5% increased gas mileage

[reese.leblanc]

Ted, can I assume that raising the timing to that level (i.e. 50*-60*) in the vacuum would be done in the 1500-3500 range? I would think that doing it in the 0-1000 ranges would significantly affect trying to set up idle, etc?

[RETed]

Originally Posted by reese.leblanc

Ted, can I assume that raising the timing to that level (i.e. 50*-60*) in the vacuum would be done in the 1500-3500 range?

Yes, and all the way up to redline...
Above 4kRPM's, it's more for high RPM decel.
Most of us run decel fuel-cut off, so there is little to zero fuel in the combustion chambers.
Ultra high advanced ignition timing is purely for emissions reasons and has nothing to do with power.

I would think that doing it in the 0-1000 ranges would significantly affect trying to set up idle, etc?

In actuality, I doubt the ECU would even go into those ranges...
Really deep vacuum under 2kRPM is almost impossible to hit in most normally running engines.
The "best" vacuum is usually at idle.
(Most of us run anywhere from stock -5 degrees to up to +10 degrees total advance on idle.)
Cracking the throttle will cause the vacuum to head towards "0".
When idle speeds start to drop (500 RPM or less), vacuum heads to "0".
If you're running idle control, your idle control / BAC valve is going to bypass air when RPM's start dropping toward idle speed, so this hurts vacuum too.
I like to just "flatten" the map in those areas, just so the map looks pretty.
It's unlikely the ECU has to access those portions of the map in reality.


-Ted