Can anyone tell me info on the max ignition advance for a Saturn SOHC?
Mine gets to 38 or 39 max. I run 87 octane fuel, no additives. I'm trying to find out if there is some point at which it either can't go beyond, or where there is no fuel economy improvement. From what I understand, the farther advanced it can run without pinging, the better the fuel economy will be.
I've seen 39 and 40, but its been rare to see a 40. There is a guy on Saturnfans with an SC2 (DOHC) that has had momentary 47.5 advance running 93 octane.
If i recall correctly, for every additional degree of advance, fuel economy should increase, until it gets to the point where it pings and it all goes to hell in a handbasket. On the old cars my dad used to advance till it pinged, then back it off a degree or so.
It seems like I remember seeing 41* on my SOHC Saturn once or twice but 39-40 was more common. My '99 DOHC would routinely cruise at 45-46 at ~70 mph on the way home from when I had the Singh Grooves put in and the intake cam timing adjusted.
Horsepower is how hard you hit the wall, torque is how much of the wall you take with you.
Put a tank of Shell V-Power 93 in it, reset, and relearned. Highest seen was 41, but I'd say it was typically running up to 1 degree more advance. Very minor mpg gain, maybe 1 mpg on the highway. When tank gets to 1/3, I'll fill with 87 and repeat to simulate 89, and see if its any better.