Similar thread:
http://ecomodder.com/forum/showthrea...ate-28617.html
I'll share my thoughts from it with a few updates:
As an 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, or increasing AFR, in the highest gear possible (or lowest RPM). And... that acceleration is only useful if upon reaching the intended speed one immediately starts to Pulse and Glide, at least in a 5spd. This is because the gear ratios are locked for a particular gear, so in order to take advantage of the higher efficiency near WOT one must provide a lower RPM return, via the P&G technique.
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.
If you want to give your brain a stretch on this material, take a look on these 1960 tests on tractors, in particular, HP-Hr/Gallon, and note the better efficiency at higher load, of course these did not have a WOT enrichment device on them, so the most efficient engine is the one that took the biggest advantage of the combustion stroke. Think of the HP-Hr/Gallon as comparable to KiloWatt Hours/Gallon on an electric generator, if you can get more power (KwH) out for the same gallon, your doing better.
TractorData.com Oliver 88 tractor tests information
Hope that helps,
Steve