Timing on bigger cams

[SSpdDmon]

Anyone have issues with decelerating surges on a 230+/230+ cam? Was out with my friend's Torquer v.2 this weekend and he had some pretty nasty surging when off the gas below 1700rpms. Fuel trims were -3~+1, so I knew it wasn't fuel. So, we experimented with spark. I upped the spark advance to 42 degrees in the 'base spark in gear' table for the cells he was hitting during the surging (~.14 grams/cyl) and 95% of it went away. I was just curious if anyone else noticed a problem/solution like this and where their timing is at??? Is 42 degrees too much??? Can I/should I go more to get the remaining 5%???

[killaz]

lurk:

[GMPX]

Did you happen to have a Wideband on it?, I understand the fuel trims were not showing anything nasty, but it would have still been interesting to see what AFR's it was running.

Cheers,
Ross

[oztracktuning]

It wasnt DFCO was it?

[SSpdDmon]

Don't think so...the rpms were too low for DFCO I'm pretty sure.

[oztracktuning]

It can be activated quite low - it seems the first thing that happens is the timing starts to decay to the DFCO required level and then the injectors pulse small. In the transition the cars can feel funny especially if they start to decay from a high timing level.

[SSpdDmon]

It can be activated quite low - it seems the first thing that happens is the timing starts to decay to the DFCO required level and then the injectors pulse small. In the transition the cars can feel funny especially if they start to decay from a high timing level.

True, but the more I think about it....the more I know it wasn't DFCO he was feeling. If the changes I made to the base spark table helped, then it couldn't have been DFCO because it uses its own linear spark table that's a lot closer to 0*. This was 0% throttle, drivetrain engaged (TC locked), less than 1700 rpms in 4th and commanded spark was in the low 30's.