lobuxracer

iTrader: (2)

Not first, but first to do it the way they do it and as quickly as they do it.

eefmydee

Alright so I found some answers. The shift solenoids on a basic transmission are basically on/off position solenoids. The ones on the AA80E however are controlled by variable voltage and it can vary pressure directly the appropriate clutch pack itself. How they redid the circuits inside the valvebody also allows them to limit lag by giving the shift solenoids pressure control over the clutch packs. This is a major difference from other transmissions and why for a "conventional style transmission" it can shift fast. Also to shift gears, all it has to do is activate/deactivate the appropriate shift solenoids and since the shift solenoids can control pressure on the clutch packs (which will control how it engages, on other transmissions the clutch hydraulic solenoid is responsible for this ) you would not have to change anything else or adjust any other solenoid. Fast smooth shifting is possible for up and downshifting and it does not require you to disengage the lockup function on the converter when shifting up or down. I have to say this is definitely a better way to control the transmission for comfort or for performance.

I guess I found my answer.

I believe my original theory could possible work on other transmissions but I would have to attempt it to find out and that is my current quest. If anyone has anymore information please chime in or post up links please. The thread has been greatly appreciated.

ROK

This is my kind of thread. Me likey.

So most, if not all, auto review goobers dismiss the F box as a conventional automatic that happens to shift pretty well, but is less desirable than the popular DCTs we find in the 911s and M cars today.

I'm no propeller head and likely don't own a car long enough to appreciate this, but speaking to the "Toyota way", I'm interested to learn more about the true pros-cons between DCT and Toyota's tlocking unit around quality, reliability and durability.

Porsche's pdk is clearly more responsive, but I noticed it concedes in the area of smoothness esp when in auto mode during slow traffic or parking maneuvers. Everyday stuff. Rather than dismiss one as better or worse than the other in absolutes like the view count crazy, lazy YouTube auto peasants do, I think it'd be cool for a tranny expert to go deep.

I happen to really appreciate the F car transmission and want to know more.

eefmydee

One thing I know for sure is that you can make a conventional automatic really really smooth. That is a Pro. I had an arguement with my brother because I told him that when concerning comfort all around and smooth shifts that you cant feel, the conventional transmission will take the cake on that one. He got really defensive and said that the PDK could probably do that better. I have watched many reviews with cars that have DCT and they all mention that the shifts are too harsh in traffic. M6, Alfa Romeo 4C, are some very specific cars where there was a major complaint on tranny harshness. Seeing that lexus has always manufactured living room furniture on 4 wheels and the customer demographic of lexus is so not into racing the cars they get, why spend money on a DCT? I think the way they did the AA80E was great and they really pushed the boundaries on the convetional trannys. The AA80E has its own patent FYI. If you could keep comfort, shift almost as fast as a DCT, Rev match downshift, doing a slight redesign but not a complete redesign where serious R&D is not needed, still use parts that have already been developed (valve body, lockup torque converter, planetary gear set) while pushing boundaries and not loosing your sales demographic needs, you got a win.

lobuxracer

iTrader: (2)

This is a really good look into why the AA80E, and certainly we know Lexus did many things with their F cars to retain the Lexus image - low NVH, smooth operation, even the throttle pedal programming in normal mode is subdued. Hit the sport button (true for both IS F and GS F), and the nature of the car changes but still retains many of the qualities Lexus owners expect.

With so many enthusiasts lamenting the demise of the manual gearbox and the number of available new models with conventional manual transmissions dwindling, I am not surprised that DCT has taken hold in the performance realm. But it is surprising to hear DCTs suffer in low speed traffic. The trucking industry has had computer controlled clutches for a very long time now (Mercedes since the late 90's), but I recall one of the major benefits being clutch service life, and smooth operation is key to extended life on friction devices. Maybe the Germans are assuming DCTs will be purchased by performance enthusiasts and they will be more tolerant of rough operation at low speeds because they've tuned them to work well at heavy load - more like track conditions - than focused on NVH or passenger comfort.

Sadly all of this will become ancient history as the march of electric motor driven vehicles becomes the new norm. Just another reason to keep maintaining my older cars.

yardie876

I have heard of DCTs being clunky at low speeds also. To counteract that, Acura has added a torque converter to their DCTs to aid in smooth shifts at lower speeds. Wonder if it is a successful innovation or not.

jdmSW20

iTrader: (12)

As far as how DCT drives, its true. When i had an E92 M3 with DCT, it did get weird in low speed scenario when in regular "drive" setting. If i were slowing down to make a right for example, but in regular "D" shift setting, its like the car would get confused what gear to down too and sometimes would stay in like 4th or 5th then drop to 2nd or 3rd to get back to appropriate speed. It was annoying to say the least, but in "S" setting or manual setting, it was lightning no matter what.

honestly when in a daily driver, traffic situation ill take the auto trans any day of the week. but in racing, spirited driving situation that DCT was hard to beat. What impresses me most with the ISF is it upshifts just as fast as the DCT in my opinion, only place the DCT wins is it downshifts just as fast as it upshifts and thats where the ISF auto is behind the DCT. But aside from that alone, the AA80E is just as impressive in its own right

eefmydee

the idea to put a torque converter on a dct should of been buried along with the person who thought of it. thats dumb as ****. Dct is already heavy enough and with adding components it doesnt help. I think the AA80E is 215lbs and if other peoples dct are heavier thats a win for toyota. still no where near the weight of a manual tranny but weight is a huge role in performance. if anyone knows the weight of other dct post please. by the way there are companys that make a performance lockup converter. FTI transmsissions being one of them. If anybody still rocking an automatic and wants to hook it up see if they got something for you.