Ve Tuning Spark Surge

So I'm trying to tune my VE table, and while I'm cruising, if I let off the throttle, the spark advance drops to 0, then back up to whatever, and causes this surge. I tried adding fuel to the 800 rpm, 50 kpa cell in the VE table which used to be in the 70's. That made the surge less severe, but I still have no idea why the spark advance drops to 0.

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Speed density uses the low octane timing table and the timing is very low in the higher cylinder airmass area's at low revs. Try logging cylinder airmass to see where it's following the timing table. Add timing to that spots and see if it helps. Personally I've never tuned a VE table on a 3800 as it's a MAF based computer.

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Originally Posted by 5FDP

Speed density uses the low octane timing table and the timing is very low in the higher cylinder airmass area's at low revs. Try logging cylinder airmass to see where it's following the timing table. Add timing to that spots and see if it helps. Personally I've never tuned a VE table on a 3800 as it's a MAF based computer.

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I've tried to log cylinder airmass before, and I couldn't quite figure it out. I tried adding a channel, and nothing shows when I search airmass, but I'll try adding a graph. I definitely think you're right though. I didn't notice just how low the table goes in that area until you pointed it out. Do you think it would be safe to just highlight that entire corner and set it to say 16*?

I went out and changed both the high and low spark tables to 16* in that low rpm, high cylair area, and that didn't work. So then I changed them both to 20* as well as set the max torque timing table to 20* in that area as well. That still didn't fix the surging. Also, I still wasn't able to figure out how to log cylinder airmass.

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I'm not exactly sure then. Does it only do this in open loop VE tuning?

Not sure why you can't log cylinder airmass either, it should be a supported channel because the timing tables use rpm and cylinder airmass.

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Originally Posted by 5FDP

I'm not exactly sure then. Does it only do this in open loop VE tuning?

Not sure why you can't log cylinder airmass either, it should be a supported channel because the timing tables use rpm and cylinder airmass.

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Yes, this only occurs in open loop VE tuning. As far as logging cylair, idk. I know it's not a sensor, its a math calculation, and I believe the ECM uses both a "standard" cylinder airmass calculation, and a math function labeled 6 cylinder MAF airmass. Because when I was setting up one of my histograms, I had to use the 6 cylinder MAF cylinder airmass instead of the standard one. Which in VE tuning the MAF is unplugged, so I can't use that math function.