how the ecu calculates g/rev

[linksys42]

Does any one know exactly how the ECU calculates lbs/min airflow or g/rev? What sensors and calculation does it use to get the final number? Thanks

 

[2gGSX]

The car actually gets g/rev first. How it actually gets this is a function of many variables including (but probably not limited to) barometer, intake temperature, and AvgAirVolPerRev (which correlates to MAFRaw).

 

[turboglenn]

Are you talking about lbs/minute of airflow? It uses a variety of data from air temp, air speed and parameters from other sensors to calculate it all using complex algorithyms. But basicly the "karmen" style MAF meter (what our cars have stock) contains a heated wire and the ariflow coming in cools it down.. The ECU then adds voltage to bring the wire back up to temp, and then calculates airflow based on how much voltage it takes to bring that wire back to it's baseline temperature. There's also a MAP sensor in our manifolds that is used in conjunction with the other sensors to help in accurate calculation of airflow. It's a quite complex group and use of sensors, but also very simple in other aspects. Is there something particular you are trying to figure out? Or are you just wondering for basic knowledge? The more in depth you can explain, the better my chances are to be able to explain it in a way that's able to be understood.

This is from the best of my memory of the stock ECU, I haven't had one in my car in about 9 years now and most cars i tune already have something other than the stock ECU in them from the moment i'm contacted to tune or wrench on them. One of the first things i do is get rid of the government mandated OBD-II systems that come in the cars i work on/build. So if im mistaken on any part of my explanation of the misti MAF meter, some one feel free to correct me.

I do not claim to be the all knowing, nor am i trying to apear like i'm a know it all. I just try to understand things to the best of my ability and if possible, share my knowledge with others so we can all become better informed and have the knowledge available to hopefully make the next best advancement in our sport and tuning in general. I hope no one takes my posts as "cocky" as that's NOT how i try to come across at all.

And, By the way.... I would like to give a big "THANK YOU" to the Admin/Mod who has given me the ability to contribute in this forum in particular.. I am very please to say teh least

 

[linksys42]

I am trying to modify variables/calc's for (load mut 2byte) request for evoscan so that it calculates the g/rev correctly for a 97-99 4g63t instead of the EVO. So if you have the exact processing of sensors and the exact multipliers the ECU uses to calculate the load mut 2byte or g/rev I am willing to listen and that would be great! If not, I guess I am going to have to email the creator Hamish. Thanks

 

[Locke]

Are you talking about lbs/minute of airflow? It uses a variety of data from air temp, air speed and parameters from other sensors to calculate it all using complex algorithyms. But basicly the "karmen" style MAF meter (what our cars have stock) contains a heated wire and the ariflow coming in cools it down.. The ECU then adds voltage to bring the wire back up to temp, and then calculates airflow based on how much voltage it takes to bring that wire back to it's baseline temperature. There's also a MAP sensor in our manifolds that is used in conjunction with the other sensors to help in accurate calculation of airflow.

[...]

So if im mistaken on any part of my explanation of the misti MAF meter, some one feel free to correct me.

The "karmen" style MAF sensor used by the 4g63 is not a hot-wire, like those used by GM and Toyota.

Air passes over a vortex generator in a Karmen Vortex MAF, which creates a wake in the air flow. This wake in the airflow is called a Karmen Vortex, and the frequency of the vortices created are measured and sent off as a MAF signal. The frequency of the vortices, which vary depending on air velocity, is measured by a foil mirror which reflects a light over a photocoupler.

A g/rev is a measurement of a mass of air per revolution. See http://www.dsmtuners.com/forums/showthread.php?t=272951.

 

[turboglenn]

The "karmen" style MAF sensor used by the 4g63 is not a hot-wire, like those used by GM and Toyota.

Air passes over a vortex generator in a Karmen Vortex MAF, which creates a wake in the air flow. This wake in the airflow is called a Karmen Vortex, and is the frequency of the vortices created are measured and sent off as a MAF signat. The frequency of the vortices vary depending on air velocity. They are measured by a foil mirror which reflects a light over a photocoupler.

A g/rev is a measurement of a mass of air per revolution. See http://www.dsmtuners.com/forums/showthread.php?t=272951.

Thanks for the correction on that. Like i said, i haven't dealt with many MAF systems in quite some time, as most everything i work with is converted to Speed Density. I must have been confusing the karman style with what ford uses on the EECV system. Sorry about that it was late and i was propping my eyelids up with toothpicks just to see the screen :

 

[linksys42]

The "karmen" style MAF sensor used by the 4g63 is not a hot-wire, like those used by GM and Toyota.

Air passes over a vortex generator in a Karmen Vortex MAF, which creates a wake in the air flow. This wake in the airflow is called a Karmen Vortex, and the frequency of the vortices created are measured and sent off as a MAF signal. The frequency of the vortices, which vary depending on air velocity, is measured by a foil mirror which reflects a light over a photocoupler.

A g/rev is a measurement of a mass of air per revolution. See http://www.dsmtuners.com/forums/showthread.php?t=272951.

Thanks, I understand the idea at how the karmen maf sensor calculates the vortex when passed over the divider with the two slits/opening in the rear in the center passage in the maf housing. What I am trying to figure out is where I can monitor that request at the ecu/obdII port. I would like to figure out how the digital tuning pocket logger logs/views the lbs/min. You wouldn’t have any idea what the request number is for the ecu would ya? Thanks again

 

[laserspeeddemon]

The "karmen" style MAF sensor used by the 4g63 is not a hot-wire, like those used by GM and Toyota.

Air passes over a vortex generator in a Karmen Vortex MAF, which creates a wake in the air flow. This wake in the airflow is called a Karmen Vortex, and the frequency of the vortices created are measured and sent off as a MAF signal. The frequency of the vortices, which vary depending on air velocity, is measured by a foil mirror which reflects a light over a photocoupler.

A g/rev is a measurement of a mass of air per revolution. See http://www.dsmtuners.com/forums/showthread.php?t=272951.

Good Read, made my head hurt a little though.

 

[ekanddsm]

Are you talking about the g/rev value that you see on the logger? And you would like to know how the ecu calculates that and where it does it in evoscan?

 

[linksys42]

Are you talking about the g/rev value that you see on the logger? And you would like to know how the ecu calculates that and where it does it in evoscan?

Kind of, evo scan already calculates that but the reading for it is off and there are discrepancies between my pocket logger and evoscan because it is using the calculations and variables for the evo. Every thing else is correct tps, timing, air flow in hz, fuel trims, oxygen sensor, air temp, speed, knock but the lbs/min an estimated value and I am trying to figure out how pocket logger request or estimates lbs/min so I can correct the math using the correct eval for the final output.

 

[2gGSX]

Simultaneously log (if that's possible, if not then two sequential logs will work too) RPM, g/rev, and airflow with both EvoScan and Pocketlogger, then post it up.

 

[linksys42]

Simultaneously log (if that's possible, if not then two sequential logs will work too) RPM, g/rev, and airflow with both EvoScan and Pocketlogger, then post it up.

That’s not going to work because both loggers connect to the obdII port and it wouldn’t matter. They are way to far off. It is a number/variable in the code/eval that is off. This is the eval for g/rev on how evoscan calc’s [LoadMUT2Byte]/95. Loadmutebyte eval is 0.3125*x , X being the value from the ecu. I am just going to email Hamish the creator about the source. Thanks again

 

[2gGSX]

Try making 2 pulls and logging them with EvoScan followed by the pocketlogger? Short of this being a multi-factoral issue, I don't believe that you can't run a regression on their individual datasets and come up with a correction factor.

 

[Ceddy]

Does any one know exactly how the ECU calculates lbs/min airflow or g/rev?

From Christian's 1G Disassembly:

airVol16 = numPulsePerCasInterrupts * litreOfAirPerAirflowSensorPulse * 603.68

Using again 1.18g/litre air density we get

airVol16 = numPulsePerCasInterrupts * litreOfAirPerAirflowSensorPulse *1.18 * 603.68/1.18
= numPulsePerCasInterrupts * gramsOfAirPerAirflowSensorPulse * 512
= gramsOfAirPerCasInterrupts * 512

In that case, airVol16/512 can be seen has having units of gramsOfAirPerCasInterrupts
(grams of air entering one cylinder). Note that the factor of 512 is not random, the
factor 0.808 is used to get it in that case...

The DSM ECU doesn't really use grams/rev for its calculations, instead it uses a bunch of Air Volume and MAF variables. It gets this data from the MAF which the ECU reads as Hertz. Karmen hertz are translated into air volume using a table.

You need to know which Air Volume variable you are logging, then it can be converted to G/rev.

If you are logging the Karmen Hz try dividing by 6.53, this will give the approximate grams/rev.
You can then multiple grams/rev by rpm to get grams/second.

How do you like EvoScan so far?

 

[linksys42]

From Christian's 1G Disassembly:




The DSM ECU doesn't really use grams/rev for its calculations, instead it uses a bunch of Air Volume and MAF variables. It gets this data from the MAF which the ECU reads as Hertz. Karmen hertz are translated into air volume using a table.

You need to know which Air Volume variable you are logging, then it can be converted to G/rev.

If you are logging the Karmen Hz try dividing by 6.53, this will give the approximate grams/rev.
You can then multiple grams/rev by rpm to get grams/second.

How do you like EvoScan so far?

Its nice being able to log knock, IDC and it has a hp calc like dsmlink that helps out a lot when seeing if the adjustments I have made are helping or hurting coupled with my wide band it's great. Only problem I am having is that my afc is keeping me in a lower airflow map and bumping up the timing and knocking with my 650's it a pain in the ass. But I need to retune it just dropped the fuel pressure to 38psi to take some fuel away. Need to get back out and tune it again just would like to be able to log g/rev or lbs/min so I can see what map I should be running in I can always just use my logger to see the lbs/min then convert to g/rev but I would like to be able to see them in a row with all the items in evoscan. thanks