KR problem, detailed.
03-27-2005, 06:14 PM
#1
Registered User
Thread Starter
Join Date: Jan 2004
Location: San Francisco
Posts: 1,322
KR problem, detailed.
I was noticing that i was getting knock retard, even at idle. Ranging from 3-12°. I have an lt4 knock module, new knock sensor, no egr, and the car is tuned to run in open loop the whole time, so no o2 issues. I scanned the car using freescan at both warming up at idle, and a WOT run. What is "BASE PW?" I notice that it doesnt rise smoothly and ocassionally (while the car is reving up) it jumps from 7 to 19, and thats when the KR kicks in. Also I notice the "Air Flow" at points jumps, from example 94.91 to 168.91. At that point, the knock retard at 94.91 airflow is 1.1 and when the airflow jumps to 168.91 the knock retard jumps to 8.2! If anyone can help me out, I have both freescan logs, and I also have lt1 edit. I am not sure if the first step should be to start tampering with the current edit file (max retard) or not. Thanks Everyone!
03-27-2005, 11:17 PM
#4
Administrator
Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 70,664
Re: KR problem, detailed.
Your signature shows a lot of "HP adders"..... but you don't mention upgraded injectors. What size injector are you running?
The maximum possible pulse width is a function of the RPM. At 4,000rpm, there is 30mSec available in 2 rotations of the crank, so your duty cycle would only be 67%. At 6,000rpm, it takes 20mSec for two rotations of the crank, so you would be "maxed out" if you saw those pulse widths at 6,000rpm or higher.
when you open the throttle suddenly, the air flow increases, so the pulse width increases. The increase is not necessarily linear, since the PCM, on seeing the rapid opening of the throttle blades provides for a nighly enriched mixture, the same way an accelerator pump would add extra fuel on a carbed setup. If you are getting knock retard at low load and part load, its only going to get worse as you increase the load on the engine.
If you have knock retard at idle, look for DTC 43.
The maximum possible pulse width is a function of the RPM. At 4,000rpm, there is 30mSec available in 2 rotations of the crank, so your duty cycle would only be 67%. At 6,000rpm, it takes 20mSec for two rotations of the crank, so you would be "maxed out" if you saw those pulse widths at 6,000rpm or higher.
when you open the throttle suddenly, the air flow increases, so the pulse width increases. The increase is not necessarily linear, since the PCM, on seeing the rapid opening of the throttle blades provides for a nighly enriched mixture, the same way an accelerator pump would add extra fuel on a carbed setup. If you are getting knock retard at low load and part load, its only going to get worse as you increase the load on the engine.
If you have knock retard at idle, look for DTC 43.
03-27-2005, 11:29 PM
#5
Registered User
Thread Starter
Join Date: Jan 2004
Location: San Francisco
Posts: 1,322
Re: KR problem, detailed.
I have SVO 30lb injectors. I understand everything you are saying. More details in the PM i sent you. also I have no DTC's..the knock sensor is working like it is suppose to. But since this "spike" is occuring all of a sudden, the Burst knock is what is causing the KR..
Thread
Thread Starter
Forum
Replies
Last Post