You are here: Forums Hybrid Vehicles Lexus RX 400h Lexus RX 400h: Driving Tips & Tricks

Lexus RX 400h: Driving Tips & Tricks

110 messages,  Last post on Sep 10, 2007 at 8:21 AM

You are in the Lexus RX 400h Forum. Your Host is pf_flyer

What is this discussion about? Lexus RX 400h, Hybrid Cars, Fuel Efficiency (MPG), SUV

Messages Page 6 of 11 1 ... 3 4 5 6 7 8 9 ... 11 Prev Next Last

Go To Msg # Search This Discussion

#51 of 110 engine braking by eman5 Jun 27, 2005 (5:06 pm)
Is there any reason or benefit to downshift to "B"? I haven't found any explanation for this transmission setting in my owner's manual.   PIREP: Only 450 air-conditioned, 50-50 city-highway, carefully driven miles so far, and only 20.1 mpg. Pulling to the right. Great car overall. Hoping the mpg will improve... Replies to this message: rx400_owner (Jun 27, 2005 10:49 pm) eman5 (Jun 28, 2005 6:32 am) rx400_owner (Jun 28, 2005 8:47 am)
#52 of 110 Re: engine braking [eman5] by rx400_owner Jun 27, 2005 (10:49 pm)
Replying to: eman5 (Jun 27, 2005 5:06 pm) Eman, It shouldn't be pulling. There was a post a while ago by someone who had trouble with that (I think it was this board but it might have been another one I read). It turned out the mechanic doing the prep had gotten the alignment wrong. The owner was told that the settings are different between the RX330 and the RX400 so the mechanic had made a mistake.   On mileage, did you reset the mileage meter after you got the car? The prep leaves it with a fairly low reading. Unless you are only making very short trips or have something very adverse going on, the mileage should be better than that even with AC.   You would only use B on a long down grade where the regenerative braking wasn't enough. B engages engine breaking - kind of similar to going to 2nd gear on a conventional transmission except from what I've heard, the effect isn't as strong. For instance I expect to use it coming down the Sierras or the Grapevine in LA. Replies to this message: eman5 (Jun 28, 2005 6:32 am) rx400_owner (Jun 28, 2005 8:47 am)
#53 of 110 Re: engine braking [rx400_owner] by eman5 Jun 28, 2005 (6:32 am)
Replying to: rx400_owner (Jun 27, 2005 10:49 pm) Yep, I've reset the consumption meter several times. I'm taking it in to get the alignment and mpg checked (if it doesn't improve) when the license plates arrive. Will post f/u.   Thanks to you and wwest for "B" info. Does B add any juice to the battery, or does it only affect the ICE? Replies to this message: rx400_owner (Jun 28, 2005 8:47 am)
#54 of 110 Re: engine braking [eman5] by rx400_owner Jun 28, 2005 (8:47 am)
Replying to: eman5 (Jun 28, 2005 6:32 am) "B" only affects the ICE and it will reduce the amount available for regeneration. I assume if you step on the brake while it is in B you will get engine braking plus regeneration plus, depending how hard you are braking, the brake pads.   If you just coast down hill with B on, I don't know if you get engine braking plus regeneration or only engine braking - I haven't had a chance to try it yet. It should be easy to tell if you are getting regeneration. The generator produces a slight whine and the power meter goes into the negative region.   I expect some time this summer I'll get it up into the mountains and get a chance to try out the B function.
#55 of 110 "B"...... by wwest Jun 27, 2005 (9:22 pm)
Enables engine compression braking, sort of a low power "jake brake" if you will.   Typically used as a way to save brakes from overheating coming down a steep mountain pass...   But be extremely carefull using it on wintertime adverse roadbed conditions, reserve your front traction patch for directional control, NEVER braking!
#56 of 110 "B" by wwest Jun 28, 2005 (8:03 am)
Basically the battery will still be charged using regenerative braking but not as fast as otherwise. Just remember to take it out of B afterward or recharging will be low longterm.
#57 of 110 The "B" position by skyfish400h Jun 29, 2005 (5:30 pm)
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. Replies to this message: dylan hixon (Jun 29, 2005 7:08 pm) rx400_owner (Jun 29, 2005 8:19 pm) skyfish400h (Jul 02, 2005 2:00 pm)
#58 of 110 The "B" position by skyfish400h by dylan hixon Jun 29, 2005 (7:08 pm)
Replying to: skyfish400h (Jun 29, 2005 5:30 pm) 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.
#59 of 110 The "B" position [skyfish400h] by rx400_owner Jun 29, 2005 (8:19 pm)
Replying to: skyfish400h (Jun 29, 2005 5:30 pm) 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). Replies to this message: skyfish400h (Jul 02, 2005 2:00 pm)
#60 of 110 The "B" position by skyfish400h Jul 02, 2005 (2:00 pm)
Replying to: rx400_owner (Jun 29, 2005 8:19 pm) 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.

Messages Page 6 of 11 1 ... 3 4 5 6 7 8 9 ... 11 Prev Next Last

Go To Msg # Search This Discussion

You are here: Forums Hybrid Vehicles Lexus RX 400h Lexus RX 400h: Driving Tips & Tricks