Coefficient Table A20 [RPM_Airflow] disection

[Redline Motorsports]

Ok so.....here we go....or at least I go...

It appears that these torque tables are similar to the VVE tables we have. There must be another long string polynomial calculation to generate these values. Since airflow directly corelates to torque I am curious how this tables ties into the VVE values.

The tables calls out the values to be percentage...of what or applied to what? Can we assume that the controller builds a torque map like a VE and uses it for look up which is why we are able to get a trans to shift better by changing these values? Its also noted that its tied to the GM_TRQENG_C pid which is a value in torque. When we raise this table we actually see this PID increase the values....this shows that this table acts like a limiter.

I'm wondering how we can take raw measured air and turn it into the correction value to properly solve this table (well at least as best we can).

14522

Since its referenced off cam angle its only one column that's effected based upon rpm...maybe Ross can enlighten us to the math behind this table so I can continue to not sleep!

HT

[GMPX]

It goes something like this I think....

http://images.fineartamerica.com/images-medium-large/maths-formula-on-chalkboard-setsiri-silapasuwanchai.jpg

[GMPX]

But in all seriousness Howard, showing the result of the calculations is one thing, reversing it back to recreate the coefficients is on a whole new level of pain. What we show in the Tune Tool is all the torque model tables, not necessarily does each one of those interact with the next. The VVE is different, it takes all 15 coeffs and works on them in one chunk with a few variables in to get an end result.
With the torque model it's not as simple as saying ok, lets do this:
Get value from B8220 "Coefficient Table A20 [RPM_Airflow]"
Multiply it with B8200 "Coefficient Table A21 [RPM_RPM]" and subtract it with the next and so on.
With the torque tables we have several variables used in the final calculation.

Airflow
RPM
MAP
Spark Timing
Intake Cam Position
Exhaust Cam Position

Even just to display the end result you need to give the formula those values to plot it. It really is quite a mind bender and as crude as it might sound, probably your best option at this stage is to do some controlled experiments on the numbers. I maybe wouldn't be too concerned on the Spark modifiers to the tables, but if you took say for example a 2011 Corvette, logged the useful torque PID GM.TRQENG_C that shows us the outcome of these tables and 'tweaked' the coeffs then you might get a feel for what you need to alter without really understanding the science behind it.
And copy some of what GM have done, if you are boosting an LS3 then it's probably not a bad idea to copy/paste all those torque coeff tables from an LSA calibration as a starting point.

[gmh308]

It goes something like this I think....

http://images.fineartamerica.com/images-medium-large/maths-formula-on-chalkboard-setsiri-silapasuwanchai.jpg

Nooooooo...Thats the WMD formula :).

[MarkR8]

I have just recently mucked around with these tables.
I basically copied GM tables from an LS7 into my tune to see what sort of differences there are and OMG its a whole level of pain to contemplate what the coefficients are applied to but the VVE now climbs quickly and power is increased dramtically.
There is still VVE work to do on my tune ATM but idle is coming along well and there is a noticeable increase in power and torque.
There is a lot to be grained from these tables and I would go as far as to say, they have a lot to do with how GM get the 6.2 to deliver 427HP in base form to 525HP in their crate motors with little more than differences in camshafts.

I'll post up a before and after VVE table when I am done

Mark

[Ls1_Rulz]

I have just recently mucked around with these tables.
I basically copied GM tables from an LS7 into my tune to see what sort of differences there are and OMG its a whole level of pain to contemplate what the coefficients are applied to but the VVE now climbs quickly and power is increased dramtically.
There is still VVE work to do on my tune ATM but idle is coming along well and there is a noticeable increase in power and torque.
There is a lot to be grained from these tables and I would go as far as to say, they have a lot to do with how GM get the 6.2 to deliver 427HP in base form to 525HP in their crate motors with little more than differences in camshafts.

I'll post up a before and after VVE table when I am done

Mark

any update ...?

[MarkR8]

So far I would say the car is driving much better. The VVE tables are about 90% correct and look much different to prior to modifying these coefficient tables.
Crazy numbers for min idle air have had me chasing my bum a little bit and idle is slowly coming along well. I have had good transition, good coastdown and good idle but not all at the same time.
At the moment I wish I knew more about the B1835/B1836, B1838/B1839 and B1840/B1842 tables and what they really do.
Once the idle is nailed I will be very happy with the tune and believe the coefficients make a massive difference.

[huttner1]

hi guys does your 6.2 bounce at idle in park ??? i have one that is ... can i get some help ??

[TBMSport]

So far I would say the car is driving much better. The VVE tables are about 90% correct and look much different to prior to modifying these coefficient tables.
Crazy numbers for min idle air have had me chasing my bum a little bit and idle is slowly coming along well. I have had good transition, good coastdown and good idle but not all at the same time.
At the moment I wish I knew more about the B1835/B1836, B1838/B1839 and B1840/B1842 tables and what they really do.
Once the idle is nailed I will be very happy with the tune and believe the coefficients make a massive difference.


Just started tinkering with this and ...YES...world of pain doesn't begin to cover it. I too had idle issues, but I think I got that handled. Also have my mid range power. Now trying to find my off idle to mid range power again.

[hog]

I have just recently mucked around with these tables.

There is a lot to be grained from these tables and I would go as far as to say, they have a lot to do with how GM get the 6.2 to deliver 427HP in base form to 525HP in their crate motors with little more than differences in camshafts.

I'll post up a before and after VVE table when I am done

Mark
You are comparing a 426hp LS3 that is rated using the SAE J2723 "Certified" Power spec, where the air intake and exhaust is specific for that excat car/model to the same engine with a cam/calibration change that is rated at 525hp using a different specification where its exhaust and air intake and calibration isnt specified for the testing. You cant directly compare the 2 power numbers on an equal footing.

That would be like comparing the SAE Certified Power J2723 spec used to verify the 2006 LS7 which made 505hp/470 lb/ft torque, I'd be willing to bet that if the 525hp 6.2 crate engine was run on teh engine dyno, then a stone stock LS7 was ran on the same dyno, the 2 numbers would be very close, with the LS7 probably nudging by the 525hp crate engine.
The LS7 was the 1st engine certified using the new J2723 Certified Power spec. It is responsible for engine rating going from the nearest neat 5 or 10 hp, to the exact power the engine produced.
A lot of the Asian cars lost power, some up to 30 hp.

peace
Hog