You are here: Forums Hybrid Vehicles Lexus RX 400h RX400H surge power on stopping

RX400H surge power on stopping

14 messages,  Last post on May 20, 2009 at 5:29 AM

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

What is this discussion about? Lexus RX 400h, Accidents, SUV

Messages Page 2 of 2 1 2 Prev Next Last

Go To Msg # Search This Discussion

#9 of 14 Re: RX400H surge power on stopping [marmi] by wwest Apr 25, 2009 (10:44 am)
Replying to: marmi (Apr 24, 2009 6:46 am) I have probably said this before, but...   These are FWD vehicles, so it is EXTREMELY important not to allow braking of ANY kind, engine, regen, or actual frictional braking, to result in wheelskid/slip and therefore raise the potential for an accident due to loss of directional control.   To that end VW has just introduced a new engine RPM control design that will automatically up-rev the engine should the driver inadvertently downshift to a level wherein the rotation decline of the front driven wheels is so rapid lockup will soon result.   So we may now see a resurgence of FWD amd F/awd vehicles with stick shifting.   "..rolling through a toll booth...."   Hmmmm....   Metal expansion joint, slightly WET metal expansion joint.....??   Or "plastic" road striping, WET "plastic" road striping...??   Most modern Anti-lock systems are desired to pre-empt wheelskid/lockup by sensing that the wheel(s) rotation rate is decling so rapidly the lockup will soon result. With light to moderate braking and with the hybrid battery SOC being fairly low you may very well be relying on regen braking ENTIRELY.   If ABS activation is required then regen must first be INSTANTLY cancelled in favor of frictional braking ONLY. For a programmer there is no simple nor easy solution to this problem. The best solution, given the situation, need for ABS due to impending wheel lockup, it seems to me that it would be better/best to bring the frictional braking on line in a moderate way. Previous regen braking level was heading toward wheelskid/lockup, best to bring frictional braking on line at a slightly lower braking level.   So the driver feels a "lurch" forward.....   As I have said before, why not disable ABS altogether unless VSC indicates maintenance of directional control, directional correction, is required..?   The most of those brief instances of low traction due to expansion joints, plastic striping, and "bumps", would be transparent, "non-events".
#10 of 14 Mr. West--help by nmrk Apr 25, 2009 (9:23 pm)
I have read your explanations re the surge--but am now confused. What should I do to either deal with or get rid of this surge problem. I haven't run into anything but it worries me. I am also thinking of getting rid of the car. I like it but don't trust it. On the other hand--is this a common problem with cars utilizing similar technology?   Thanks for your attempt to educate me--but now I am confused.   NMRK Replies to this message: wwest (Apr 25, 2009 10:28 pm) nmrk (May 06, 2009 7:37 pm)
#11 of 14 Re: Mr. West--help [nmrk] by wwest Apr 25, 2009 (10:28 pm)
Replying to: nmrk (Apr 25, 2009 9:23 pm) Is it really a surge or more like what I describe, a slight or moderate loosening of braking..??   A true SURGE forward, actual forward acceleration, would indicate other problems. Replies to this message: nmrk (May 06, 2009 7:37 pm)
#12 of 14 Re: Mr. West--help [wwest] by nmrk May 06, 2009 (7:37 pm)
Replying to: wwest (Apr 25, 2009 10:28 pm) Mr. West:   My Lexus is resting this week--however, when I next drive it, I will try to ascertain whether I am sensing a "surge" versus, as you suggest, a "loosening of braking." You may be correct that what I am experiencing is loosening of braking. I would never take my foot off the brake to coast into a parking place so should not smash into anything. I had the car checked again at the Lexus dealer and nothing appeared to be abnormal.   Thank you for replying.
#13 of 14 Re: RX400H surge power on stopping [wwest] by billysbarn1 May 17, 2009 (3:40 am)
Replying to: wwest (Mar 27, 2009 9:27 am) Here is my pennie's worth! I have a 2006 400h and I notice when going down a steep hill, especially when the engine is cold, (but perhaps that is when I hit the first steep hill) that as I am gently braking the regen is putting a nice amount of power back in the battery and the meter is well into the blue, then after a few seconds the braking lifts off for a fraction of a second, the car runs away and the charging stops but the friction brakes kick in. However, I think that is because I subconsciously press the pedal slightly harder and all is well again. Then I release the pedal and press gently and regen kicks in again and drops out after a few seconds and the process continues as described above till I get to the bottom of the hill.   I thought that was normal and happening because the regen wasn't able to provide enough braking but perhaps not....   I am used to it now and it's no problem to me.   Enjoy your car.. I do I have no intention of changing it for another 10 + years!!   Billy Replies to this message: wwest (May 20, 2009 5:29 am)
#14 of 14 Re: RX400H surge power on stopping [billysbarn1] by wwest May 20, 2009 (5:29 am)
Replying to: billysbarn1 (May 17, 2009 3:40 am) My '01 AWD RX300 does something strange, "washboardy" road feel, when lightly braking going down a slight grade with the roadbed wet. It's as if the ABS is very lightly modulating the brakes. I seem to remember that someone at the dealer told me that it was the EBD, Electronic Brakeforce Distribution, activating.   If your "H" has the same EBD feature then it is likely that regen would have to be disabled when it activates.

Messages Page 2 of 2 1 2 Prev Next Last

Go To Msg # Search This Discussion

You are here: Forums Hybrid Vehicles Lexus RX 400h RX400H surge power on stopping