Whats the best cruise scenario, throttle - RPM - timing

[legerwn]

2008 Hummer H2 (square block)
L92, 6.2L, GPI LLT 2 cam (2250 rpm and up)
2600 Circle D, 6L80 Trans
Thermal Barrier on Piston crown
DFL-1 coating on piston skirts
LT Headers with full 3" duals, X-pipe

Working on the trans tune and trying to hone in on the best gears,
What works best, higher throttle openings, lower RPMs, less timing or lower throttle opening, higher RPMs, more timing
Current testing,
75mph, 6th gear with OD gets me, 40% throttle, 1600 rpms, 20* timing
75mph, 5th gear with OD gets me, 31% throttle, 2050 rpms, 32* timing
75mph, 5th gear W/O OD gets me, 29 to 30% throttle, 2300 rpms, 32* timing

Neal

[hjtrbo]

Is your goal fuel economy?

[legerwn]

All around best performance,

[hjtrbo]

Let the butt dyno work. Or leave it in 4th for even better performance.

[legerwn]

I agree, the butt dyno says 5th with higher RPMs yields less down shifts on gradual grades while cruising on the interstate while 6th is very lazy and down shifting regularly. With the cam I have I need in the area of 2000 rpm cruise or a little higher for good all around performance.

Fuel economy and Hummer H2 should no be used in the same sentence

Looking like 4:56 gears will get me in the ball park,

Thanks Neal

[grubinski]

What works best, higher throttle openings, lower RPMs, less timing or lower throttle opening, higher RPMs, more timing
Current testing,
75mph, 6th gear with OD gets me, 40% throttle, 1600 rpms, 20* timing
75mph, 5th gear with OD gets me, 31% throttle, 2050 rpms, 32* timing
75mph, 5th gear W/O OD gets me, 29 to 30% throttle, 2300 rpms, 32* timing

Neal

I go on the ***assumption*** that the lowest (cyl_air * rpm) is better for economy.

So my car running in 6th might be .230 cyl air, 1600 rpm, and in 5th .200 cyl air, 2400 rpm. Since .230*1600 (368) is lower than .200*2400 (480) I'm better off in 6th, because I'm moving at the same speed and putting less air (thus fuel) through the engine.

I have a lot less timing at 1600 than 2400 to stop the car bucking in parking lots, but it still is much more efficient by this measure to be at lower rpm when cruising.

Mike