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Hybrid Vehicles Lexus RX 400h Lexus RX 400h
2334 messages, Last post on Oct 11, 2009 at 10:42 AM
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both have truly functional, rear torque biased, AWD systems and therefore will be inherently safer in wintertime adverse roadbed conditions and snowchains can be readily used on the rear wheels only, or both back and front. A case in point. The new Lexus AWD GS300 uses the VSC's yaw sensor signal to automatically route engine torque away from the front driveline when the front tire's traction coefficient is needed primarily to prevent loss of directional control. Now if the RX series could just be fitted with the GS300's wet clutch so the engine torque, leading or lagging, could be shifted away from the front in the same circumstances.... The RX series, including the h, are based on a FWD platform and are therefore front torque biased, a circumsatnce that is potentially highly hazardous on a slippery roadbed. Additionally, due to tight suspension clearance at the rear snowchains can ONLY be used at the front resulting in an extreme exacerbation of the wintertime dangers. Also, if it happens that you need to defog the windshield of a BMW you will get INSTANT and PROPER response from the climate control system when you activate the defog/demist/defrost mode. HOT airflow to the interior surface of the windshield and lots of it, even on the hottest of summer days. Whereas with any Toyota or Lexus automatic climate control system you will not only NOT get the proper response in this circumstance these systems will be much more likely to rapidly increase the windshield fogging situation, leaving it up to you to quickly modify the operational charactoristics in order to clear the windshield. The newer, 2004+, RX series is even worse. Just as the A/C is disabled as a result of the OAT declining below ~35F, releasing all of the previously condensed moisture on the evaporator vanes to the process of evaporation into the system airstream, the system also automatically switches to footwell/windshield air outflow mode. Up until this moment the interior windshield surface has recieved no warming airflow and now its CHILLED surface may very well be subjected to a super-saturated, very HUMID system airflow. ZAP!! You're blind, no forward vision! Be careful out there.
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Latest CR survey for reliability, http://www.consumerreports.org/main/detailv4.jsp?CONTENT%3C%3Ecnt_id=754189&FOLDER%3C%3Efo- lder_id=113261&ASSORTMENT%3C%3East_id=333137&bmUID=1130553212850 http://www.cnn.com/2005/AUTOS/10/26/cr_most_reliable/index.html Very impressive start for the 400h. I have had zero problems in the first 8,000 miles. |
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| 99 out of 100 RX400h owners will report no problems. | |
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Replying to: wwest (Oct 28, 2005 9:30 am)
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Replying to: hendjaz (Oct 29, 2005 12:39 pm) Otherwise agreed, as long as the Rh and OAT is in the range wherein the A/C can efficiently dehumidify the incoming airstream the Toyota/Lexus system will work perfectly fine. But that probability becomes less likely as the OAT declines below ~45F and impossible below about 35F. But the real problem occurs just below that 35F point when the A/C is totally and completely disabled by design (it wouldn't be functional anyway). The only way to defog/demist the windshield beyond that point is to throw HEAT at the windshield, lots of it initially until the windshield is fully defogged and then enough hot flow afterward to maintain the windshield interior surface above the dewpoint of the cabin atmosphere. The potential problem that I foresee is that just as, simultaneously with, the Lexus climate control switching the airflow to the footwell and windshield (presumably from dash, cooling, airflow mode) the A/C compressor is being disabled. The evaporator might be covered with condensate as a result of the previous A/C operation and now that condensate will begin to evaporate into the cold and dry incoming wintertime airflow. Super-saturated airflow that a substantial portion thereof is now headed for a COLD interior windshield surface.
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Replying to: wwest (Oct 29, 2005 4:54 pm) |
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automatic climate control. 2005 RX330 owners manual, page 246, right column. "The "Floor/Windshield" air flow mode may be applied automatically, if the outside temperature is lowered (??) down to below 0C (32F). This is not a malfunction. "The Floor/Windshield" air flow mode turns on the defogging and defrosting function with the purpose of cleaning(??) your front view for safe driving". This firmware change has arisen because too many of us, all the way back to 93, were experiencing unexpected and sudden windshield fogging shortly after the A/C is automatically disabled as the outside temperature declines below ~35F. Once the A/C is disabled it is already too late, but I guess we should give Toyota/Lexus/NipponDenso an "E" for effort. The best procedure for owners to use is to manually select the combined mode, Floor/Windshield, once it is obvious that the outside temperature has declined below ~45F. That way the interior windshield surface will be preheated in in the event the outside temperature continues to decline and the A/C become inoperative. Actually I find that the idiot thing remaining in cooling mode, coolish and dry airflow from the dash outlets, is extremely discomforting during predominantly cool or even cold weather. I suspect no one at the corporate engineering level of any of these companies is aware of the adverse effects of radiant cooling (lack of radiant heating, actually) on the human body.
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The best way to stay in control of humidity and temperature is to take it into the service center and have them set the user option for Automatic Airconditioning to OFF. That way it will not go switching inot to AUTO mode when you least expect it, and you can drive around in the snow with the AC on if you want to. It will not switch off because it thinks you are cold enough. |
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Replying to: wwest (Oct 30, 2005 3:17 pm)
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Replying to: falconone (Oct 31, 2005 4:31 pm) |
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