Tranny TC Lockup and Temp Sensor
02-13-2005, 06:40 AM
#11
AudiWorld Super User
Don't think there is anything different on the facelift TCU's
JeffB bought a TCU out of a S8 for his 98 A8 that he is putting the tranny in. Everything is exactly the same from what he said.
There has always been a CAN bus between the TCU and ECU on the pre facelift cars, but they added an infotainment and convience CAN bus on the facelift cars.....so I don't think it would matter, but who knows?
There has always been a CAN bus between the TCU and ECU on the pre facelift cars, but they added an infotainment and convience CAN bus on the facelift cars.....so I don't think it would matter, but who knows?
02-13-2005, 06:48 AM
#13
I am sure that the performance would be much better with open TC.
If you drive 30 mph with locked TC in 4 th gear the rpm is around 1100. There is NO torque there, but if the TC is open it revs up to 1800-2000 where we can see some power. When I step on the gas, I would rather have an open TC than wait for the down shift.
02-13-2005, 08:00 AM
#14
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Chip Reader / Flasher Tool for TCU & ECU?....
Dont know if this would be of help to anyone, but I found it the other day.<ul><li><a href="http://www.dataman.com/S4.html">Dataman</a></li></ul>
02-13-2005, 10:13 AM
#15
Is this the same Planetary Discusssion
<ul><li><a href="http://www.howstuffworks.com/automatic-transmission.htm">http://www.howstuffworks.com/automatic-transmission.htm</a</li></ul>
02-13-2005, 11:12 AM
#16
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Correct; lockup converters were introduced for fuel efficiency, not performance.
More energy to the wheels, and less spent as heat in the TC.
Good for mileage, bad for torque multiplication (none).
Good for mileage, bad for torque multiplication (none).
02-13-2005, 04:52 PM
#17
From where will it get engine load & torque if not via CAN-BUS?
It seems unlikely that the new TCMs are backward compatible when the hardware for communication with the ECM changed.
(If pre-2000 TCMs talk CAN-BUS, it's well hidden on the wiring diagrams.)
Tom
(If pre-2000 TCMs talk CAN-BUS, it's well hidden on the wiring diagrams.)
Tom
02-13-2005, 07:41 PM
#18
Isn't the converter lockup excessive only when in Tiptronic?
On a 2001 at least, it seems quite willing to unlock the clutch when accelerating or climbing hills in D. But in Tip, it locks up above 26 mph almost all the time except for coasting and shifting. It may unlock while climbing a hill under sustained heavy throttle, but only after a long time. I haven't figured out the rules for that. I guess they were trying for a converterless, manual transmission feel in Tiptronic, trying to satisfy customers offended by a torque converter at work.
The frequent unlocking in D suggests that it's not normally on the edge of cooking its fluid, but at the same I wouldn't want to drive in the mountains or for hours in traffic without a functioning temperature sensor (which triggers more converter lockup if the fluid goes above 120 C, according to the transmission self study pdf linked here a while ago). Some Subarus in the 1990s came with ATF temperature warning lights (maybe they still do), and they also featured on 1970s cars with a torque converter ahead of a manual transmission, which is not so different from ours in Tiptronic with the lockup clutch defeated.
Tom
The frequent unlocking in D suggests that it's not normally on the edge of cooking its fluid, but at the same I wouldn't want to drive in the mountains or for hours in traffic without a functioning temperature sensor (which triggers more converter lockup if the fluid goes above 120 C, according to the transmission self study pdf linked here a while ago). Some Subarus in the 1990s came with ATF temperature warning lights (maybe they still do), and they also featured on 1970s cars with a torque converter ahead of a manual transmission, which is not so different from ours in Tiptronic with the lockup clutch defeated.
Tom
02-13-2005, 11:41 PM
#19
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Audi's A8 literature says the Tiptronic transmission ...
"selects from over 200 shift programs to match the driver's needs". It sounds like that there's 198 too many, the correct one for Tip mode and "D" might eliminate these problems.
02-14-2005, 04:03 AM
#20
Re: Audi's A8 literature says the Tiptronic transmission ...
Maybe the question facing the engineers about converter clutch lockup in Tip was: do you always lock and never have to worry about overheating the transmission fluid, or do you leave it unlocked but restrict access to the high gears if they're being overused and the converter is heating up the fluid, then have to explain to customers why Tip started to ignore the their requests to glide up hills all day at 35 mph in 5th?
Not that I think replacing one generally good set of rules with 200 programs is a cause of hunting. That probably has more to do with sensors and maybe actuators aging in unpredicted ways, allowing what the engineers thought could not happen: the conditions to unlock the converter clutch being met right after locking it.
Tom
Not that I think replacing one generally good set of rules with 200 programs is a cause of hunting. That probably has more to do with sensors and maybe actuators aging in unpredicted ways, allowing what the engineers thought could not happen: the conditions to unlock the converter clutch being met right after locking it.
Tom