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#16
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I am, and have been for years, waiting in eager anticipation for someone to crack the TCU and then we can really start to have fun. I think that a combination of revising the map for the duty c solenoid and shift map will make the car really come alive. The only problem I worry about with modifications to the transfer map like is increased clutch wear if we increase the rear bias too much. I hypothesize that this is why it is conservative from the factory. With Subaru's overall goal of preventing wheel spin from occurring in the first place, it makes sense that they would want as even of a torque split as possible, all other things being equal. The difference in the JDM and other versions is that it has the Variable Torque Distribution (VTD) type transfer system that includes a mechanical planetary center diff that defaults the torque split to the 35-65. The US SVX would have had this system (it was introduced to the world on the SVX) but at the time the government required that the vehicle be able to operate in 2WD for emissions testing which is not possible with the VTD system. This VTD system didn't come our way until the outback VTD of only a few years back.
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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) |
#17
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Can you definitely confirm that pressure engages the clutch?
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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$hit! |
#18
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The JDM transmission (swapping to a JDM TCU will only cause problems, not create the effect you're looking for) is based on the VTD-4WD design which was introduced in 2001 on the automatic WRX here in the states. It's something like a 36/64 split normally. The transfer clutch mechanism is designed differently.
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#19
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Tom |
#20
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Exactly as I see it and why I accept your idea in principle, but not without reservations.
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
#21
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Actually you are correct, it does "bleed" pressure off of line to reduce clutch pressure. Fully open at 12v dumps the fluid and there is FWD. I'm not sure why i seemed to have forgotten that fact earlier
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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) |
#22
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Trevor,
trust me you don't even want to waste your time with this one as the people providing you information are providing you even worse information than usual/average. There are a several things of importance which are well beyond their reckoning. First of all as is typical of most automotive transmission fluid circuits what you are actually dealing with is a play of pilot pressure versus line pressure not simply the control of one fluid pressure. Secondly the friction materials in an automatic transmission have a coeficient of friction which varies wildly according to the torque applied. Thirdly the atf used has a friction profile (on a side note many of the problems with heat/performance complained about on the 4eat are a result of users using a fluid with an inapropriate friction profile) which is far from linear. |
#23
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WOW that's not very nice. I don't see the need to make assumptions about facts that are beyond other people's reckoning. All of that is true, and it is not hard to see that the pressure is actually pilot pressure. I mean, there is a pilot valve... and there is a transfer control valve... but those don't appear relevant when discussing a resistor to the duty solenoid c...
This reminds me of what is wrong with this board People calling other people stupid, making statements like "There are a several things of importance which are well beyond their reckoning" If you would like to explain, in detail, including all of these things that are beyond reckoning, that modification to the control circuit in this fashion is a bad idea, then be my guest. Maybe you think it's a good idea? I look forward to you explaining, in full detail, exactly what the effect of this might be, such a wealth of knowledge should not be lost to the world. Don't forget to include: The pilot pressure and why it is important to consider that in this context. The coefficient (that's 2 f's, mind you) of friction which varies wildly according to the torque applied. (keep in mind coefficient means number so an equation would be relevant, since you brought it up) Oh, and the friction profile of the fluid. This one may need a graph. Oh, and don't forget to include the equation. Gee, seems like that would take an awful lot of writing to say that increasing transfer pressure could cause clutch wear and modifying the solenoid could cause, among other things, its failure?
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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) |
#24
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Nifty,
My appologies. I wasn't trying to insult you in fact my comments were not directed towarards anything you said. I was simply addressing the "reservations" which Trevor was rightfully reserving. Any condescendeing tone was my bad and just an admission of frequency in which the information given to Trevor as rock solid fact is in fact wrong, wrong, wrong, wrong. I really wouldn't like to explain in detail the play of pilot pressure vs line pressure, or the coefficient of friction vs torque, or the friction profile of the fluid. That was the whole point of my comment. Trying to apply a linear modification to a circuit with two non linear inputs and a non linear control..........well, you get the picture. Quote:
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#25
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I also admit my spelling has gotten really bad as of late
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#26
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I require no instruction in regard to fluid mechanics or associated control systems. I can find nothing within your text which makes any form of logical statement in regard to the topic at issue.
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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$hit! |
#27
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Ok, my bad. You go about adding resistors to solenoid c then.
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#28
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I nor anyone else intends to rush into anything and there are other options. That is why an interesting discussion is under way.
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
#29
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What about my idea of a variable tone generator? Would that not cycle the Duty C in a user controllable fashion?
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[SIGPIC]http://www.subaru-svx.net/forum/image.php?type=sigpic&userid=5569&dateline=1207440 507[/SIGPIC] Naught but by the grace of God "42" Current Stable By Age:'89 Subaru XT6 Silver "Audrey" as in Hepburn '96 SVX LSi #767Brilliant Red "Lil Red" Now on the front burner. Looking for a totalled, but running parts car. |
#30
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God I wish I knew Assembly. I'd tackle that TCU code we have sitting around and do this damn test to prove once and for all what our duty cycles are.
Until then I'll leave it to the mechanical guys... |
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