Originally Posted by
lude-de
I've worked on this for two days now, and I've gotten to the point that I'm going to post my questions.
My situation is unusual. I am working with the ODB1 Honda ECU that is chipped and has a data port installed. From this I can poll for information that the ECU is using to manage the engine.
I am getting IAT in Fahrenheit , MAP in PSI, RPM and VSS in MPH.
Here's an example of the numbers
IAT = 88.39
MAP = -16.97
RPM = 3094
VSS = 60.89
IAT F to K = 304.3
MAP PSI to kPa = -117.06
RPM = 3094
VSS = 60.89
I plug that into the first formula to get IMAP:
IMAP = RPM * MAP / IAT
1190.218994413408 = 3094 * -117.06 / 304.3
Then I plug that into the MAF formula:
MAF = (IMAP/120)*(VE/100)*(ED)*(MM)/(R)
MAF = (1190.218994413408/120)*(80/100)*(2.056)*(28.97)/8.314
MAF = 9.918491620111732 * .8 * 2.056 * 28.97 / 8.314
MAF = 56.84564559003256
Then I plug that into the MPG formula with adjustments because I'm in MPH and not KPH:
MPG = (14.7 * 6.17 * 454 * VSS) / (3600 * MAF / 100)
MPG = (14.7 * 6.17 * 454 * 60.89) / (3600 * 56.84564559003256 / 100)
MPG = 2507288.59794 / 2046.443241241172
MPG = 1225.19332440382
Now, as much as I'd like this to be true... it sadly isn't. I'm getting around 30 - 31.5 MPG on a tank of gas. I've checked my conversions several times and I'm sure they are correct.
Can someone please put a second set of eyes on these equations to help me figure out what's wrong here. Unfortunately, I don't have an ODBII car to compare numbers with.
Thank you in advance.
