Toyota/Lexus hybrid SUVs - Jay Maynard

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Wednesday, 23 March 2005


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0732 - Toyota/Lexus hybrid SUVs

wbwolf points to a couple of articles in the Japan Times in his latest entry. Toyota is about to introduce two hybrid versions of the SUVs known in the US as the Lexus RX330 (to be known as the RX400h) and the Toyota Highlander.

The article says that the new vehicles will get 17.8 km/L, or 41.9 MPG (5.6 L/100km) according to my HP48SX. I wonder just how they came up with that answer, as it's about double the RX330's number. Personally, I doubt its accuracy unless you're talking about strictly stop-and-go city driving, where a hybrid shines. My results would almost certainly be lower than the pure gas version, as the vehicle weighs more, and hybrids provide no advantage at all in highway driving - where the same 3.3-liter engine as in the RX330 would be running full-time.

current mood: [mood icon] awake

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Comments:


[User Picture]
From:unspeakablevorn
Date: - 0000
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the EPA's gas mileage calculation is well known to be inaccurate. However it may also be that the hybrid engine is more than twice as efficient as a regular engine for city driving.

Vorn
[User Picture]
From:korgmeister
Date: - 0000
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Considering that hybrids recharge using regenerative braking, wouldn't that break the conservation of energy principle?
[User Picture]
From:unspeakablevorn
Date: - 0000
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Not necessarily. A hybrid's gasoline engine can shut down completely during braking and coasting - where on a normal ICE it must maintain a certain RPM. If the RPM it must maintain is high enough, a large amount the engine running during city operation on an ICE would be when the engine doesn't need to run for a hybrid. Meanwhile the other half of the equation is that some of the acceleration that would normally be done entirely on the ICE is also handled by the electric motor.

Vorn
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From:korgmeister
Date: - 0000
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*blinks* The engine shuts down? Entirely?

And restarts again?

Wouldn't this increase the wear on the engine incredibly? Not to mention the battery drain from using the starter motor so much.

Doesn't seem very efficient if you ask me. Seems more like a horribly wasteful kludge. If you explain this to me I'd be grateful.
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From:vakkotaur
Date: - 0000
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Starting a cold engine does cause greater wear, but re-starting a warm engine is no big deal. It's already warm (or hot) and the oil is already spread through the engine and also warm. Assuming the design is similar to that used in the Prius, the gasoline engine would not be shut down if the outside temperature were below 0 F. Also, before the first time the gasoline is engine is started after it's been sitting for a while (where any car would be off rather than idling) an electric pump pumps the antifreeze through the engine. This may seem odd, but here the coolant is used to bring the engine temperature up. The antifreeze, or some of it, is stored in what is pretty much a thermos bottle to keep it warm after the last run of the engine. This makes even the the first start of a trip not so quite wearing on the engine.

[User Picture]
From:jmaynard
Date: - 0000
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In addition to vakkotaur's comments, I'll point out that a hybrid has a huge battery bank, and starting the engine isn't the major drain that it is on a conventional car...it's less than the drain from the drivetrain motors.
From:rendtheheavens
Date: - 0000
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yeah we get the overall message you're tryin to send....those dang liberals and their hybrids are evil evil evil............and it's all lies from liberals.........
[User Picture]
From:jmaynard
Date: - 0000
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Actually, I've got two points:
1) The doubled fuel economy seems like smoke and mirrors to me, I don't doubt that the economy is higher, at least in city driving, just not that high.
2) A hybrid wouldn't do me much good at all, since 95% of my driving is on the highway at speeds of at least 55 MPH - where a hybrid runs entirely on the gasoline engine. Therefore, I almost certainly won't be one of those in the long line to buy one.

If someone else decides that a hybrid meets their mission requirements, then they should certainly buy one.
[User Picture]
From:shelbystripes
Date: - 0000
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Car and Driver magazine reports that the RX400h will have an EPA city rating of 30MPG, which seems much more likely--and still a good gain over the RX330's 18MPG rating. They're showing a slight gain for highway driving on the RX400h, 25MPG vs. 24 for the RX330, which is about to be expected (the hybrid's gas engine is tuned for 10 fewer horsepower for the sake of fuel efficiency because it has the electric motors to make up for the power loss and help it accelerate); something nice for a next vehicle, but not good enough for a highway driver to rush out to get one right away.

C&D also reports, incidentally, that the RX400h won't have the 'antifreeze thermos' that the Prius has.

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