I have a 15 year old VMSpc unit on a 2001 Cummin's engine. It has worked perfect but my old Toshiba gave up and I had to replace it. The new laptop works fine with the VMSpc program but my fuel usage calibration is out of whack. The old computer had it to 99% accuracy but I forgot how to adjust the program to calibrate it. Please help me. I show 9.1 mpg and actual is 8.5.
Also where can I get a manual for my unit?
The fuel setting you're looking for is an Engine Correction--you can find that under...
You may then do a bit of division from recent trips; GPS miles traveled vs ECU ODO (as seen on the VMSpc).
That factor; to account for tire-size differences (amongst others) will give you a multiplier of something more than...or less than...1.0 It will likely be more like a Multiplier of .92 or 1.07 --only slightly different.
Once that is dialed in, you can make any needed Fuel rate adjustments, too.
The Manual can be followed by the link, over on the right of this page: VMSpc Download; you'll see a link for the v3 and v4 software.