Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!





Lexus RX 400h and 450h

194959799100103

Comments

  • larsblarsb Posts: 8,204
    maggiebrowneye says, "Maybe with the hybrids having the extra batteries, their weight could be causing these problems."

    Well, if that were indeed the case, it would mean that EVERY Toyota Highlander and RX400h would be having this issue, and we know that is not happening.

    Good luck on the Michelins, and keep an eye on them. If you rotate them at every oil change, you are very unlikely to have further issues.
  • Who is "we". Are you affiliated with Lexus/Toyota? I see a lot of people complaining about the tires. Just google Lexus Hybrid tire wear. Something is not right and I think an investigation needs to be done.
  • larsblarsb Posts: 8,204
    "who is we?"

    "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.
  • stevedebistevedebi LAPosts: 3,719
    "Converting the RXh engine to the Atkinson cycle to improve FE even more, 20-30% maybe...?

    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.
  • wwestwwest Posts: 10,706
    Can you tell me why you think the engine ECU firmware would need to be changed/modified?

    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.
  • stevedebistevedebi LAPosts: 3,719
    "Can you tell me why you think the engine ECU firmware would need to be changed/modified?

    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...
  • wwestwwest Posts: 10,706
    "..It's a great unknown..."

    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.
  • stevedebistevedebi LAPosts: 3,719
    "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."

    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... :shades:
  • wwestwwest Posts: 10,706
    Yeah, I guess I'll just have to go ahead and do it to prove my position.

    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.
  • hallinihallini Posts: 13
    Do you know of any changes from the 2007 model? I'm wondering if I should wait a few more months for a 2008. The 2007 I ordered is scheduled to arrive in June.
  • dorenescardorenescar Posts: 28
    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. :)
  • cyclone4cyclone4 Posts: 2,257
    The lease on my wife's 2005 RX400H expires in late April of 2008. I have heard some rumblings that the next generation battery (lithium ion) will be introduced for the the 2009 RX in the fall of 2008. Has anyone else heard anything about this? If that is the case, we can extend the lease for several months and get the brand new 2009 RX400H which I suppose will have superb gas mileage along with all the other goodies.
  • wwestwwest Posts: 10,706
    An "improved" battery will only result in better hybrid FE if the new battery has a subtantially lower internal resistance over the current one. I doubt if the losses from this "account" even with the current battery amount to more than about 10% so that leaves us with only that 10% to be gained.

    Unless Toyota comes up with an emtirely new, more efficient method, in which case a higher capacity battery might be required.

    My guess would be that the greatest advantage of an LI battery would be in weight reduction.
  • cyclone4cyclone4 Posts: 2,257
    I know little or nothing about the electronics or technology involved here but if what you say is true, then why are folks getting so excited about the possibilities if the LI battery?

    Everything I have seen/read about the LI, suggests that it will revolutionize the hybrid vehicles. I remember an article a few months ago quoting a very high ranking executive with Toyota confidently speaking about the next generation of hybrid batteries and how they will be much smaller, more powerful, and greatly increase fuel efficiency.
  • wwestwwest Posts: 10,706
    "very high ranking executive with Toyota.."

    There is an old joke about stock brokers that seemingly applies here...

    "If his mouth was moving then he was lying."

    (Apologies to Jim Marolich.)

    Unless more ways, methods, are found to recover energy that would otherwise be lost, what purpose would a higher capacity battery serve(***)?

    In point of fact the effort seems to be in reverse at the moment.

    While it is undoubtedly most appropreate to use, primarily, the front tires' higher traction coefficient for regenerative braking, that brings up questions of overall safety.

    Ford was recently granted a US patent that directly addresses the potential safety issues that arise from regenerative braking on FWD or front torque biased AWD vehicles.

    The Ford hybrid patent implementation requires monitoring the OAT sensor and significantly reducing the level of regenerative braking to be used if the OAT is near or below freezing. The second aspect of the patent calls for immediate disabling of the regenerative braking capability the INSTANT ABS activates during actual brake application.

    Obviously the industry is becoming concerned, FINALLY, about the potential wintertime use hazards of FWD and front torque biased AWD vehicles.

    Personally I would be for adding a "clutch" function to all of the current crop of hybrids now in the market place. Almost all of these, maybe ALL, use regenerative braking to SIMULATE engine compression braking.

    Wouldn't the best FE be attained if I, as the driver, could decide whether coasting or regenerative braking would be the more effective mode?

    When I let up on the Prius' gas pedal, currently, it goes immediately into regenerative braking mode. There are quite clearly times, via the advantage granted by human visual resources, that I KNOW simply coasting would be more advantagous.

    My lawn tractor has one pedal for both declutching the engine and braking. The first bit of travel declutches the engine and thereafter the brakes are increasingly applied.

    Or in the case of hybrid vehicles why not give me the option of "arming", enabling, regenerative braking via a light touch of the brake pedal. Simply lifting the gas pedal would put me in "coasting" mode and if I wanted to slow down via simulated engine braking just a light touch of the brake pedal would be required.

    *** And by-the-by you may want to take note of the current "crop" of Toyota hybrid vehicles. With the exception of the Prius and Camry Toyota seems to be heading toward satisfying the rich boy-racer segment of the buying public via use of hybrid capability for SUPER-CHARGING.

    If your desire is to own a 600HP LEXUS LS then you will not be unduly concerned that most of the energy being put into that high capacity, efficient, and lightweight LI battery comes directly from MG2, itself directly driven by the ICE.

    But then yes, all-in-all, when compared to a 600HP regular gasoline engined car and the LS hybrid I have no doubt that the hybrid will come out on top insofar as FE is concerned.

    And what about that? What would be the public, stegma, feeling, attached/surrounding a 600HP Lexus LS with purely gasoline power? Are Toyota/Lexus executives pulling a "fast" one.

    But is that truly where the general public wishes the hybrid market to be...??
  • cyclone4cyclone4 Posts: 2,257
    Once again I emphasize that I know very little about these things. But does it not make sense that if a battery is invented that is more powerful, keeps its charge a lot longer, is much lighter, etc., that the ICE will be in use considerably less? I also ask that if your theory is true and that fuel efficiency will not markedly improve with new generation batteries, then how is it that the next generation of Prius is expected to attain gas mileage in the range of 80-100 mpg.

    While it is true that Toyota has strived for more power rather than fuel efficiency with the luxury sector hybrids to this point, common sense would dictate that in the future, fuel efficiency will become more of a priority as well. Otherwise, you may as well kiss the hybrids "good-bye". There comes a point when there is a complete overkill with power/performance. The public will demand better fuel efficiency. I believe that we can have both good fuel efficiency and good power in the luxury field.

    And BTW, I do not believe that the high ranking Toyota executive was lying. I would expect that an American executive would lie before a Japanese executive would.
  • gagricegagrice San DiegoPosts: 28,690
    Disadvantages to the Li-Ion battery. I would bet that this is much of why Toyota has not yet used this battery technology to date. There are companies that claim to have over come some of these problems. How much will they sell them for? TPE has researched this more than I have and may be able to add.

    A unique drawback of the Li-ion battery is that its life span is dependent upon aging from time of manufacturing (shelf life) regardless of whether it was charged, and not just on the number of charge/discharge cycles. So an older battery will not last as long as a new battery due solely to its age, unlike other batteries. This drawback is not widely publicized.[6]

    At a 100% charge level, a typical Li-ion laptop battery that is full most of the time at 25 degrees Celsius or 77 degrees Fahrenheit, will irreversibly lose approximately 20% capacity per year. However, a battery stored inside a poorly ventilated laptop may be subject to a prolonged exposure to much higher temperatures than 25 °C, which will significantly shorten its life. The capacity loss begins from the time the battery was manufactured, and occurs even when the battery is unused. Different storage temperatures produce different loss results: 6% loss at 0 °C(32 °F), 20% at 25 °C(77 °F), and 35% at 40 °C(104 °F)

    Lithium-ion batteries can easily rupture, ignite, or explode when exposed to high temperatures,[12]. They should not be stored in a car during hot weather. Short-circuiting a Li-ion battery can cause it to ignite or explode. Never open a Li-ion battery's casing. Li-ion batteries contain safety devices that protect the cells inside from abuse. If damaged, these can also cause the battery to ignite or explode.


    http://en.wikipedia.org/wiki/Lithium_ion_battery#Disadvantages
  • wwestwwest Posts: 10,706
    Okay, let's put a 1x1x1" 1 lb battery in the hybrid that can store an infinite level of energy for an infinite time.

    Now let's fill it ONLY with "free", otherwise lost, energy recovered via regenerative braking...

    Can anyone think of another readily available energy source that would result in the new Prius attaining more than the current 42MPH city.
  • stevedebistevedebi LAPosts: 3,719
    "'If that is the case, we can extend the lease for several months and get the brand new 2009 RX400H which I suppose will have superb gas mileage along with all the other goodies."

    You are referring to a 5000 lb vehicle, right? With a V6 engine, correct? A Luxury model?

    That combination is not going to get "superb" gas mileage, except in comparison to a V8 SUV. The only way to get significantly better MPG is to use a smaller engine, which will result in less performance. I don't think Lexus will go for this concept.

    Better batteries and larger electric motors will benefit MPG, but not to the extent that it would benefit a smaller, lighter vehicle.
  • cyclone4cyclone4 Posts: 2,257
    I am obviously not expecting Prius-like gas mileage. Not even close. However, why not something like 35 mpg average? A new generation battery should be able to attain such a goal. Otherwise, I see no future in luxury hybrid vehicles. Gas mileage HAS to improve, period.
Sign In or Register to comment.