This is pretty interesting.I still think that the reason that P&G works is because you pay the internal friction penality of the ICE motor with as few RPMs as possible,which would probably mean that it will cost less ICE friction loss accelerating to a speed and shutting the ICE off-or dropping the RPMS a lot like the Hinda does.This would explain why rjbarlows hard acceleration "works".Normally hard acceleration would be a killer,but not in this case.For example-a gasoline motor only car
Accelerate to 60 miles per hour with a 4 cyl-take 12 seconds at constant accel.You will probably average 4000 rpms over the 12 seconds.It will cost 800 rpms,you will travel maybe .1 mile.A crude guess is that you could glide at least another .9 mile,and the total one mile trip would average ~30 miles per hour-2 minutes-.
Now start the trip at 30 miles per hour-your Toyota Corolla will be turning about 1500 rpms to do 30 miles per hour.It will take 2 minutes to go 1 mile.It will take 3000 revs of the motor to go 2 miles.
PG takes 800 revolutions-to go 2 miles in 2 minutes
Steady speed-3000 miles per hour- takes 3000 revolutions to go 2 miles.
Granted those 800 REVs will be higher friction revs-higher piston speed,and more pressure on rings from increased cc pressure.
I can't see any reason for the P&G to work otherwise.Pay the internal friction and general inefficiency penality of the ICE motor with as few Revolutions as possible ,and in the range where the ICE motor is efficient-close to full throttle near the torque peak where you are getting good volumetric efficiency.Of course you don't want to go way above the torque peak to near the hp peak-too inefficient.
The numbers used here are rank guesses to to help my thinking out loud.I didn't really do the arithmetic to show that 800(hard revs) revs cost less friction than 3000-soft- revs-I'm not up to chasing down the formulas for that.
In short get up to speed using revs near the torque peak with fairly heavy throttle pressure(doesn't the Prius CVT motor do essentially that?),and then do whatever it takes to get the ICE to go off,or to drop the revs waay down.
The aerodynamic forces seem to be against P&G-takes 1.33 squared times the power to overcome aero forces at 40 miles per hour vs 30 miles per hour-this is 1.7 times the power.The other forces are generally just proportional to speed-not the square of the speed.The payoff has to be the decreased revs.If 1 hp is the power it takes to overcome areo forces at 30 miles per hour-it takes 1.77 hp at 40 miles per hour and .44 hp at 20 miles per hour.
I think the decreased revolutions have to be where the payoff is on P&G.Now,I could be wrong-not 1st time.Thanks.Charlie