Last post on Jul 08, 2012 at 5:54 PM
You are in the Toyota Camry
What is this discussion about?
Toyota Camry, Sedan
#976 of 1078 Re: 2009 Camry LE V6 Question/Problem [exler]
Feb 10, 2010 (10:50 am)
"...why does Toyota(/etc) have to change stuff that does not need change?.."
While there are some very definite advantages to DBW, some HIGHLY advantagous, Toyota/etc's base reason for adopting DBW fleet wide had its origins in a design flaw in the U140E/F ("F" = F/awd) transaxle developed initially for the RX300.
Since Toyota/etc wanted to adopt (~2002) the more fuel efficient U140E across the fleet something had to be done to "cover-up" the design flaw. So DBW was adopted to "protect the drive train", prevent premature failures of the U140E transaxle when a downshift could not be accomplished in the time allotted, driver expectation of downshift "time".
So DBW was used to "hold-off" rising engine torque in response to gas pedal position/depression for 1-2 seconds to allow the extended time needed for the transaxle to accomplish a downshift shortly following an upshift.
Here we are, 2010, and Toyota/etc is still struggling with this same issue. Whereas Ford, with the new Edge, simply adopted a variable displacement ATF oil pump, low volume for HIGH engine revs and incrementally higher, selective volume, for lower engine revs.
#977 of 1078 Re: 2009 Camry LE V6 Question/Problem [wwest]
Feb 10, 2010 (11:20 am)
Interesting theory you have there. (Wondering where it was published initially. Was it by Toyota, or a third party engineering journal?)
I'm sorry, but I don't understand exactly the meaning of your sentence, "prevent premature failures of the U140E transaxle when a downshift could not be accomplished in the time allotted, driver expectation of downshift "time". "
The part that confuses me, I guess, is the reference to the "timing" of a downshift. I wouldn't have thought that most drivers/owners gave a rat's butt about the timing of a downshift in their automatic tranny. If you could use a "real driving scenario" to explain what this means, I'd appreciate it.
Also, my question is (I'm an unlucky buyer of an 07 Camry, which I believe was its first year of application in that model).....what was wrong with the good old "planetary gear system" (or whatever the heck it was) OLD style Camry transmission? I never heard any horror stories about it. Were there lots that I missed? (since I was busy driving my 1997 manual transmission model?)
Thanks for additional insight, Willard.
#978 of 1078 Re: 2009 Camry LE V6 Question/Problem [wwest]
Feb 10, 2010 (11:23 am)
>Whereas Ford, with the new Edge, simply adopted a variable displacement ATF oil pump, low volume for HIGH engine revs and incrementally higher, selective volume, for lower engine revs.
That's much more effective from an engineering standpoint, but it probably costs more than covering up a shift lag by changing the engine control in the software. What I think you're saying is the complaints about a long shift lag when someone was slowing down on a ramp and floored the accelerator to merge into a coming available slot caused toyota to change their software. Now the engine doesn't produce much power for a period of time until the transmission has had time to effect the long downshift time and is ready for more engine torque. So the car just doesn't go anywhere but feels like the motor is accelerating but it's only at low power.
Is that it?
#979 of 1078 Re: 2009 Camry LE V6 Question/Problem [notmybmw]
Feb 10, 2010 (11:24 am)
I don't think planetary gear system automatics have been used since the demise of the GM 4-speed Hydramatic back around 1964, with the notable exception of hybrid-electric cars like the Toyota Prius.
Just a suggestion for Mr. West: Please avoid obscure abbreviations and all caps, and try to explain things in a way a non-engineer can understand.
#980 of 1078 Re: 2009 Camry LE V6 Question/Problem [notmybmw]
Feb 10, 2010 (12:24 pm)
Prior to developement of the U140E/F transaxle the ATF gear type oil pump was always pumping at full volume, the volume that was dictated by the engine RPM. Just downstream was a pressure holding accumulator and beyond that a pressure relief value so line ATF pressure never exceeded a specified level.
Much the same as the power stearing punp, HUGE energy loss due to pumping so much fluid up to pressure and then simply dumping it back into the sump if it was not needed.
With the U140E/F the spring loaded pressure relief valve was eliminated in favor of an ECU controlled solenoid that determined the ATF line pressure in "real-time". So while the ATF pump was still pumping VOLUMES of fluid most of the time it was no longer doing so under a HUGE back pressure.
So if ATF line pressure was to be controlled, varied, under real-time requirements, there was no reason to keep the pressure holding accumulator. So it too, was abolished.
Now, with the engine at idle, the condition it is likely to be in when you release the gas pedal for a short/brief coasting period, and with the upshift resulting from that same gas pedal release, there is, will be, NO reserve ATF pressure in preparation for that upcoming(??) downshift.
#981 of 1078 Re: 2009 Camry LE V6 Question/Problem [notmybmw]
Feb 10, 2010 (12:29 pm)
"..real driving scenario.."
The post following yours does a very good job of that.
Or else you could find Toyota/etc's own examples, three of them, as stated in the TSB released in the of 2003 as applies to that year's Camry.
#982 of 1078 Re: 2009 Camry LE V6 Question/Problem [imidazol97]
Feb 10, 2010 (1:59 pm)
Thanks, Keith. (I see Willard agrees that your answer hits the nail on the head.)
It was EXACTLY that kind of scenario or the equally or even MORE dangerous one of slowing down to make a turn across a line of ONCOMING traffic at an intersection that led me to confronting my dealer about the dangers of the DBW in the first place.
Here in Canada.....at least here in St. Catharines Ontario...our dealers were in COMPLETE denial of (or just out of the info loop on) any DBW problems and said simply "It's normal".
When I finally confronted them with the TSB for ECM re-do,(I downloaded it off this site) they tried to tell me the paper I was holding wasn't a TSB and wasn't even a Toyota document. (They were about 5% right, because the Canadian TSB's look slightly different and have a different name......but it was the same damn content and detail...needless to say, I was pissed when they finally conceded to performing the fix.)
#983 of 1078 Re: 2009 Camry LE V6 Question/Problem [notmybmw]
Feb 10, 2010 (2:21 pm)
When the TSB was applied did the dealer inform you that the firmware revision, REFLASH, only makes it less likely these 1-2 second downshift delay/hesitation events will occur, not a full cure...FIX...?
The new firmware simply tries to predict, forecast, what the driver's next action will/might be when pressure is removed from the gas pedal. A fast/rapid release is presumed to mean that the driver wishes to slow the car using (presumably) engine compression and so the transaxle will remain in the current (low,lower??) gear ratio. On the other hand a light/slow release of foot pressure on the gas pedal and the presumption will be that the driver simply wishes to enter cruise mode and if an upshift is appropreate then the transaxle will upshift.
The transaxle, STILL, cannot perform a QUICK downshift following an upshift if the engine RPM is at idle or close by.
#984 of 1078 Re: 2009 Camry LE V6 Question/Problem [210delray]
Feb 10, 2010 (4:51 pm)
OK, delrayMike.....you got me! Yes, I did take auto mechanics in highschool back in the early Sixties. (Just like ME.....in my early Sixties!!)
BUT you gotta admit, whatever they did to the Camry's transmission.....they sure screwed it up compared to what it used to be.
#985 of 1078 Re: 2009 Camry LE V6 Question/Problem [wwest]
Feb 10, 2010 (5:08 pm)
Good question, Willard, but, no......the dealer was totally unfamiliar with the TSB. I literally was the first person who had ever shown it to him. Neither the service manager (who WAS, admittedly new in his job) nor any of his experienced staff, had ever heard of the TSB for the ECM. (We ARE in a bit of a backwoods here, with a population of only about 100K, but I would have expected more than this from Toyota. We're in a one-horse town where one company owns about six franchises....Toyota, Lexus, BMW, Mini, Acura, Chrysler, Hyundai, Mercedes......have I named every brand you can think of yet?......www.performancecars.ca ......so they have a large amount of "attitude" to say the least.
My TSB was ill-performed: they failed to take the car out on the road for the mandatory "training regimen" and they also didn't have the stickers on hand to apply under the hood, to show that the work had been performed. (as dictated by the TSB.) The told me they'd MAIL it to me!! Laughable.