01-03-2013, 03:09 PM
Try #2 for posting...don't know where the first reply went...Here's the short version...
Originally Posted by lude-de
#1 - MAP value figured wrong. You're reading manifold vacuum, not manifold pressure. Subtract your reading from ambient baro pressure (use 29.92 for starters) and work with that instead.
#2 - F to K is off slightly.
#3 - There's an extra /100 in the final solution.
When I do the calculation the right way, I get about 31-ish MPG.
02-25-2014, 09:29 AM
On-Line Gasoline MPG Calculator (Using MAF and/or MAP/IAT/RPM)
You may find this useful for "checking your work".
As many of you have discovered---based on comments here and email that I regularly receive---getting all the units and calculations exactly right can be hard. And, in an embedded system without floating-point support, avoiding integer overflow errors can proved difficult.
Bruce D. Lightner