Just for the fun of it I decided to pull up the MAF reading on my torque app. It is reading .5 CFM at idle and 1.1 CFM at 2,000 rpm. So considering you guys are also getting low readings with the UG. I'm inclined to think that the ecu just reports their values differently.

 

Good idea, Buddy, Was that reading independent of the ECM? 0.5 CFM equals 236 grams/second and 1.1 CFM would equal 519 g/s on the converter I found on line, values in the range that the UG says it expects.

Today I connected my Actron CP9580 code scanner to the OBDII plug and set the units to metric so the MAF would read in g/s like the UG and I set it to graph the MAF in real time as I drove the same route to the boat house as before with the UG ( the Actron said “calculating scaling” when the graph was selected, but apparently was not saying the MAF output itself was scaled). The Actron MAF values were 0.06 at idle to 0.55 climbing the hill from the boat house and the top scale of the graph changed to 0.60 so it may have gone a little higher than 0.55. So.... the Actron is showing exactly the same MAF values as the UG.

No reply from the LR dealer yet about any firmware update as UG suggested there might be. Also no answer from UG on whether It is possible to tell it to scale MAF by 1000; just that 9141 is the only protocol our Discoveries use, that different protocols would get the same MAF values anyway, and to try calibrating the fuel usage. I'll have to drive a lot further than the last time since it is reporting so little fuel used that it couldn't calibrate.

 

I took the reading from the ODBII port so I assume it came from the ECU. Maybe I just had my units wrong. I thought .5 CFM was low. But honestly I don't know much about MAF's.

 

Three wires, one's battery voltage, the second is the voltage supplied from the MAF and the third is ground supplied by the ECU. Fairly easy to check for broken positive/gound and the MAF voltage signal is simple too. On MAF signal there should be zero wild spikes, should increase smoothly with throttle increase just like a TPS. Some MAF's report voltage some are frequency. Either can be checked with a digital VOM on DCV.

 

What year Disco, Buddy? The readings might be different for different year ECMs. I believe Tom's is a 98 like mine and his MAF readings from the OBDII were similarly low.

 

I thought from the description in the manual that the ECM was responding to changes in resistance of the heated wire as air passes over it. The MAF seems to be working and the ECM is apparently correctly using the signal it gets from the MAF and the graphing function of my Actron Code reader did show a fairly smooth MAF response to RPM and load.

The question now seems to be what values the ECM is passing to the OBDII VS the OBD standard values that UltraGage expects to be passed; it seems to be low by a factor of 1000 on our 98 Discos.

 

Mine is a '97

 

our trucks dont report the "A" element in the equasion ... there was a topic about this a week or two ago.

I have no idea how to convert the value reported with somethin that actually makes sense for us

((A*256)+B) / 100

A is always 0 on our trucks.... so it shows B /100

 

What are the A and B values? Aare these inputs from two different sensors? So if the B value is from the MAF and A is from something else we are getting B/100?

 

A and B are just byte values returned from the ECU regarding the MAF sensor (took me a bit to figure this out...)

each byte is a value between 0 and 256.

(so A appears to be an overflow for B's value?)


Basically we never get a raw value, we get the value the ECU read and decides to give us.

In theory they could be reporting cfm, or gpm, or who knows what.. would take a rover tech or engineer to determine this