I need some advice about how best to handle a SA problem. I noticed that, when cold (<45*c) my SA was retarding a bunch, like 15*. This significantly impacted the idle quality as well as made for general poor performance.

Through research I finally figured out what was causing this. As I'm running a TPI L31 (vortec heads) and then swapped in a higher stall converter, I was getting some knock retard in the high load low rpm range. So I kept reducing SA in that area (now down to 10* at 400-1000 rpm). As I did so, the problem with cold performance got worse and worse. (I think what I really need is to significantly increase AE, as it appears I'm getting a lean spike due to the converter flash at quick throttle transitions.)

Not being the sharpest knife in the drawer, it took me a while to connect these dots. The $8D code basically removes the MAP from the SA equation until > 44.5c (113f).Additionally it uses the "Spark Advance Temp. Correction Vs. Load Vs. Temp." table to further complicate matters.

Seems I have several options to choose from:

Effectively disable "Spark Advance Cold Disable Temp." by setting it to -40. What could be the downside to this option?

I could set the 100kPa SA back up to 20.4* (stock $8D) since it never actually sees 100kPa in operation.

Only other option would be to try and calculate a correction for the coolant correction bias table, though this seems awfully complicated.

Any input is welcomed.

 

if I understand your post correctly, i believe all you need to do is play with this table. When cold you want to add spark typically, and also needs to be richer fuel wise. Idle speed should be a bit higher as well typically

at normal operating temps, you dont want any spark modifications in this table so values should be 0. At overheating temps may want to subtract some spark.

 

Thanks.
If this is true (and I have no reason to think not) why does the $8D table pull SA in this particular region? Would this have something to do with emissions and/or cat converter?

 

It could…im not sure but it could technically put more heat inside the exhaust and thus heat the cat up quicker. Id have to see if any other adders are used anywhere else. Others may comment

 

As mentioned it is to help kick off the cat-con. Doing this SA pull dumps a lot of heat into the exhaust, which is a good thing to help a cat start to work.

As you found $8D has some strange SA functions. Best to disable the cold start SA table shenanigans. And check the stall saver SA and disable how it works. It helps stall a modified engine.

RBob.

 

I agree with RBob... $8D has too many little side tables that mess with the spark advance...

I zeroed out the Coolant Temp Correction vs Load vs Temp table. Also zeroed out the spark advance/retard vs idle speed error tables and the power enrich spark advance. Basically, I wanted the spark controlled only by the main spark advance tables.

Keeps things a little more stable at idle speeds.

 

Thanks for the help. Much appreciated.