Whit,
There is the fuel map for everything (cruise, idle, WOT, etc). At operating
temperatures, the computer uses the O2 sensor in conjunction with the fuel
map to set
the fuel air ratio at idle and cruise (closed loop mode). Under WOT and
deceleration the computer operates in "open loop mode" (ignores the O2
sensor and does
not fine tune the fuel map. Under acceleration (up to approx. 7/8 throttle
setting), the computer is still looking at the O2 sensor, anything greater
and the computer
just relies on the pre-programmed fuel map and does not make any adjustments
based on the inputs from the O2. I hope this helps.
Frank
> -----Original Message-----
> From: Whit [SMTP:bigdog@netdog.com]
> Sent: Wednesday, October 14, 1998 8:17 PM
> To: dakota-truck@buffnet.net
> Subject: RE: DML: RE: Fuel Pressure Regulators
>
> At 06:19 PM 10/14/98 -0700, you wrote:
> >Whit,
> >The hi performance PCM (computer) has a new fuel map associated with it,
> the
> >net result is that the injector pulse width is increased wherever the
> >software designer
> >figured he or she needed additional fuel. I really don't know where the
> >transducer is but if you hook up a scan tool, one of the options that you
> >can check is the
> >fuel pressure. I haven't been able to find it in the engine compartment,
> so
> >I would suspect it is somewhere near the fuel tank or incorporated in the
> >fuel pump
> >assembly. The Vortech supercharger kit includes an additional in-line
> fuel
> >pump and a FMU that changes the fuel system into a semi return system and
> >the FMU
> >just restricts the return line to boost fuel pressure. On my truck, we
> check
> >fuel/air ratio in the exhaust path before the Cat. (expensive equipment
> >required and
> >generally used in conjunction with a dyno). If you really feel that you
> are
> >not getting enough fuel (need to verify this on a dyno), you could
> explore
> >the avenue of
> >higher fuel pressure or step up to a larger injector even yet. Remember
> >though, in cruse and idle (operating temperature), the O2 sensor in
> >conjunction with the
> >computer is controlling your fuel/air ratio. Only at WOT do the fixed
> fuel
> >maps come into play.
> >
>
> So there is no mapping at cruise and idle? Does the computer just add or
> reduce fuel until a certain O2 level is obtained? When you say WOT, does
> that mean only at full throttle as implied or does the fuel mapping really
> kick in at a partial WOT. It is not that often that I floor the thing.
> My
> biggest problem is that not much happens until I hit WOT, then it performs
> OK.
>
> Whit
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