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#181
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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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2007 GS 450h-Active Stabilizer/Radar cruise 1994 L Blue 3.70 VTD ASE Master Automobile ASE Advanced Level Specialist Toyota Master Diagnostic Technician (former life) |
#182
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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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Subaru ECU and TCU Website 1992 Alcyone SVX Version L 1992 Alcyone SVX Version L 1994 Alcyone SVX S40-II 2004 Subaru Legacy 2.5 SE Sports Tourer 1996 Subaru Legacy 2.2 GX Wagon 1988 Subaru Justy J12 SL-II |
#183
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Re: Gearshift Maps
Quote:
Harvey.
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One Arm Bloke. Tell it like it is! 95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels. 97 Liberty GX Auto sedan. 320,000Kls. 04 Liberty 30R Auto Premium. 92.000kls. |
#184
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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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2007 GS 450h-Active Stabilizer/Radar cruise 1994 L Blue 3.70 VTD ASE Master Automobile ASE Advanced Level Specialist Toyota Master Diagnostic Technician (former life) |
#185
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Re: Gearshift Maps
Quote:
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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Subaru ECU and TCU Website 1992 Alcyone SVX Version L 1992 Alcyone SVX Version L 1994 Alcyone SVX S40-II 2004 Subaru Legacy 2.5 SE Sports Tourer 1996 Subaru Legacy 2.2 GX Wagon 1988 Subaru Justy J12 SL-II |
#186
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Re: Gearshift Maps
Quote:
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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One Arm Bloke. Tell it like it is! 95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels. 97 Liberty GX Auto sedan. 320,000Kls. 04 Liberty 30R Auto Premium. 92.000kls. |
#187
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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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Subaru ECU and TCU Website 1992 Alcyone SVX Version L 1992 Alcyone SVX Version L 1994 Alcyone SVX S40-II 2004 Subaru Legacy 2.5 SE Sports Tourer 1996 Subaru Legacy 2.2 GX Wagon 1988 Subaru Justy J12 SL-II |
#188
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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
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Re: Gearshift Maps
Quote:
The TCU has to match the C solenoid, for both the Euro and the JDM. Harvey.
__________________
One Arm Bloke. Tell it like it is! 95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels. 97 Liberty GX Auto sedan. 320,000Kls. 04 Liberty 30R Auto Premium. 92.000kls. |
#190
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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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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
#191
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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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2007 GS 450h-Active Stabilizer/Radar cruise 1994 L Blue 3.70 VTD ASE Master Automobile ASE Advanced Level Specialist Toyota Master Diagnostic Technician (former life) |
#192
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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.
__________________
Subaru ECU and TCU Website 1992 Alcyone SVX Version L 1992 Alcyone SVX Version L 1994 Alcyone SVX S40-II 2004 Subaru Legacy 2.5 SE Sports Tourer 1996 Subaru Legacy 2.2 GX Wagon 1988 Subaru Justy J12 SL-II |
#193
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Re: Gearshift Maps
Quote:
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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One Arm Bloke. Tell it like it is! 95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels. 97 Liberty GX Auto sedan. 320,000Kls. 04 Liberty 30R Auto Premium. 92.000kls. |
#194
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Re: Gearshift Maps
Quote:
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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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! Last edited by Trevor; 08-24-2009 at 05:47 PM. Reason: P.S. added |
#195
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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
__________________
Subaru ECU and TCU Website 1992 Alcyone SVX Version L 1992 Alcyone SVX Version L 1994 Alcyone SVX S40-II 2004 Subaru Legacy 2.5 SE Sports Tourer 1996 Subaru Legacy 2.2 GX Wagon 1988 Subaru Justy J12 SL-II |
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