At 07:37 PM 5/10/2016, Scott wrote:
>lol..as far as I'm concerned ...like in engine air intake ....the piston
>going down is SUCKing in air ..
>Sucking ..
>just like the cooling down coolant Sucks coolant back into the pressure
>bottle.

We think that way because we're surrounded by air and have to press
against it to make little pockets of vacuum.  If we were surrounded
by vacuum instead it would be pretty clear that the pressurized air
is pushing its way in.

It's all a matter of context.  We look at the fuel pressure regulator
and think that it's changing the pressure in the fuel ring, because
we measure it relative to atmospheric pressure.  But the fuel
injector thinks that the regulator is keeping the pressure exactly
constant, because its reference is the inside of the intake manifold,
and the regulator keeps the pressure at a constant offset from
whatever the intake manifold pressure is.  If you put a pressure
gauge in a sealed box and connected the box to the  FPR vacuum line
you'd see that it's really keeping the pressure constant so that the
injector will always inject the same amount of fuel for a certain
number of milliseconds of open time, no matter what the engine is doing.

Yrs,
d