Polynomial Equation for Torque Calculation

[Tapout Tuning]

I'm sure it's posted here somewhere, but I can't seem to locate the actual equation for how torque model is calculated using all the coefficients.

• EQ Ratio
• Airmass
• Airmass Sq
• RPM
• Spark
• Spark Sq
• Spark Airmass
• Spark Sq. Airmass

Does anyone have the actual polynomial equation for this? I'd like to plug the formula into Excel and work with it. Thanks in advance!

[Higgs Boson]

maybe if you make changes to the virtual torque editor and compare the results you can come up with the equation

[Redline MS]

APC Based Base Torque = Krpm + (spark • Kspark) + (spark2 * Kspark2) + (apc * spark * Kapc-spark) + (apc • spark2 * Kapc-spark2) + (apc * Kapc) + (apc2 * Kapc2)

[Tapout Tuning]

APC Based Base Torque = Krpm + (spark ? Kspark) + (spark2 * Kspark2) + (apc * spark * Kapc-spark) + (apc ? spark2 * Kapc-spark2) + (apc * Kapc) + (apc2 * Kapc2)

Appreciate your help! Any chance you could expand on this a little bit?

• What does 'APC' stand for? Is this a calculation for Airmass Based?
• How do you derive Krpm? Is it rpm/1,000?
• How do you derive Kspark?
• Does spark2 mean SparkSq?
• What is Kapc?
• Where does EQ Ratio fit into the equation?
• Where does Airmass fit into the equation?
• And what about all the MAP based tables?

Sorry for all the questions. I just figured there must be a single formula that incorporates all these parameters.

[Ben Charles]

Air per cylinder

[Redline MS]

Appreciate your help! Any chance you could expand on this a little bit?

• What does 'APC' stand for? Is this a calculation for Airmass Based?
• How do you derive Krpm? Is it rpm/1,000?
• How do you derive Kspark?
• Does spark2 mean SparkSq?
• What is Kapc?
• Where does EQ Ratio fit into the equation?
• Where does Airmass fit into the equation?
• And what about all the MAP based tables?

Sorry for all the questions. I just figured there must be a single formula that incorporates all these parameters.

Your asking good questions but this is a much greater discussion then can be laid out on a forum like this.

Just a couple notes;

This is one of a couple poly calcs that make up the string of final airflow which leads to torque. Anything with a 2 is a squared value. EQ is a factor AFTER the base calculation. The K represents a GM term in there route language not relevant for the math for this calculation. There is another string for MAP and its similar to the APC calc.

Bigger question is why are you bothering to go through this exercise? The only real way to solve this is with Matlab although you can jamb it through Excel.

[Tapout Tuning]

Your asking good questions but this is a much greater discussion then can be laid out on a forum like this.

Just a couple notes;

This is one of a couple poly calcs that make up the string of final airflow which leads to torque. Anything with a 2 is a squared value. EQ is a factor AFTER the base calculation. The K represents a GM term in there route language not relevant for the math for this calculation. There is another string for MAP and its similar to the APC calc.

Bigger question is why are you bothering to go through this exercise? The only real way to solve this is with Matlab although you can jamb it through Excel.

Very much appreciate your input on this. That's exactly what I'm trying to do - set it up in Excel. I want to gain a better understanding of how the ECM actually calculates torque, rather than just continuing to guess. So often it seems like I 'solve' a problem by increasing the Airmass Based or decreasing the MAP Based. But I never really understand how what I'm doing is actually working.

I would love to set up the Airmass Based calculation in Excel. Then set up the MAP Based calculation. Then apply the Equivalency Ratio factor. In the ideal world I would like to see the final Excel number match the ECM torque number. I can't be the first person who ever wanted to truly understand what's really going on with all these torque coefficient tables.

[Redline MS]

Very much appreciate your input on this. That's exactly what I'm trying to do - set it up in Excel. I want to gain a better understanding of how the ECM actually calculates torque, rather than just continuing to guess. So often it seems like I 'solve' a problem by increasing the Airmass Based or decreasing the MAP Based. But I never really understand how what I'm doing is actually working.

I would love to set up the Airmass Based calculation in Excel. Then set up the MAP Based calculation. Then apply the Equivalency Ratio factor. In the ideal world I would like to see the final Excel number match the ECM torque number. I can't be the first person who ever wanted to truly understand what's really going on with all these torque coefficient tables.

I know what your trying to do. However there are many variables not accessible with HPT or EFI Live that play into this string....its a complicated self feeding algorithm. GM uses a program called Simulink (which is based of Matlab) to take in the values noted on both the two air model calcs and the torque calcs and covert them to the coefficients in the cal. Airflow and torque go hand and hand. This is why nailing the air model is first and foremost before address the torque models. Also realize that "torque" models" are both a limit and a predicted scenario and understand why and when they are referenced is the next chain in the process. With well over 12000 parameters in this current controller; the access we have is far from what's really needed to do an OEM job.

[Tapout Tuning]

I know what your trying to do. However there are many variables not accessible with HPT or EFI Live that play into this string....its a complicated self feeding algorithm. GM uses a program called Simulink (which is based of Matlab) to take in the values noted on both the two air model calcs and the torque calcs and covert them to the coefficients in the cal. Airflow and torque go hand and hand. This is why nailing the air model is first and foremost before address the torque models. Also realize that "torque" models" are both a limit and a predicted scenario and understand why and when they are referenced is the next chain in the process. With well over 12000 parameters in this current controller; the access we have is far from what's really needed to do an OEM job.

Great stuff! Is there any way to discern and/or control when the ECM uses the Airmass Based model versus the MAP Based model?

[Redline MS]

Great stuff! Is there any way to discern and/or control when the ECM uses the Airmass Based model versus the MAP Based model?

We typically will lower the high speed enable values to below idle which will bias the model toward the MAP based....reality is that even lowering that it still looks at the MAP..... The models are often used independently for fueling and torque reporting so if possible both of them dialed in and working will avoid a lot of other issues. The MAP is used more for transient fueling where the MAF works more effectively for linear airflow (steady state). The two working together is how the controller deals with manifold filling which has a big impact on the transient fueling....

[Tapout Tuning]

We typically will lower the high speed enable values to below idle which will bias the model toward the MAP based....reality is that even lowering that it still looks at the MAP..... The models are often used independently for fueling and torque reporting so if possible both of them dialed in and working will avoid a lot of other issues. The MAP is used more for transient fueling where the MAF works more effectively for linear airflow (steady state). The two working together is how the controller deals with manifold filling which has a big impact on the transient fueling....

Makes perfect sense. Thanks again for sharing some of your wisdom!

[Wheeler]

My understanding is k = current time event.

[djyankees31]

This thread might be of some help.

https://forum.hptuners.com/showthrea...e-run-modeling

[Ghostnotes]

This thread might be of some help.

https://forum.hptuners.com/showthrea...e-run-modeling

This...

I downloaded the patent paper a few months ago and going slowly through it, helped me understand things better. Help can be sketchy here but early on in my learning curve I realized the "what" as in tuning your air, fuel and spark FIRST was most important and a lot of problems go away......to a point. After that the other problems can be handled more systematically as they come along during the learning stages. Which is where I'm still at. The "how" was my biggest Achilles. Meaning how to set the information and what to scan in the scanner....still is.

As an instrumentation engineer in oil and gas, I calculate mass flow, volumetric flow, density and temp all day long. How to put it together in HPT is for some reason is tough and unclear for me sometimes.

For Instance when I replaced my MAP with a 3 BAR, I scaled it with the proper offset and max, but do I scale the range to match the full sensor scale or what I will only be able to reach as 100%?