What affects MAX Torque?

I am tuning an LFX V6 but still tunes like a Gen V.

While doing WOT pulls from 2K-5K, the throttle is not fully opening below 4K indicating the engine is outputting more torque than the MAX Torque value says it should.

Looking at the Virtual Torque Table, it says I should see Torque in the 280-290 ft-lb range, but the MAX Torque PID is registering around 215 ft-lb. The lower value leads to the throttle being closed down from WOT. I upped the Peak Torque Table to eliminate that potential source and it now appears the MAX Torque value is the culprit.

Looking at the other entries in the Max Torque section I find optioned out of consideration, either by disabling or entering a value greater than it will ever see.

Can someone explain how the MAX Torque value is reduced some 27% from the Virtual Torque Table value?

Are you monitoring the actual torque PID? Or are you assuming the torque value is whatever the Virtual Torque Tables say?

I am monitoring MaxTq, CmdTq, EngTq. DriversPedal%, and Actual Throttle %.

You need to monitor Peak Eng Torq, Max Eng Torque, Immediate Eng Torque, Eng Torque, Driver Demand Torque Requested, Immediate Axle torque commanded and Actual axle torque. Once you monitor these things it will give a more clear picture as to what is going on. Take a log and post the logs and tune, including the stock and modified tunes.

To be able to tell what Virtual Torque Table area you are in will require you to monitor Cam angle, desired cam angle, Pressure Ratio, base advance, timing advance and torque management advance.


Without seeing any of this data I am GUESSING that maybe you have modified the MAF model or VVE model too much. Increasing the MAF increases the value(airmass) used to calculate Torque. But also increasing the VT tables increase the calculated torque which affects Max Torque. It's really a bunch of calculations of different things to come up with a torque number and you need to get everything lined up.


A quick way to see if your torque model is off somewhere is to lower your Virtual Torque table where you are seeing Torque higher than Max torque. I've only seen this work if the VVE table is stock though. Essentially, without datalogging the above PID's to see whats going on along with posting the tunes, no one will really be able to help.

TriPinTaZ,

I am monitoring all those things you mention. Viewing the Virtual Torque Table for various points along the pull considering Cam Angles, Spark, AirMass, and RPM, it shows values of 280-290 Ft-lbs - TABLE VALUES.

Looking at the MaxTq values during the pull the values are 220 or so. So the MaxTq values are about 27% less than expected. The program sees the engine is producing more power than expected and closes the throttle.

Re-reading

https://www.hptuners.com/help/vcm_ed...vanced_e78.htm

It would appears that the AT may be sending a limit to the ECM. Trying to understand where and how if this is the case.

Virtual Torque tables is just a human friendly "virtual" value that is derived from the coefficient values which are used in conjunction with MAF, VVE, and Spark to calculate torque from a complex equation. Changing the Virtual Torque Tables directly affects the Max Torque value.

Have you tried increasing your Virtual Torque tables in the area where the Max Torque is lower than calculated torque? Sorry to say but you're wasting your time with that e78 document. It's to vague to help anyone IMO. You will find better info reading recent threads in the gen v forum here.

TriPinTaZ

I appreciate your comments and understand adjusting the VTTs might be the next logical step.

With the discrepancy in the MaxTq values and VTT entries - and as a newbie tuner - I thought I would draw upon the experience of the tuner community before messing things up.

To some extent we are all reverse engineering our tunes and I thought others may have tripped across this before.

The question becomes, "How much of a first adjustment for a 'dipping a toe in the waters' test?"

I finally figured out what was going on. My Virtual Torque table was displaying in metric unit of measure NewtonMeter instead of ft-lbs.

Figured it out when Rhett at the Tuning School shot me a screen dump of the table he came up with from my tune and it was quite a bit lower than what I was getting. Of course the Virtual Torque Table does not show units of measure.

When displaying in ft-lbs, everything makes sense.

Dale

QUOTE=djwarner;584774]I finally figured out what was going on. My Virtual Torque table was displaying in metric unit of measure NewtonMeter instead of ft-lbs.

Figured it out when Rhett at the Tuning School shot me a screen dump of the table he came up with from my tune and it was quite a bit lower than what I was getting. Of course the Virtual Torque Table does not show units of measure.

When displaying in ft-lbs, everything makes sense.

Dale[/QUOTE]

So what tables(s) did you change to fix the issue?

The Virtual Torque table. It acts as a limit. When the engine is capable of producing more torque than the table says it should, the system closes the throttle and retards spark.

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