LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

What's acceptable knock retard readings?

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Old Jun 23, 2003 | 12:55 PM
  #1  
JAFO1994's Avatar
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From: Oshkosh, WI., United States
What's acceptable knock retard readings?

I'm getting no knock retard in closed loop regular driving, but a little at WOT. My log shows no retard in first gear, 5 degrees hit's for one line at 4200 rpms in second then drops off as the rpms's climb, and then 7 degrees hit's for one line in third gear at 4400 rpms and drops off as rpm's rise also. Is this too much or normal. The retard is only there for one or two lines and then drops down to 0 rather fast. I do have a squeak that sounds every time the car shifts, but I think thats the belt slipping or CIA. Would that cause it? I ran it at WOT a second time and got very little retard in second gear, only 3 degrees. Also, I get 100% TPS reading when it's about 3/4 throttle, even though TPS voltage doesn't max out until full throttle. Anybody offer any help.
Old Jun 23, 2003 | 01:04 PM
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You're looking for 0 knock retard. Are you running cheap gas or a car with high coolant and/or air temps? Those are some common causes that would induce detonation.
Old Jun 23, 2003 | 01:09 PM
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Air temp is in the 80's here with 100% humidity. It's been raining for a over a week and I finally got a dry road to run, but it was overcast and the air was so thick you could cut it with a knife. The road also wasn't the smoothest. I'm not sure if that matters.
Coolant temp was 177.
Old Jun 23, 2003 | 02:06 PM
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In general, you want "0" knock retard at all times. However, I have found that there is often a small "blip" of retard on shifts.... with lifting throttle shifts on my M6, it was possible to get 5 - 8deg of knock retard, ONLY at the shift points (5,800rpm). I would suspect an A4 would exhibit similar tendancies.

However, for the PCM to simply start pulling timing in the middle of a gear... e.g. 4,200-4,400rpm.... would be costing you power. Is it possible you have any mechanical noise that happens at that point.... rattling exhaust, the steering shaft hitting headers, headers hitting the body, etc.?
Old Jun 23, 2003 | 02:20 PM
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I don't have any noise that I can pickup even with windows open, besides the screetch from the CIA or belt when it shifts. I looked at my logs from this morning when it was cooler outside and my knock counts were lower at 1500. I had a few 5000 rpm shifts there and no knock retard to follow. My Knock counts this afternoon on my WOT pass showed knock counts at 2000 across the board, except when I got Knock retard they were a little higher. Can higher air temp cause the knock counts to go up. I was also wondering if the ram air scoop on the bottom of my car was causing too much flow in or disturbance to cause map readings to cause the KR, since KR got worse in 3rd gear than 2nd gear and none in 1st.
Old Jun 23, 2003 | 02:40 PM
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If you can, post your results for us to look at. If not, can you put down the description a bit better on when it happens?

I use Datamaster, however, an excel spreadsheet will also work.

Ben
Old Jun 23, 2003 | 02:51 PM
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I'll post it tonight, my laptop is in the car right now and i'm at work right now. I would really appreciate if someone could take a look at it and offer advice. I just have Bryan's mail order tune right now. I have it saved on spreadsheet. Thanks
Old Jun 23, 2003 | 03:31 PM
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Do some research, because I know that humidity plays a part in octane ratings, detonation, etc... The air is denser and I know that does affect the engine.
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