MAF Calibration
Oct 31, 2006, 07:12 PM
#1
MAF Calibration
I know we can change the fuel tables for any respective load/rpm value that the car may hit, but i dont think that this is the optimal way to tune a MAF regulated car.
The fuel tables are afr targets, not injector durations, like commonly used on MAP regulated cars.
I think that the best way to tune our cars would be to have access to the MAF calibration table, then all you do is setup your fuel table to have your desired afr targets, then when a change is made, or you need to re-tune, all you have to do is change the MAF calibration table (single row table with load only). This is the way that Cobb does it in their street tuner software, and it is very easy to use, and takes no time to tune or retune fuel.
Do our ecu's not have this table? I'm sure it does. But someone with better knowledge on the subject please chime in here.
I know the Cobb software is coming out for us after Sema, but i would rather use EcuFlash due to its portability. (and the price is nice too!
)
Just thinking we need to find this table and use MAF tuning the way it was meant to be used.
I'd even be willing to chip in for a little compensation for whoever can find and implement this functionality.
The fuel tables are afr targets, not injector durations, like commonly used on MAP regulated cars.
I think that the best way to tune our cars would be to have access to the MAF calibration table, then all you do is setup your fuel table to have your desired afr targets, then when a change is made, or you need to re-tune, all you have to do is change the MAF calibration table (single row table with load only). This is the way that Cobb does it in their street tuner software, and it is very easy to use, and takes no time to tune or retune fuel.
Do our ecu's not have this table? I'm sure it does. But someone with better knowledge on the subject please chime in here.
I know the Cobb software is coming out for us after Sema, but i would rather use EcuFlash due to its portability. (and the price is nice too!
) Just thinking we need to find this table and use MAF tuning the way it was meant to be used.
I'd even be willing to chip in for a little compensation for whoever can find and implement this functionality.
Oct 31, 2006, 07:17 PM
#2
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yes we have acess to the table the only problem is we are not 100% sure what values the computer uses to tell load.
Our MAF's Dont reag g/s they read Karman Vorticies, much harder to tune for.
Our MAF's Dont reag g/s they read Karman Vorticies, much harder to tune for.
Nov 1, 2006, 05:48 AM
#4
It probably is.. But the left-hand column that has the Int16 value may not be a value we expect..
As far as I have been able to tell, that value (if you convert it using the same conversion for the Airflow RequestID) is INDEED the frequency, but nobody has been able to verify this as of yet..
My only data is inferrential based on other tables I was looking at that matched MAF Frequency to Flow, and the load value listed on the right, seemed to match to the translated value (in HZ)
That doesnt make it correct, it only means that I might have figured it out.. We won't really know until someone tries it..
As far as I have been able to tell, that value (if you convert it using the same conversion for the Airflow RequestID) is INDEED the frequency, but nobody has been able to verify this as of yet..
My only data is inferrential based on other tables I was looking at that matched MAF Frequency to Flow, and the load value listed on the right, seemed to match to the translated value (in HZ)
That doesnt make it correct, it only means that I might have figured it out.. We won't really know until someone tries it..
Nov 1, 2006, 05:50 AM
#5
Lets put it this way.. If it was indeed the value in HZ.. There are two issues..
1 - The conversion factor is mathematical, is this a configurable parameter, and if it is, what else affects it (IE MAF Size value)
2 - If this is a conversion factor that can easily be changed, and the configurable parameters can be altered.. This can actually be a big deal, Since the GM MAF sensor outputs a square wave signal in KHZ, can the parameters be altered to natively cooperate with a GM sensor???? Stay tuned..
1 - The conversion factor is mathematical, is this a configurable parameter, and if it is, what else affects it (IE MAF Size value)
2 - If this is a conversion factor that can easily be changed, and the configurable parameters can be altered.. This can actually be a big deal, Since the GM MAF sensor outputs a square wave signal in KHZ, can the parameters be altered to natively cooperate with a GM sensor???? Stay tuned..
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Nov 5, 2006, 09:32 PM
#8
MalibuJack, have you found out any more info on this?
Can we tune fuel by simply modifying the Maf calibration, or not?
I mean, if we know the load, and the RPM, wouldn't we only have to change the calibration to make changes in the afrs?
Can we tune fuel by simply modifying the Maf calibration, or not?
I mean, if we know the load, and the RPM, wouldn't we only have to change the calibration to make changes in the afrs?
Nov 6, 2006, 04:27 AM
#9
It doesnt really work that way, you can use the maf calibration to hit load targets, but its really best left alone unless you have a specific need to alter it.
The problems people have with the MAF are not really calibration, but anomolous readings, and you really can't work around that with the calibration settings.
The problems people have with the MAF are not really calibration, but anomolous readings, and you really can't work around that with the calibration settings.
Nov 8, 2006, 06:00 PM
#10
So, our ecu's do not work the same way that the Subaru ecu's, is that correct?
Cobb's claim to fame is that they can tune an entire Subaru with just altering the maf calibration. I have to say, i have done it several times, and it is pretty sweet.
If that is true then i wonder how their street tuner sw will work with our cars, i mean it will work, but it will offer no real advatages over ecuflash, except the built in logging, which is quite nice.
Cobb's claim to fame is that they can tune an entire Subaru with just altering the maf calibration. I have to say, i have done it several times, and it is pretty sweet.
If that is true then i wonder how their street tuner sw will work with our cars, i mean it will work, but it will offer no real advatages over ecuflash, except the built in logging, which is quite nice.
Nov 8, 2006, 07:38 PM
#11
Well.. I suppose its possible to do it that way with the MAF calibration table.. But its roughly equivalent to tuning with an S-AFC... Not enough is currently known about that table to be able to effectively use it at the moment, we are not sure what other components of the ECU are affected by altering that.
Nov 8, 2006, 08:45 PM
#12
I agree wholeheartedly with Jack's comments. Tuning by altering the MAF table is what an AFC and piggybacks generally do. They don't directly alter the ECUs MAF table, so to speak, they just change the signal before it gets to the ECU.
But, this method is basically a way to trick the ECU so that you land in lower load cells, which will in turn generally increase your timing and lean your fueling, based on the maps in the ECU.
This is not the recommended way to tune a car, especially if you care about real data, such as true mass airflow, true load, etc, etc. Before people had access to the stock ECU for DSMs and Evos, a S-AFC was an option, but now that we have access to the ECU (entire ECU for DSMs with DSMLink) and a lot of the ECU for the Evo already, with ECUFlash, it would be foolish to only tune using a MAF table. You will never be able to get the resolution by tuning one table as you would using multiple tables, and on top of that, you would never know where you stood in comparison to other people's logs because your data would be altered due to the altered MAF table. Your data just doesn't mean much anymore at that point, since it's all 'wrong', altered, etc.
The MAF table does have it's place in tuning, however. The only time this table should ever be used is to calibrate an aftermarket MAF/MAS so that the mass airflow can be calibrated back to the stock MAF. This was a very common thing with DSMLink and I did it with my Eclipse. I could have just used the artificially high airflow readings that the GM Maf was giving and tuned accordingly, but then my data would be invalid, so to speak, in the same way that the data becomes invalid when you use a S-AFC/piggyback or something that alters the true airlfow readings.
To make a long story short, tuning by solely using the MAF table should not be done. We have much better control over timing, fueling, etc, by using their own respective tables and we get to keep all of our 'real' data.
Eric
But, this method is basically a way to trick the ECU so that you land in lower load cells, which will in turn generally increase your timing and lean your fueling, based on the maps in the ECU.
This is not the recommended way to tune a car, especially if you care about real data, such as true mass airflow, true load, etc, etc. Before people had access to the stock ECU for DSMs and Evos, a S-AFC was an option, but now that we have access to the ECU (entire ECU for DSMs with DSMLink) and a lot of the ECU for the Evo already, with ECUFlash, it would be foolish to only tune using a MAF table. You will never be able to get the resolution by tuning one table as you would using multiple tables, and on top of that, you would never know where you stood in comparison to other people's logs because your data would be altered due to the altered MAF table. Your data just doesn't mean much anymore at that point, since it's all 'wrong', altered, etc.
The MAF table does have it's place in tuning, however. The only time this table should ever be used is to calibrate an aftermarket MAF/MAS so that the mass airflow can be calibrated back to the stock MAF. This was a very common thing with DSMLink and I did it with my Eclipse. I could have just used the artificially high airflow readings that the GM Maf was giving and tuned accordingly, but then my data would be invalid, so to speak, in the same way that the data becomes invalid when you use a S-AFC/piggyback or something that alters the true airlfow readings.
To make a long story short, tuning by solely using the MAF table should not be done. We have much better control over timing, fueling, etc, by using their own respective tables and we get to keep all of our 'real' data.
Eric
Last edited by l2r99gst; Nov 8, 2006 at 08:48 PM.
Nov 9, 2006, 02:25 PM
#14
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The Subarus use a 0-5v MAF and the table in the ECU covers the entire range with a large amount of data points, so it is helpful for dialing in an intake on those cars.
The MAF table in the Evo maxes out well before the MAF does though. It is helpful for dialing in your part throttle fuel trims though, especially around idle, if you have large injectors or if you have a weird airfuel spike during boost transition that you can't hit with the normal maps.
The scaling of the data and axis for the MAF tables in Ecuflash is wrong, but it is easy to figure out what they should be and change them in the definition.
The MAF table in the Evo maxes out well before the MAF does though. It is helpful for dialing in your part throttle fuel trims though, especially around idle, if you have large injectors or if you have a weird airfuel spike during boost transition that you can't hit with the normal maps.
The scaling of the data and axis for the MAF tables in Ecuflash is wrong, but it is easy to figure out what they should be and change them in the definition.
