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Had to chime in, sorry for my first post being in mid thread, but as a instructor and a tuner this is something I get asked alot.
The short an simple answer is that disregarding air resistance or losses due to great average speed, the ideal eco-acceleration should be the maximum acceleration available prior to entering open loop, or pulling ignition timing due to knock, in the highest gear possible.
I tend to accelerate under heavy load in 5th gear (as soon as its reasonable to take), but reduce the acceleration enough to stay in closed loop.
This minimizes frictional losses in the engine by using the piston stroke, valve duration and pumping losses to their maximum ability and since rotational losses are not load dependent the greater power output increases the efficiency of each engine power stroke by reducing the loss %.
Its the same idea as having to withdraw $400 from a ATM, would you do it all in one hit or in 10 little hits? Your gonna get dinged $1.00 for each transaction so might as well minimize the number of transactions by maximizing the available amount in each one.
Its the same reason why the same engine in a turbo diesel variation can get better mileage then in that engine in non turbo diesel variation. The extra RPM needed in the non turbo causes unnecessary frictional losses.
Hope that helps,
Steve
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