Super Charged MarkVlll's in here for Question

Roadboss

Roadboss

On Work Release
I no longer have an accurate Fuel economy display. The only thing accurate about it is the gallons to empty reading. When I check milage the old fashion way I get 20 MPG and the display will show an average of 25+, and an instant check will be rediculous at 30+. I do have the correct gear in the transmission, and of course the chip has been programmed to them.

I truly miss having this display, and wanted to know if others have this problem and if any one has found a way to fix it.

Thanks
 
Charlie, you know my answer to this, but just for the record:

95 Mark VIII w/vortech 42lb + proM MAF - MPG display way off
97 Mark VIII w/vortech 42lb + proM MAF -MPG off, but by less that on the 95 ( I assume OBD II)
97 Mark VIII w/eaton 42lb + proM MAF- MPG really way off (???)
98 Mark VIII w/eaton 42LB + Stock 90mm Cobra MAF - MPG off, but just by a little.

I run 42 injectors for a while on the 95 without the blower and it was already not showing right.
So I assume it's not as much whether it's supercharged, but if the injectors and MAF used are different from stock.
 
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I was looking into what the deal was with it and today when I filled up it confirmed my guess so far. The stock injectors are 24lb, the current injectors in pullied are 42lb. If you assume a linear relationship in flow behavior a 24lb injector will flow about 0.57 as much as a 42lb injector given the same pulse width. So today at the pump my car showed 27 mpg, calculating mileage from the trip meter and the gallons it took to fill the car I calculated 15.5 mpg. So dividing 15.5/27= 0.574, this confirms my guess. It will take a few more tank of a consistent 0.57 ratio for me to say its right but so far so good. So that's what I know.
 
Jeremi would have to chime in with what MAF is in Pullied. I'm not sure if or how the MAF would effect the MPG calculation. I would assume that the MPG is based on the pulse with of the injectors and the known fuel flow of the injector. Thats why I was guessing that its some scale factor based on injector size. Try it out for your next tank of gas, lets conform or disprove this.
 
If that holds water then I wonder if there is a means to implant that new ratio into the system. I am not an electric wiz so have patients with me.
 
Roadboss said:
If that holds water then I wonder if there is a means to implant that new ratio into the system. I am not an electric wiz so have patients with me.
Click to expand...

I'm not sure either, I don't think it would be anything short of a reprogram of the module that calculates that. I don't even know if that module has reprogramable memory. I think I might start looking into it, that would be pretty cool to have it be accurate.
 
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