I don't have time to get into helping much, but I have effectively run 26 degrees BTDC timing all the way to 6.5K but you need good fuel, just real good pump gas, keep the coolant below 200 degrees F and IAT below 90 degrees. With no Knock retard. J J
Hmmm, good data point. So I'm at 12.2:1 afr and 15-18* advance to get rid of the knock. What does that imply? Crappy gas (Chevron)? We're running 91 octane so we could take a few degrees off for that right? Still seems a ways away.
Get some good gas, Sunoco 93/4 whatever, Mobil. Try for no Ethanol. I can make good power at 13 + A/F because of head efficency. But good gas is number one to get first!!! I can only get chiity gas here in New England so I add 4 gallons of 100LL Avgas per tankful. J
I have to agree with getting good fuel. I don't know what you have in Cali. I know here in Minn, the winter blend fuel is shitty compaired to summer blend. I think each person is going to pick there best gas station in there area. then tune for that fuel. It could vary a lot in the tune from one car to the other. Because in reality your stuck with what available close by for daily use.
So bad fuel is a possibility. Is it a huge probability? Given that I'm at 12.2 a/f and it looks like 15* to 18* timing is as far as I can go is it almost a sure thing that it's the gas? Concensus is still out on afr. Shoot for 12.2 or 12.8? Or does it just depend where you see the most power. Seems that afr should be flat across the rpm range. Concensus is that the target for timing should be around 25* advance (gas allowing). That number would be considered good if you can hit it (without knock) within the 12.2 to 12.8 afr range? I was thinking pick an afr and then tune for timing advance short of knock. Maybe give priority to timing and adjust afr down from 12.8? would be a better approach?
The other issue is our knock sensors which are very sensitive to any sounds that are not true detonation (exhaust, valvetrain, rod knock, etc.) and harmonics. When my car was CMR tuned, they had to turn the sensitivity down an additional 20% over what the Predator already did.