RED HORSE

Even though both my cars have factory GPS, Santa Claus brought me a new Garmin Nuvi 3790 LMT. I was going to return it until I read the literature with it and learned it was also a Code Reader/OBD II scanner. I bought the transmitter that plugs into the OBD II port and low and behold in addition to giving any codes that are set it also reads various engine parameters as you drive.

Now the question. One of the parameters reported is Engine Load. This is reported as a per cent. I would like to know what it is measuring. When the gauge reads 50% load what is it measuring and how is it measuring it? Mass air flow, coolant temp, etc. are all understood, but I don't understant what or how engine load is being measured and what it means. Any of you engineers out there have an answer?

simsgw

Not a clue. I certainly could derive my own number from the data the engine computer has on hand, but to know what the factory chose that particular value to mean requires a technical spec and I don't have that one. From your description I can't even be sure whether you're seeing a dynamic value or just an average over some time period. Does it change if you read that port while driving? If so, the most obvious way to derive an "engine load" would be delivered torque as a percentage of the engine rating. Or possibly driveshaft horsepower, which itself is a value we derive from torque and engine speed.

Gary

AYHSMB

Calculated Engine Load
California Air Resource Board (CARB) defines this as airflow divided by peak air flow. Peak air flow may be adjusted for altitude via barometric means if available. For diesel engines, the number is current output torque divided by peak output torque at current rpm. We have noted that vacuum leaks can have dramatic effects on this value.

and even more detail here :

http://obdcon.sourceforge.net/2010/0...ed-load-value/

simsgw

No kidding? Got it first try. Should go back to making such guesses for a living.

Gary

RED HORSE

It does vary during driving. Some interesting, to me at least, observations are that driving my PDK in auto results in significantly higher (about 20 or 30%) readings than when I'm driving in PDK manual mode.