MPG calculation???

D

Danoz93

Registered
What method does our Mark VIII use to calculate fuel mileage?

Does it count injector duty cycle and caclulate from there or does it use a different method?

Also, if the fuel pressure goes down the car would compensate by having a longer duty cycle and wouldnt that result in a lower mpg reading?
 
RE: MPG calculation???

just guessing, but I would say that it was something mechanical, instead of seeing fuel pressure. Maybe off the throttle position or RPMs?
 
RE: MPG calculation???

Ripped this out of the manual...

Fuel Computer
The fuel computer of the message center indicator (10D898) uses information from other modules and sensors to perform its calculations. The message center indicator also outputs a filtered signal to the fuel gauge in the instrument cluster (10849).

RANGE

The Range feature will inform the driver of the distance that can be traveled before refueling.

The Range (Distance to Empty) feature is calculated using the fuel flow signal from the powertrain control module (PCM) (12A650), the speed signal from the vehicle speed sensor (VSS) (9E731) and the fuel level signal from the fuel pump module.

The fuel flow and speed signals are used to calculate a running average fuel economy, which is multiplied by the fuel remaining to give the Range.
Running Average Fuel Economy is not the same number as the Average Fuel Economy displayed by the message center indicator.
Running Average Fuel Economy is based on the past driving history and cannot be reset except by a battery disconnect.
When the Range decreases to 80 km (50 miles) to empty, the message center will display the LOW FUEL LEVEL warning.
With a fuel tank (9002) full of fuel (160 ohm signal from fuel sender) and after a battery disconnect, the Range should be approximately 740 km (460 miles) to empty.
STATUS

The Status feature has two displays, fuel-to-empty and fuel-used. The Status switch will change the message center indicator between the two displays.

The fuel-to-empty calculation:

is obtained using the fuel level signal from the fuel pump module.
is also used by the message center indicator to send a signal to control the pointer on the magnetic fuel gauge in the instrument cluster.
 
RE: MPG calculation???

What gen is that from? Reason I ask, is my 93 used to recalculate DTE when it hit 80 miles, and depending on the driving I had been doing.. ie on an Interstate Trip... would sometimes change to say 100 or 110 miles to empty.
My 98 does not do this.... just keeps counting down from 80 until 50 and then gives the low fuel warning...



Rex
98 White Pearlescent LSC / 02 Silver Mustang Premium GT
http://www.mark8.org/users/pvteye/98LSC032a.jpg
 
RE: MPG calculation???

ok, now what signal is "fuel flow" ? I guess that is what i am trying to get at.

It is usually measured at one of two locations, fuel injector or at the fuel pump itself. And how it is measured. i.e. what type of sensor.
 
RE: MPG calculation???

I can only give you what info I have and that was it up there. It was for a '96 Mark VIII.

I guess 'fuel flow' is measured by injector pulse width since the computer keeps track of that anyway. It would require no additional sensors. But that's just a guess. I was never really that interested in it so I never bothered to learn it.
 
You must log in or register to reply here.
Back
Top