krusty wrote:Not past MBT for that given scenario of load by any chance?
Nope, all my engine are tuned spot on for the spark as I did them on the dyno myself. But they were tuned on 98 mostly. But like I said, even on 91 or the better E10, I never have knock in any other condition but for the 2 places in Melbourne without fail in my travels. And if I can counter this successfully using that table for the worst possible scenario which this is, both conditions and setup on the car, I have the means to safely tune to get the most of any engine current and going forward.
My experience is the larger the cam the more this knock limiting is raised to the point it doesn't surface. I also run a straight pod, but so far 99% of the condition, my MAT temps rarely exceed 40 odd.
Some things I have tried, increasing the WOT AFRs, did absolutely nothing and when I bought my red car, it had a mystery memcal in it, but it was so rich it poured black smoke and sooted up the rear bumper, yet it knocked like a MF in the same spots in Melbourne but worse, and also when the engine was still cold but the weather was hot. So it's timing was probably way too high, it also still rang the cast iron logs which lowers the knock limit a lot too and MBT tanks as well.
I also run an 82 stat now, mainly for easier warm up counter intuative. This lowered the threshold for this knock somewhat but was no magic bullet by any means, and with yesterdays testing, the coolant temps got over 100 and I never got it to knock, so it's far less of a factor.
This tells me, AFR and coolant temp has less influence in these engines as oppose to timing, but the main factor seems to be air intake temps more than anything for a given fuel.
Fuel octane is the other big factor. I ran that same engine on the red car on E85 for a week and cranked the WOT timing to 40 deg to find the knock limit, I never did and going any higher was probably going to break something with the sheer pressure opposing the piston on it's way to TDC.
I also ran the new engine for the red car with high comp and bigger cam on 98 accidentality with 10 or so too many degrees timing and it never had an issue. The MBT came in at peak at WOT of 20 deg.
