DirtyDaveW

I've been logging my car with datamaster and during WOT (100% TPS) the RPM's are steadily climbing, no knock retard, and all is well in the universe. Because I have a forced induction setup and a professional tune(albeit mail order), my upper RPM/KPA timing tables are in the mid 20's in the 'over 4000 rpm' table. As the 3rd gear rpm escalates into the 4000's, this happens...

• Rpm: 4,075 advance: 25 knock retard: 0
• Rpm: 4,175 advance: 25 knock retard: 0
• Rpm: 4,225 advance: 40 knock retard: 0
• Rpm: 4,325 advance: 22 knock retard: 3.3
• Rpm: 4,375 advance: 24 knock retard: 3.3
• Rpm: 4,475 advance: 23 knock retard: 2.6
• Rpm: 4,500 advance: 21 knock retard: 7

Now the same RPM range in 1st and 2nd do NOT have ANY knock retard, nor does the mystery '40' degrees of advance appear. Do any of you guys know from where that '40' degrees could have been retrieved?
Thanks,
Dave

bobdec

I can show how OBD1 works, s/b similar to OBD2. There are two timing tables Main 0-4000 RPM and Extended 4000-7000 RPM, together 336 timing settings based on specific engine operating ranges. From low RPM high vacuum (idle) to high RPM no vacuum (WOT). The actual timing can vary from the table EG knock can pull up to 10* from the setting and in PE mode the PCM can add 2-3 * to the setting. Your info almost looks like someone had a typo when entering the data. Since 4000-4500 RPM data is actually in two tables Main and Extended, maybe one is incorrect, also when in 1st or 2nd your MAP may be different and you could be using a different timing cell, than in 3rd, that's a guess. Below is a pic of STOCK '95 LT1 timing settings just for reference.

[IMG][/IMG]

DirtyDaveW

Well, thanks to Datamaster, I was able to pin down some things. I went into my file and added a bit of fuel in some regions and subtracted some timing in the upper KPA's . Just took a test drive and tada! no more knock retard!! Now to gently add a degree at a time and retest till I get KR again then I'll back off.