Originally Posted by
murfie
Cars run completely off the MAF or completely off a MAP sensor, depending on what they have, the non existent sensor is inferred through the SD model. No failing MAF to correct anything as there's no backup sensor to determine airmass from. You added an external sensor to correct the inferred MAP value.
Y= A x^2 + B x + C
Y is inferred map
x is load, more specifically cylinder airmass derived from MAF value and RPM. Load comes from current cylinder airmass / Maximum cylinder airmass. cylinder displacement of .00168 is the maximum cylinder airmass in pounds. using pounds per minute and revolutions per minute, you can get pounds per revolution. You divided that by 4 as there are 4 intakes per revolution in a V8 and thats the cylinder airmass in pounds. This is the value put into the equation above to solve for Y and get a MAP value. You can use this until you hit the MAF lb/min PID limit at 86.68, then you need to use the airload value to get the MAF values that are higher than that since the air load doesnt have the same PID bit limit.
So using the HPT calculator they want you to log air load(X values) and an external MAP sensor(actual Y values), and populate a new relationship in their calculator and calculate new coefficients. IMHO Its not very good at this. doing it in an excel sheet and using linest or the equivalent 2nd order polynomial function works better to come up with your own coefficients. If you hate excel there are websites you can populate with X and Y values per RPM, that will also do it for you. Populating the coefficients then using the calculator to check they work is a good thing and the calculator works very good for that. The other option is to just guess at coefficients and look at the changes populated in the calculator until it matches what you logged. I don't recommend that as it can be time consuming.