[rescue] LCD monitor diagnosis

Phil Stracchino phil.stracchino at speakeasy.net
Thu Apr 27 11:57:53 CDT 2006

Don Y wrote:
> We track our gas mileage (autos).  Currently, by logging the
> elapsed miles (disciplining ourselves to reset the trip odometer
> at each fillup) and the printed receipt from the gas pump
> (thousandths of gallons).  And, a few seconds of mental arithmetic
> to divide one into the other.
> The other day I mused that the car should be able to do this
> *for* us.  After all, it knows how many miles it has traveled.
> Just type in the number of gallons consumed (or, with accurate
> metering of the injectors, let it figure that out as well!).

Exactly.  Many cars with factory trip-computer options ALREADY allow you
to view instantaneous fuel consumption based on how much fuel is being
pumped through the injectors and how fast the car is going.  It would
take minimal extra logic to also keep a running average over, say, the
last ten and last thousand miles.

For that matter, I've long thought it's time we had cars with ACCURATE
fuel guages.  And it's easy to do:  Instead of mounting the tank on dumb
bolts with a float and sender in the tank, chuck the sender and hang the
tank on four loadcells.  Monitor the output from the load cells, say,
twice a second.  Average the results, correct for tilt of the vehicle,
keep a 60-second buffer, and have the guage display a rolling average of
that 60-second buffer.  If any cell reads differently from the other
three by more than twice the expected margin or error for, say, twenty
consecutive readings, drop it from the pool and flag a warning.

This ought to be able to keep track of how much fuel is in the tank to
plus or minus a few ounces of fuel, not plus or minus two or three
gallons (which seems to be the best the current eighty-year-old guage
technology is capable of).

As an added bonus, you could even track how much fuel the loadcells say
you have against how fast the engine computer says you're using it.  If
the fuel level in the tank is going down faster than you know you're
using fuel, issue a fuel-leak warning.

 Phil Stracchino                     Landline: 603-886-3518
 phil.stracchino at speakeasy.net         Mobile: 603-216-7037
 Renaissance Man, Unix generalist, Perl hacker, Free Stater

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