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  #181  
Old 04-04-2009, 03:16 PM
NiftySVX NiftySVX is offline
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Re: Gearshift Maps

What are everyone's thoughts on adjusting the torque converter unlock curve (stick d, normal mode) to be slightly more aggressive? I have always thought that it required a bit too much throttle to unlock the converter. It seems like it is necessary to depress the throttle enough to get the car to downshift to 3rd to get the acceleration i want (such as when traveling in a pack of traffic) but I i would not have pushed it that far if the converter was easier to unlock. I find that when i am traveling at around 45-55 mph and i want to accelerate fairly rapidly (such as an on ramp from one freeway to another) i tend to quickly blip the throttle to get the thing to switch over to power mode so that it will unlock the converter.

Also, what about changing the "countdown" timer for the power mode? I find that it always goes back to normal annoyingly quickly. Would it be possible to modify the code in such a way that the base time used in the calculation that was described earlier in the thread to be longer, like say a minimum of 10-15 seconds before a return to normal once activated?
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  #182  
Old 07-23-2009, 04:26 PM
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Re: Gearshift Maps

Following a lot of conjecture about how the Solenoid C mapping works, I made the time to look at it today. I haven't figured out the exact details yet, but I can give a rough overview.

Based on what I've found, I think that the theory about torque split being based on a percentage difference in speed between front and rear wheels is wrong. Here is what I think happens.

On the USDM model, ROMID 705404, the solenoid C subroutine is at address EE80.

There are 5 maps, one for each gearstick position: R, D, 3, 2, 1. These maps are stored at CCE1, CD32, CD83, CDD4 and CE25 respectively. There is a separate special case for when the stick is in N.

Each map is a lookup table 8 x 9. The Y axis is Throttle. The X axis is a little harder to understand. It's the VSS1 signal multiplied by the Ratio of the current gear. Ryan Press refers to this parameter as the "Input Shaft RPM" in his analysis of the Legacy TCU. But I'm not so sure. I think it is only the input shaft speed when the front and back wheels are turning at the same speed. But anyway, we can puzzle over that.

I think the TCU is looking at how fast the input shaft is turning compared to the amount of throttle applied. The sweet spot of the map is in the middle, when you are travelling at a steady speed, high duty cycle = power up front.

If there is wheel spin then there will be less resistance to the engine's torque and therefore the input shaft will be spinning faster relative to the amount of throttle applied. The map lookup gives a lower duty cycle and power shunts to the back.

Alternatively, when you are accelerating against the car's inertia, the input shaft will spin slower relative to the amount of throttle applied. Again, the map lookup gives a lower duty cycle and power shifts to the back.

That is why, with an SSM, you can see the torque split change during acceleration, not just when there is a speed difference between front and rear wheels.

Once the base value has been selected from the map, small adjustments are made for ATF temperature and Battery Voltage.

There is also a special case that when the ABS triggers, the duty cycle gets set between 70 and 76 percent, proportional to vehicle speed.

There is a bit more to it that I don't yet understand, but I think I've got the basics right. Any mechanical gurus want to offer an opinion?
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  #183  
Old 07-23-2009, 05:52 PM
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Re: Gearshift Maps

Quote:
Originally Posted by b3lha View Post
Following a lot of conjecture about how the Solenoid C mapping works, I made the time to look at it today. I haven't figured out the exact details yet, but I can give a rough overview.

Based on what I've found, I think that the theory about torque split being based on a percentage difference in speed between front and rear wheels is wrong. Here is what I think happens.

On the USDM model, ROMID 705404, the solenoid C subroutine is at address EE80.

There are 5 maps, one for each gearstick position: R, D, 3, 2, 1. These maps are stored at CCE1, CD32, CD83, CDD4 and CE25 respectively. There is a separate special case for when the stick is in N.

Each map is a lookup table 8 x 9. The Y axis is Throttle. The X axis is a little harder to understand. It's the VSS1 signal multiplied by the Ratio of the current gear. Ryan Press refers to this parameter as the "Input Shaft RPM" in his analysis of the Legacy TCU. But I'm not so sure. I think it is only the input shaft speed when the front and back wheels are turning at the same speed. But anyway, we can puzzle over that.

I think the TCU is looking at how fast the input shaft is turning compared to the amount of throttle applied. The sweet spot of the map is in the middle, when you are travelling at a steady speed, high duty cycle = power up front.

If there is wheel spin then there will be less resistance to the engine's torque and therefore the input shaft will be spinning faster relative to the amount of throttle applied. The map lookup gives a lower duty cycle and power shunts to the back.

Alternatively, when you are accelerating against the car's inertia, the input shaft will spin slower relative to the amount of throttle applied. Again, the map lookup gives a lower duty cycle and power shifts to the back.

That is why, with an SSM, you can see the torque split change during acceleration, not just when there is a speed difference between front and rear wheels.

Once the base value has been selected from the map, small adjustments are made for ATF temperature and Battery Voltage.

There is also a special case that when the ABS triggers, the duty cycle gets set between 70 and 76 percent, proportional to vehicle speed.

There is a bit more to it that I don't yet understand, but I think I've got the basics right. Any mechanical gurus want to offer an opinion?
I think you may have been lead astray Phil. I think the transmission that Ryan Press is referring to is the latter box with the extra speed sensor on the turbine shaft. This is used in conjunction with the crank rpm to measure the difference in the speed in and out of the torque converter. This is then used to give a more accurate measure of the load that the engine is under, so that the box can be operated better.

Harvey.
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  #184  
Old 07-24-2009, 10:32 AM
NiftySVX NiftySVX is offline
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Re: Gearshift Maps

Good work, I agree. The comparison between throttle opening and, for US cars at least, the front speed sensor is likely what most of the AWD duty is based on for normal driving. Although, it is true that none of the SVX transmissions had the input shaft speed sensor, this was added later to check for slippage among other things already mentioned. But it could just as easily be used for the calculation as the speed sensor that is on the final drive on the later units. Again, good work, and good thinking.

This is my favorite thread ever, and I've been a part of this community for ten years.
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  #185  
Old 07-24-2009, 04:44 PM
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Re: Gearshift Maps

Quote:
Originally Posted by oab_au View Post
I think you may have been lead astray Phil. I think the transmission that Ryan Press is referring to is the latter box with the extra speed sensor on the turbine shaft. This is used in conjunction with the crank rpm to measure the difference in the speed in and out of the torque converter. This is then used to give a more accurate measure of the load that the engine is under, so that the box can be operated better.

Harvey.
Ryan's box is from a 1990 Legacy. But that's not really important.

As I said, the SVX Sol C duty maps seem to be based on (VSS1 [ie. rear output shaft speed] * current gear ratio) vs Throttle. I'll post more details when I have them.
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  #186  
Old 07-24-2009, 09:51 PM
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Re: Gearshift Maps

Quote:
Originally Posted by b3lha View Post
Ryan's box is from a 1990 Legacy. But that's not really important.

As I said, the SVX Sol C duty maps seem to be based on (VSS1 [ie. rear output shaft speed] * current gear ratio) vs Throttle. I'll post more details when I have them.
Well he is not talking about a 90 model box, as he talks about " input shaft RPM", and Subaru didn't have one till the later box with the "input shaft sensor" and the clutch instead of the band.

It would be really useful if you could post the C solenoid map for say, 2nd gear for both US and UK AWDs, that would cover the differences that they have.

Harvey.
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  #187  
Old 08-23-2009, 04:56 PM
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Re: Gearshift Maps

I've just been looking at a 1995 Aussie TCU that Harvey sent me. It is identical to the 1996 UK TCU that I copied from Gez's car. Label "MS", ROMID 705625.

Earlier Aussie cars presumably use Label "FF", ROMID 705622 like the earlier UK cars.

According to Harvey there was a hardware change to the gearbox solenoids aroiund 95, and that is why the software was updated. So you have to use the right TCU for the transmission.

I'll be looking into this in more detail.

Phil.
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  #188  
Old 08-23-2009, 05:37 PM
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Re: Gearshift Maps

An Australian customer of mine has used the ECUtune UK TCU ROM built on the 705622 code in his 92 Australian SVX with very good results.
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  #189  
Old 08-23-2009, 05:37 PM
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Re: Gearshift Maps

Quote:
Originally Posted by b3lha View Post
I've just been looking at a 1995 Aussie TCU that Harvey sent me. It is identical to the 1996 UK TCU that I copied from Gez's car. Label "MS", ROMID 705625.

Earlier Aussie cars presumably use Label "FF", ROMID 705622 like the earlier UK cars.

According to Harvey there was a hardware change to the gearbox solenoids aroiund 95, and that is why the software was updated. So you have to use the right TCU for the transmission.

I'll be looking into this in more detail.

Phil.
Phil it also appears that the JDM trans had the same change. The early ones 92 to 94, used a Normally open C solenoid. Later was 95 to 97. Used a Normally closed solenoid.
The TCU has to match the C solenoid, for both the Euro and the JDM.

Harvey.
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  #190  
Old 08-24-2009, 12:02 AM
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Re: Gearshift Maps

Kia ora Phil,

The only scenario which could make the change advised by Harvey a logical progression, would require that the later model cars were fitted with the US centre clutch type transmission. I have never seen even a suggestion to this effect.

To change the C solenoid, for no apparent reason, thus requiring an extensive change in the software, does not add up.

All the best, Trevor.
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  #191  
Old 08-24-2009, 07:44 AM
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Re: Gearshift Maps

Do the VTD transmissions of this vintage experience frequent duty c failures like the ACT-4s do? I would imagine a failure of this solenoid on one of these would cause a fault that would result in no ability to "lock" the center diff. This would probably go unnoticed by the driver in most cases, but if this was a common failure they may have changed the solenoid to try and improve the system's reliability. Just a shot in the dark guess...
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  #192  
Old 08-24-2009, 03:42 PM
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Re: Gearshift Maps

I will take another look at the differences between the early and late UK and JDM TCUs to see if I can come up with any answers.
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  #193  
Old 08-24-2009, 05:12 PM
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Re: Gearshift Maps

Quote:
Originally Posted by NiftySVX View Post
Do the VTD transmissions of this vintage experience frequent duty c failures like the ACT-4s do? I would imagine a failure of this solenoid on one of these would cause a fault that would result in no ability to "lock" the center diff. This would probably go unnoticed by the driver in most cases, but if this was a common failure they may have changed the solenoid to try and improve the system's reliability. Just a shot in the dark guess...
Yes they do have the same problems with the solenoid as the US models. They will bind, and they will spin the back wheels with the valve not working, you certainly would notice, as it can sit still on the grass spinning both back wheels.

I don't see it as often, as we see the US version, maybe 5 cases over the years, but that could just be due to there being more of the US type.
I would guess that it was to improve the operation of the valve, but why did they use the two different types in the early models.

Harvey.
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  #194  
Old 08-24-2009, 05:42 PM
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Re: Gearshift Maps

Quote:
Originally Posted by oab_au View Post
Yes they do have the same problems with the solenoid as the US models. They will bind, and they will spin the back wheels with the valve not working, you certainly would notice, as it can sit still on the grass spinning both back wheels.

I don't see it as often, as we see the US version, maybe 5 cases over the years, but that could just be due to there being more of the US type.
I would guess that it was to improve the operation of the valve, but why did they use the two different types in the early models.

Harvey.
If, as has been claimed, a N/C solenoid is fitted to late model VTD SVX transmissions, the solenoid valve will fail to the normal and closed position. Unless there has also been mechanical changes, the transmission will fail with the clutch closed and front rear lock up. Surely this state of affairs would be noticed by the driver.

Failure could be due to the loss of an energising signal, an open winding in the solenoid, or the solenoid becoming jammed closed.

If the car “can sit still on the grass spinning both back wheels.” the clutch is surely not closed. Everything indicates, that in fact there has been no change in the C solenoid. What evidence is available supporting the statement, which claims a change has taken place?

P.S. It is absolutely clear why a N/O valve is found in earlier models and indeed why it would not be desirable for any change to have taken place.
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Last edited by Trevor; 08-24-2009 at 05:47 PM. Reason: P.S. added
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  #195  
Old 08-25-2009, 05:19 PM
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Re: Gearshift Maps

I've been comparing the TCU software for 705622 (1992 UK "FF" TCU) and 705625 (1996 UK "MS" TCU). I don't doubt that Harvey is right about the solenoid change, but if the solenoid has changed from NO to NC then I expect the software that drives it would need to change. However, I can't see any difference in the software. The driver for the C solenoid is quite straightforward. It works like this:

The duration of one wavelength is defined as 20000 units. If the frequency is 50Hz, then 1 unit = 0.0025 seconds.

When the diff-lock fuse is inserted on a Euro TCU, the program sets the "On_Time" to 19000. That's 95% of 20000, a 95% duty cycle. On a USDM model, when the FWD fuse is inserted, the program sets the "On_Time" to 1000, that's 5% of 20000, a 5% duty cycle.

The actual duty cycle is implemented by a timer like this:

Code:
When timeout occurs:
    Toggle the Solenoid State
    If Solenoid is ON
        Set timer to On_Time
    Else
        Set timer to (Wavelength minus On_Time)
    EndIf
As far as I can see, the algorithm is identical in the early and late models.
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