Tranny TC Lockup and Temp Sensor
 

I noticed that tozoa8 and skiracer had mentioned the transmission temp sensor, has anybody tried spoofing this yet for results? I'd asked about this topic earlier and wanted to see if others have tried it yet.

I've finally gotten my TCU's swapped out of my car again to do some checking and I'me working through how to rig up a B&amp;M electronic switch improver into the tran temp sensor circuit.<ul><li><a href="https://forums.audiworld.com/a8/msgs/85738.phtml">https://forums.audiworld.com/a8/msgs/85738.phtml</a</li></ul>

I was tinking about it.
 

The TC locks in 2-3-4-5 gears if the speed exceed 20-25 mph and the ATF temp. is above 30 C. I was thinking that make a relay connected to the TCU so when the car is in 4th or 5th gear the TCU reads real temp, but in the city I drive mostly in 3rd gear so the relay will trick the G93 temp. sensor so the TC will be open. The down side is worse fuel economy and more heat in the tranny. It would work only with an extra tranny cooler with electric fan.

Maybe it could be integrated into the Tip mode?
 

I've wondered about the tranny overheating issue as well ... if the TC lockup isn't activated, the fluid is going to be getting more heat.

The other item I'm not certain of is the response from reading real temp to "fake" temp. Stated another way, how fast does the TCU make a transition from one mode to the other?

From the Bentley, I found the following for the G93 readings -
20C - 0.83 K Ohm
60C - 1.28 K Ohm
120C - 1.88 K Ohm

My assumption is that it gets into a panic on overheating at the 120C reading.

From your previous post you mention 30C as the cut-off for the cold mode, good catch on that. I could tell that a transition occured but wasn't able to capture when.

Also ... near as I can tell, our TCU's are using an
 

AMD series Am29F200B . Know anyone that is any good at reverse engineering this stuff?

I can't imagine that heat would be a problem ...
 

in city driving in 1st thru 3rd gears with an unlocked torque converter. And if it is a problem, you'd get plenty of warning. The tranny cooler is dumping the heat into the radiator, and you'd see it on the temperature guage.

I'm actually kinda paranoid about it ...
 

my conspiracy theory is that the engineers are using TC lockup as a crutch. My reasoning is as follows.

With a (relatively) small displacement motor with a high RPM torque peak,
1. One who engineers is tempted to run a high stall speed to give average Joe the sensation that the car really charges away from a stop.
2. However, the downside is that the high stall speed causes the TC to be loose and inefficient. The inefficiency is counter to why a small displacement motor was chosen to begin with.

The crutch to balance the high stall speed and maintain efficiency is this wacky notion we've identified of a car that has the TC lockup occur as early as second gear at 25 MPH.

Relative to tranny temp, my gut feel is that the TC is designed to be so loose that it will overheat, and based on issues we collectively have had with the fluid the problem might be serious. But then again, I don't know for certain.

This crutch seems to be also running rampant in Japanese makes as well, based on conversations I've had with others external to the Audi world.

Average versus maximum ATF fluid temp
 

I agree that an unlocked TC may run hotter, but a TC clutch that uses a modulation strategy is almost certainly more severe ATF service.

The unlocked TC is just a turbine spinning in ATF, and that will heat up the fluid. The modulating clutch, however, is allowing partial slippage of clutch plates "lubricated" with ATF. The shear forces must be extremely high, which results in very high localized temperature, even if the average ATF temp is lower.

We may be saying the same thing, but I think this questionable control philosophy is designed to improve fuel economy as much as anything else. The TC locks at low speed and partial throttle rather than revving up to the stall speed. The TC still provides torque multiplication, and I believe that performance would actually be better without the lockup.

Found this engineer's web site, and ...
 

the automotive section has a "Transmission and Driveline Engineering" forum. From a quick scan, it seems some knowledgeable and experienced folks hang out here. Perhaps bounce some of our questions off of them?<ul><li><a href="http://www.eng-tips.com/threadarea.cfm">Eng-tips.com</a></li></ul>

Here's a few pictures
 

So I put my 1998 A8 TCU in my car, it makes no difference on hunting or thump.....still does it.

I took the cover off my 97 TCU and see that there are two 44 pin chips. A 44 pin chip stores the mapping on the ECU.

First, the TCU:

<img src="http://www.audipages.com/upgrades/tipchip1.JPG">

And a GIAC modified tip chip for an A6, it does not appear it uses a 44 pin chip where the A8 does. I have inverted it for better viewing pleasure.

<img src="http://www.audipages.com/upgrades/tipchip2.JPG">

<img src="http://www.audipages.com/upgrades/tipchip4.JPG">

Here are my ECU Chips for an example:

<img src="http://www.audipages.com/upgrades/ecu5.JPG">

<img src="http://www.audipages.com/upgrades/ecu8.JPG">

The markings on the TCU 44 pin chip are:


AN82527
L7103748C
B 58 265
Large "i" next to bottom three lines
(Circle around M and C) m c '91 `92

I'm destined to learn how to modify an Audi TCU, I think I was born with this, it's just coming to me now though.....when I turn 40 later this year, it should be a clear, shining, light?

What about using a 2000 TCU to work on the tranny.
 

Have we even tried this yet? I know they did major revisions to the coding in 2000 based on what many people have told me. So i wondered if the CAN bus would prevent us from being able to use it.