Here are my observations on the utility of this setting...
It clearly DOES evoke the regenerative brakeing since when at steady speed, changing from D to B caused the power needle to move into the blue range. The amout it moves seems to be dependant on a at least a couple of things. 1) how fast you are going 2) whether you are on a down grade! This last one surprised me and was a very welcome discovery. The vehicle knows that you need it more on the down grades and provides it to you. Awesome.
One oddity in its behavior and this may be related to engin break in since mine still only has a few hundered miles on it... the needel will move deep into blue, swing back to zero and then settle just under zero in the blue when I first shift into B. I'm thinking the part where it is giving up some of the regenertative braking is where it expects the ICE to pick up the slack, but since it is not fully broken in the ICE is not up to the task.
Anyway, I'm likeing the B position. I can use it to maneuver in traffic without taking my foot off the gas peddle. There is some lag and the effect is not as great as I would like, but it is serviceable. And on the downgrades... like I said, the car KNOWS... erie.
My understanding of "B" is that it fulfills a fedaral safety requirement that automatic transmission cars have some sort of "low" setting to provide speed control without the brakes. It uses engine braking, so it is not something that makes sense with a hybrid system. The only time you might need it is on a long down hill where the batteries become fully charged, and the conventional brakes might heat up excessively. Otherwise it is sapping power that could go to the batteries.
The manual is very clear that using B costs in fuel efficiency. If you use B instead of braking you are wasting energy by rotating the engine against friction in place of getting regeneration. If you don't want to throw energy away, you will use the brake to slow down in traffic and B for severe down grades (where you would be using it instead of brake pads).
This may be true, but using the B in heavy traffic or just instead of the brake to control your position in traffic is worth the penalty (for those occations) so as not to have to move from back and forth between acc and brake so much.
It is just another reason why this is such a great car. It accomodates so many different driving styles. And one can choose high power and maneuverablity one minute and high efficiency the next, more so than with any other vehicle on the road.
It is an interesting phenoma how the mpg drops so quickly waiting for a light to change....Wife pointed out that maybe if there were more miles driven it would drop more slowly...I drove the bmw down the mountain around eighteen miles..UP and down but generally dropping..Got to the little community, and pulled over to mess with the i drive which is tedious...MPG dropped from thirty two to thirty in nothing flat..Started the drive back up the mountain and the mpg rose very quickly back to thirty two and a bit...Got back near the house and got the two lights and it dropped back to thirty just lke that..Went the next mile and a quatre and it was back up to thirty two...I was very impressed with the mpg for the longer trip, but I feel if I had been stuck in traffic at all it would have been much lower...Seems this stationwagon 5 gets eighteen in traffic and city and thirty or more on general road..Next to check out interstate at eighty mph Tony ps I place this report here as we almost got the rx h and think the board would be interested, as I would be if the shoe were on the oher foot...
Now that some parts of the country are getting some serious snow I am interested in how the 400h handles in the snow. I am particularly interested in finding out if it has any advantages over the 330 given the electric motors.
A foot of wet snow isn't even a good test for a lousy FWD car. And two feet of wet snow is only good for testing ground clearance.
If you want to know how good your "drive" system is then try driving uphill on packed snow or ice. And if you happen to have a death wish try driving downhill while braking on packed snow or ice in any FWD car.
Just as long as you don't downshift it (as one might do safely in a RWD vehicle) to slow your descent. And don't put that AWD vehicle in the same category as the RWD unless you know for sure that it's rear torque biased, most aren't.
Think about, compare, a FWD vehicle with a tractor-trailer rig going down an incline, very slippery slope, without drag chains on the rear wheels of the trailer.
I've driven FWD cars with skid control down snowy hills with no issues whatsoever. AWD is good for acceleration. How would AWD assist in going down a hill??
I don't think any of us expect and AWD 400H to perform in the snow/ice as well as a Volvo XC90 AWD.
The question was "how will it do?" and someone commented that the recent snow in Buffalo will be a good test. I think you guys took his comments too literally.
I would like to know how a stock 400H will do in the snow, though I suspect it will be terrible. Gotta put some decent tires on it for it to have any chance. But with some good m/s tires, I wonder if the 400H is adequate in snow country. I'm worried about spinning those tiny motors, as is Toyota: The RX 400h was not designed for serious off-road use. The regular RX 330 isn't exactly an off-road vehicle, either, but it handles gravel roads just fine. RX 400h drivers, on the other hand, should stick to the pavement or risk damaging the hybrid drivetrain.http://www.lexus.com/models/rx_hybrid/road_test.html
I take that comment as a caution wrt icy driving conditions, as well, but maybe it only applies to gravel (and sand?).
I'm not interested in it as a mountain climber. I'm interested in it as the most environmentally-conscious fun driving experience out there. (I do wish the colors were "sportier," however.)
I wouldn't be too concerned. The gas engine gets you underway with FWD and the electric motor (rear) merely provides assist upon initial acceleration. Hardly heavy duty at all.
We had 4 inches of snow here in the western Midwest last night (Wednesday night). I needed to be at work at 4 AM this morning. Since my snow tires have not been installed yet on my LS430, I decided to drive my wife's RX400h to work. The streets, for the most part, were not yet plowed. I had absolutely no trouble at all in the snowy and icy streets. The car had wonderful control. Even stopping at stop signs going down hill was a breeze. To summ it up, the car handles very nicely in this type of snow & ice. By the way, the tires are all season tires (nothing special).
On another note however, I have been finding that the gas mileage has dropped off substantially with the colder weather. We are now only averaging about 23-24mpg on the highway & about the same in the city. In the summer months we were getting about 27 on the highway & at least 30 in the city. Driving home today (city driving) in 20 degree weather, I averaged only 22 mpg. Has anyone else seen this type of dramatic drop in gas mileage or has something gone wrong with our vehicle? The gas engine seems to be running a heck of a lot more than when it is warm.
Thanks for the real world snow report, many of us are wondering how the 400h will handle in snowy weather. Yes cold weather has taken the same toll on my mpg. The ICE runs alot more when i crank up the heat. In the fall i could turn on the heated seats, with out the climate control, its too cold for that now.
quote cyc-"On another note however, I have been finding that the gas mileage has dropped off substantially with the colder weather. We are now only averaging about 23-24mpg on the highway & about the same in the city. In the summer months we were getting about 27 on the highway & at least 30 in the city. Driving home today (city driving) in 20 degree weather, I averaged only 22 mpg. Has anyone else seen this type of dramatic drop in gas mileage or has something gone wrong with our vehicle? The gas engine seems to be running a heck of a lot more than when it is warm."-end quote
You are a victim of Mother Nature, mi amigo !!
Cold weather reduces MPG in ALL cars, not just Hybrids, but it's more noticable in hybrids because we all care so much about the MPG.
Here are some reasons why you will see reduced MPG all winter:
Getting low MPG in cold weather is not a problem with hybrid technology, per se. If it was, there would be ZERO drivers achieving EPA numbers in the winter months, and that is not the case.
There are many reasons for cars not achieving max MPG in the colder months...
Car engines must warm up to a certain internal operating temperature before they most efficiently use the fuel. Winter months and colder temps make that transition from cold start to most efficient take a little longer.
Also: If your car is relatively new, new cars go through what is called a "break-in period" where the metal engine parts are still grinding against each other more rigidly, creating more friction, which also reduces efficiency. Over time, the "extra metal" shaves off and gets lubricated better (expecially if you use Synthetic Oil) and the friction is reduced, which affect MPG numbers.
Winter formula fuels used in most states hold less energy and this also hurts MPG.
Generally speaking, colder weather in many areas means "rain, snow, or slush or ice" on the roads - these things add additional resistance which the tires must push out of the way to contact the road, so they hurt MPG in that way.
Tire pressures also are lowered by the cold weather too. Most people fail to properly inflate their tires all year, but ESPECIALLY in the winter when it is cold and you might have dirty tires and you just dont want to deal with spending time in the cold airing up a dirty tire. Low tire inflation can cause blowouts and adds quite a bit of rolling resistance, which forces the engine to work harder to "push" the car forward, thus using more fuel.
Additional idling uses more fuel and hurts overall MPG, and many people in cold climes by habit or necessity are warming their cars up in the morning. That is good practice to stay warm, but BAD for MPG numbers. While idling in your garage or driveway or carport, it is getting 0 miles to the gallon !!
People who use the defroster in a Hybrid are many times using the A/C compressor to help reduce the humidity in the car and clear the fog. That is a MPG killer too. The compressor can be turned off, but usually by default it comes on.
You might want to invest in an Engine Block Heater, which will help a lot in getting your engine up to prime operating temperature faster. I'm getting one for my 2004 Honda Civic Hybrid very soon.
Thanks for all this detail larsb. I pretty much knew all this but it is nice to spell everything out. A lot of this is common sense. However, my concern is that it has been such a dramatic drop in gas mileage from what we were getting during warm weather, that I thought something may be wrong with the hybrid system. I guess, that's just the way it is and the way it will be for a few months of cold weather.
Specifically toward hybrids, your cold weather performance will be reduced because the batteries are less efficient at charge and discharge when they are cold. This will mean the 400h will trend more toward the 330 performance because the electrics portion of the HSD is not working to its full potential.
Now, I'm sure Toyota thought of this and has installed heaters in with the batteries to keep them within certain thermal limits, but it still takes time (and energy) for those heaters to take effect.
As for the tire inflation pressure. It needs to be clear that you still only inflate the tires to the recommended COLD tire inflation pressure, regardless of the time of year or the weather. Having said that it is true that city driving will probably not raise the tire temp to optimum levels and this could affect your MPG. Highway driving should still heat up the tires, so you don't want to overinflate them and then get on the turnpike where the tires will be dangerously overpressurized.
As the owner of a Civic hybrid in my second winter, I can tell you that the Honda IMA system does not work well (in regard to maxmizing MPG) until the engine reaches optimum operating temp.
Since my commute is short, less than 10 miles each morning, I lose MPG every day due to the warmup not happening fast enough, regardless of my battery charge.
The battery can be 100% and it will not matter at all if the software is not using the electric drive.
I cannot be sure this applies to the RXh hybrid batteries but most batteries, certainly the common wet-cell type, can hold a higher charge in colder weather than in warm or hot weather.
Most battery chargers controlling automative battery charging, alternator output voltage, have a method of sensing ambient temperatures and will charge the batteries to a higher voltage level as temperature declines.
"Most battery chargers controlling automative battery charging, alternator output voltage, have a method of sensing ambient temperatures and will charge the batteries to a higher voltage level as temperature declines."
I think they heat the battery compartment. Batteries hold charge better when cold, but they provide energy better when warm...
The batteries used in the 400h are more sensitive to thermal extremes than your typical lead/acid. Because of that Toyota needed to take more care to ensure that the batteries will be a peak performance when needed.
On cold days when the batteries are colder than their operating range they will be of dimminished use to the HSD system. As the interior of the car warms up (or if heaters are used in the battery compartment) then they will "come on line" as they reach operating temp. While this is happening you are burning gas and therefore getting less fuel efficiency in cold weather.
Conversely, that same is true on hot days when the batteries are above their operating temp. They will not be able to supply peak current and therefore the gas engine will have to pick up the demand.
Just as a point of observation, I think the main reason the batteries are inside the cabin with the passengers is that they perform best with the same thermal range as is comfortable for humans. There is a synergy there.
"Just as a point of observation, I think the main reason the batteries are inside the cabin with the passengers is that they perform best with the same thermal range as is comfortable for humans. There is a synergy there."
Hmmm, cuddle up with your hybrid batteries, anyone?
Is the RX 400h driveable on sand? I need a vehicle that can be driven off-road, expecially loose sand on beach as I go surf fishing frequently. Does the manual for this vehicle have anything to say about settings for driving on sand? Any opinions are appreaciated. Thanks.
Just got my RX400h Friday night and still learning a lot. Just over 100 miles on it and wondering a few things about the hybrid battery.
- So far have not seen the charge level go to the top of the battery, just up to the + - signs. Will it normally go higher after running more?
- I have been surprised at how quickly the battery level drops down with the car not running for a few hours or overnight. Is this typical?
- Coast or brake? When I coast, the display shows energy going from wheels to battery but the power meter is at 0. When I brake, the power meter goes down into the blue showing it is charging a lot. So is it better in the long run to wait until brakes are needed to slow down or start coasting and slowing down as soon as possible?
- Brake vs B? What are pros and cons of using B shift position compared to using brakes? Any point to to using B position when approaching stop signs/lights?
Though we tried the RX 400h on a couple of cane haul roads, Lexus engineers were quick to point out that although the RX 400h is technically an all-wheel-drive vehicle, it's not a capable off-roader. True, the mass majority that will buy this hybrid SUV won't ever take on any thing worse that a graded dirt road, or on snow. However, sand is to be avoided. With the aft electric motor being air cooled, there's a concern for excessive heat build up, which would cause the system to shut down (to protect itself), temporarily leaving its passengers stranded. If you want to go off road, the Lexus RX 400h is not for you.
beach driving or loose sand is a bad idea for the 400h. it is possible for one of the electric motors to overheat in that situation, perhaps shutting down or burning out.
I hesitated to respond as it would look like I am too anti-hybrid. I would hate to see someone pay that kind of money and get stuck on the beach. Not to mention the salt damage to a $50k vehicle. An old beater jeep is the best way to go. PS I'm glad as an owner you agree with my advice.
dont ever hesitate to respond when your information is accurate and aimed at helping someone, i was also going to suggest he check out the FJ Cruiser, Car and Driver has a recent review of sorts, and im by no means a mopar person however the new Jeep rubicon with its new engine looks like a great choice for off road.
The Fj has my attention, looks good. I really did like my 64 LC, especially off road. I like wandering around the desert when the flowers are in bloom. Sand can be very tricky and hard on a vehicle.
The batt meter will show a charge all the way to the top under certain conditions like long down hills where brakes are used alot. But normally it keeps it at about 2 bars below "full" and will turn off the engine before it goes above that.
The HSD batteries are very small. They are only good for short operation and peak demand. The batteries are also very sensitive to temperature so when you come out to the car in the morning they are cold and therefore may display a lower charge level. It is not that they have drained overnight. In fact the propulsion batteries (the ones displayed on the screen) are not used at all when the car is off. That drain is taken from the 12v battery under the hood.
It is always better to coast. Braking (even regenerative braking) has parasitic losses associated with it that eat away at your economy. As soon as you see a need to reduce speed ahead take your foot off the acc pedal completely. This "foot off" (then gradually back on) technique can also be used to maintain a constant speed once you are at cruise. It seems to trick the HSD system into using the eclectics and the ICE together more than it would if you just eased off on the acc.
The B pos uses ICE engine compression to slow the car rather than the electrics. This means you lose the energy that could have been put back into the batteries. It is mostly for long down hills where the batteries are full and you loose the drag caused by the regeneration. It keeps you from having to ride the brakes (disks) so that they will work when you really need them.
Hope this helps you better understand the amazing vehicle you have just purchased. Good luck, have fun.
I sometimes use the B pos to maneuver in traffic without having to move my foot to the brake pedel. But as soon as the need is past, I move it back into D.
Before you make that decision maybe we should define what you mean by driving on the beach. Rip-roaring dune buggy style, no. Loose sand dunes no.
Packed sand or sand permeated with water I would NOT hesitate to take my 1978 Porsche Targa out on, being careful with the throttle.
But for that matter other than the conditions I have stated I wouldn't advise taking any vehicle out on with the exception of that otherwise worthless VW powered dune buggy.
Would you take your RX330 on loose sand? I think that would be a better vehicle for the environment than a LR3. If he likes the looks of the RX400h the RX330 is nearly identical without the worry of over heating the electric motors.
"Why would there be any special worry about overheating the motors on a sandy beach? "
Because, unlike the AWD RX300, the AWD 400h gets it's AWD from all electric motors. If the electric motors work too much, they overheat and simply quit. Bingo, stuck in sand.
For FWD owners, the Prius forum has several posts by Prius owners in which they got stuck in snow when the front wheels lost traction - the computer shut down the entire car rather than let the electric assist overheat. Since both vehicles use the same drive system, I suspect the FWD 400h would do the same.
Can you, or anyone, be certain the Prius "shutdown" was due to overheating of the "drive" motors?
With traction control when wheelspin/slip develops due to engine torque the brakes are used to reduce, control, the rotational speed of the driven wheel(s).
In the case of FWD the engine is also instantly dethrottled since front wheelspin/slip is a certain indication of loss of traction and that can quickly result in loss of directional control.
With RWD the engine dethrottling is typically delayed for a few hundreds milliseconds to allow the driver time to react and feather the throttle.
In any case with the Prius or any Toyota vehicle with traction control if the driver persists with depressing the gas pedal after traction control starts braking the wheels and dethrottling the engine then about 45 seconds later the fractional HP low duty-cycle ABS pumpmotor will be disabled to prevent it from being over-heated and failing.
Having never experienced the above timeout I suspect that with continued wheelslip/spin the engine drivetrain would then be fully disabled.
But my point was/is that if the sand base is packed and/or smooth and you drive in a "smooth" way, feathering the throttle as you would on a slippery surface, then the drive motors would have no reason to overheat.
If you do get stuck and think you need to use wheelspin, say in rocking back and forth, to get unstuck then the first thing to do is disable the traction system. You can do that easiest by unplugging the MAF/IAT module while the engine is running. The engine will die but you can restart it after reconnecting the module.
It will then take a few drive cycles for the engine fault to clear and the VSC/Trac system will again be enabled.
I suggest you read the Prius problem reports of the stuck in snow issue. That will clear things up. The vehicle simply stopped and would not move. I don't recall if it had to be towed to the dealer or if it worked after a certain period of time.
The HSD has the computer deciding if the propulsion system is working correctly or not. There are now two known conditions where the Prius will not move: less than 20% battery charge (won't even startup), and slippery snow situations.
Note that in the Prius you cannot turn off the traction control, which probably would have allowed the wheels to move. I don't know if traction control can be disabled in the RH400 or not.
"If you do get stuck and think you need to use wheelspin, say in rocking back and forth, to get unstuck then the first thing to do is disable the traction system. You can do that easiest by unplugging the MAF/IAT module while the engine is running. The engine will die but you can restart it after reconnecting the module."
You are advocating that the average driver unplug engine modules while the engine is running? I suspect that would void your warranty, and don't think that the engine won't throw an exception code when you do that, which will be recorded and noted the next time the car is hooked up to the engine code analyzer. If the traction control system was meant to be turned off, there would be an "on/off" switch.
I really, REALLY doubt that I need to read the reports to find out the conditions under which the Prius stopped dead in the snow.
Light weight vehicle, TINY tires = low traction coefficient. 45 seconds of wheelspin/slip to the point of disabling the ABS pumpmotor isn't very long so most drivers would simply say "it stopped on me as soon as I encountered the slippery stuff".
And I wouldn't recommend, lightly, disconnecting the MAF/IAT module. But if you're stuck out in the cold with seemingly no other option....
And by the way that specific recommendation to disable VSC/Trac was made to me by the service manager at Lexus of Bellevue as an alternative to the procedure published recently in AutoWeek.
And yes, the system will store a fault code, but no damage will result and if one were concerned about warranty issues you could always "dummy" up... "Gee, I don't have any idea why it would store that code".
I just got my 400h yesterday. How does the ICE get started? You don't hear any kind of starter noise as it engages. It just seems to start running magically.
Does anyone have any experience with driving the RX400h on dirt roads? The Owner's Manual and the Lexus web site say not to the drive the 400h "off road". Does that mean you can't drive it on dirt roads? Or does it mean you can't drive it on very uneven terrain that you would normally think of as 4 wheel drive country? It kind of stinks if you can't even drive it on a dirt road.
"Does that mean you can't drive it on dirt roads? Or does it mean you can't drive it on very uneven terrain that you would normally think of as 4 wheel drive country?
The rear wheels have electric motors whic will overheat if they are used too often. So you could go on those dirt roads, but probably not mud. The AWD is designed for infrequent use, when the front wheels temporarily lose traction. Don't plan on driving it anywhere that you would need a lot of 4WD.
"Thank you for contacting Lexus Customer Satisfaction. We are dedicated to providing superior service. In circumstances that require our attention, we will assist in the resolution process.
The RX 400h is intended for use for paved driving. Off-road use should be limited, for example: a flat dirt road will be fine. Serious off-roading like large mud puddles, fording streams, rock climbs, etc. should NOT be performed by the RX 400h. Your local Lexus dealership may be able to tell you if your RX 400h can handle your local road conditions. We apologize for any misunderstanding you may have had. Please be assured that your inquiry has been documented.
If you require further assistance, please respond to this e-mail, or contact Lexus Customer Satisfaction at 1-800-255-3987, Monday through Friday, 5:00 a.m. to 6:00 p.m., or Saturday, 7:00 a.m. to 4:00 p.m., Pacific Standard Time."
Looks like we can do some driving on non-paved roads.
Comments
It clearly DOES evoke the regenerative brakeing since when at steady speed, changing from D to B caused the power needle to move into the blue range. The amout it moves seems to be dependant on a at least a couple of things.
1) how fast you are going
2) whether you are on a down grade!
This last one surprised me and was a very welcome discovery. The vehicle knows that you need it more on the down grades and provides it to you. Awesome.
One oddity in its behavior and this may be related to engin break in since mine still only has a few hundered miles on it... the needel will move deep into blue, swing back to zero and then settle just under zero in the blue when I first shift into B. I'm thinking the part where it is giving up some of the regenertative braking is where it expects the ICE to pick up the slack, but since it is not fully broken in the ICE is not up to the task.
Anyway, I'm likeing the B position. I can use it to maneuver in traffic without taking my foot off the gas peddle. There is some lag and the effect is not as great as I would like, but it is serviceable. And on the downgrades... like I said, the car KNOWS... erie.
It is just another reason why this is such a great car. It accomodates so many different driving styles. And one can choose high power and maneuverablity one minute and high efficiency the next, more so than with any other vehicle on the road.
If you want to know how good your "drive" system is then try driving uphill on packed snow or ice. And if you happen to have a death wish try driving downhill while braking on packed snow or ice in any FWD car.
Think about, compare, a FWD vehicle with a tractor-trailer rig going down an incline, very slippery slope, without drag chains on the rear wheels of the trailer.
Invitation to disaster.
The question was "how will it do?" and someone commented that the recent snow in Buffalo will be a good test.
I think you guys took his comments too literally.
I would like to know how a stock 400H will do in the snow, though I suspect it will be terrible. Gotta put some decent tires on it for it to have any chance. But with some good m/s tires, I wonder if the 400H is adequate in snow country. I'm worried about spinning those tiny motors, as is Toyota:
The RX 400h was not designed for serious off-road use. The regular RX 330 isn't exactly an off-road vehicle, either, but it handles gravel roads just fine. RX 400h drivers, on the other hand, should stick to the pavement or risk damaging the hybrid drivetrain. http://www.lexus.com/models/rx_hybrid/road_test.html
I take that comment as a caution wrt icy driving conditions, as well, but maybe it only applies to gravel (and sand?).
I'm not interested in it as a mountain climber. I'm interested in it as the most environmentally-conscious fun driving experience out there. (I do wish the colors were "sportier," however.)
On another note however, I have been finding that the gas mileage has dropped off substantially with the colder weather. We are now only averaging about 23-24mpg on the highway & about the same in the city. In the summer months we were getting about 27 on the highway & at least 30 in the city. Driving home today (city driving) in 20 degree weather, I averaged only 22 mpg. Has anyone else seen this type of dramatic drop in gas mileage or has something gone wrong with our vehicle? The gas engine seems to be running a heck of a lot more than when it is warm.
You are a victim of Mother Nature, mi amigo !!
Cold weather reduces MPG in ALL cars, not just Hybrids, but it's more noticable in hybrids because we all care so much about the MPG.
Here are some reasons why you will see reduced MPG all winter:
Getting low MPG in cold weather is not a problem with hybrid technology, per se. If it was, there would be ZERO drivers achieving EPA numbers in the winter months, and that is not the case.
There are many reasons for cars not achieving max MPG in the colder months...
Car engines must warm up to a certain internal operating temperature before they most efficiently use the fuel. Winter months and colder temps make that transition from cold start to most efficient take a little longer.
Also: If your car is relatively new, new cars go through what is called a "break-in period" where the metal engine parts are still grinding against each other more rigidly, creating more friction, which also reduces efficiency. Over time, the "extra metal" shaves off and gets lubricated better (expecially if you use Synthetic Oil) and the friction is reduced, which affect MPG numbers.
Winter formula fuels used in most states hold less energy and this also hurts MPG.
Generally speaking, colder weather in many areas means "rain, snow, or slush or ice" on the roads - these things add additional resistance which the tires must push out of the way to contact the road, so they hurt MPG in that way.
Tire pressures also are lowered by the cold weather too. Most people fail to properly inflate their tires all year, but ESPECIALLY in the winter when it is cold and you might have dirty tires and you just dont want to deal with spending time in the cold airing up a dirty tire. Low tire inflation can cause blowouts and adds quite a bit of rolling resistance, which forces the engine to work harder to "push" the car forward, thus using more fuel.
Additional idling uses more fuel and hurts overall MPG, and many people in cold climes by habit or necessity are warming their cars up in the morning. That is good practice to stay warm, but BAD for MPG numbers. While idling in your garage or driveway or carport, it is getting 0 miles to the gallon !!
People who use the defroster in a Hybrid are many times using the A/C compressor to help reduce the humidity in the car and clear the fog. That is a MPG killer too. The compressor can be turned off, but usually by default it comes on.
See this science page for more explanation:
http://tinyurl.com/3s7lo
You might want to invest in an Engine Block Heater, which will help a lot in getting your engine up to prime operating temperature faster. I'm getting one for my 2004 Honda Civic Hybrid very soon.
Good Luck, and hang in there !!!
Now, I'm sure Toyota thought of this and has installed heaters in with the batteries to keep them within certain thermal limits, but it still takes time (and energy) for those heaters to take effect.
As for the tire inflation pressure. It needs to be clear that you still only inflate the tires to the recommended COLD tire inflation pressure, regardless of the time of year or the weather. Having said that it is true that city driving will probably not raise the tire temp to optimum levels and this could affect your MPG. Highway driving should still heat up the tires, so you don't want to overinflate them and then get on the turnpike where the tires will be dangerously overpressurized.
Since my commute is short, less than 10 miles each morning, I lose MPG every day due to the warmup not happening fast enough, regardless of my battery charge.
The battery can be 100% and it will not matter at all if the software is not using the electric drive.
Most battery chargers controlling automative battery charging, alternator output voltage, have a method of sensing ambient temperatures and will charge the batteries to a higher voltage level as temperature declines.
I think they heat the battery compartment. Batteries hold charge better when cold, but they provide energy better when warm...
Thanks for the update, but the point is the same - the batteries are not cold, they are warm...
On cold days when the batteries are colder than their operating range they will be of dimminished use to the HSD system. As the interior of the car warms up (or if heaters are used in the battery compartment) then they will "come on line" as they reach operating temp. While this is happening you are burning gas and therefore getting less fuel efficiency in cold weather.
Conversely, that same is true on hot days when the batteries are above their operating temp. They will not be able to supply peak current and therefore the gas engine will have to pick up the demand.
Just as a point of observation, I think the main reason the batteries are inside the cabin with the passengers is that they perform best with the same thermal range as is comfortable for humans. There is a synergy there.
Hmmm, cuddle up with your hybrid batteries, anyone?
- So far have not seen the charge level go to the top of the battery, just up to the + - signs. Will it normally go higher after running more?
- I have been surprised at how quickly the battery level drops down with the car not running for a few hours or overnight. Is this typical?
- Coast or brake? When I coast, the display shows energy going from wheels to battery but the power meter is at 0. When I brake, the power meter goes down into the blue showing it is charging a lot. So is it better in the long run to wait until brakes are needed to slow down or start coasting and slowing down as soon as possible?
- Brake vs B? What are pros and cons of using B shift position compared to using brakes? Any point to to using B position when approaching stop signs/lights?
jc
Though we tried the RX 400h on a couple of cane haul roads, Lexus engineers were quick to point out that although the RX 400h is technically an all-wheel-drive vehicle, it's not a capable off-roader. True, the mass majority that will buy this hybrid SUV won't ever take on any thing worse that a graded dirt road, or on snow. However, sand is to be avoided. With the aft electric motor being air cooled, there's a concern for excessive heat build up, which would cause the system to shut down (to protect itself), temporarily leaving its passengers stranded. If you want to go off road, the Lexus RX 400h is not for you.
lolop, "Lexus RX 400h" #477, 18 Nov 2004 9:20 pm
PS
I'm glad as an owner you agree with my advice.
The batt meter will show a charge all the way to the top under certain conditions like long down hills where brakes are used alot. But normally it keeps it at about 2 bars below "full" and will turn off the engine before it goes above that.
The HSD batteries are very small. They are only good for short operation and peak demand. The batteries are also very sensitive to temperature so when you come out to the car in the morning they are cold and therefore may display a lower charge level. It is not that they have drained overnight. In fact the propulsion batteries (the ones displayed on the screen) are not used at all when the car is off. That drain is taken from the 12v battery under the hood.
It is always better to coast. Braking (even regenerative braking) has parasitic losses associated with it that eat away at your economy. As soon as you see a need to reduce speed ahead take your foot off the acc pedal completely. This "foot off" (then gradually back on) technique can also be used to maintain a constant speed once you are at cruise. It seems to trick the HSD system into using the eclectics and the ICE together more than it would if you just eased off on the acc.
The B pos uses ICE engine compression to slow the car rather than the electrics. This means you lose the energy that could have been put back into the batteries. It is mostly for long down hills where the batteries are full and you loose the drag caused by the regeneration. It keeps you from having to ride the brakes (disks) so that they will work when you really need them.
Hope this helps you better understand the amazing vehicle you have just purchased. Good luck, have fun.
I sometimes use the B pos to maneuver in traffic without having to move my foot to the brake pedel. But as soon as the need is past, I move it back into D.
Packed sand or sand permeated with water I would NOT hesitate to take my 1978 Porsche Targa out on, being careful with the throttle.
But for that matter other than the conditions I have stated I wouldn't advise taking any vehicle out on with the exception of that otherwise worthless VW powered dune buggy.
Level terrain, loose sand,no sweat.
Packed sand, rolling terrain, no sweat.
Wet sand, flat terrain, no sweat.
Unless you intend to play leadfoot...
And yes, I would take my AWD Rx300, or its FWD equivalent, out on loose sand having driven my 78 Targa on loose sand many times, but very gingerly.
But again, there is NO vehicle other than a dune buggy that I would willingly take out on loose sand for playing leadfoot.
Because, unlike the AWD RX300, the AWD 400h gets it's AWD from all electric motors. If the electric motors work too much, they overheat and simply quit. Bingo, stuck in sand.
For FWD owners, the Prius forum has several posts by Prius owners in which they got stuck in snow when the front wheels lost traction - the computer shut down the entire car rather than let the electric assist overheat. Since both vehicles use the same drive system, I suspect the FWD 400h would do the same.
Can you, or anyone, be certain the Prius "shutdown" was due to overheating of the "drive" motors?
With traction control when wheelspin/slip develops due to engine torque the brakes are used to reduce, control, the rotational speed of the driven wheel(s).
In the case of FWD the engine is also instantly dethrottled since front wheelspin/slip is a certain indication of loss of traction and that can quickly result in loss of directional control.
With RWD the engine dethrottling is typically delayed for a few hundreds milliseconds to allow the driver time to react and feather the throttle.
In any case with the Prius or any Toyota vehicle with traction control if the driver persists with depressing the gas pedal after traction control starts braking the wheels and dethrottling the engine then about 45 seconds later the fractional HP low duty-cycle ABS pumpmotor will be disabled to prevent it from being over-heated and failing.
Having never experienced the above timeout I suspect that with continued wheelslip/spin the engine drivetrain would then be fully disabled.
But my point was/is that if the sand base is packed and/or smooth and you drive in a "smooth" way, feathering the throttle as you would on a slippery surface, then the drive motors would have no reason to overheat.
If you do get stuck and think you need to use wheelspin, say in rocking back and forth, to get unstuck then the first thing to do is disable the traction system. You can do that easiest by unplugging the MAF/IAT module while the engine is running. The engine will die but you can restart it after reconnecting the module.
It will then take a few drive cycles for the engine fault to clear and the VSC/Trac system will again be enabled.
I suggest you read the Prius problem reports of the stuck in snow issue. That will clear things up. The vehicle simply stopped and would not move. I don't recall if it had to be towed to the dealer or if it worked after a certain period of time.
The HSD has the computer deciding if the propulsion system is working correctly or not. There are now two known conditions where the Prius will not move: less than 20% battery charge (won't even startup), and slippery snow situations.
Note that in the Prius you cannot turn off the traction control, which probably would have allowed the wheels to move. I don't know if traction control can be disabled in the RH400 or not.
"If you do get stuck and think you need to use wheelspin, say in rocking back and forth, to get unstuck then the first thing to do is disable the traction system. You can do that easiest by unplugging the MAF/IAT module while the engine is running. The engine will die but you can restart it after reconnecting the module."
You are advocating that the average driver unplug engine modules while the engine is running? I suspect that would void your warranty, and don't think that the engine won't throw an exception code when you do that, which will be recorded and noted the next time the car is hooked up to the engine code analyzer. If the traction control system was meant to be turned off, there would be an "on/off" switch.
Light weight vehicle, TINY tires = low traction coefficient. 45 seconds of wheelspin/slip to the point of disabling the ABS pumpmotor isn't very long so most drivers would simply say "it stopped on me as soon as I encountered the slippery stuff".
And I wouldn't recommend, lightly, disconnecting the MAF/IAT module. But if you're stuck out in the cold with seemingly no other option....
And by the way that specific recommendation to disable VSC/Trac was made to me by the service manager at Lexus of Bellevue as an alternative to the procedure published recently in AutoWeek.
And yes, the system will store a fault code, but no damage will result and if one were concerned about warranty issues you could always "dummy" up... "Gee, I don't have any idea why it would store that code".
If you are unwilling to get the facts then I'm afraid we cannot hold a meaningful conversation on this subject.
RE: Dummying up a code. The codes are generally stored for a specific reason. One might get away with it, or one might get one's warranty voided.
But that's okay, I almost always operate outside the box so a "meaningful" conversation would have probably been useless.
The rear wheels have electric motors whic will overheat if they are used too often. So you could go on those dirt roads, but probably not mud. The AWD is designed for infrequent use, when the front wheels temporarily lose traction. Don't plan on driving it anywhere that you would need a lot of 4WD.
"Thank you for contacting Lexus Customer Satisfaction. We are dedicated to providing superior service. In circumstances that require our attention, we will assist in the resolution process.
The RX 400h is intended for use for paved driving. Off-road use should be limited, for example: a flat dirt road will be fine. Serious off-roading like large mud puddles, fording streams, rock climbs, etc. should NOT be performed by the RX 400h. Your local Lexus dealership may be able to tell you if your RX 400h can handle your local road conditions. We apologize for any misunderstanding you may have had. Please be assured that your inquiry has been documented.
If you require further assistance, please respond to this e-mail, or contact Lexus Customer Satisfaction at 1-800-255-3987, Monday through Friday, 5:00 a.m. to 6:00 p.m., or Saturday, 7:00 a.m. to 4:00 p.m., Pacific Standard Time."
Looks like we can do some driving on non-paved roads.