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Sedans Toyota Avalon 2008 Toyota Avalon
626 messages, Last post on Nov 24, 2009 at 6:42 PM
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Replying to: wwest (Feb 10, 2009 2:42 pm) The tranny is delicately complex: way too many hydraulic circuits, sensors and actuators. But I’ll see if I can find a common denominator here regarding the dragging issue This stuff certainly defies just about anyone’s common sense. Amaury ’08 Limited
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Replying to: amauhry (Feb 11, 2009 9:40 am) These days that would be the source code for the engine/transaxle controlling ECU/microprocess(s). And I don't think either of us will have access to that. The best, and maybe the only, close alternative will be the manufacturer's disclosed information about the dynamic operation, shift pattern, etc. The new RX/Venza F/awd system's electrical schematic, as a "for instance" includes the OAT (Outside Air Temperature) as an input. That could/might mean the outside temperature is being taken into consideration to determine when to engage, or how hard to engage, the rear drive clutch. Or it could mean the new F/awd system is subject to overheating(***) and the system operates accordingly. *** The Ford Escape was an early adopter of this "new" F/awd system and actually had an instrument panel warning to indicate that the F/awd system was overheating (rear clutch pack was implied) requiring the driver to pull over long enough for the system to cool. The Mazda CX-7 uses this same system and has added water cooling for the PTO (Power Take Off) to prevent it from overheating. My point is that it often requires many resources, sometimes somewhat obtuse resources, in order to try to figure out how these microprocessor controlled systems operate.
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I just got gas for my '08 Avalon; it had 16 miles to go and the low fuel indicator was on. I was only able to squeeze in 16.005 gallons and I really tried hard. Why is it with all the electronic gadgets and things there can't be an accurate gas gauge?
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Replying to: tfelton (Feb 11, 2009 6:44 pm) |
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Replying to: wwest (Feb 11, 2009 10:12 am) "And I don't think either of us will have access to that". Sitting on my desk are blueprints of stuff that ranges in the million of dollars (electromechanical, hydraulics, logic controller diagrams; you name it); would you like to take a peak? Cars’ blueprints are proprietary information only NOT top secret information. Not available in Google of course, but obtainable nevertheless. In this arena, I have the advantage mi amigo. "And I'm quite sure the lockup clutch remains disabled in the lower gear ratios wherein the converter's torque multiplication aspect is more often required than not. There is also the case that were it actually locked up, say in 1st or 2nd gear, you might stall the engine with a quick release of the gas pedal." Looking at this stuff, it’s clear to me that the automatic transmission has its own set of clutches; so even if it is engaged to the torque converter clutch (lockup), provisions can be set in place to engage/disengaged whatever set of planetary/sun gears depending on unique trait designs. The fact is, with such design characteristics logics can be implemented to have the transaxle downshifts even when YOU let go of the gas pedal in whatever gear wheather you're on flat or going downhill (have you ever heard about automatic engine braking when going on a downward slope as the tach needle shoots sky high?). This is all against your perception of how tranny works. Amaury ’08 Limited
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Replying to: amauhry (Feb 12, 2009 1:44 pm) "..The fact is..." Yes the whole idea of computer firmware control of the electric solenoids which in turn control the various clutches via porting hydraulic pressure is to have total control and viability of the transaxle. But just as you would NEVER declutch a stick shift in a low enough gear ratio that would result in a high level of engine compression braking absent being sure, certain sure, of the roadbed traction coefficient these transaxle should never also. No blueprints, source code, just common everyday horse sense. |
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Replying to: amauhry (Feb 12, 2009 1:44 pm) No, and I'm quite sure you haven't either. Modern computer controlled transaxles (assume FWD) will only downshift in the above circumstance provided there are first "armed" via the driver applying some level of actual braking, even light braking. "sky high" is a pretty subjective term and so it is not one I would use in describing the level of engine RPM rise that would be likely to occur with an "automatic"(no shifter or paddle movement) FWD downshift. "Automatic" FWD downshifts, even RWD downshifts, dare not be that dramatic in the described circumstance, automatic downhill engine braking. A driver induced, shifter movement, downshift, maybe, but NEVER an automatic one.
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Replying to: wwest (Feb 12, 2009 9:01 pm) …design files from companies you know; all rightfully obtained. And the invitation remains open. Amaury ’08 Limited
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Replying to: amauhry (Feb 13, 2009 7:48 am) 73's
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Replying to: wwest (Feb 13, 2009 9:19 am) They said it appeared something "Funkie" was going on, but that they couldn't tell what, because they can only replace the whol thing and they can't take apart, because they have to return it to Toyota just as they replaced it. It's not suppose to be to cold this weekend, so I may not know if it fixed the problem or not. $577.00 to fix under warranty. I point this point so folks will know what they might be in for AFTER the warranty has expired. Almost $1200.00 for both sides, if needed. That would suck. Hell, I would consider trading for a new car at that point, but that's just me - any excuse to have a new car Here's hoping. Skip |
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