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About Thackeray

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  • Lexus Model
  • Year of Lexus
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    Greater London
  1. That's interesting. Thanks for the explanation.
  2. Many thanks for all the explanations. I think I'm a bit clearer on what is going on here. I was going to say that it's a bit misleading of Lexus to say that the IS300h has a compression ratio of 13:1. From the explanations here, it sounded as if they should be saying the expansion ratio (not the compression ratio) is 13:1. And then I came across this site which has some graphics of the issues. Effectively, they seem to be saying the same thing as I was thinking - namely that Lexus should call this the expansion ratio. But then on the other hand, do Lexus technical departments really not know the difference between the compression ratio and the expansion ratio? It's all a bit puzzling.
  3. Ah, that's interesting. Seems to make sense based on the octane rating. I wonder if there's any way to confirm it.
  4. Thanks for the detailed explanation - that's very helpful. So I'm guessing that you're not saying that the compression is actually reduced. Just that the 13:1 compression ratio would be even higher if the valve were designed to close as soon as the piston began its compression stroke.
  5. Could you explain a bit more what this means? Lexus quotes the compression ratio as 13.0:1 on the IS300h engine. Is that just a hypothetical figure for a non-Atkinson cycle and in reality the compression ratio is lower than that?
  6. I have to say I've found the acceleration pretty much instantaneous in Sport mode. But then I'm probably comparing it with my experience in recent years with turbo diesel cars, where after pressing the accelerator you had a pleasant restful interlude before the car would suddenly begin to move faster when the turbo kicked in. The IS300h has no turbo but it has electric motors which provide maximum torque from stationary. What you think of the IS300h will probably depend on what you're used to previously. If you're using Eco or Normal mode the engine will usually not be running when you're stationary. So when you press the accelerator you briefly only have power from the electric motors. These respond instantaneously but they're probably providing less than half the car's total power. A fraction of a second later, the engine starts up and adds to the torque; but the delay might add to the feeling of lag if you're trying to accelerate hard. But I find that in Sport mode the engine generally keeps running when you come to a stop. This makes full power available from standstill. Added to which the computer makes the accelerator response much sharper in Sport mode. Eco mode is designed for use in traffic where you're repeatedly stopping and starting and you never need maximum acceleration. It also makes the accelerator response much more leisurely.
  7. Hope you have fun. A couple of suggestions for the test drive. Make sure you have the artificial engine sound turned off for at least part of the drive so that you can hear what the car sounds like without artificial sound effects. The jargon name is Active Sound Control and there's a volume control/off switch low down to the right of the steering wheel. It's fun to turn on sometimes but for a test drive I would want to be able to hear the car itself for some of the time. The other thing to remember is that the car has no gears, no clutch, no torque converter, no dedicated starter motor. That means that you don't get the up and down revving you would get in a manual gearbox car. The power delivery is more like in a jet plane or a power boat. I expect most people don't sit in a plane thinking, "When is the pilot going to change gear?" But many magazine reviewers miss the familiar up and down revs of the manual gearbox. Even if you're used to an automatic, there are still no jolts between gear ratios in the IS300h as there would be in a conventional automatic. This is disconcerting to many people. Personally, I think the hybrid drive is an impressive bit of engineering and I like how it makes the car pretty silent most of the time. Gearboxes and clutches are essentially 19th century technology. I like the way the hybrid drive is truly 21st century technology, only made possible by the development of the computer. Incidentally, people say the hybrid drive is noisy when you put your foot down. What this means is that the engine revs at a constant high rate (like a power boat) until you take your foot off the accelerator. But it's the engine that's making the noise at high revs, not the hybrid drive (sometimes called a power-split device or a CVT.)
  8. Auto wipers and snow

    Maybe I've misunderstood what you're saying. But my original point at the top of the thread was that on the IS300h when the wipers are on auto they turn themselves on and off automatically. (They also vary speed automatically.) My concern was what happened when they turned themselves on automatically and the wipers were frozen to the screen. One answer is to turn off the auto setting before the snow comes. But are you saying you have auto wipers but they don't turn on automatically?
  9. Auto wipers and snow

    Oddly enough, going out in the snow today the windscreen wipers weren't frozen to the screen. But when I tried the washers after a while - nothing happened. They were frozen. (Has someone been diluting my screenwash?) Heated nozzles would have been handy. When I got back home I had another go. The interesting thing was that after the initial whirring you get from the screenwasher it went silent. No matter how much I pulled the wiper stalk there was no whirring noise. Could it have been one of these automatically resetting circuit breakers mentioned above? Anyway I poured some cold water on the nozzles in the hope of unfreezing them. Then I tried again after an interval. The whirring noise was back (had the circuit breakers reset?) and the washers were now working. Finally, I topped up the reservoir with some more antifreeze screenwash - let's hope it doesn't happen again.
  10. Auto wipers and snow

    That's interesting. Never knew that. I suppose if you find the relevant fuse it would be possible to tell if this is installed on the IS300h just by looking at it. Perhaps I'll do that when the weather isn't so cold. I don't want to be fiddling about with fuses with ice-cold hands! In the meantime, maybe somebody already knows if the IS300h has resettable circuit breakers on the windscreen wiper circuits. That will be useful to know if someone else has already checked!
  11. That's a good point. I hadn't thought of that. I usually have S-flow turned on as most of the time there are no passengers in the back. But that probably slows down the demisting effect of the airconditioning. I'll try turning it off to see if the extra airflow to the back will speed up the demisting.
  12. Does anyone know if the auto wipers have some sort of protection from damaging the mechanism when the wipers can't move? Now that the snow has arrived, I'm wondering what the wipers will do if the car is covered with snow and you turn on the ignition. if the windscreen is covered with thick snow, I would expect the wiper sensor to respond by activating the wipers. But if the wipers are frozen solid to the windscreen that presumably has the potential to cause some damage to the wipers, mechanism, motor or all three. Maybe Lexus have thought of this and incorporated some sort of safety mechanism to prevent damage. But the manual doesn't say anything about it as far as I can see. Does anyone know the answer? In the meantime, I've been leaving the auto wipers disabled during the cold weather. Is that an unnecessary precaution?
  13. Another slight irritation are the climate control temperature sliders. Ergonomically poor. You can't operate them without looking at them. Blind passengers are unable to set a preferred temperature. Sometimes I'm turning on the demister and graze my hand against the slider and it resets the temperature. I then can't correct it until the road is clear and I can look away from the traffic to the temperature display. Meanwhile, I freeze or boil (depending on the season) as the temperature is reset. This, however, is just a slight irritation. Much more irritating is the way most car journalists say how great they are. "Wow, this is so cool!" they say, echoing what the Lexus marketing department probably said (only in Japanese) in a pointless meeting about how to make the car more cool. Never mind the engineers at the meeting who probably said nervously , "But wouldn't it be more practical to have just a round knob with a pointy bit at the top so that you could set it to the mid-way position by feel alone? Then you could adjust it higher or lower while driving, without having to look at it." "But that wouldn't look cool at all," the marketing people probably replied (in Japanese, of course). "That would look simple, practical and easy to use, which we definitely don't want. This isn't a Volvo. And not only that - it wouldn't trick British car journalists into thinking it was a super modern feature that they could copy from our press release."
  14. Here's a link to the discussion of when indicators cancel. It turns out that other people's cars work the same way mine does. Whether this is an irritation or not may come down to what your local roundabouts are like and how sharply you have to turn your steering wheel to the left when entering them. The roundabouts I use often cause this irritation.
  15. Interesting post. Let's hope Lexus designers read this forum. Heated seats - I don't have a problem with them. I quite like the idea that the heat fades as the cabin warms up. Rear window demister - it could certainly be more powerful. It's quite slow to demist, unlike the front. Though again, when the cabin warms up, unlike some other forum members, I don't need to keep it turned on, as long as the air conditioning is on and working properly. Satnav, audio - entirely unintuitive. Even after reading the manual it was hard to get it to work. Lexus clearly didn't do any user testing. If I was in Toyota/Lexus management I'd want to know why the satnav/dab radio etc had not been put through proper professional user testing. That means getting users who have never seen the system before - but have some basic knowledge of the conventions used on computers/audio systems - to try and make it work. This is a flaw in the design process. Lexus take note! Service intervals too short - agree. Boot lid - I don't have this problem; it just releases by a few millimetres and stays almost shut until you lift it. Maybe yours needs adjustment. Electronics - Haven't had this problem. Battery capacity too small. I've left this one till last as it's an interesting point. Although it feels fun to be running on the battery and it's nice and quiet, and the mpg gauge says you're doing 99 mpg, I think this is misleading. In reality, whenever you're running on electricity alone it's only efficient use of energy when you're using electricity recouped from braking. Using the engine to generate electricity and then using that electricity to drive electric motors can't be as efficient as just using the petrol engine - there must be losses as heat when you introduce the intermediate stages. So that means if you're going to design a hybrid, rather than an all-electric car, you have to size the battery to make best use of the regenerated electricity you can get from braking. There's no point in saving the energy generated by the petrol engine when it can be used to drive the wheels directly. And you have to balance the weight and space taken by the battery against how much output it can store. I don't know how much that is but it's obviously a trade-off. So what about quietness when using electricity? Personally, I find being able to tell whether you're running on battery alone is only perceptible at very low speeds, say, around 5 mph, 10 mph max. Above that I mostly can't hear when the petrol engine is running and when it isn't. I've turned off the EV light, as I found it was too much of a distraction. (Yes, I like the fun of knowing when it's running on battery only, too. But ultimately I decided it's an unnecessary distraction from watching the road, so I turned it off.) What I'd like to add to your list is the indicators. As I've mentioned in another thread, they turn off too soon. If you're turning right at a roundabout, they turn off as soon as you enter the roundabout and turn the wheel a bit to the left. This is irritating as you have to turn them on again to keep indicating right.