8 degrees retard on stock timing table.

**Scrufdog** · 07-13-2014

For my 1995 Burb, in my sig.

So I noticed this awhile ago when I advanced the entire table 4 degrees. A lot of retard around 1600 RPM, especially at low vacuum, 70-75kpa. My current tune has the timing tables back to stock and I'm still getting the same 8 degrees retard in the same area. Base timing at the distributor is 0 degrees.

The cap/rotor/wires/plugs are all about 4 months old. Havent pulled the plugs to see how they are doing yet, wanted someone to sneak a peak at what I got going on, maybe I missed something somewhere in the tune. Overall the Burb runs great and gets about 13mpg.

I've attached needed files.

Thanks

**Scrufdog** · 07-13-2014

forgot to add picture

**steveo** · 07-13-2014

8 degrees of retard is a lot, that means the knock sensor is getting pegged. at low vacuum like that, it's a concern for sure.

since the stock timing tables are always conservative in high MAP areas, i'd be inclined to try adding about 10% more fuel in the area of concern to determine if the knocking is due to insufficient fuel in that area. trying to cure knock with less timing is often the wrong answer.

another thing is, though.... 1600rpm and 70+ kpa? it shouldn't be spending much time there. that's lugging territory.

at the same time you're trying to resolve that problem, you should be trying to make your transmission shift earlier so it never spends much time there.

**Scrufdog** · 07-13-2014

i find the right slight incline to get it to hold 1600 rpm at 70 kpa. I was thinking about a little more fuel as well. I've run the BLM tables through the Correction Tables a few times, but I wouldnt mind trying a little more fuel there.

I'm assuming the knock is stock with 210,000 miles on it. Do they become more sensitive as they age? Never messed with them much.

Interesting thing perhaps, or not, is that even when I bumped the entire spark table up 4 degrees, I was still getting the same 8 degrees of retard.

**steveo** · 07-13-2014

I was still getting the same 8 degrees of retard.

may very well be false knock, then.

if you can verify it's not real knock you can probably just disable knock retard entirely for that region and call it a day.

again, not an automatic trans expert, but 70kpa @ 1600rpm should be shifting imo. i would never operate an engine with that load at that rpm. as a ballpark, could be 2300rpm @ less than 50kpa and take less fuel, being easier on the engine. not that it should be knocking, but i just dont like seeing logs with lots of running at that kind of load.