[Shop-talk] How do they do that?

[David Scheidt]

On Sun, Apr 11, 2010 at 5:18 PM, Eric Murray <ericm at lne.com> wrote:

>
>
> OTOH, the car is guessing that you filled up the tank.  It can't measure
> the input to the tank, only the outflow.  So it is possible that it is
> underestimating the amount of fuel you put in.
>
>
Really?  Most cars I've owned have had a float in the gas tank, that told
the driver how much gas was in the tank.  No reason the computer can't use
that information.  Resolution is probably not good enough to tell the
differnce between adding 10.2 and 10.3 gallons, but they can be pretty
good.

And some EVAP systems can tell what the volume of air in the fuel tank is;
fuel volume is calculated by subtraction.  (I don't know if any car actually
uses this information, but it's a derivable quantity in some advanced EVAP
systems.  )

-- 
David Scheidt
dmscheidt at gmail.com