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 Post subject: Why is pressure being used to adjust requested torque?
PostPosted: Wed Nov 25, 2020 11:27 pm 
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Joined: Fri Aug 21, 2020 6:05 am
Posts: 315
I've been slogging through a ROM for a naturally aspirated 2005 Outback (E2WG200G) using another ROM as a starting point (a similar and already defined ROM - E2VG222B)

Turns out that the calculation for Requested Torque in E2WG200G is different, and goes like this:
1. Use Engine Speed and Accelerator Pedal Angle to lookup a "Pressure Value" that ranges from 0 to -760 (most likely measured in mmHg)
2. Subtract this from Manifold Relative Pressure and multiply the result by 0.25. Then take the Max of this and zero. Call this result "Pressure Adjustment"
3. Use Engine Speed and Accelerator Pedal Angle to lookup "Requested Torque" (as per most ROMs)
4. Final Requested Torque is then the sum of "Requested Torque" plus "Pressure Adjustment"

Essentially this means that when the "Pressure Value" is less than (ie: more negative than) Manifold Relative Pressure, the Requested Torque is increased by a quarter of the difference.

I'm wondering if this has this been seen elsewhere? And does it make sense? What does the constant of 0.25 represent?

Note also that the Requested Torque table is transposed to other ROMs (ie) Engine Speed is on the x-axis and Accelerator Pedal Angle on the y-axis. As a result, the Target Throttle Plate Angle table is also transposed. See RR pic. I've also attached a pic of the decompiled function (I'm doing the disassembly in Ghidra).

Attachment:
RR pic.JPG


Attachment:
Ghidra Decompiler.JPG


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 Post subject: Re: Why is pressure being used to adjust requested torque?
PostPosted: Mon Apr 19, 2021 7:03 am 
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Joined: Fri Aug 21, 2020 6:05 am
Posts: 315
Well, after many more hours slogging through this ROM (E2WG200G), I think I can answer my own question. Attaching it here in case it is useful for others.

Still some things I don't understand (happy to hear if anyone knows the answers):
- have I correctly guessed what these parameters are?
- why is "Transmission Torque" adjusted by one quarter of the difference between MRP and "Theoretical MRP"? (perhaps some empirical adjustment?)
- these Torque parameters aren't used at all by the ECU, so why bother with them at all? (perhaps they are passed to the ABS via CAN?)


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