Excess KR at WOT
Thread Starter
Launching!
Joined: Dec 2001
Posts: 250
Likes: 0
From: Albuquerque, New Mexico
Excess KR at WOT Been helping a friend tune his C5 with LS1-Edit. We got the LTFT's to -.08 and -1.1; the O2's at WOT are .89 and .90 at 6300rpm. However, at this WOT the advance is only 19 degrees with 6 degrees of knock retard. The table shows it should be 28. Outside temp was 80 and engine cooling temp was 185 and airflow through the MAF was 31 lbs. Adding 19 plus 6 is 25 degrees; where is the other 3? Low octane table would have given 23. Any suggestions on what to do next?
Re: Excess KR at WOT john, try to put the car on a dyno and hook up a wide band O2 sensor. the stock O2's should not be used to tune with. FWIW...my atap logs show O2's between .960 and .915 on 1/4 mile passes.
if you don't have access to a wide-band, install a MAFT and richen up the mixture in hopes of curing the KR. if not done already, install the stock MAF. if you can't get 100 octane fuel, try Sunoco 94 Ultra. Make sure the exhaust isn't banging against anything (suspension pieces or chassis). good luck.
if you don't have access to a wide-band, install a MAFT and richen up the mixture in hopes of curing the KR. if not done already, install the stock MAF. if you can't get 100 octane fuel, try Sunoco 94 Ultra. Make sure the exhaust isn't banging against anything (suspension pieces or chassis). good luck.
Thread Starter
Launching!
Joined: Dec 2001
Posts: 250
Likes: 0
From: Albuquerque, New Mexico
Re: Excess KR at WOT Thanks 2MCHPWR. We are using LS1-Edit to tackle this, and running EASE scans (much quicker than A-Tap). Hmmmmm, my understanding is that if the PCM sees a richer condition, it will think there is a load and PULL timing. Am I backwards?
Re: Excess KR at WOT Vettepartz, your logic is backwards. if the PCM sees a (very) lean condition, it will pull back timing. lean conditions under load are what causes real detonation & knock.
TECH Fanatic
Joined: Nov 2001
Posts: 1,324
Likes: 0
From: Corona CA
Re: Excess KR at WOT Hmmm... I was playing with MAFT, when I richened the mixture, it pulled timing. I got the best hp at .87 02's 29° timing. Leaner pulled timing due to KR, but richer did as well.
Thread Starter
Launching!
Joined: Dec 2001
Posts: 250
Likes: 0
From: Albuquerque, New Mexico
Re: Excess KR at WOT I thought that the A/F ratio was set by the PCM using an algorhythm based on MAF, RPM, TPS and IAT readings. THEN, if this is a rich setting, it assumes there is a load and retards timing. We have found from the EASE scans that a richer setting (above .91 from O2's in open loop) will pull some timing.
