Just wondering if anybody has found a way to retrofit say, a super duty mpg gauge or some other form of a gauge that will calculate actual mpg verses trying to do it by math. I always forget and fill up without looking or something stupid like that.

I haven't heard of anyone doing anything like that BUT if it can be done someone here will figure out how to do it I bet. I prefer the ol' calculator method myself, haven't found many of those other ways to work very well, myself.

Only way to know exact fuel used for sure is with a totalizer that compares fuel sent to IP vs fuel returned back to the tank, all other methods are calculations of some fashion or other.

I wonder why there isn't a system like I've seen on some Chryslers that calculates MPG among other things in real time. The data is there, PCM monitors fuel delivery rate and road speed.

TDG I think those Chrysler mpg meters are electronic versions of the old mechanical vacuum mpg meters that gave mpg by monitoring changes to vacuum for more or less mpg display, but I could wholly be wrong and it's possible they have totalizer system that should work in out truck if you could get the "brain" part if the sytem as well as the sensor that converts gpm to mpg.

I don't know what they use to calculate, the ones I was referring to are on Jeep Grand Cherokees, gives you real time MPG, total MPG and estimates distance til you run out of fuel. I've heard they're pretty accurate, but I've never owned a vehicle with one. It sits in an overhead console, like the ones that come in our trucks. I'm just wondering if someone could go in there and wire it up to a 6.5 ECM and have it perform the same sort of thing, or design a similair one. I can only imagine it would be even more accurate, Diesel Fuel Metering system has got to be as precise, if not more precise than the gasoline ones right?

I don't know what they use to calculate, the ones I was referring to are on Jeep Grand Cherokees, gives you real time MPG, total MPG and estimates distance til you run out of fuel. I've heard they're pretty accurate, but I've never owned a vehicle with one. It sits in an overhead console, like the ones that come in our trucks. I'm just wondering if someone could go in there and wire it up to a 6.5 ECM and have it perform the same sort of thing, or design a similair one. I can only imagine it would be even more accurate, Diesel Fuel Metering system has got to be as precise, if not more precise than the gasoline ones right?
Caddy's have had these for a long while, but they lacked exactness then and now. I believe the only real way to figure MPG is to fill the tank before and after trip and divide by miles driven. Some might want to use GPS for the mileage traveled but seems to work for most I know. :exactly:

I agree, no doubt that is the most accurate.
But the PCM constantly calculates Fuel Delivery Quantity, and you can watch it with a scanner. If you take that and Vehicle speed, which are both monitored by the PCM, why couldnt' you tap into that data and make a very reasonably accurate, real-time MPG calculations?

I agree, no doubt that is the most accurate.
But the PCM constantly calculates Fuel Delivery Quantity, and you can watch it with a scanner. If you take that and Vehicle speed, which are both monitored by the PCM, why couldnt' you tap into that data and make a very reasonably accurate, real-time MPG calculations?
Returned fuel

Obviously, you couldnt use the system I described on this '93 truck, but it would work on '94 +. For the mechanical ones, you could use 2 digital flowmeters, one for supply, one for return, and a device to calculate the difference, being delivered quantity and divide vehicle speed by that value to give you a distance / consumption rate, or MPG.

Obviously, you couldnt use the system I described on this '93 truck, but it would work on '94 +. For the mechanical ones, you could use 2 digital flowmeters, one for supply, one for return, and a device to calculate the difference, being delivered quantity and divide vehicle speed by that value to give you a distance / consumption rate, or MPG.
This is about only way it will work meter for supply vs meter for return.

PCM indicated flow is a request & not actual delivery to engine/thru IP correct??

If you have a Laptop, the scanner programs allow a " Calculated " Instant and average MPG.
Uses Fuel Rate and MPH, Accuracy will depend on how your speedometer is
calibrated to actual. Still the best MPG accuracy is " average over several tanks of fuel
and miles driven ( Odometer error factored in ).

check out>

http://www.floscan.com/html/marine/models/multifunction/series9000.html


http://www.diy-boat.com/Pages/Archives/links/2002_3/engine/engine.html

Figure 1 Sample Installations of FloScan Fuel Flow Meters Diesel (bottom) engines have flow sensors mounted on the forward and return fuel lines and often pulsation dampers to prevent pulsating fuel from causing measurement errors.

both sites say for Diesel supply & retn are required to monitored

If you have a Laptop, the scanner programs allow a " Calculated " Instant and average MPG.
Uses Fuel Rate and MPH, Accuracy will depend on how your speedometer is
calibrated to actual. Still the best MPG accuracy is " average over several tanks of fuel
and miles driven ( Odometer error factored in ).
For a Diesel ours for instance there will be a fudge factor as fuel returned goes into the calculation to be accurate, truth be known modern fuel injected gas engines probably also need monitored returns as well

Probably work real well with the Peninsular Marine engines. Just got to becareful about floating the valves.

That might work, this is more like what I had in mind...

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7963712258&category=33596

Here's a couple more, pretty cheap, anyone here have the electronics knowledge to make one work on a 6.5???

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=7962997810&fromMakeTrack=true

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=7963114467&fromMakeTrack=true

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=7963606056&fromMakeTrack=true

I think you would be better off with one from a Blazer/Jimmy/Bravada overhead console like this one:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33695&item=7963093973&rd=1&ssPageName=WDVW

Most of the older models don't have the Homelink transmitter, just the digital information center, which can display outdoor temp (or maybe intake air?), direction, and fule mileage and distance/gallons to go. From what I have seen, they need 12 volt battery and ignition power, temp sensor, VSS, and Serial Data line from the PCM. What I can't seem to find out is if the OBD Serial Data line on our trucks (at least 96-up) will provide the DIC with the information it needs to properly calculate fuel mileage with the 6.5.

I have seen a guy use one of these DIC's from a 4.3L, and install it in a 02 1/2 ton truck, and it worked perfectly for fuel mileage calculations. Here is the link for that install if anyone is interested:

http://www.fullsizechevy.com/forums/showthread.php?t=128132&highlight=dic

I paln on attempting this soon. I swapped my overhead from my 97 with one from a 96 Tahoe that will fit the DIC (trucks have a real oval shape where it mounts, SUV's get a more rectangle shaped place for it- I can post pics for those needing clarification), but I am still trying to find out what information it needs from the Serial Data line, and if my PCM will provide that information. Obviously the VSS provides the miles travelled, but I am not sure how it would know the fuel level unless gas engine PCM's provide that (which is possible).

I am not sure if the fullsize SUV's ever got one of these. I don't think that they did until '99 or so in the Denali and Escalade. I will have to read my FSM to see if any information is in there.

Well, I am still thoroughly confused as to whether or not this will work. I think I have even more difficulty since my truck is almost all mechanical. I hope somebody figures something out though. Thanks for all the help.

I have a MPG display both instant and average on my Lincoln Town Car and the MPG is always lower than the calculated by tracking miles and gallons used. I guess I rather have it read lower than too high and run out of fuel......which you shouldn't if you pay attention. I guess the return fuel is a factor.