> Ah, I see what you're saying: you're prepared to accelerate down the hill
to
> a speed above what you were doing on the flat, and let that carry you
part
> of the way up the hill on the far side. Yes, I agree: coating in neutral
> will involve less braking so you'll go further up the other side before
you
> have to go back on the power.
Yes, accelerate insofar as highway RPM engine pumping losses are a
deceleration.
There are many cases where you will actually have to use gas on a
downhill to overcome compression, whereas if you were coasting, you'd
be at idle and a constant speed. The hybrid powertrains recognize
this and shut the gas motor off.
> But I was assuming that considerations such as speed limits and safety
> (there may be a bend as the hill goes from downhill to uphill) require
you
> to restrict your speed with some form of braking. Now that braking can
be
> conventional disc brakes, engine braking or regenerative braking.
I am not talking about just rolling to a higher speed. Find a minor
downgrade. Drive down it at speed...then put your car into neutral
and check your consumption meter in both cases.
> I was querying the statement that coasting downhill in gear uses more
fuel
> than doing it in neutral, and you've agreed with me that it doesn't
*while
> you are going downhill*.
Of course, zero throttle is zero throttle.
But many downgrades require nonzero throttle, as they are mild.
> I'm surprised that the assertion about optimal engine speed resulting in
> better fuel economy isn't true. Maybe you do get better economy, but
this is
> ffset by the losses in converting mechanical (kinetic) energy to
electrical
> energy in a generator and then back to mechanical in the motors.
I didn't say that ASSERTION wasn't true, I said that the assertion
that the hybrids do so well MPG-wise was because of "optimal engine
speed." That's categorically incorrect.
Trav
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