"Ray Block" <bpracing@worldnet.att.net> wrote:
:> From: jon@dakota-truck.net
:>
:><snip>
:> Maybe
:> your fuel pressure is higher or lower than the algorithm used to
:> calculate the gas mileage thinks it is, or your injectors are
:> flowing more or less than they should be?
:>
:> --Jon-
: If the injectors are flowing more or less...they would affect your A/F
: ratio. Regardless of pressure, whenever you're in closed loop mode the
: computer will adjust the pulse width to get the proper A/F ratio determined
: from the O2 sensor. If it was unable to keep it correct it would set a
: code. (voice of experience from my race truck) :-(
Yep, that is what I was thinking... As the injectors get
progressively more clogged, the A/F ratio leans out and the
computer increases the pulse width to compensate. If the
PCM is just using some sort of lookup table based on the
injector pulse width along with some sort of counter perhaps,
then the mpg calculator may just be making an assumption
that there is more fuel being used than actually is, especially
if there is no tie-in with something else like the fuel tank
sender to compensate over time. The clogging may not yet
be at a point where the computer is unable to correct the
A/F ratio to stoich, but it may have progressed enough to
affect the gas mileage calculations. Or, the computer
just might not be all that accurate. :-) I wouldn't know
since I don't even have a vehicle with a MPG readout. :-)
--
-Jon-
.- Jon Steiger -- jon@dakota-truck.net or jon@jonsteiger.com -.
| '96 Kolb Firefly, '96 Suzuki Intruder, Miscellaneous Mopars |
`-------------------------------- http://www.jonsteiger.com --'
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