Proper Toque Model Calculation

[TriGun]

Just for the sake of curiosity, I built the torque model of my 2010 Camaro SS/L99. What I’m trying to do is enabling the ECM to calculate the correct engine torque after I added a supercharger. I’m sure this is essential for the transmission to be able to adjust the shift timing and pressure.

Before I show the result let start by the torque equation:

TRQ.1 = A1 x Airmass + A2 x Spark + A3 x Spark x Airmass + A4 x Spark.Sq + A5 x Spark.Sq x Airmass + A6

TRQ.1 is the stock engine torque (Nm).
A1 from “Airmass A” Table referenced by RPM
A2 From “Spark A” Table referenced by RPM
A3 from “Spark.Airmass A” Table Referenced by RPM
A4 from “SparkSq A” Table referenced by RPM
A5 from “SparkSq.Airmass A” Table referenced by RPM
A6 from “RPM A” Table referenced by RPM

I found that the best table to show the calculated torque on, is the High Octane Spark table. Because all the data needed exist in that table (air mass, spark and RPM) so this is what I got:

Airmass based Torque Model.png

And the 3D graph is as follows:

Airmass based Torque Model 3D-Graph.png

Now, to correct the torque calculation we need a dyno to measure the new torque after adding the supercharger.

Let’s assume the stock engine produces 400Nm of torque at 5000rpm and 0.8g air mass. And the modified engine (with a supercharger) produces 560Nm of torque at the same RPM and air mass.

So the torque is increased by 40%

To correct the equation we can simply multiply the equation by 1.4

TRQ.2 = 1.4 x (A1 x Airmass + A2 x Spark + A3 x Spark x Airmass + A4 x Spark.Sq + A5 x Spark.Sq x Airmass + A6)

Where TRQ.2 is the corrected torque value.

From the above equation we can simply multiply all coefficients ( An) by 1.4 in the tables at that RPM to get the new torque calculated.
But the supercharger does not increase the torque equally at all RPM’s. So we can say, it increase the torque as follows:

Torque Model Coeff Multipliers.png

(Where 1 is 100% and 1.1 is 110%...etc.)

We can just multiply all the tables by the same multipliers as above to get the corrected torque. The same applies for other based toque models (Airmass, MAP, E85…etc.)
Ex.

Airmass based Torque Model - After Modification.png

Airmass based Torque Model 3D-Graph - After Modification.png


In the other hand, I think the Max Torque Timing table needs also to be corrected so that the ECM can calculate the percentage engine load correctly.
I’m not sure of what I did is correct or not. Waiting for your comments and help.

But the first question is: when the ECM use the Airmass based Torque Model and when it switch to the MAP based Torque Model?

[GPGTP]

uhhh, this might be a dumb question. But wouldn't the computer calculate more torque based on more airflow though the maf & VE table.....I'm not 100 sure but I think these tables are more put to use when scaling a tune.

[TriGun]

Yes you are right. but the calculated torque value is not correct. These table are generated for every engine according to its power band and torque curve, any power adder will alter those.

So you have to recalibrate these table according to your new torque curve and power band, to enable the engine and transmission to calculate the correct delivered engine torque.

look at this for more information: http://forum.efilive.com/showthread....ts-via-the-ECM

[DSteck]

Yes, but your method is not the right way. The increased airmass will make it change the most. You can't just multiply all of it by X because I won't use the same values as before. You'd have to manually tweak it.

[TriGun]

Yes, but your method is not the right way. The increased airmass will make it change the most. You can't just multiply all of it by X because I won't use the same values as before. You'd have to manually tweak it.

This is what I'm trying todo by multiplying each RPM range by how much percent the torque is increased in that range only. See Fig. 3 which show different multiplication factor for each RPM range.

[DSteck]

You wanted to multiply all tables by 1.4. That's what I'm saying is wrong.

[Redline MS]

If your fuel mass factors (fuel injector data) is correct AND you properly remodel the coefficients and MAF, the report torque will be correct. The issue are the other tables that limit the measurement to be used...

We are enabling our chassis dyno to output torque back into our calibration software and have been playing with a correction formula to back solve to make a much better correction to that limit table....which we have had with EFIL for a while..

That table solves quite a bit of this but its all been through black magic adjustments..

What until the SERIES 11 stuff hits the scene hard......

HT