DanT55 Posted April 20, 2010 Share Posted April 20, 2010 Hey Guys, Since I have an 09 it is a 2nd gen 5EAT. This is from the Subaru website regarding the TCU functionality/interface with the ECU on the 2nd gen 5EAT. The 2008 TCU has a faster microprocessor, providing quicker response and quality shifts. Physically, the TCU is lighter, which contributes to reduced overall vehicle weight and improved fuel economy. (This and other weight reduction measures have resulted in the transmission weighing approximately eight pounds less.) In addition, the new TCU has several programs that give the driver greater control and provide a quality ride. The transmission control unit works with the engine electronic control unit to “blip” engine speed when the driver manually downshifts with the transmission in Sport mode. Engine speed automatically raises to coincide with road speed in the lower gear, which results in smooth, almost seamless downshifting. Another new feature in Sport mode is automatic downshifting during aggressive braking so the engine can help brake. Further, the TCU holds the transmission’s gear when cornering. Lateral G-forces are detected throughout the corner. If entering a corner in one gear, the transmission will not shift to the next higher gear, even if the driver lifts off the accelerator pedal. When exiting the turn, the driver can reapply the accelerator without causing a downshift. These capabilities help the driver maintain control throughout a turn without the vehicle’s balance being upset by a gear change, then reapply power for a smooth exit. On hills, the TCU utilizes new hill logic. When ascending or descending, the TCU can better calculate the optimal gear for a given road condition, resulting in less frequent shifting on hills – uphill or downhill. OIL PRESSURE CONTROL SYSTEM: Lighter, quicker oil pressure control helps to make the transmission more responsive when downshifting. REDESIGNED TORQUE CONVERTER: Changes to the fluid characteristics along with less oil in the torque converter contribute to quicker acceleration and engine response during acceleration. Slip lock-up has been added to the 2nd Generation 5EAT, too, improving response. More engine power goes to the driveline with greater efficiency, resulting in improved fuel economy. SIMPLIFIED MECHANICAL FUNCTIONALITY: Mechanical transmission components that provided functions made unnecessary by the improved functionality of the TCU have been eliminated. This results in reduced power loss due to friction and to the reduced overall weight of the transmission. Both contribute to improved fuel efficiency. STRENGTHENED FINAL GEAR: Making the transmission’s final gear stronger improves durability. LARGER TRANSMISSION COOLER: More efficient cooling helps to improve fuel economy and transmission life. Either way I am hoping utc_pyro can get into the unit and figure out what makes it tick. Even if its not applicable to my unit it would be a good start. Regards, DT Link to comment Share on other sites More sharing options...
utc_pyro Posted April 20, 2010 Author Share Posted April 20, 2010 Hum, that's something that I'll have to figure out after the 2005-2007 TCU is opened up. It sounds like the 2008+ TCU has alot of the features I was going for on the older ones... If they trouthfully did use a new CPU in the TCU, we'll need some one to crack one open to see what they changed it to before we can decompile it's code. Also, this is about the best resource I've found on the mechanical finctions of the 5AT (5EAT as we call it). I'm sure the ME's of the forums can look through it and let me know what functions to tweek on the electrical side to get better performance. http://www.seccs.org/tech/2006%20Impreza/Service%20Manual/Mechanism%20and%20Function/5AT%20Auto%20Trans.pdf Link to comment Share on other sites More sharing options...
KyLegacy 2.5GT Posted April 20, 2010 Share Posted April 20, 2010 By just taking a quick look at the document at lunch, I believe we should look into adjusting the following components first: Pilot Valve A Pilot Valve B Input Clutch Control Valve Direct Clutch Control Valve The other valves and components listed on the valve body change the way the car drives on and off throttle and at a stop. I will look more into this tonight when I get home, but I believe these 4 are the ones we look into modifying. When I say modifying, I mean able to bump up the line pressure. This will allow us to put more pressure on the clutches to support more torque. We will have to see if the line pressure is controlled by the voltage supplied to the solenoid or by keeping the solenoid closed longer. Reference 5AT-14 and 5AT-15 EDIT: I also noticed that the torque converter lockup is only programed in 5th gear while in normal drive mode and then switches to 3rd, 4th, and 5th gear when in sport or manual. If we could control the torque converter to lock up in second when in sport mode, this would eliminate that nasty slip between gears. If the lockup is too harsh, we could always change the control solenoid to only let the clutch slip for a fraction of the time that it does now. This document is awesome!!!!!! I wish I knew about it earlier!! I will combine my thoughts and post tonight. I will look into some of the book I had from my Motorsports Engineering classes that I took back in college and see if there is any other insight on automatic transmissions. Link to comment Share on other sites More sharing options...
fishbone Posted April 20, 2010 Share Posted April 20, 2010 One thing I wonder about is how the lock-up should behave at WOT. I see mine trying to grab and lock-up at least at 2 points when I do a WOT pull in 3rd gear to redline. Maybe it'd be best to have it not lock up; let the converter do it's thing. I am not sure how sturdy the lock-up clutch is. Link to comment Share on other sites More sharing options...
KyLegacy 2.5GT Posted April 20, 2010 Share Posted April 20, 2010 One thing I wonder about is how the lock-up should behave at WOT. I see mine trying to grab and lock-up at least at 2 points when I do a WOT pull in 3rd gear to redline. Maybe it'd be best to have it not lock up; let the converter do it's thing. I am not sure how sturdy the lock-up clutch is. The manual says: By engaging the lockup clutch in the torque converter, the slip in the torque converter is eliminated and power is transmitted more effectively. Based on the signals from the TCM, the lockup solenoid is controlled in order to let the lockup control valve operate and adjust apply pressure/release pressure, to consequently vary the lockup clutch engagement force. I don't think we should keep the lockup clutch from engaging, I believe that it possibly needs more line pressure to be able to handle the torque that we are feeding to the transmission. I just read in another post that a lot of tuners will engage the lockup clutch in the gear that they are testing in on the dyno. I say more pressure in the lockup clutch because most of us will be accelerating the torque converter faster to redline then we would on a stock engine. Accelerating faster and with more torque will easily cause more slipping. I also found out the the TCM also sends a signal back to the ECU that retards the engine timing between shifts to provide a more 'comfortable' shift (and to possibly keep from damaging the clutches). The transmission also has a g-force sensor that we may be able to tap into and calibrate to tell us our cornering and straight line g-forces when at the track! If this whole program can be setup to use Rom Raider, then we can log g-forces as well. After reading the majority of the document, I think we should stick to adjusting the line pressure values under certain throttle positions or engine loads to a higher value. Our sports mode is really considered 'climb assist', we should really turn it into a 'sports mode'. After we feel comfortable with adjusting line pressures, we can change the downshift points to allow better engine braking when off of the gas pedal. Link to comment Share on other sites More sharing options...
utc_pyro Posted April 21, 2010 Author Share Posted April 21, 2010 Glad you like it! I dont remember how I found it, but it was buried deep inside an Impreza manual, and it was not listed under the directory for it. I think subaru stuck it in there thinking they would put out a 5eat STI, but the didn't put it out for another few years. I notice as well what gears it would lock up in, I really want to change that. The "CVT" sim crap gets on my nerves.... It shold be simple enough to run the overheat/hill assist map on lockup full time. Also agreed that we should turn "sports" more into a true sports mode. I'd probably be safer to test new thing on that mode, as it's the equivalent of swapping to that "map" in the ECU world. We would still have "normal" to limp home under if something isnt right. The G-Fource sensor is only lateral g's, so it's probably not going to give all the info you want. The idea of having it monitorable is nice though, and very possible. Hopefully the RomRader devs will take interest in this project after we get some progress and add support. About a year ago the FXT crowd was screaming for 4EAT support, but no one would take the first step. This will help them as well. The TCU supports SSM just like the ECU, and it's connected in parallel on the "K-Line" to the ODB-II port. Thus one just needs to set the "target" address properly and map out the TCU parameters. Link to comment Share on other sites More sharing options...
DanT55 Posted April 21, 2010 Share Posted April 21, 2010 Nice find on that manual. Seems the 5EAT is a very technical beast. Very impressive to say the least. DT Link to comment Share on other sites More sharing options...
utc_pyro Posted April 23, 2010 Author Share Posted April 23, 2010 It's here! Starting an new thread in about two hours... I'll have detailed pics and my "first look" at the thing. Some things look bad, some look not so bad. We'll see! Edit: New post here: http://legacygt.com/forums/showthread.php/5eat-tcu-reverse-engineering-136175.html?p=2923282#post2923282 Link to comment Share on other sites More sharing options...
RIPjeep2002 Posted April 23, 2010 Share Posted April 23, 2010 It's here! Starting an new thread in about two hours... I'll have detailed pics and my "first look" at the thing. Some things look bad, some look not so bad. We'll see! YES! Can't wait to see! Link to comment Share on other sites More sharing options...
sic GT Posted April 27, 2010 Share Posted April 27, 2010 Hey Guys, Another new feature in Sport mode is automatic downshifting during aggressive braking so the engine can help brake. I think this feature is not exclusive to 2008-9. I get the same downshift / gear hold feature under hard braking with my 2006 5EAT. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.