• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

OBD1 PMD MPG Gauge using MPGunio

94turbo-

94turbo-

Member
Messages
55
Reaction score
0
Location
Prince George BC
I'm going to purchase a MPGunio gauge for mpg gauge, they are programmable and versatile, BUT they are built for gas engines. They monitor a fuel injector pulse duration ad calculate mpg from that signal and pulses from the speedo system. I'd like to tap into the PMD for this signal. Anyone know if the PMD does pulse width and which pin? I am without an oscilloscope now so I'd be guessing. Sinse my truck is OBD1 I cant use scangauge11.

Otherwise I'll have to use flow sensors on the diesel forward and return lines and this gets tricky and expensive. One other option is to loop the return line to the forward line pre the lift pump and monitor that one sensor, however the flow will be very low and may be impossible to accurately calibrate.

Any info would be appreciated!
 
Looping the return line into the supply line is going to create problems. Even with a check valve the injector chatter slightly airiats the fuel and at high rpm and hot fuel you will get a miss from this. I'm not saying it couldn't be solved but be aware of it before you start.
I remember reading about these, please let us know how it works out.
 
I do this neat trick when I fill up. I divide my milage by the amount of fuel i burnt. Its free
 
94turbo- said:
Yes I do that too, but I'd like to know instant mileage instead.
Click to expand...

Instant MPG isn't that useful and you risk causing problems with fuel lines or PMD taps. Air needs to be returned to the tank. Heat from the fuel system needs to be returned to the tank. Cool fuel improves IP life AND hot returned fuel melts gelled fuel in the tank on cold days.

The distance your foot is down, RPM, Boost, and EGT can act as a indicator as to your instant MPG. The EGT is more instant MPG to me than anything else. So is the exhaust smoke level if any.

Another way to have a useful MPG or distance remaining is have a fuel gauge that reads in gallons. (or whatever you measure stuff in) This way you can know miles traveled and get a better picture of the current MPG and your remaining mile range on remaining fuel. The trick is remembering the MPG goes down quick from flat lands to mountain grades.

Instant MPG is a crock of feel good anyway because it reports like 99 MPG when the fuel valve closes and 0 MPG at a stop and idle. Yet you will be getting around 15 MPG per tank. The real range is 7 MPG WOT all the time pulling to slightly over 15 MPG. IMO 7 MPG moving is as low as it can get... The top number depends on the top speed you drive.
 
I can't answer your question, but I can give a possible alternative...

I have a ScanGaugeII that I originally bought to be able to read and clear codes on the fly, but also figured that it had some nice, extra features. Two of these are an instant MPG and an average MPG (during the time the engine is on). It took a few tankfuls for it to "learn", but it does seem to pretty close to actual (hand calculated). It is close, but it does read about 1mpg high from what I can tell. It might be dead on, but it's hard to tell because it only gives the average while the engine is running - once the engine is turned off and back on, the average resets. The ScanGauge is nice, though, as it has a bunch of extra features. Turbine Doc was the one who turned me onto this a while ago.

Oh, and about "coasting"... Sometimes I get an "instant" MPG of about 1,400 MPG! :)

EDIT: Scratch that... I just noticed you have OBDI - ScanGauge is for OBDII... sorry!
 
Very useful informatIon guys! I'd hoped a scangaugeii would work, but obd1 is just a simple system, 1 step above a mechanical type system. This MPGunio needs to see a pulse that varies in width that opens the injector for that time, being a diesel that pulse would run the pump. Hence pulses from the PMD. I no longer own an oscilloscope so I was hoping for a yes or no, does one of the PMD lines have a varying pulse width, and which one? Once I know that I can calibrate the unit.
 
Ultimately I'd like to get and share the hard numbers on the most available upgrades to this 6.5 engine. With how high the cost of diesel is these days I think such information is handy. Turbo master, optical bump, free flowing air filter,tires, oils, can be reported. This unit can report 0-60 times and much more.


I may even try water misting, but I need a base line.

Anyway I need to find out the pmds function or use sensors to get the fuel used, I thought with members programming their own chips someone would have the PMD info I need. I'll keep searching, thanks.
 
You must log in or register to reply here.
Back
Top