How truck calculates mileage

[DIESELMAN]

Originally posted by JHardwick

I don't agree with you DIESELMAN.



I can't site specifics, but I don't buy it.



What you are telling me is that this Cummins will always get the same MPG regardless of who is driving it ... ... ... ... leadfoot/*****foot.



Put it to the floor and the ECM will only allow a certain fuel flow regardless, only dependant on what the programming will allow.



I agree that a TPS to an ECM is nothing like a cable to an 850 double pumper ... ... ... ... ... ... . but come on.

?? I didn't say that, what I said was that if you add an EZ, then drive EXACTLY the same, and never extract the maximum flow, ie, floor it, it will use the same amount of fuel to accomplish the same amount of work, plus or minus some amount of efficiency at certain RPM Ranges.



?? For a given TPS position, the engine will attempt, under ECM control and varied by factors such as temperature, pressure, BTU Content etc, to produce a given level of torque againts the load. 1/2 throttle today with my empty truck will consume less fuel than 1/2 throttle tomorrow pulling 13,000 pounds.



?? The ECM has all the flow information to calculate accumulated flow without making a huge approximation based on a $5 potentiometer.



If I were to regulate gas flow into the bessier processor by how far a valve was opened by operator X, I would only blow stuff up, I regulate flow by knowing pipe and orofice size, and pressure, and time, and am correct to within microliters per thousands of liters. And I do so knowing only pressure, duration, and 4 lines of code.



I don't need to know anything about making steel, or anything else I could write code for, only the physics involved at arriving at a given recipe and delivering material to the process.



Interesting none the less. I may be wrong, but sheez, that'd be a first , where is Carlton Bale on this subject????

 

[KBennett]

I wonder if temperature has anything to do with the calculation?



I took a trip to Colorado Springs this weekend. On the way down the overhead said 17. 9 when I got there. Variables: 65*F, averaged 75mph with cruise control ON. On the way back the overhead said 22. 1 when I arrived home. Variables: 50*F, averaged 70 mph with the cruise control off. I tried to keep the tach around 2000 RPM.

This was taken with the same load and the same fuel. Could the cruise control be so bad that mileage would drop that much with only a 5 mph drop in speed? I still have over a half a tank of fuel by the gauge and I have not re-fueled yet.

 

[rbattelle]

I thought cruise improves mileage?

 

[fox]

I can get better mileage not using the cruise control. Increase speed going down hill/overpass, and decrease going up. It can be bothersome to other drivers so be curtious!

With my DDII injectors, it appears the overhead is high by about 20 %.