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Sedans Toyota Camry 2007 Toyota Camry Transmission Questions
851 messages, Last post on Nov 01, 2009 at 2:21 PM
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Replying to: kiawah (Sep 04, 2007 4:50 am)
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Replying to: 1st_toy_owned (Sep 04, 2007 7:34 am)
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| I have a 4cyl 2007 Camry XLE, and had the TSB installed a month ago. For the most part, the TSB fixed hesitation in normal driving. There is a huge difference in behavior before and after the TSB. However, as others have noted in this forum, I still get the bloom in acceleration when using cruise control on up-hill drives. My most recent trip was from Charlotte to Raleigh NC, much of it uphill along route 85. I set the cruise at 70, and noticed that the engine/transmission would hold at high revs for 3-5 seconds after a downshift to increase acceleration (the bloom); and, immediately after downshift, the car would accelerate like a bat out of hell. After 3-5, revs would drop down where they should be. This is completely new to me (I have never driven a car before that behaved this way.) I will ask the dealer when I go back in for an oil change in the next two weeks. | |
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Replying to: joel16 (Sep 05, 2007 3:44 am) These days the OD lockup clutch is being used, engaged, in gear ratios other than actual OD. Keep in mind that in cruise control the engine/transaxle ECU/control system has more "look forward" capability then were you "foot" driving. So, 70MPH as you approached an uphill hwy section and once you reached the uphill section the speed began to decline and the ECU quickly determined that the 70MPH speed could not be sustained in the current gear. So it commanded a downshift along with a disengagement of the lockup clutch. You're now downshifted into ~4rd and the cruise control makes use (for your 3-5 seconds) of the torque converter's "edge" to regain the lost speed. Now, once the set speed is regained there is no longer a need for the torque advantage of the converter so the lockup clutch is re-engaged. Yes even in 4rd gear, or maybe even in 4th, 5th and OD for a 6 speed automatic transaxle. Keep in mind that these days the engine/transaxle ECU firmware is more than ever designed to conserve fuel. What it "wants" to do is operate the engine at the lowest possible RPM that just barely produces enough engine output to handle the current load. But operating the engine right on the "CUSP" like this, just above lugging will mean requiring a quick downshift for even the slightest increase in engine output torque. Or conversely, an upshift if the load lightens. So, as you started the climb up that hill the ECU "learned" that top gear (lockup/OD) could not be used to sustain your desired, "set" roadspeed. And in the process of that "learning" the roadspeed had dropped by ~2-3MPH. Maybe it was actually the knock sensor signal (long before it became audible to your ears) resulting from the engine "descending" into lugging that "triggered" the downshift decision. So, the ECU commands a downshift, first, to regain the lost speed using the torque gain of the converter, and then, knowing the desired speed cannot be sustained in the previous higher gear ration, simply engages the lockup clutch to sustain the current level of engine output. I think what may have happened recently is that with the advent of so many CVT's in use the engineers have come to realize how consistently using the correct, MOST correct, gear ratio for the moment is so important for the aspect of improving FE. So now we have 6 speed, 5 plus OD, automatic transmissions that quite regularly use the lockup clutch to provide up to 9 levels of reduction gearing plus OD. A whole lot of shiftin' going on. Having recently driven two '07 models, rentals, I would say somewhat uncomfortably so....
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Replying to: wwest (Sep 05, 2007 7:42 am) |
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Replying to: wwest (Sep 05, 2007 7:42 am)
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Replying to: joel16 (Sep 05, 2007 11:01 am) Don't forget that the auto mags get samples hand picked by the manufacturers to test. They don't get some random car off the line. |
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Replying to: stlpike07 (Sep 04, 2007 3:01 pm) This the first Toyota we have ever owned. We bought it looking for a good MPG car from a reliable maker and we are starting to wonder about the reliability of the car. We have had it in 3 times to fix the dash. The trim piece around the clock (by the windshield) has popped up 3 times. |
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Replying to: joel16 (Sep 05, 2007 3:44 am)
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