Little blips of knock retard at cruise.
Jul 13, 2009 | 05:33 AM
#1
Thread Starter
TECH Apprentice
Joined: Dec 2002
Posts: 309
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From: Socal
Little blips of knock retard at cruise.
I have the following:
- A totally stock 2004 Sierra 5.3L (LM7)
- 91 Octane Chevron Gas (highest available for consumer grade here)
- A high-octane timing table that has been blended about 50% toward the values of the optimal timing table. I've also used a HPP3 tune as a guide.
- Unmodified low-octane timing table.
Over the course of a two hour drive to Big Bear, including the climb from sea level to 7000 ft, I saw some KR. Mostly in the 1* range. Hot weather (100*) A/C on. I logged the trip at 10 frames/second.
As an example, I logged a little over 3000 frames (300 seconds) at 2000 RPM, 0.40g/cyl DYNCLAIR. Filtering for KR > 0, I see 300 frames (30 seconds) of time in that cell. The average KR during those 30 seconds was 1.1*. I'm commanding an AFR of 15.3 for that cell using lean cruise, and timing is set at 32*. The HPP3 93 octane tune has it at 35*. The HPP3 87 octane tune has it at 33*. Factory 87 tune is 27*.
Bear in mind I'm quite new to this, but is the above what I'm looking for to back off timing? Or is this false knock or otherwise a non-issue?
- A totally stock 2004 Sierra 5.3L (LM7)
- 91 Octane Chevron Gas (highest available for consumer grade here)
- A high-octane timing table that has been blended about 50% toward the values of the optimal timing table. I've also used a HPP3 tune as a guide.
- Unmodified low-octane timing table.
Over the course of a two hour drive to Big Bear, including the climb from sea level to 7000 ft, I saw some KR. Mostly in the 1* range. Hot weather (100*) A/C on. I logged the trip at 10 frames/second.
As an example, I logged a little over 3000 frames (300 seconds) at 2000 RPM, 0.40g/cyl DYNCLAIR. Filtering for KR > 0, I see 300 frames (30 seconds) of time in that cell. The average KR during those 30 seconds was 1.1*. I'm commanding an AFR of 15.3 for that cell using lean cruise, and timing is set at 32*. The HPP3 93 octane tune has it at 35*. The HPP3 87 octane tune has it at 33*. Factory 87 tune is 27*.
Bear in mind I'm quite new to this, but is the above what I'm looking for to back off timing? Or is this false knock or otherwise a non-issue?
Jul 13, 2009 | 09:02 AM
#3
I fought cruise type KR for the longest time. Never did stop it with tuning. Richened cells, leaned cells, timing drops.... you name it. Those have virtually disappeared after installing and oil catch. I'm guessing small drops of oil from the PCV system where making it into the intake and causing them.
Aug 4, 2009 | 09:44 AM
#7
fourth gear TC locked ISNT low load. Thats why it KR's a bit. Mine will do it from time to time with less timing and around 15.3 AFR.
Last edited by charcold-bowtie; Aug 4, 2009 at 09:49 AM.
