Re: 2005 Honda Civic LX gas mileage

"Graham W" <graham@xxxxxxxxxxxxxxxxxxxxx> wrote
> Elle wrote:
> >> I did say "virtually constant" and you missed a significant factor
> >> (for in-tank pumps in the Honda/Rover cars) which is that the fuel is
> >> sucked into the pump without being replaced by air from the outside
> >> thus reducing the absolute air pressure in the tank. You can verify
> >> this by listening for the 'whoosh' of air into the tank when you
> >> undo the tank's filler cap.
> >
> > One should note here that, as long as the tank is not vented to
> > atmosphere, then the pressure due to the air above the fuel level in
> > fact will be reducing (contrary to the implication above)
>
> It isn't contrary - that is exactly what I said - "reducing the absolute
> pressure in the tank"!

You seemed to be implying this reduced the pump work. On the contrary, lower
pressure on the fuel in the tank increases the pump work necessary to move
it to the injectors, etc.

That junk you posted did nothing more than bolster my original point, but in
a manner that muddies the issue.

> > as long as
> > the fuel level goes down. Thus the pressure at the pump inlet will
> > be even lower than if the tank were vented to atmosphere.
>
> Agreed.
>
> > With no venting, even more pump work is necessary than with venting.
>
> Agreed again.
>
> > It's mere theory, and in this application out in left field, because
> > the pump is such a low power device, raising say 1 gallon / hour a
> > few psi, well less than 1 hp of motor power, I'd guesstimate with
> > some rough calculations.
>
> Your figures are a bit adrift though. Yes I know they are guesses but
> since the pump needs to raise the delivery pressure at the filter so
> that the engine's FI is supplied with enough fuel at the most extreme
> of power demands and RPM, the volume at a guess is far higher than
> 1 gallon / hour.

Whatever "at a guess" means.

Of course the flow varies. Why would you suggest otherwise, except to be a
jackass?

I don't work with absurd numbers such as 90 mph, but instead numbers for the
typical driver in the U.S.

You're not greeted with seriousness or patience by me, because of that
vulgar email you sent.


.

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