Attn dsteck and amric: surging LS3 Camaro, pointers needed- timing spikes

[BAD LS1]

After doing all the changes in Amric's c6 tune noted here:
http://www.hptuners.com/forum/showth...hpoints&page=3

This thing still has the timing twitches that sets off the surges. Primarily worst around very very light throttle input needed to keep it around 65mph on the freeway on level ground. Some is also noted at light throttle accel too (see pic attachments) i probably done have the proper stuff logged here but you can get the gist of where and when its doing it.

Also on a side note, this thing has mid throttle misfires too im trying to work out, almost like lean misfires... nothing shows up on a wideband it happens so fast but only does it in 4th and 5th between 2000 and 2500. New tr55 plugs gapped at .032". nothing shows up on the logs either when it does it.

Please take a look at my stuff attached here and help me out with some suggestions if you can.

This is a 2010 camaro with a 231/247 .617/.624 113lsa cam in it. It runs awesome everywhere, makes awesome HP and has great maners aside from these two areas.

Thanks.

[DSteck]

Pull timing out from main spark in the problem areas and smooth it. A 13º overlap cam should tame down pretty quick.

[NTIMID8]

M6 Spark smothing?

[DSteck]

M6 Spark smothing?

Turning that off gets rid of the spikes, but the drivability doesn't get any better.

[BAD LS1]

Ok made some adjustments, the timing is lower, but the spikes still just yank the same amount yet...

Also is there a way to get the thing to go into PE sooner based on TPS more so? the HOT setting adj doesnt seem to do much, but i think that would fix my lean misfire issue too.

It runs a ton better at slower speeds as far as surging goes though, highway speeds, still surges like a mofo.

[BAD LS1]

So far so good, i have it maintaining about 23.5 degrees during those low rpm cruise speeds now with the coast down about 2 degrees under. It only timing surged once during an odd condition but it seems the magical spot where it will provoke it is at 27% tps on the scanner. Taking the timing away reduced the torque enough where i have to keep my foot into it enough to maintain speed at about 34% vs 28-30% before which keeps it away from the trouble point. i can roll through my neighborhood now at 25 in 4th basically idling in 4th at 1k and no bucking. It does drive a ton smoother overall and i still have the timing in the upper 30s when above 2k yet for responce.

[DSteck]

Glad it worked out. That's basically what happens... you force the engine to load up more. I still get decent fuel economy on the highway (24mpg or so) in my Z06, and still have plenty of response, because as soon as I tip into the throttle and cylinder load goes up, timing goes right back in. People have claimed that pulling the timing out screws up response, but I haven't found that to be true.

[BAD LS1]

Glad it worked out. That's basically what happens... you force the engine to load up more. I still get decent fuel economy on the highway (24mpg or so) in my Z06, and still have plenty of response, because as soon as I tip into the throttle and cylinder load goes up, timing goes right back in. People have claimed that pulling the timing out screws up response, but I haven't found that to be true.

consequnetly i reduce the timing from the upper 30's to the upper 20's where i was having that said misfire condition and its just about non exsistant now too, basically cutting back some cylinder pressure and the need for more fuel during that small window. I will fiddle with it all some more and report back, but there is some compelling evidence that as you mentioned timing adjustment is the key to controlling bucking. The light surging effect i can feel doesnt bother me at all and it only does it when the o2's switch at the same time instead of opposite of eachother.