wideband.
