I'm working on doing a tune for my LS4 (5.3L DOD) Monte Carlo SS. Nothing special, just some timing tweaks, throttle response tweaks and I want to play with the DOD system a bit and see if it gains anything on the fuel mileage.

Factory, the DOD system is VERY touchy, if you are going up any type of small incline, or if you have the cruise set to anything over 65 MPH, the dod system pretty much remains disabled. I want to play with the vacuum enabler table, as from my log data that appears to be what's holding the system out of DOD during the conditions discussed.

Now, I know that keeping it in DOD under these circumstances may allow some of the 'feel' from the V4 mode to be transmitted to the driver as it's working the 4 cylinders in operation more. I'm not too concerned with the 'feel' or noise during v4 mode, but want to see where that line is as far as fuel economy going from V8 to V4. I believe that the factory programming leaves a few MPG on the table in sacrifice of driver comfort/feel.

Has anyone ever played much with it, or have some advice on the subject? Car seems to do rather well currently MPG wise, usually pulls 24-26 MPG highway (65mph cruise speed), and DOD system operates within the programmed parameters, no DTC's present.

Thanks!