Quick guide to simultaneous VVE/MAF calibration for gen4+

[Bwilliams]

Great.

Probably should have added instructions so I'll add them here.
Find out what the IDs are that you are logging for these parameters:

• Mass Airflow
• STFT Bank 1
• LTFT Bank 1 (Optional depending on tune config)
• STFT Bank 2
• LTFT Bank 2 (Optional depending on tune config)
• Wideband Bank 1
• Wideband Bank 2 (Optional)
• EQ Ratio Cmd
• Engine Speed
• Intake Manifold Absolute Pressure
• Volumetric Efficiency
• Manifold Air Temp

Head across to the spreadsheet and plug your IDs into the blue ID column.
Copy smokeshows formula(s) back into your math parameter(s)

The use of average is optional. I use an average of 200 for closed loop in all my logs as it seems to line up the GMVE data with the O2 sensor swings nicely. For open loop I do not use average. Play around with it to suit your own tastes.

[[email protected]]

I still see a lot of people using the old method of disabling the MAF to calibrate their VVE on 4th generation LS stuff, that generally being E38 controllers and up. This isn't necessary anymore because you can log those GMVE values in real time with HP Tuners. All you need to do is use the proper math parameter(s) and filters to transform the data into the classic '% error' you're used to, which I will describe here. One thing to remember, as you always should when calibrating anything airflow related...it must be at steady state. So you should be using a method of your choosing to filter out transients, which I won't get into here. This method also assumes using short term fuel trims (LTFT disabled), so any open loop guys or calibration into the power-enriched range will have to incorporate fueling error from a wideband.

The math:
GMVE STFT % error = ((MAF_af)*(1+(STFT_avg)/100)-(GMVE_af))/(GMVE_af)*100

Because steady state will always be looking at the MAF for airmass calculations, you must base your GMVE airflow error on the MAF airflow error. First, I normalize the STFT percentage so 0% becomes 1. A STFT of 5% would yield 1.05. Then multiply this by current MAF airflow to get an error corrected MAF airflow. From this value you subtract GMVE airflow to get a raw GMVE airflow error. Then, divide that error by the GMVE airflow to get your normalized VVE airflow error. Multiplying by 100 turns this back into % error to make pasting into the editor simpler.

To break the GMVE airflow calculation down a bit...

GMVE_af = (MAP*GMVE/IAT)*RPM/60*4

Take MAP in MEGApascals (important) and multiple by the raw GMVE value from CAN and divide by the IAT in KELVIN (also important). This gives a single cylinder airmass. To get flow rate, multiply by RPM, divide by 60 to get revolutions per second, and multiply by 4 for the number of induction cycles in one revolution. If you have a 4 or 6 cylinder, multiply by 2 or 3, respectively.

The full math parameter: GMVE STFT =
(([16.71]*(1+(.01*[6.156]+.01*[8.156])/2)-[12.56]/60*4*[11.92]*[2312]/[2127.240])/([12.56]/60*4*[11.92]*[2312]/[2127.240]))*100

Take this error data and plot it in your histograms and you would normally and save a bunch of time and disabling stuff in the calibration. As always, the more data points you get the better you filter out data noise.

Screen capture of the parameter working...

Attachment 101145

Notice at the cursor point, the average STFT in the third graph is showing -4.4%, so a MAF airflow overestimation. However the GMVE airflow, being slightly lower is showing only 0.3% error, so it's right on for that operating point.

Attachment 101147


Update (06Nov2020): See the post below for information on improving this process using MAT versus IAT (if parameter is available)
https://forum.hptuners.com/showthrea...l=1#post631001

Just curiosity, why not log the actual corrected gmve value then copy and paste without the need to multiply by percent? That would also make it useful for building a gmve table from scratch using a calibrated maf. Or am I wrong?

[Cringer]

Just curiosity, why not log the actual corrected gmve value then copy and paste without the need to multiply by percent? That would also make it useful for building a gmve table from scratch using a calibrated maf. Or am I wrong?

You can do that. However, this adds complexity and room for error when you convert the flow rate (grams/sec) from MAF into the values for the VVE table, which is cylinder airmass (in milligrams) multiplied by intake air temp (in Kelvin) divided by manifold pressure (in KPa). In my mathematical experiments, converting the flow rate into cylinder airmass never matches the cylinder airmass as determined by the ECM.

I would direct you to a much easier way:
read this:https://forum.hptuners.com/showthrea...-the-Same-Time
and then: https://forum.hptuners.com/showthrea...ynamic-airflow

[gokart2]

I am getting confused in trying to get this to work. I just typed up a huge thing and lost it when trying to post....lost the token? Whatever.

Ok.

GMVE. I do not have this parameter. GM gen5 I4. Should I put a ticket in to request it?

I found some math for it.....but when creating the parameter I don't understand which unit to have the output be?

Because of that, the GMVE_af calculation fails due to what seems like the wrong unit from the GMVE math.

I also do not have Volumetric Efficiency (mg*K/kpa) parameter. Only Volumetric Efficiency Airflow (mass flow rate). So I assume I need a ticket to add Volumetric Efficiency (mg*K/kpa) parameter?

There's slightly more to my issue but I am stopping here for the time being untile I resolve these issues.

Thank you, any help is GREATLY APPRECIATED!

[Cringer]

I am getting confused in trying to get this to work. I just typed up a huge thing and lost it when trying to post....lost the token? Whatever.

Ok.

GMVE. I do not have this parameter. GM gen5 I4. Should I put a ticket in to request it?

I found some math for it.....but when creating the parameter I don't understand which unit to have the output be?

Because of that, the GMVE_af calculation fails due to what seems like the wrong unit from the GMVE math.

I also do not have Volumetric Efficiency (mg*K/kpa) parameter. Only Volumetric Efficiency Airflow (mass flow rate). So I assume I need a ticket to add Volumetric Efficiency (mg*K/kpa) parameter?

There's slightly more to my issue but I am stopping here for the time being untile I resolve these issues.

Thank you, any help is GREATLY APPRECIATED!

GMVE is not a log-able parameter. It is a made up term/idea/concept. You need to create your own custom math parameter and then chose a name...which people universally call "GMVE".

Of late the whole concept of how to tune VVE is a bit controversial and a dividing point among us (which is perhaps why you are getting a lack of a response here). Historically, all you could do is fail the MAF to force speed density to tune VVE. Then later the concept of GMVE came out (I think from Marcin/Red Hot Supra). Then in the last year or so I have proffered it is best to utilize the dynamic airflow to properly calibrate both MAF and VVE. I don't want to re-open fresh wounds, you can do your own research (look at my post directly above your post and read those). Whatever method you use, I would encourage you to use the link in my sig line to get the VVE Assistant to help. There is a learning curve and you will need to watch the videos on how to use it properly.

However, if you do not have Volumetric Efficiency (mg*K/kpa), then yes, log a support ticket to HPT to add it. In the meantime (or if they never add it), I would encourage you to try my methods which do not rely on that specific channel.

[gokart2]

GMVE is not a log-able parameter. It is a made term/idea/concept. You need to create your own custom math parameter and then chose a name...which people universally call "GMVE".

Of late the whole concept of how to tune VVE is a bit controversial and a dividing point among us (which is perhaps why you are getting a lack of a response here). Historically, all you could do is fail the MAF to force speed density to tune VVE. Then later the concept of GMVE came out (I think from Marcin/Red Hot Supra). Then in the last year or so I have proffered it is best to utilize the dynamic airflow to properly calibrate both MAF and VVE. I don't want to re-open fresh wounds, you can do your own research (look at my post directly above your post and read those). Whatever method you use, I would encourage you to use the link in my sig line to get the VVE Assistant to help. There is a learning curve and you will need to watch the videos on how to use it properly.

However, if you do not have Volumetric Efficiency (mg*K/kpa), then yes, log a support ticket to HPT to add it. In the meantime (or if they never add it), I would encourage you to try my methods which do not rely on that specific channel.

I put a ticket in to request Volumetric Efficiency (mg*K/kpa). I realized GMVE was not an actual PID literally a minute before seeing this.

I appreciate the tool/video links. I will look into them.

I initially started calibrating my MAF the "older way" I guess I'd call it? Setup the cal, did some logging. Updated the cal....then got scared. I noticed my AFR bouncing a bit rich and lean at points, mainly lower airflows. Which I was told was normal by another... knowledgeable tuner. I noticed I had it locked in.....shit......can't remember...... believe open loop. I thought the AFR was supposted to be basically right at stoich with no added fueling? So I was confused and contemplating I had it locked in the wrong fueling loop?

One question....is it supposed to be locked in open loop for MAF calibration in the "old way" to do it?

Again, I greatly appreciate you pointing me in the right direction.

[Cringer]

I put a ticket in to request Volumetric Efficiency (mg*K/kpa). I realized GMVE was not an actual PID literally a minute before seeing this.

I appreciate the tool/video links. I will look into them.

I initially started calibrating my MAF the "older way" I guess I'd call it? Setup the cal, did some logging. Updated the cal....then got scared. I noticed my AFR bouncing a bit rich and lean at points, mainly lower airflows. Which I was told was normal by another... knowledgeable tuner. I noticed I had it locked in.....shit......can't remember...... believe open loop. I thought the AFR was supposted to be basically right at stoich with no added fueling? So I was confused and contemplating I had it locked in the wrong fueling loop?

One question....is it supposed to be locked in open loop for MAF calibration in the "old way" to do it?

Again, I greatly appreciate you pointing me in the right direction.

Closed Loop = Stoich -> narrowband O2 sensors
Open Loop = Rich* -> wideband O2 sensor
*note an exception that after start up the car may be in OL before switching over to CL and the ECM is commanding lambda of 1.00

Also SD (speed density) is NOT Open Loop. SD means you failed the MAF and are using VE or VVE for your entire airflow model. Unless you have a good reason to, it is best to run in hybrid mode (allowing the ECM to swap and blend back and forth between MAF and VVE at any given time).

In Closed Loop the bouncing around stoich is intentional and it is for the functionality of the cats. The overall aggressiveness and frequency it dances around stoich can be controlled and tuned, that is a conversation for another day.

Please do not tune for stoich in OL with a wideband. The factory narrowbands are basically EPA controlled emissions equipment. This is a good thing! They are accurate and high quality. And most importantly, when you go back to enable CL...your ECM is not going to use the wideband; it is going to use the narrowbands. So use the narrowbands for everything you can. Only use the wideband for OL loop operations. Widebands are usually never as quality that the narrowbands are, and are certainly not scrutinized for emissions purposes like the narrowbands.

I use 4 charts in the scanner when I tune:
1) MAF CL (uses STFT + LTFT*)
2) MAF PE (uses wideband EQ error*)
3) VVE CL (uses STFT + LTFT*)
4) VVE PE (uses wideband EQ error*)
*...or really the dynamic air formulas I mentioned before

[gokart2]

Could someone supply me a stock readout that has (ID 2312) Volumetric Efficiency (mg*K/kPa)? I put a ticket in and this is what was asked of me. IDK how to see the parameter via a tune file? I tried looking through the sample tunes. Assume the "2014 Chevy Corvette E92 - 12660065" sample tune would have it?

Also tried looking through the sample logs with no luck? None had it activated.

Requested:
- Tune file that has this parameter available

Please and thank you.

[Cringer]

Could someone supply me a stock readout that has (ID 2312) Volumetric Efficiency (mg*K/kPa)? I put a ticket in and this is what was asked of me. IDK how to see the parameter via a tune file? I tried looking through the sample tunes. Assume the "2014 Chevy Corvette E92 - 12660065" sample tune would have it?

Also tried looking through the sample logs with no luck? None had it activated.

Requested:
- Tune file that has this parameter available

Please and thank you.

You can download the log file in this post for an example: https://forum.hptuners.com/showthrea...l=1#post773680

[smokeshow]

I am getting confused in trying to get this to work. I just typed up a huge thing and lost it when trying to post....lost the token? Whatever.

Ok.

GMVE. I do not have this parameter. GM gen5 I4. Should I put a ticket in to request it?

I found some math for it.....but when creating the parameter I don't understand which unit to have the output be?

Because of that, the GMVE_af calculation fails due to what seems like the wrong unit from the GMVE math.

I also do not have Volumetric Efficiency (mg*K/kpa) parameter. Only Volumetric Efficiency Airflow (mass flow rate). So I assume I need a ticket to add Volumetric Efficiency (mg*K/kpa) parameter?

There's slightly more to my issue but I am stopping here for the time being untile I resolve these issues.

Thank you, any help is GREATLY APPRECIATED!

GMVE is the aftermarket's 'street name' for GM's VE parameter...creative, right. Volumetric Efficiency (mg*K/kpa) is GMVE. It is a loggable parameter, made up by GM. It is a 'read by memory address' parameter though, so HP Tuners doesn't always have it defined in every OS out there. As GM changes software periodically, memory addresses tend to move around. HPT will be able to sort it out for you. The VE airflow term also works in a pinch...calculated VE airflow and the CAN reported VE airflow line up just fine in most cases. Just has a high flow limit.

[gokart2]

GMVE is the aftermarket's 'street name' for GM's VE parameter...creative, right. Volumetric Efficiency (mg*K/kpa) is GMVE. It is a loggable parameter, made up by GM. It is a 'read by memory address' parameter though, so HP Tuners doesn't always have it defined in every OS out there. As GM changes software periodically, memory addresses tend to move around. HPT will be able to sort it out for you. The VE airflow term also works in a pinch...calculated VE airflow and the CAN reported VE airflow line up just fine in most cases. Just has a high flow limit.

Few questions after they added Volumetric Efficiency (mg*K/kpa) for me.

Does this appear to be the correct math if I'm rocking a 4 cylinder, minus STFT bank 2 and multiplying by 2 instead of 4 for induction cycles?

(([16.71]*(1+(.01*[6.156]))-[2135.56]/60*2*[11.92]*[2312]/[2126.240])/([2135.56]/60*2*[11.92]*[2312]/[2126.240]))*100

stftdiff.PNG

This:

"This method also assumes using short term fuel trims (LTFT disabled), so any open loop guys or calibration into the power-enriched range will have to incorporate fueling error from a wideband."

I am currently an open loop guy and have LTFT active.....and have a wideband. How should I go about this aspect of things? What is more optimal and /or how do I "incorporate fueling error from a wideband"?

Thanks again for the help guys. It's been a bit of a struggle coming to GM from Chrysler tuning. And from NA to forced induction. Regardless I am learning an awful lot and appreciate all the excellent information you guys provide. Sorry to be the little 4 cyl guy impeding in the V8 forums, but there's no information or help elsewhere. Feel like I'm treading new waters here....?

[gokart2]

Few questions after they added Volumetric Efficiency (mg*K/kpa) for me.

Does this appear to be the correct math if I'm rocking a 4 cylinder, minus STFT bank 2 and multiplying by 2 instead of 4 for induction cycles?

(([16.71]*(1+(.01*[6.156]))-[2135.56]/60*2*[11.92]*[2312]/[2126.240])/([2135.56]/60*2*[11.92]*[2312]/[2126.240]))*100

stftdiff.PNG

This:

"This method also assumes using short term fuel trims (LTFT disabled), so any open loop guys or calibration into the power-enriched range will have to incorporate fueling error from a wideband."

Assuming my math is correct.....I disabled LTFT, all PE and temp controls, and CFCO/DFCO. Only thing I'm slightly confused about is locking it in closed loop? I assume set "[ECM] 2529 - O2 Sensor Ready Voltage: If the O2 voltage drops below this value, the O2 Sensor is ready for closed loop. Set low to disable closed loop." to the highest possible number to keep it forced into closed loop?

Keep it steady state with slow throttle input? Stay out of boost because of no PE obviously?

[hjtrbo]

You can leave EVERYTHING stock, dfco, cfco, o2, MAF (not) fail, VVE (not) disable, DTC's etc etc etc etc etc. You use filters to mask events like open loop, dfco, purge etc.

I don't mean to sound rude; the type of questions you're asking make me think this variant of vve / maf tuning is not for you. I would click the links in cringer's signature and go that way.

[gokart2]