Regen Braking Issue When Turning

[Griswald]

I feel it is a safety issue. The car surges forward. With winter coming & traction decreasing, this could cause a major issue.

That is NOT CORRECT...there is no way in this physical universe that a malfunctioning or quirky brake system could ever make a vehicle "surge forward". All that is happening is the vehicle is not decelerating in a linear manner and YOU "feel" that as surging forward.

 

Physics don't lie...only adding power can make a vehicle go faster.

[FernMTL]

Many of us experience this problem. It's not about the brake system, It's about the regen brakes that stop working for a fraction of seconds, then re-engage. Which makes the car to ''surge foward'' at low speed. Because at low speed, the engine gives power to the wheels even if you don't push the gaz pedal.

It happens to me everytime I turn left under 15 mph while braking, which is everytime I park in my driveway.

 

Not much of a safety issue, until a kid pass by my car when the car ''stop'' braking.

Edited December 4, 2015 by FernMTL

[md13ffhguy]

I don't think my wife or I have ever experienced this in either car, or at least we've not been aware of it.

[murphy]

I don't think my wife or I have ever experienced this in either car, or at least we've not been aware of it.

It is easy to reproduce the "feeling". Find a manhole cover that is an inch or so below the level of the street. Drive over the cover with either front wheel while braking with regen braking only. It feels like the car surges forward but it is actually the instantaneous loss of all braking while the wheel is floating in the air before it drops down and makes contact with the manhole cover. Pressing hard enough on the brake pedal to engage the friction brakes will prevent the "feeling".

 

It happens because regen braking is not possible if either front wheel loses contact with the ground.

[md13ffhguy]

It is easy to reproduce the "feeling". Find a manhole cover that is an inch or so below the level of the street. Drive over the cover with either front wheel while braking with regen braking only. It feels like the car surges forward but it is actually the instantaneous loss of all braking while the wheel is floating in the air before it drops down and makes contact with the manhole cover.

OK, then I'll take back saying never. I have experienced that phenomenon on such occasions. THAT'S what all this fuss is about? While seeming odd, coming from a "normal" car, I'm not alarmed by it. Can't imagine this would ever turn into a recall. Nor do I think this would ever result in anyone losing control of the car.

[corncobs]

I think there is some truth to the "close to an ABS event" comment the Ford engineer. Here is why.

 

So far everything we have heard is at low speed <20 MPH but I had the sensation at least twice on a freeway exit ramp. Even though it only lasts for a fraction of a second at 45 - 50 MPH it's no joke.

 

Reason I think there is some truth to the ABS event comment is that is all instances the ramp was slightly wet and I could definitely feel the car being on the edge of having grip at that speed.

 

Yes I should have taken the exit slower and it wouldn't have happened but the FFH handles so well and predictable (except for the sudden lack of regen braking) it's part of the fun driving this car.

[Texasota]

It happens because regen braking is not possible if either front wheel loses contact with the ground.

If the above is true and this is the cause of the issue reported by the OP, then it would seem very unlikely that the issue was caused by a subsequent software change/fix made by Ford.

[murphy]

If the above is true and this is the cause of the issue reported by the OP, then it would seem very unlikely that the issue was caused by a subsequent software change/fix made by Ford.

Regen braking is applied by the motor acting as a generator. The force is applied to the input shaft of the differential. It is a standard differential, not a limited slip differential. Think what happens with one wheel on an icy surface, That wheel spins and you go nowhere until the traction control kicks in and applies the friction brake to the spinning wheel. If the traction control was fast enough to apply the friction brake to the wheel that is off of the ground the problem would not exist.

[TX NRG]

If the above is true and this is the cause of the issue reported by the OP, then it would seem very unlikely that the issue was caused by a subsequent software change/fix made by Ford.

There are two different situations where the sudden loss of regen deceleration for a fraction of a second results in occupants experiencing the "lurching forward" feeling. In my experience, one has happened all along, the second appears to be new and a result of a software update.

 

One is where one of the front wheels loses contact or traction with the ground so regen braking is deactivated temporarily. I've experienced this on a few occasions over the 2.5 years I've driven my car and have had to quickly hit the brake pedal harder to engage the friction brakes to make up for lost braking time.

 

The 2nd is where regen braking appears to be temporarily deactivated while decelerating while the wheels are turned with the outside wheel rolling slightly faster than the inside wheel. The computer algorithm seems to be misinterpreting this as a wheel slip/loss of one wheel traction situation as in case #1. I've never experienced this in any of my driving. Until tonight. Dry flat parking lot, 55 degrees F, regen braking into a diagonal parking space the car "lurched" when the braking disappeared for a fraction of a second. Almost crossed over the front line of the space. I'll have to watch out for this now.

 

The only thing that changed was that I had my car serviced earlier in the day and had the recall work done with their software upgrades.

[machoman1337]

I read through the descriptions carefully and I'm going to go easier on the braking-when-turning to see if I myself can replicate the issue (and thus do my part to help). It looks like I brake a little more aggressively than you guys do (I tend to have bad luck with lights, and most of the intersections don't have visible countdown timers which makes lights tricky to anticipate) which is why I have yet to feel anything like this.

 

Also many intersections here lack left-turn arrows and those which do have the arrows annoyingly require 3 cars on the sensors to trigger the arrow, which contributes to my frequent use of fast, aggressive turns which tend to invoke the friction brakes early (since I often have to sit in the intersection and wait for a yellow light).

 

As for turning into parking spaces - I back in 99.9% of the time (the 0.1% being for the odd place that draws the lots at an angle to the curb/wall), which could produce different results from front-in parking (never encountered this "slipping").

 

Does anyone know if the gas models of the Fusion experience slipping in the brakes after the PCM/RCM reprogramming? I know the gas models don't have regenerate brakes but if they are also experiencing any deficiency in the braking system that can help us make a stronger case. Hybrids are the minority of Fusion purchases - the reason other complaints were turned into recalls is that the gas model owners also experienced them (e.g. door latches, steering gear bolts) and there were enough voices to attract attention.

 

Still love the Fusion and plan to keep it, but if it's written off in an accident, I may buy an Ecoboost model instead and avoid the highly complex hi-tech powertrain.

[machoman1337]

Tried replicating this myself. If I understand it correctly, there is noticeable loss of braking control for a fraction of a second during the turn?

 

Unfortunately even when I went super light footed I wasn't able to replicate the problem. I experienced slippage once but it was raining cats and dogs so that was probably the real cause.

[hybridbear]

It is easy to reproduce the "feeling". Find a manhole cover that is an inch or so below the level of the street. Drive over the cover with either front wheel while braking with regen braking only. It feels like the car surges forward but it is actually the instantaneous loss of all braking while the wheel is floating in the air before it drops down and makes contact with the manhole cover. Pressing hard enough on the brake pedal to engage the friction brakes will prevent the "feeling".

 

It happens because regen braking is not possible if either front wheel loses contact with the ground.

I have told you many times that this IS NOT the issue being discussed in this thread. Please stop inserting misinformation into the discussion.

 

OK, then I'll take back saying never. I have experienced that phenomenon on such occasions. THAT'S what all this fuss is about? While seeming odd, coming from a "normal" car, I'm not alarmed by it. Can't imagine this would ever turn into a recall. Nor do I think this would ever result in anyone losing control of the car.

No, murphy has been spouting misinformation in this thread. All cars do what murphy describes. He is stating misinformation & causing confusion.

 

I think there is some truth to the "close to an ABS event" comment the Ford engineer. Here is why.

 

So far everything we have heard is at low speed <20 MPH but I had the sensation at least twice on a freeway exit ramp. Even though it only lasts for a fraction of a second at 45 - 50 MPH it's no joke.

 

Reason I think there is some truth to the ABS event comment is that is all instances the ramp was slightly wet and I could definitely feel the car being on the edge of having grip at that speed.

 

Yes I should have taken the exit slower and it wouldn't have happened but the FFH handles so well and predictable (except for the sudden lack of regen braking) it's part of the fun driving this car.

This is also NOT the issue being discussed in this thread. The issue being discussed here happens at low speeds where the car is nowhere near the limit of grip. Experiencing weird behavior when tires are starting to slip would not be unexpected.

 

There are two different situations where the sudden loss of regen deceleration for a fraction of a second results in occupants experiencing the "lurching forward" feeling. In my experience, one has happened all along, the second appears to be new and a result of a software update.

 

One is where one of the front wheels loses contact or traction with the ground so regen braking is deactivated temporarily. I've experienced this on a few occasions over the 2.5 years I've driven my car and have had to quickly hit the brake pedal harder to engage the friction brakes to make up for lost braking time.

 

The 2nd is where regen braking appears to be temporarily deactivated while decelerating while the wheels are turned with the outside wheel rolling slightly faster than the inside wheel. The computer algorithm seems to be misinterpreting this as a wheel slip/loss of one wheel traction situation as in case #1. I've never experienced this in any of my driving. Until tonight. Dry flat parking lot, 55 degrees F, regen braking into a diagonal parking space the car "lurched" when the braking disappeared for a fraction of a second. Almost crossed over the front line of the space. I'll have to watch out for this now.

 

The only thing that changed was that I had my car serviced earlier in the day and had the recall work done with their software upgrades.

The 2nd issue is what we are talking about here. This is another case of the issue being cause by a software update.

[sleamiller]

My FFH has done this twice now. Both were turning into my driveway. The first was a few months ago I believe and it was such a lurch that for a moment I wondered if I had been rear ended as I turned into my drive. I'm usually in EV+ at this point and my road is paved but my drive is gravel. The road goes downhill but the drive is more flat. It happened again two nights ago and I thought I was going to go into the culvert. That kind of acceleration/lack of braking will get your adrenaline going like nothing else. I'm not amused. It is a definite safety issue. I'm taking my car to the dealer next Thursday but after reading this thread I don't have a lot of hope. I stop when I pull into my drive to get the mail so I'm not sure how fast I am going but it's not fast by any stretch. If the dealer can't find an issue then I will log the issue on the NTSB site.

[lolder]

File a report with NHTSA here: https://www-odi.nhtsa.dot.gov/VehicleComplaint/

[hikyuuri]

Old topic, I know, but wanted to add to it.

I never really paid attention to it before, just attributed it to tire slippage, or just how the system handles transitioning from the regen braking to the service brakes as speed decreases. However, I experience the exact same sensation in my 2014 FFH.

 

I have to make a right hand turn at the bottom of a hill every day to get home from work. The hill is long enough that I can coast and achieve 50MPH, though most of the time, I stick around 40 due to the turn (woo, free energy for the battery!). Usually, I achieve a 100% brake score on this hill as I have really timed it out on when I have to brake and how hard I have to break. By the time I enter the right turn lane, I am going around 30MPH, and when I make the turn I am usually somewhere between 5mph and 15mph (weather depending and the mood I am in). Quite often, I will feel the car lurch forward as if the brakes went out, then suddenly brakes will return just a fraction of a second later. Since I didn't actually come to a full stop, I don't get a brake score, but I know it would be quite high (easily above 90%).

 

There are no potholes, manholes, or anything else on this turn. We live in the middle of the country, so there are not even curbs, let alone manhole covers. Just nice, fresh, smooth asphalt. This happens basically any weather (I live in MN, so I get all the extremes), with any cargo weight, and basically any battery charge (except when it is full, in which case the service brakes are already engaged).

 

I get the feeling its something about how the car is trying to transition from the regen braking to the service brakes in the middle of the turn. I *sometimes*, though extremely rarely, get the same sensation when going down a long hill and the car suddenly transitions from regen to service brakes due to the battery being fully charged (around 70 on the SoC). I have never heard the ABS kick in (you can usually hear the ABS pump whining when it is actually being used), so I don't think its an ABS issue on its own, but something with the transition between regen and service brakes.

 

At this point, I just expect it to happen, so I always counter it by over braking during my turns. I have been driving the car for 3 years now, and of all the quirks, this is definitely annoying, but something I have trained myself to expect and work around.

[raulino]

Hey I hope you'll see this given its been a few years since you incident,
I have a similar issue, well now its two.
I've notice this happen to me also (2018 Fusion Hybrid)
I thought it was the road but I've noticed it happens regardless of road quality.
on top of this I had an incident where I felt like the brakes didn't grab on as hard as it should, I was able to recreate the issue once and 
brought it to my local dealership, they said they couldn't find anything so now I've had to open a case with Ford Motor.

Have you experienced anything like this also? where you're on your brakes and they feel like they're not grabbing on as hard as they should?

[murphy]

2 hours ago, raulino said:

Hey I hope you'll see this given its been a few years since you incident,
I have a similar issue, well now its two.
I've notice this happen to me also (2018 Fusion Hybrid)
I thought it was the road but I've noticed it happens regardless of road quality.
on top of this I had an incident where I felt like the brakes didn't grab on as hard as it should, I was able to recreate the issue once and 
brought it to my local dealership, they said they couldn't find anything so now I've had to open a case with Ford Motor.

Have you experienced anything like this also? where you're on your brakes and they feel like they're not grabbing on as hard as they should?

If you go over a hole in the road or a sunken manhole cover that leaves one of the front wheels hovering in the air the regen braking will instantly go to zero.  Because of the way a differential works the floating wheel will turn backwards.  No force can be transmitted back to the motor which is what is providing the regen braking.  The first time it happened to me it felt like the car was accelerating.  Pressing harder on the brake pedal will engage the friction brakes which will resolve the issue.  Nothing is wrong with the car.