"Mike" <mik@[EMAIL PROTECTED]
> wrote in message
news:idtUj.2680$Cn4.1797@[EMAIL PROTECTED]
>
>> How much fuel does an engine use when you are going downhill with your
>> foot off the throttle, using engine braking? I'd expect it to be about
as
>> much as with the engine idling.
>
>
> Most don't use any fuel as the computer shuts the injectors off on
decel.
> You can see this on a scan tool by monitoring injector pulse width which
> will go to zero.
>
>> Is the fuel consumption the same if you coast downhill with the engine
on
>> but the clutch pressed and/or the transmission in neutral?
>
> It would be higher in that case as the injectors would be supplying
fuel
> to the engine.
Ah, so if you go downhill with your foot off the throttle and the car in
gear, fuel consumption will be zero because the computer will reduce the
injector pulses to zero, but if you do the same with the car in neutral,
there will still be fuel being injected at the idling rate? I hadn't
realised that the computer could distinguish between these two cases.
So in a modern car, my grandpa's old fuel-saving technique (a left-over
from
driving during WWII!) of slipping the car into neutral as he was slowing
down on the approach to a junction would actually be counter-productive!
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