The cracked nut

Ok things seem to be going pretty well now.

I have totally axed PE mode as I was getting a "bog" when throttle went past its trigger position and enrichment started often at too low rev's. Now it comes on progressively after 85kpa richening up at max torque. Delco recommended a trigger of 80kpa rather than the factory 15kpa, but with the custom OS thats not required as I can command it with table B3647.

Ive been reading lots. Too much advance isnt good. In fact less advance in theory is good depending on what the power output is and at what point of the cycle it occurs. Afterall if you can spark after TDC on the power stroke and have max force expended on the downwards stroke then you are not wasting combustion pressures on slowing down the compression of the charge.

Here is my current spark table as of today.


So in summary its not important to get hung up on how much advance you can run. Your engine will be tuned to its fuel based on many aspects including its VE, combustion chamber design etc. Im running 22.5 deg at max torque around 4000rpm. It wont take any more without KR. In fact it might run even harder with a little less advance. What I did notice however is that after adding a few degrees at the lower end things have got very lively in the low and mid ranges, so much so that I requred a full 5% more VE across the board. I did take some timing off the upper end and some minor VE adjustments, however the engine is now running well.

Previously through the 70+ tunes that its now had in it I could pick out times when certain area's and parts ran well. Now I cant detect any part which needs improvement. Well not quite true. Id like a little more straight off idle..

I may richen up to 12.6:1 at WOT peak torque as Im running 12.8:1 and some recent reading suggests I should go a little richer and lean it to 13.1:1 above and below this point. Though near the redline and fuel cutout, I think a lean towards the high 12's would be more prudent there.
I dont think timing could be improved much more, subject to a dyno tune.

I must get some 0-60 times to see where I am now. In fact no more posts till I have done so :)