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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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Replying to: larsb (May 10, 2007 12:09 pm)
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Replying to: maggiebrowneye (May 10, 2007 12:40 pm) "We" are the people like me (and maybe you) who frequent hybrid car forums. I know for a fact this is not a widespread problem on the Lexus/Toyota hybrid SUVs. One of my best friends has a Highlander Hybrid with about 17K miles on it and he does not have the problem. It's not been reported as a major issue affecting dozens of cars at other mainstream hybrid websites. It has indeed been reported by a few owners, and that's probably because of some sort of equipment malfunction specific to those vehicles. I would urge owners with this problem to take it up with their Toyota/Lexus dealer and get it resolved. My only contentious issue is that one cannot blanketly say "This is for sure a design problem caused by the hybridization of the vehicle." Because if that were true, then there would have been a recall for this problem. I just looked on the NTHSA complaint site and there is one single complaint of this type of inboard tire wear. That's not to diminish your or anyone else's issues - it's merely to point out that this has no indications of being a widespread issue. PS. No, I'm not associated with Lexus or Toyota other than being a fan of their cars. I own a 2007 TCH and have previously owned several other Toyota vehicles, none of which had design problems.
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Replying to: wwest (May 08, 2007 4:22 pm) Mill the heads to raise the compression ratio to ~13:1 and then custom grind the intake cams so the intake valves remain open for ~30% of the compression stroke." You forgot about modifying the engine CU software to account for the change in cycle. Ok, take a 45K car, void the warranty on the engine and hybrid components. Not recommended.
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Replying to: stevedebi (May 11, 2007 10:54 am) I don't see it. In probably well over a million Lexus miles the only abnormal failure I've experienced is the alternator slip ring early wear at ~100,000+ miles in my 92 LS. I stopped buying the extended warranty after about the third Lexus.
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Replying to: wwest (May 11, 2007 12:28 pm) I don't see it. " The HSD has two parts that must work in tandem; the electric motors and the ICE engine. If either is changed the ECU software needs to be adjusted. The electric motors are run by the ECU based on the OTTO cycle. The software would be different for the Atkinson cycle. Different engine power curves. Without modified software, you might very well have worse mileage, performance, or who knows what. It's a great unknown. I would expect (without having access to the Lexus software) that such a system would be very underpowered. The electric motors are programmed to assist based on the higher power of the Atkinson cycle, and would not supply adequate electric propulsion at slower speeds. As I said, I don't think anyone is going to crack open the engine to attempt such a thing anyway...
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Replying to: stevedebi (May 14, 2007 11:26 am) Not really... The factory supplied software must be, and IS, designed to continuously "learn" and relearn the most optimal operational parameters for any given engine. If you doubt this then put a flow restrictor, a rather SERIOUS flow restrictor, just downstream of the MAF/IAT sensor module in ANY modern day engine. You'll find the engine performance quite seriously degraded but no complaints from the ECU. Or even simpler, maybe. Disconnect the battery and then mechanically block the throttle butterfly valve from opening beyond, say, 70%, reconnect the battery and drive away with a seriously derated engine from a torque/HP performance standpoint. What do you think the torque/HP output, performance, of one of these engines would be at 200,000 miles vs fresh out of the factory? How do you think the firmware might be written in order to "handle" that transition. The Atkinson cycle, nor even the Miller cycle if it should come to that, does not change nor interfere with the idle, cruise, or POWER band A/F mixture ratios. So the MAF/IAT sensors have no effect one way or another, nor does the "front" oxygen sensor. The only affect I might see/forecast is the impact on the operating temperature of the catalyst in the converter. There would be a much more complete "burn" of the A/F mixture within the combustion chamber resulting in lowering the temperature of the gasses entering the exhaust manifold.
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Replying to: wwest (May 14, 2007 4:18 pm) Can you provide links to the information about exactly what the ECU software does in the Toyota HSD system? I can't. I stand by my statement - the electric system would not match the ICE anymore. It's not a matter of running the ICE, it is a matter of running the HSD, in which the ICE and electric are combined into one smooth, continuously-operated transmission system. You should not change the ICE component without changing the electric components. I suspect Toyota spent a lot of time designing, testing, and optimizing the software to account for this first implementation of Atkinson cycle ICE (the Prius uses OTTO) with HSD. Of course, I also don't have access to HSD firmware or software code, so in theory either of us could be right. I think we must agree to disagree here... 
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Replying to: stevedebi (May 16, 2007 11:23 am) Oh, if you buy the factory shop/repair manuals and read and comprehend the diagnostics section concerning each and every sensor you end up understanding pretty much how the software "fits" together. |
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Replying to: twq83 (Apr 21, 2007 6:41 am) |
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We don't know if this is accurate, but the salespeople who sold us our 07 two weeks ago said that there were no mechanical or features changes for 08. Cosmetic changes include chrome handles and a new grill; both of which didn't seem substantial to us. They most likely will also have some color options, such as the burgundy color added to the gas rx's 08 lineup. Good luck with your purchase. 
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