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Hybrid Vehicles Lexus RX 400h Lexus RX 400h: Driving Tips & Tricks
110 messages, Last post on Sep 10, 2007 at 8:21 AM
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Replying to: gagrice (Mar 06, 2006 7:37 pm)
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Replying to: vpotluri (Mar 07, 2006 6:14 am) Packed sand or sand permeated with water I would NOT hesitate to take my 1978 Porsche Targa out on, being careful with the throttle. But for that matter other than the conditions I have stated I wouldn't advise taking any vehicle out on with the exception of that otherwise worthless VW powered dune buggy.
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Replying to: wwest (Mar 07, 2006 3:37 pm)
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Replying to: gagrice (Mar 07, 2006 3:42 pm) Level terrain, loose sand,no sweat. Packed sand, rolling terrain, no sweat. Wet sand, flat terrain, no sweat. Unless you intend to play leadfoot... And yes, I would take my AWD Rx300, or its FWD equivalent, out on loose sand having driven my 78 Targa on loose sand many times, but very gingerly. But again, there is NO vehicle other than a dune buggy that I would willingly take out on loose sand for playing leadfoot.
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Replying to: wwest (Mar 07, 2006 5:46 pm) Because, unlike the AWD RX300, the AWD 400h gets it's AWD from all electric motors. If the electric motors work too much, they overheat and simply quit. Bingo, stuck in sand. For FWD owners, the Prius forum has several posts by Prius owners in which they got stuck in snow when the front wheels lost traction - the computer shut down the entire car rather than let the electric assist overheat. Since both vehicles use the same drive system, I suspect the FWD 400h would do the same.
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Replying to: stevedebi (Mar 16, 2006 9:32 am) Can you, or anyone, be certain the Prius "shutdown" was due to overheating of the "drive" motors? With traction control when wheelspin/slip develops due to engine torque the brakes are used to reduce, control, the rotational speed of the driven wheel(s). In the case of FWD the engine is also instantly dethrottled since front wheelspin/slip is a certain indication of loss of traction and that can quickly result in loss of directional control. With RWD the engine dethrottling is typically delayed for a few hundreds milliseconds to allow the driver time to react and feather the throttle. In any case with the Prius or any Toyota vehicle with traction control if the driver persists with depressing the gas pedal after traction control starts braking the wheels and dethrottling the engine then about 45 seconds later the fractional HP low duty-cycle ABS pumpmotor will be disabled to prevent it from being over-heated and failing. Having never experienced the above timeout I suspect that with continued wheelslip/spin the engine drivetrain would then be fully disabled. But my point was/is that if the sand base is packed and/or smooth and you drive in a "smooth" way, feathering the throttle as you would on a slippery surface, then the drive motors would have no reason to overheat. If you do get stuck and think you need to use wheelspin, say in rocking back and forth, to get unstuck then the first thing to do is disable the traction system. You can do that easiest by unplugging the MAF/IAT module while the engine is running. The engine will die but you can restart it after reconnecting the module. It will then take a few drive cycles for the engine fault to clear and the VSC/Trac system will again be enabled.
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Replying to: wwest (Mar 16, 2006 10:58 am) I suggest you read the Prius problem reports of the stuck in snow issue. That will clear things up. The vehicle simply stopped and would not move. I don't recall if it had to be towed to the dealer or if it worked after a certain period of time. The HSD has the computer deciding if the propulsion system is working correctly or not. There are now two known conditions where the Prius will not move: less than 20% battery charge (won't even startup), and slippery snow situations. Note that in the Prius you cannot turn off the traction control, which probably would have allowed the wheels to move. I don't know if traction control can be disabled in the RH400 or not. "If you do get stuck and think you need to use wheelspin, say in rocking back and forth, to get unstuck then the first thing to do is disable the traction system. You can do that easiest by unplugging the MAF/IAT module while the engine is running. The engine will die but you can restart it after reconnecting the module." You are advocating that the average driver unplug engine modules while the engine is running? I suspect that would void your warranty, and don't think that the engine won't throw an exception code when you do that, which will be recorded and noted the next time the car is hooked up to the engine code analyzer. If the traction control system was meant to be turned off, there would be an "on/off" switch.
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Replying to: stevedebi (Mar 16, 2006 2:26 pm) Light weight vehicle, TINY tires = low traction coefficient. 45 seconds of wheelspin/slip to the point of disabling the ABS pumpmotor isn't very long so most drivers would simply say "it stopped on me as soon as I encountered the slippery stuff". And I wouldn't recommend, lightly, disconnecting the MAF/IAT module. But if you're stuck out in the cold with seemingly no other option.... And by the way that specific recommendation to disable VSC/Trac was made to me by the service manager at Lexus of Bellevue as an alternative to the procedure published recently in AutoWeek. And yes, the system will store a fault code, but no damage will result and if one were concerned about warranty issues you could always "dummy" up... "Gee, I don't have any idea why it would store that code".
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Replying to: wwest (Mar 16, 2006 3:05 pm) If you are unwilling to get the facts then I'm afraid we cannot hold a meaningful conversation on this subject. RE: Dummying up a code. The codes are generally stored for a specific reason. One might get away with it, or one might get one's warranty voided.
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Replying to: stevedebi (Mar 17, 2006 2:23 pm) But that's okay, I almost always operate outside the box so a "meaningful" conversation would have probably been useless. |
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