Last post on Jan 26, 2013 at 10:00 AM
You are in the Toyota Highlander Hybrid
What is this discussion about?
Toyota Highlander Hybrid, Brakes, SUV
#4 of 137 Re: braking question [cdptrap]
May 11, 2006 (11:41 am)
You're onto something there. I have noticed it on mine. May have something to do with the ISC (Idle Speed Controller). When you are close to stopping, the power flow switches direction and goes back to the wheels (to simulate ICE idle). This could be contributing the surge. Let's see what others have to say.
#5 of 137 Re: braking question [nomorebenz] - the "surge"
May 11, 2006 (1:13 pm)
I've noticed this "surge" only a few times when I've been coasting towards a light or stop sign and the car seems to hit a slight bump in the road - but only when it hits a bump or other obstacle like a tiny pothole. I wondered what it was - felt like the car wasn't braking for maybe half a second and almost like it jumps slightly and then the brakes work just fine. I wondered if it was me or what. . .should we talk to Toyota about this? Is it a safety issue?
#6 of 137 Re: braking question [nomorebenz] - the "surge" [mmreid]
May 11, 2006 (6:07 pm)
the 'surge' is normal as the regenerative braking adjusts depending on the amount of charge needed for the battery.
#7 of 137 Re: braking question [nomorebenz] - the "surge" [mmreid] [katzjamr]
May 12, 2006 (11:18 am)
This may be "normal" but it is disconcerting at the least, and seems like it could be dangerous. Yes, it occurs most often after I have been coasting (like stopping as I am coming to the bottom of a hill). Sometimes the surge or "brake gap" puts me a little further forward than I want to be - and in the case where I might be stopping in an emergency, might put me in the intersection or on someone else's bumper. If anyone learns more from their dealer/mechanic about a possible fix, please post it!
#8 of 137 Re: braking question [nomorebenz] - the "surge" [mmreid] [katzjamr] [poodlgal]
May 12, 2006 (6:05 pm)
I just returned from an 88 mile round trip to a small town up the road using paved 2 lane roads with little traffic. Two things:
First, as I was returning home, I was descending a l-o-n-g downhill grade ;;; ah, regeneration time ( I was traveling about 50mph). At the bottom of this downhill grade was a stop sign. So, I began breaking at a reasonable distance out. Then, about 20 yards out I hit a short (about 2 feet) rough spot in the road. The brakes released for less than a second and reapplied with out my doing anything. The added stopping distance couldn't have been much. But wonder what would have happened if the rough area would have been, say 10 or 20 feet long?? By the way, the anti-lock brake system did not come on.
Second, I was averaging about 27.3 mpg for about the first 200 miles of driving. Then, before today's short 88 mile trip, I was down to about 26.7 mpg and 300 miles. About 50 of these miles were highway and the rest around town (Stop and go but seveal blocks in between the stops). After todays highway trip at 50-55 mph, I'm again up to 27.4. Unlike the EPA estimates, I'm getting better highway mileage than city. I'm thinking that with a long city type stop and go period, more of the ice gas is used for recharging the battery than is the case during highway driving. In a week or so I am planning a 600 mile trip one way utilizing interstate highways all the way. I'll see what it does at 60-70ish.
#9 of 137 Re: braking question [nomorebenz] - the "surge" [mmreid] [katzjamr] [poodlgal]
May 12, 2006 (6:52 pm)
in a true emergency your car is equipped with sensors that know you are pushing harder than normal on the brake and will boost the braking power higher than usual, the surge or brake gap will not happen in an emergency, in fact vehicle will stop more quickly.
#10 of 137 Re: braking question [nomorebenz] - the "surge" [mmreid] [katzjamr] [poodlgal] [katzjamr]
May 13, 2006 (12:46 am)
I believe your observation is valid.
I also noticed this sensation of "brake slip" when braking gently after coasting. The slip is so slight and fast, it leaves little time to react. The brakes kick in right after but it is disconcerting the first couple of times.
When braking more decisively, the slip never happens and the car stops quickly.
I wonder if when we brake gently enough, the system is still using regenerative braking and not the mechanical brakes. If so, it seems reasonable that when a tire loses traction for a second, the VDIM shifts power to other tires causing the surge sensation because of power transfer.
It is possible we normally will not feel this function while coasting or with foot on the gas pedal. It becomes detectable when we are on the brakes because the VDIM operates the braking system.
Just a guess. Someone asked earlier if this is a "problem". I think it is worth a call to Toyota for clarification. If nothing else, the call may cause them to research and look into it. If we all call, they will take it more seriously.
#11 of 137 Re: braking question [nomorebenz] - the "surge" [mmreid] [katzjamr] [poodlgal] [newski3]
May 13, 2006 (8:56 am)
"..brakes released...." "reapplied"
In the instance you describe your "braking" may have been TOTALLY due to regeneration...
If so, and the front wheel(s) began to slip (no ground contact momentarily..?), even ever so slightly, in that rough spot (gravel, sand..??) the regeneration would instantly cease operation (release the "brakes") to simulate what would otherwise be a true Anti-lock Braking System, ABS, "function".
I quite sure, certain sure, Toyota and Lexus wishes they could perform that very same functionality, absent a quick shift into neutral, with engine compression braking. That would improve the overall safety factor of FWD or front biased AWD vehicles substantially.
#12 of 137 Re: braking question [nomorebenz] - the "surge" [mmreid] [katzjamr] [poodlgal] [newski3] [wwest]
May 13, 2006 (10:33 am)
I discounted the cause to be ABS because I did not feel or hear the rapid movement of the brake pedal, which has occurred on all of my other cars when ABS kicks in. Maybe the HH's ABS does not work that way.
An added note: I do not recall seeing (although I must admit I wasn't looking for) the "slip" warning light as the HH manual describes.
The rough spot was just that, rough. I did not even see it with my eyes. No sand or other debris was present. There was a slight drizzle so maybe a tire slip occurred??
#13 of 137 Re: braking question [nomorebenz] - the "surge" [mmreid] [katzjamr] [poodlgal] [newski3]
May 14, 2006 (2:39 pm)
Great information on the mpg.
I am having very similar results as yours.
We live in foothill type community and so are usually going up or down a grade of some type.
Living semi-rural we are getting about 27 mpg but go strictly highway, up & down some serious grades, using cruise and assiting it on the climb till near top, & we are getting 29.4 mpg.
After highway driving & switching to city we've seen 29.6 mpg. Once we start the semi-rural driving again it drops to 27 mpg or so.
This is all by the dashboard. We've mannually calculated the mileage and found it to be about 1 mpg lower than the dash but we are comparing dashboard to dashboard with our older family vehcile which averaged about 17.1 mpg in these same driving conditions.
I too noticed the vechile "surge" while braking. I could be mistaken but found decelerating a little sooner than usual seems to help.