Stay in best BSFC zone even if torque converter slips?
 

I have been playing with accelerating efficiently and I've realized that I can make my tranny shift into third quickly, then get on the throttle and hold 2500 RPM at 65-70% load. This results in fairly brisk acceleration. About 45 mph I can just let off the throttle and it upshifts and locks the torque converter.

Although I don't have a BSFC Diagram for my engine (2.0L "Beta II" in many hyundais and kias), I assume that this RPM/LOAD is near the best efficiency point. But I can't help but wonder if it is allowing the torque converter to slip too much and is undoing any extra efficiency the engine might be gaining. Whereas operating at a lower load level might result in less slippage, possibly meaning that the entire BSFC diagram for the drivetrain system gets shifted "downwards" to lower load levels.

In other words, unlike a manual transmission, I think the efficiency of the engine and automatic tranny must be considered together to make the BSFC diagram useful.

Any thoughts? Trying to avoid a detailed investigation into something that others have already figured out! (And save the gas I'd have to burn!)

Probably should figure out if the torque converter ever locks in lower gears. I think higher rpms = higher torque converter efficiency, but don't quote me on that one, it's just a hunch based on driving my mom's car.

I don't know if this is actually working, but when I drive an automatic I press the gas lightly to start, roll onto the pedal halfway as the car picks up speed, and as the rpm approaches 3000 I let off a little to coax a shift and then back on it a little, and then I take note of the rpm; Sometimes the transmission doesn't want to shift up, so I switch to neutral and then back, usually that coaxes an upshift, and then I put very little pressure on the pedal to keep it in the highest gear.