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Old 11-26-2020, 12:00 AM   #1
Wayno
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6AT - How to increase line pressure i.e. shift firmness

Requirements:

- 6AT

- IQ > 55 so you don't post in this thread asking if modifying calc tq will fix your syncho issues or anything else 6MT related.

- The following tables defined:
-- Requested Torque A
-- Requested Torque B
-- Requested Torque Base
-- Calculated Torque A
-- Calculated Torque B

TDLR:
Multiply every data cell in the above tables by the same factor to increase the line pressure by that amount.

DO NOT MODIFY:
- Any axis on the above tables.
- Target throttle plate position table.

HOW MUCH TO MODIFY:
- Increasing cacluated torque affects shift firmness in both NORMAL and SPORT modes (and assume SNOW also).
- Manual mode seems to be unaffected and the TCU and/or valve body have their own static values for the line pressures.
- I've briefy tested a 40% increase which makes shifting in normal mode feel more like sport mode, (only without the sport mode shift points obviously). It makes shifts in SPORT mode HARSH. Consider this in FI application where sport mode is not used.
- I'm going to be testing 20%, which will hopefully improve normal mode while not adversely affecting sport mode too much.

Personally I never use sport and think it's a wank, but regardless wouldn't make any tune changes that could push the valve body output high enough that it feels like it could do damage.

LONGER VERSION:

Under normal circumstances in every gear in both normal and sport modes, Calculated Torque A is used to determine both:
- How hard to shift
- When to shift

Calculated Torque B is used for low IAM, safe mode, etc, and blended with very complicated logic. Lookups on both Calculated Torque tables are done using multiple load values, not only the final calculated load value, adding extra complexity.

HOW THE ECU UP SHIFTS
- Ingnition retard,
- then RPM drops,
- then TCU sends updated gear number to ECU to indicate shift complete.

HOW HARD TO SHIFT:

To increase line pressure, increase the values in Calculated Torque A.

WHEN TO SHIFT:

The ECU determines when to shift by comparing the value of calculated torque to the value of requested torque.

If you were to increase only Calculated Torque A, then the ECU is going to think it's making more power than required and up (short) shift to a higher gear, resulting in always being under-powered.

If you were to decrease only Calculated Torque A, then the ECU is going to think it's making less power than required so it will hold gear longer, but will have lower line pressure during/after shifting, to the point where the ECU will attempt to cut timing a second time to invoke an up shift again because the TCU is slow to report the new gear to the ECU.

After adjusting Calculated Torque, you must also increase Requested Torque by the same factor to maintain the exact same shift points.

The ECU determines throttle position under normal driving by looking up the value in Requested Torque B based on accelerator angle, then dividing the requested torque value by the requested torque base value, then looking up the target throttle position based on that fraction.

Therefore, you need to increase both Requested Torque and Requested Torque Base by the exact same factor to result in the same calculated fraction.

In addition, because Requested Torque Base has now been modified, you must also update Requested Torque A and Calculated Torque B to keep them all in sync.

So, the list of tables modified in order becomes:
- Calculated Torque A
- Requested Torque B
- Requested Torque Base
- Requested Torque A
- Calculated Torque B


Example to illustrate multiplying all 5 tables by the same factor:
Attached Images
  

Last edited by Wayno; 11-26-2020 at 09:39 PM.
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Old 11-26-2020, 04:36 AM   #2
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Quote:
Originally Posted by Wayno View Post
The ECU determines throttle position under normal driving by looking up the value in Requested Torque B based on accelerator angle, then dividing the requested torque value by the requested torque base value, then looking up the target throttle position based on that fraction.
Need to update this paragraph Wayne.

Otherwise, top write up!!!
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Old 06-17-2021, 07:29 PM   #3
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Hi Wayne, trying to get me head around this. Currently using your V164 as you suggested else where and it seems to be working for me. Just before it shifts into 4th under mild throttle it seems like the TQ converter or clutches are starting to lock? causing the engine to remain at a constant rpm while car speed increases, giving the impression of slip. Is this what you were trying to eliminate in in previous Rom with the line pressure. 1st 2nd and 3rd feel ok but its just this slip? im concerned about. Cant remember if stock was like this as had quite exhaust then. Any suggestion please.
Cheers.
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Old 06-20-2021, 12:39 AM   #4
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Quote:
Originally Posted by 73TORANA! View Post
Hi Wayne, trying to get me head around this. Currently using your V164 as you suggested else where and it seems to be working for me. Just before it shifts into 4th under mild throttle it seems like the TQ converter or clutches are starting to lock? causing the engine to remain at a constant rpm while car speed increases, giving the impression of slip. Is this what you were trying to eliminate in in previous Rom with the line pressure. 1st 2nd and 3rd feel ok but its just this slip? im concerned about. Cant remember if stock was like this as had quite exhaust then. Any suggestion please.
Cheers.
I've not experienced anything like that. If concerned just grab the latest version that has dbw maps which are identical to stock over 2k rpm. I supply another file on the site with my personal dbw maps which are the same as latest version increased 20%, practically the same as the ones in this thread. No matter how much I minimised the tweaks in the middle of the maps they couldn't compete with the oem calibration.
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