NHTSA Tracking Braking Loss on Prius Hybrids

There was an autospeed article a while back in which the author adjusted his NHW10 regen to be stronger by modulating the pressure sensor signal with a potentiometer.

Assuming the Gen III uses the same sensor feedback, this may be a way to avoid the sudden transition for those who find it jarring. Reduce regen. But since this only seems to happen when the wheel slips or locks up momentarily, it might need a more nuanced approach. IE: software change.

The article has a very good explanation of the braking system too.

Here it is: Autospeed. A World First: Modifying Regen Braking

 

I may be in a unique position to reply to this issue. I owned a 2007 Prius and presently own a 2010 Prius. In regards to the loss of braking, this precise and exact same behavior occured on my 2007 Prius as it does on my current 2010 Prius. In either vehicle, if the driver is applying the breaks and hits a pothole, brake force is lost for a fraction of second. It may be perceived by the driver as longer than a fraction of a second because it can be somewhat frighting when it occurs. However, I assure you the loss of brake force does not persist for more than a 1/5 or 1/2 a second. Is this a problem? That is not for me to answer as I have never encountered a unsafe situation due to the issue. Regardless, I just want to make sure everyone is clear on one point. This is not an issue that is unique to the 2010 model year. I hope this clears the air on that aspect of the issue.

 

During the winter, freezing water under a repaved road leads to potholes like this one:

When I hit this pothole at speed while applying the brakes, there is the illusion of reduced braking ... but that happened in the past with any other pothole or vehicle. I seriously doubt this is the same as others have proposed:

• 5 ft length
• 3-4 inches deep

Bob Wilson

 

Sorry but I think that conclusion based on your personal experience might be premature.
I think it is interesting to hear from owners that have had both Generation 2 and Generation 3 Prius. However I would offer that even if you have owned both, and think you have experienced the exact same sensation in both, that doesn't mean there still isn't a difference with this "problem" between Generation 2 and Generation 3.

Information is still being gathered, definition is still being created. BUT if it turns out to be a related to a calibration issue, then there could easily be a difference and a reason the sensation seems worse with the Generation 3 BUT only some people with a Generation 3.

I have been told within this thread that the Generation 3 has a stiffer suspension. It's heavier and also has a more powerful engine. So let's say it is related to how the brakes are calibrated to react and sensors within the system being activated. (admittedly this is pure unfounded speculation, but bare with me) Let's say you have driven a Generation 2 for years and were used to the realities of the braking system. Your familiar with the sensation as manifested with your Gen 2, you purchase a Generation 3. Since it's a specific situation maybe you just don't experience often and/or when you do, you note that it's simply the same sensation you remember from your Gen 2. But if it has something to do with how the brakes are calibrated, then it could be different for one Generation 3 to the next. Maybe (and only maybe) the calibration isn't consistent. Maybe a certain percentage of Gen. 3's need to be re-calibrated. If your's IS calibrated correctly, your just going to chalk it up to being the same benign symptom or reality you always lived with, and probably think anyone else experiencing it or reporting it is either crazy or exagerating, when perhaps they aren't.

Don't jump all over me or flame me, I know this speculation is only pure speculation, I hope information continues to be gathered and ideas/experiences shared until a clearer definition exists. BUT I'm just presenting a hypothesis that could explain why some people seem to be experiencing something more often and more harshly than others.

I wish we could get someone who thinks it's not a problem and has experienced the problem in both generations, to drive the car of someone who thinks it is replicatable experience and IS a problem. I think it would take just one or two trips over a pothole or manhole cover for the person that has had both Prius to either say, "This is the same sensation I've always felt" or "No, in this particular vehicle it seems different".

Obviously with many people drawing conclusions based on their own personal experience, either with Gen2 or Gen3 or both..it becomes difficult to evaluate. I just think that there are at least some speculative reasons that "could" exist that make one persons experience with a Generation 3 different from another persons experience with a Generation 3.

 

Perhaps you should PM "Indyking" who wants to sell his Prius. You'll get some 'skin in the game' for probably a quite affordable price. He hasn't reported the braking anomaly and I believe we have one report from the Portland area.

Bob Wilson

 

ElectricMe -

The poster you are responding to has valid points, and a valid experience to relate. He's owned both G2 and G3 Prii, and has experienced (essentially) the same thing in both generation cars. Were both of his experiences identical? Maybe not?? But that's not the point. He's saying that what many of us have expereinced on our G3's, he too has felt on both his G3 and G2. Clealry, this indicates two things to me: (1) This problem, or something very similar has existed long before the G3 went on sale and (2) There would appear to be a common factor to both the G2 and the G3 that contributes to this phenomena. Were all sensations caused by exactly the same thing? Too early to tell, but, as and engineer myself, I would first look at systems common to both generations to find the answer.

You, on the other hand, have no Prius, and have never owned a Prius. So you are right about one thing - your "speculation is only pure speculation". I'm really not sure why you bothered to post what you did, that is, be critical of someone who's relaying his own expereinces with both the G3 and the G2. While you are entitled to your opinion, I think most of us here value the opinions expresed by those that actually own a Prius, far more than those that are on the outside looking in.

At this point I'm hesitant to label you a troll, but you're certainly headed in that direction.

 

I just have to say that the constant meta-debate, driver bashing, trolling, pontificating, et al, has rendered this thread all but useless. I've watched it for weeks and tried to help as I could, but at this point, I think it we would be better off with the thread locked and deleted if it can't get it back to being a useful vehicle for discussion of the problem.

 

This really comes to the heart of the debate: Is this a real problem or a problem of perception. Without repeatability, there is no way to answer that question. Bob's approach is the best we have at the moment.

I, for one, especially appreciate hearing from posters that own or have owned both the Gen II and Gen III. At the moment, that is the closest we have to a controlled study.

Tom

 

2/6/10 Update: As I posted on an earlier reply in this thread, now that I know Toyota has admitted there IS a problem, perhaps I did not experience the extreme sensation others have been talking about but to date, this is the only instance of feeling anything. Since there is a new software "fix," I will of course want that applied to my car.

I have previously posted the same thing; I had a 2005 Prius and now own a 2010 and have felt what appears to be the same sensation in both cars. In truth, I have only felt this once in the 2010 but I've only had the car about a month now. My wife is the daily driver and tells me the car's braking seems to be fine and that any momentary (fraction of a second) loss of regenerative braking is familiar to her and she is not concerned about experiencing it in the new car (she has not personally experienced it yet in the 2010).

So, my perception of this issue to date is that it is a non-issue. I (we) are aware of all the posts and the NHTSA tracking of this "issue" but to date, feel it is just normal hybrid regenerative braking behaviour in certain situations. If we expereince a braking phenomen/experience that is different or more extreme, I will surely post that.

Of course, I cannot comment on what others are experiencing or their perceived braking issues that they feel might be causing a safety issue; everyone's perception of this event is different.

We have a Level V 2010 Prius that was manufactured on November 27, 2009 and I posted previously on where the one "incident" happened.

 

After 3800 miles on my new 2010 Prius IV, I finally experienced the braking sensation discussed in this thread. My other cars are an '87 Landcruiser and a '97 Camry, so I don't have modern automotive braking with which to compare the Prius. However, it occurred on a railroad crossing under light braking during one of our rare California rainy weeks. Since I drive that route daily under ~99% dry conditions and almost always brake lightly in that spot, my single data point might suggest that poor traction is involved in some way. Reading about this effect on Priuschat meant that I wasn't even startled and knew that braking authority would be recovered by pushing slightly harder, although it took another fraction of a second to do it. So, whatever causes this effect, constructive discussion on this forum helps!

 

Maybe I didn't make my ideas clear enough. All I'm saying is that it is that it is an assumption to assume because one's personal experience with a Generation 2 and a Generation 3 feels the same to one owner, or even a lot of owners doesn't mean there isn't a problem. This "might" be a problem that isn't consistent in presentation in every generation 3, and if it has something to do with brake calibration that could easily be the case.

I'm not saying the OP's observations are not real, or not valid to him, just that ones personal experience with 2 Prius is not a definitive base to say the problem is inmaterial.

I did NOT want to use this as an example so I rambled a lot but to use an example, we all know of the recall, and Toyota evidently had two suppliers of gas pedals. So if you are a North American owner of a 2010 Camry you could experience the defective gas pedal, report it in a forum and have a lot of owners of 2010 Camry that have the different gas pedal installed that never would or will experience the problem say "This is my experience, my perception and reality of my gas pedal is different, thus I define it as NOT A PROBLEM. ......if you are truly searching for answers this is a dangerous thing to do.

I'm not trashing the OP or saying that he is incorrect, I'm just saying we have learned recently that auto manufacturing isn't always "perfect" and that there are hypothetical, speculative situations that could result in some Generation 3 owners experiencing similar but different degrees of this "problem". If it's inconsistency in calibration? I think it could easily be the case.

As far as my being a troll....head me in any direction you wish. I'd said it before but just ignore me if you don't like me. I'm not presenting information with intent to inflame or illicit negative response, but I won't shy away from an unpopular opinion just to make people happy either.

I take real exception to your statement that I'm being critical of the original Posters personal observations. I'm not. But it's speculation as well that this is "The Exact Same Problem-Sensation" as the Generation 2.--This hasn't been proved and shouldn't be accepted based on personal experience. It should be thrown into the mix as a possible reality but not accepted as the definitive truth. Again, unless you can prove that this problem/sensation is being experienced "exactly the same" between all generation 3 owners, then it's too dangerous to do.

I applaud the efforts of many people to define this problem and work towards an answer. However, what I see is often a case of I like your opinion and consider it valid and real if it's an opinion I want to agree with, but I dislike your opinion and find it invalid and trollish if it's an opinon I don't want to agree with.

 

Sigh....I'd use Smilies..but I hate them. Just to clarify I appreciate the input from Gen 2 and Gen 3 owners as well. My post was not meant as an attack on the person or the opinion. It might turn out that this is "exactly the same" sensation that exists in Gen 2 and Gen 3 braking systems. But if you don't want people jumping to conclusions or making assumptions that there is a problem based on reported opinions that it IS a problem, then quite simply you cannot afford to do the same thing on the other side. You cannot jump to the conclusion that it isn't a problem because some people that have owned a Generation 2 and Generation 3 feel that it is the same and safe sensation. And I agree we need a controlled study and Bobs approach is the closest we can have within a forum thread.

To others, I have been criticized for not owning a Prius. What can I say? I don't own one. Maybe I can't even explain my interest in Prius...I myself find it odd. But I've grown to appreciate the entire Hybrid, alternative automobile world. So I hang around Prius Chat not only to keep up with the latest news on Prius, but also it's a great forum for breaking news within the whole automotive world.

I haven't tried to fake anything. I've never offered an opinion under the guise that I'm an owner. I don't quite understand the hostility however because I have an opinion and I'm not an owner. I understand that I can't offer personal experience observations.....and I don't...but isn't it a good thing sometimes to have someone who perhaps doesn't have that "ownership prejudice"?

I can't defend the fact that I'm NOT an owner. I don't think I should have to. As far as this thread goes, my interest is based on concern about the problem, coupled with the fact that I like a mystery, I like a problem. I've followed this thread almost like reading a detective novel. How this get's defined and ultimately plays out is the solution...and I like the pursuit.

Anyway, I feel like abandoning this thread, just because whenever I offer any opinion that strays from the idea that this just isn't a problem I immediately get attacked as being a troll and NOT being an owner...which I think is unfair.

As a separate question, do most people think Prius Ownership is a 100% needed prerequisite for participation in Prius Chat? Like I said, I think NOT being an owner sometimes is an advantage as far as offering a potentially different P.O.V. on many issues.

I've enjoyed Prius Chat. Overall I like the community. But nobody likes being beat up all the time or being surrounded with obvious and subtle accusations.

Maybe it will make a lot of you happy, but I'm really considering just using Prius Chat as a news portal and not participating in discussion anymore. To take an Nixonesque pose, you won't have The Electric Me to kick around anymore....

 

What? Is this English?

Excuse me? Nobody here needs you to explain what is, from what isn't. People will assume whatever they want from this persons post. As I already pointed out to you - this person's "perspective", as the owner of both a G2 and G3, is far, far more valid than someone, such as yourself, who does not own, nor has ever owned a Prius. One should not lecture to others, or pretend to know more, about something they have not experience themselves.

What? Where did he say that? Please point this out, because I think I missed it.

He's relaying his experiences. He said nothing about it being "definitive". Period.

But I'll go so far, based on several posts on this web site from G2 owners who describe a similar experience on their vehicles, to what G3 owners are reporting...I'll go so far as to say this "penomena", or "problem" is NOT unique to the G3, and if it is an actual defect/flaw, then I would look in systems that are common to both the G2 and the G3. That said, and if it is an actual defect/flaw...why hasn't the NHTSA done an investigation, as it appears that this phenomena/feeling has been around for quite a while?

 

First issue...Clunky, bad english...but understandable...so don't be petty....

2nd issue...Again, I'm not attacking the original posters "experience or idea" but if you missed where it was being presented as "definitive". Period. Re-read this part...

"Regardless, I just want to make sure everyone is clear on one point. This is not an issue that is unique to the 2010 model year. I hope this clears the air on that aspect of the issue."-from the original post.

That sounds pretty much like it's being presented as definitive to me.

Now who's being the troll? Seems to me like your just posting things against me, in an effort to get response from me....that's personal trolling.

 

LOL. Yep, it's not unique to the G3. If you've actually read many of the posts from G2 owners (not just this guy), you would know that this feeling is NOT unique to the G3. In fact, this has been in the press (and not just reported on Prius Chat) that this "sensation" existed in G2 models.

So that part is "definitive" (as far as I'm concerned).

But what's NOT "definitive" is that there is, or is not an acrual component, design or software flaw. He says nothing about that. That is still TBD.

 

I never said the feeling was unique to the Generation 3. What I have proposed is that there might be reasons why the sensation seems to be experienced to different degrees by Generation 3 owners, and why a 2nd Generation owner that now owns a Generation 3 might feel it is exactly the same sensation but that not mean that his experience isn't different from another Generation 3 owner.

It might not be a consistent component, design or software flaw throughout the entire Generation 3 line. If it has anything to do with individual calibration of the brakes it is likely it is not.

This is a HUGE thread, but I do believe there are a few posts from Generation 2/3 combo owners that say they feel it is a different sensation.

My opinion is that we have the same "action" happening...but potentially due to unknown factors different degrees of it's perceived or real severity.

 

This individual, who owns a G3, and use to own a G2 said he expereinced the same thing on both vehicles. It's his experience, not your's, and not mine. Further, I've read several other posts on here that have said the same thing. Why do you feel it is your job to second guess what they have experienced, or to speculate that maybe they didn't experience the same thing?? What is your point?

 

It's worth bumping this post - His experience.

 

The Electric Me makes a good point, but it is getting lost in all of the long winded posts. In a nutshell, his point comes down to this:

1) Both the Gen II and Gen III exhibit some sort of brake loss sensation.

2) It may be the same in both.

However:

3) There *may* be something in the Gen III that causes it to be more prominent, or perhaps happen more often. This could be from the hardware, software, or only because more new owners are buying the Gen III.

Tom

 

Tom,

All speculation, and isn't there already enough speculation on this thread? That's my point.

However, what we do know is that several posters (not just this guy), as well as reports in the press, have said this same sensation was felt on G2 cars.

"this precise and exact same behavior occured on my 2007 Prius as it does on my current 2010 Prius."

Without additional facts/data/information, what is the point to second-guess this individuals observation that they were the same feeling? He says they were (pretty emphatically, I might add)....so I will tend to believe him until other data/info says otherwise.

To be clear, I am NOT precluding that there may be differences, but without additional supporting information, what point does it serve to further cloud the issue with pure speculation?