Differences in Cruise Control function

[md13ffhguy]

In this thread, I noted some differences in the way the cruise control (CC) functions in our two cars:

 

I have noticed that the cruise control works very differently between the standard CC in my wife's 2014 and the adaptive CC in my 2013. Going downhill in the car with ACC, the set speed is essentially maintained, however, with standard CC, the car tends to run away, picking up a significant amount over the speed limit on some downhills.

 

I ran a little experiment with the cars on a short, but fairly steep hill near my house. Both cars have ECO Cruise set to ON. Initially, I believed the difference in performance was due to one car being equipped with Adaptive Cruise Control (ACC), and the other car standard CC. Now, I'm unsure if that's a reasonable explanation. Both cars have 17" wheels with tires inflated to 38 PSI. Except for the ACC feature and model year, the two cars are virtually identical.

 

For each run down this hill, I set the CC to 40 MPH, and made sure that I was at that speed as I crested the top of the hill from the far side to the downhill test area. I touched neither the accelerator pedal, nor the brake, until reaching the bottom.

 

Car #1 - 2013 FFH SE w/ ACC (mine)

 

ACC ON - Actual vehicle speed increased to 42-43 MPH while descending, and regenerative braking automatically kicked in until the road began to level off at the bottom of the hill, which obviously helped the vehicle maintain a speed close to the set speed.

ACC OFF - Performance was exactly the same as with ACC ON.

Subsequent runs with Grade Assist (GA) turned ON did not have different results, as this feature did not seem to actually engage. I'm assuming that this is because the automatic regen braking kept the vehicle speed below the threshold at which the GA feature engages.

Car #2 - 2014 FFH SE w/ standard CC (my wife's)

 

Actual vehicle speed increased to 54 MPH while descending, and regenerative braking did NOT kick in at all.

A subsequent run with the GA turned ON at the top limited the vehicle speed to 45 MPH.

I first noticed this difference just after purchasing my wife's car, as I was driving it home. While heading down a different hill on a highway, I suddenly realized that I was traveling much faster than planned. My 2013 had kept me out of trouble on this hill, but the 2014 was moving a good 20 MPH over the speed limit before I realized what was happening. Every once in a while, when driving my wife's car, this difference in functionality still catches me by surprise.

[md13ffhguy]

There is also a difference between these cars in how the system changes the vehicle speed when pressing the SET+ button.

 

Car #1 - 2013 FFH SE w/ ACC (mine)

Assuming you've had the speed set at 30 MPH, and you want to increase speed to 40 MPH, pressing and holding the SET+ button causes the displayed set speed to rapidly increase until releasing the button at 40 (if you're good). The car then seems to gradually accelerate to the higher speed. In other words, the new speed is set, and the car catches up.

 

Car #2 - 2014 FFH SE w/ standard CC (my wife's)

 

Assuming you've had the speed set at 30 MPH, and you want to increase speed to 40 MPH, pressing and holding the SET+ button causes vehicle to begin accelerating immediately, as if the SET+ button has a more direct connection to the accelerator pedal, if that makes sense. The displayed speed increases, but it seems to equal the actual vehicle speed. You must hold the SET+ button until the car reaches the desired higher speed.

So, in my car, pressing SET+ feels like changing a computer setting, while in my wife's car, pressing the same button feels like pressing the accelerator pedal. I hope I've described this adequately, as I've struggled to find the right words to describe this difference. All I can say, is that this difference is quite noticeable, when switching from one car to the other.

 

Btw, I'm a frequent CC driver, using this feature on most every road - particularly when driving my car with the ACC.

[mwr]

On my 2015 FFH without ACC (and I don't use ECO) ...

 

- My car maintains the CC set speed downhill. We have lot of hills here, including on freeways.

 

- Pressing the SET+ (or SET-) button quickly and releasing increases (or decreeases) the CC set speed by one mph wih each press and, of course, the car speed changes to that. Pressing and holding either button increases or decreases the car (and set) speed until released. But I'm not sure it that's like your Car #1 or #2.

[corncobs]

md13ffhguy thanks for the investigation this was an interesting read.

 

My 2013 with regular CC and ECO on behaves like your wife's car.

 

+/- to change the speed setting is like mwr's 1 MPH per press.

[Texasota]

My 2013 with regular CC and ECO on behaves like your wife's car.

CC, are you saying you get no regenerative braking going downhill with CC (cruise control) on?

 

On my 2015 with regular cruise (no ACC) I get lots of regenerative braking going downhill. It maintains the speed very well until the hill grade overcomes the regenerative braking ability to maintain speed at which time the ICE begins its engine braking which can be very noticeable because of the increased ICE RPMs.

 

Md13ffhguy, you did a great job of documenting your issue/questions. I followed exactly what you are describing. This is an interesting issue as it sounds like different cars are behaving very differently going downhill. If regenerative braking is not engaging going downhill, then that seems like a significant lost opportunity for charging the HVB.

 

Concerning the SET+ (or SET-) button, if I press mine quickly 10 times the CC set speed increases by 10 and then the car slowly/gently increases to the new target speed. If I press and hold the SET+, then it accelerates briskly until I release it.

[Easy Rider]

My 2013 had kept me out of trouble on this hill, but the 2014 was moving a good 20 MPH over the speed limit before I realized what was happening.

I'm not sure that is right. I wonder if it would be different with ECO off ??

 

I don't remember ever having a car where the cruise would get that far out of whack without it being on a monster grade.....like where they post multiple huge warning signs for trucks.

 

I think one other person has already posted that his similar car has much better control than that.........although the hills might be different.

[corncobs]

CC, are you saying you get no regenerative braking going downhill with CC (cruise control) on?

 

On my 2015 with regular cruise (no ACC) I get lots of regenerative braking going downhill. It maintains the speed very well until the hill grade overcomes the regenerative braking ability to maintain speed at which time the ICE begins its engine braking which can be very noticeable because of the increased ICE RPMs.

 

Did my post indicate this? If so no that's not the case I love every extra regeneration amp I can get. It does regen as long there is "room" in the HVB in downhill and with CC engaged.

 

Edit: I read md's post again and he said that with his wife's car there was no regen. This is odd maybe he meant the regen circle like you see on using the brakes.

I can't recall if the circle appears when the GA is enabled and you are going downhill on CC.

 

There is regen any time you take the foot off the gas pedal and even more going on long downhills.

Edited December 24, 2014 by corncobs

[md13ffhguy]

Edit: I read md's post again and he said that with his wife's car there was no regen. This is odd maybe he meant the regen circle like you see on using the brakes.

I can't recall if the circle appears when the GA is enabled and you are going downhill on CC.

 

There is regen any time you take the foot off the gas pedal and even more going on long downhills.

There's the charging that occurs when moving that's indicated by the upward arrow above the battery icon, when enabled. Then there's regenerative braking, which is indicated by the spinning circle overlaying the battery icon. I get regen braking when going downhill with CC in my car, but not hers.

 

The circle does not appear when GA engages on either car, I assume because engine braking is not the same as the regenerative braking mode.

 

The GA rarely engages on my car, since the automatic regen braking that occurs when using CC seems to be enough to control vehicle speed on most of the downhills I encounter

[md13ffhguy]

- Pressing the SET+ (or SET-) button quickly and releasing increases (or decreeases) the CC set speed by one mph wih each press and, of course, the car speed changes to that. Pressing and holding either button increases or decreases the car (and set) speed until released. But I'm not sure it that's like your Car #1 or #2.

 

Yes, for single presses, they function essentially the same. It's when pressing and holding the button that there's a noticeable difference.

[md13ffhguy]

My 2013 had kept me out of trouble on this hill, but the 2014 was moving a good 20 MPH over the speed limit before I realized what was happening.

I'm not sure that is right. I wonder if it would be different with ECO off ??

 

I don't remember ever having a car where the cruise would get that far out of whack without it being on a monster grade.....like where they post multiple huge warning signs for trucks.

 

I think one other person has already posted that his similar car has much better control than that.........although the hills might be different.

 

Just tonight, we were out in my wife's car, and I drove through a neighborhood, so I set the CC right at the speed limit of 30. There's a long stretch in the middle where there are no houses, and a steep downhill to a railroad crossing at the bottom. Going down, the speed increased rapidly, and would have easily hit 50+ MPH, had I not applied the brakes for the stop sign before the tracks. While the battery was charging on the downhill, no regenerative braking was indicated until I manually applied the brakes.

 

I've experimented with ECO on and off, and it doesn't seem to have any effect on this behavior.

[DeeCee]

Sure sounds like something amiss with your wifes car. Whenever I go downhill with ACC engaged I get regen braking to hold the selected speed.. Maybe our Ford rep on the forum could chime in here?

[Texasota]

Did my post indicate this? If so no that's not the case I love every extra regeneration amp I can get. It does regen as long there is "room" in the HVB in downhill and with CC engaged.

CC, I asked that because you said your car behaved like md13ffhguy's wife's car which is the one that runs away like a freight train going down hills with cruise control on.

 

Maybe part of the confusion in this conversation is the term "regenerative braking" that we are using. I used that term (perhaps incorrectly) to indicate that my FFH maintains speed and charges the HVB while going down a hill but I have never noticed the spinning circle overlaying the battery icon when this happens. I think the only time I get the spinning circle is when pressing on the brake pedal but I could be wrong.

Edited December 25, 2014 by Texasota

[corncobs]

CC, I asked that because you said your car behaved like md13ffhguy's wife's car which is the one that runs away like a freight train going down hills with cruise control on.

 

Maybe part of the confusion in this conversation is the term "regenerative braking" that we are using. I used that term (perhaps incorrectly) to indicate that my FFH maintains speed and charges the HVB while going down a hill but I have never noticed the spinning circle overlaying the battery icon when this happens. I think the only time I get the spinning circle is when pressing on the brake pedal but I could be wrong.

Yes I agree like I said in my previous post I misread that part and my car definitely behaves different the his wife's car and charges the HVB going downhill.

 

I also agree that some confusion is added by the terminology. For me I have regenerative energy every time I coast or slow down using brakes or not.

[hybridbear]

This is also something I've found from having a Fusion without ACC and one with ACC. In the 2013 without ACC the cruise control cannot apply the brakes. Thus you get no spinning regen circle on the display. When you take your foot off both pedals you get about 8 kW of braking. This is all regular CC can do when going down a hill unless you engage the hill button on the shifter. When you engage the hill button on the shifter the car will enable regen up to the 35 kW limit, but you still will not see the regen circle spinning.

 

With ACC the car has the ability to control the brakes and turn the brake lights on. There is a completely different module governing the behavior of ACC. Thus, ACC will activate the spinning regen circle and turn on the brake lights when the spinning regen circle appears (IIRC the brake lights come on in conjunction with the spinning regen circle). That's why the hill button isn't really necessary with ACC because the car is applying the brakes for you. ACC braking will exceed the 35 kW regen limit and use the friction brake pads when needed. It would be interesting to test on a long mountain grade what happens using ACC without the hill assist button and with the hill assist button to see how the car responds. I wonder if ACC without the hill assist button will not turn on the ICE as an air pump for braking, but rather just use the brake pads. I wonder if then ACC with the hilll button would turn on the ICE as an air pump when the braking needs exceed 35 kW rather than using the brake pads.

 

Note: if the HVB is full then that 35 kW limit drops to 0 or near 0 and thus your only source of braking is brake pads or ICE compression. When we took the black FFH across the Rocky Mountains we had stretches where the HVB was full and thus we had no regen braking. On some of the mountain grades in that scenario even the ICE air pump couldn't keep the car from speeding up and I had to use the brake pedal & brake pads to keep us from going out of control. I really want to drive through the mountains again with the Energi where I can regen about 5.5 kWh into the battery versus only about 0.5 kWh maximum in the hybrid.

[hybridbear]

On my 2015 with regular cruise (no ACC) I get lots of regenerative braking going downhill. It maintains the speed very well until the hill grade overcomes the regenerative braking ability to maintain speed at which time the ICE begins its engine braking which can be very noticeable because of the increased ICE RPMs.

Do you have the hill button on the shifter turned on in this scenario? If you have the hill button off and are getting lots of regen and then the ICE turning on as an air pump this is a programming change compared to the 2013.

[md13ffhguy]

Do you have the hill button on the shifter turned on in this scenario? If you have the hill button off and are getting lots of regen and then the ICE turning on as an air pump this is a programming change compared to the 2013.

Based on his later post, I don't believe he was referring to regenerative braking, but rather that the battery was just being charged.

[Easy Rider]

Sure sounds like something amiss with your wifes car.

I agree. You should get it checked out. Sounds like somewhat of a safety hazard.

 

Given the way that major dealer's service departments work, however, (not just Ford), it might be necessary for you to find a hill to demonstrate the problem and THEN find another similar model to see if it works differently or not.

 

And if ALL of the cars of a given year and model work that way, I'd be tempted to send a comment to the NTSB.

[md13ffhguy]

I agree. You should get it checked out. Sounds like somewhat of a safety hazard.

 

I still don't have a feel for what others with standard CC experience in similar situations. I guess those who travel mostly on flat terrain aren't ever going to notice one way or the other.

[hybridbear]

I still don't have a feel for what others with standard CC experience in similar situations. I guess those who travel mostly on flat terrain aren't ever going to notice one way or the other.

As I explained, the two systems work differently. Without ACC the car does not have the ability to slow you down any more than the slight drag that occurs when you don't touch any pedals. If you want the car to be able to slow you down you must activate the hill button on the shifter, however, this button will not activate the brake lights.

 

ACC is a completely different system which controls not only the accelerator pedal but also the brake pedal. Thus it can activate the brake lights & brake for you.

 

Each of your cars is behaving as designed, they just have different designs.

 

Other cars I've owned with standard cruise control will also speed up going down hills because their cruise control system does not have access to the brakes. Some cars may automatically downshift when using cruise control to slow you down. The FFH does its version of downshifting to slow you down only when you activate the hill button on the shifter.

[md13ffhguy]

Thanks, hybridbear, for confirming what I initially thought - that the difference is due to whether or not the car is equipped with ACC. I began to be concerned when others indicated surprise about the performance of my wife's car, but I guess it's normal.

[Texasota]

Do you have the hill button on the shifter turned on in this scenario? If you have the hill button off and are getting lots of regen and then the ICE turning on as an air pump this is a programming change compared to the 2013.

I have played with it both ways (hill button both on and off). But, your explanation of what happens with standard CC and ACC is now making me wonder how much regen I was really getting with the hill button off. The hill I have been experimenting with may not be steep enough to experience the full behavior you explained. I'm curious now and will watch this closer on my next steep/long grade. Thanks for the great explanation. This is the part of your explanation that I want to watch for:

 

 

This is all regular CC can do when going down a hill unless you engage the hill button on the shifter. When you engage the hill button on the shifter the car will enable regen up to the 35 kW limit, but you still will not see the regen circle spinning.

 

Is there a way to tell how much kW regen I'm getting from one of the instrument panel displays? Or is that only available with a scan gauge or similar tool?

 

 

Based on his later post, I don't believe he was referring to regenerative braking, but rather that the battery was just being charged.

Yes, that is correct. Using the "regenerative braking" term added confusion to the discussion.

Edited December 25, 2014 by Texasota

[Easy Rider]

It may be doing all it can do.

 

I must admit that I haven't had the guts to let the speed increase to +20 or more in any of my previous cars because I chicken out and either downshift or touch the brakes.

 

This may be why they added the "downgrade assist" function in the first place........since downshifting really isn't an option.

[Texasota]

I suspect the "run away" effect will be much more noticeable when beginning at a slower initial speed. Md13ffhguy began his downhill tests with the CC set at 40 MPH and he described the car with traditional CC as speeding up to 54 MPH.

 

When I have experimented with this I had the CC initially set to 64 MPH. The braking effect of the aerodynamic forces at 64 MPH (as opposed to 40 MPH) is much larger and is probably a significant reason why I have not noticed the "run away" effect being as large as md13ffhguy has experienced.

[hybridbear]

Is there a way to tell how much kW regen I'm getting from one of the instrument panel displays? Or is that only available with a scan gauge or similar tool?

Unfortunately this data isn't available on the instrument panel.

[Texasota]

Do you have the hill button on the shifter turned on in this scenario? If you have the hill button off and are getting lots of regen and then the ICE turning on as an air pump this is a programming change compared to the 2013.

I had the oppurtunity recently to observe the behavior of my 2015 FFH doing down a very long 6% grade while having the standard cruise control (no ACC on my FFH S) set at 56 MPH.

 

I did not have the Grade Assist button fliped on (I am 100% positive that was the case). As my FFH began the descent these were my observations:

 

1. Without applying the brakes the HVB was being charged while descending the grade and it achieved the fully charged state rather quickly. I'm not positive what the charge state was at the beginning of the descent but I think it was around 2/3 full.

2. While the HVB was being charged I did not get a spinning circle overlayed on the battery graphic and the MPHs did not increase to any significant degree during this phase.

3. After the HVB charge indicator showed the battery was fully charged I then noticed I was getting ICE compression braking. I watched the RPMs of the ICE during this phase and the RPMs continued to increase in a progressive fashion until the RPMs reached approximatey 4000 RPM.

4. At that point my FFH continued to slowly gain speed and when it hit exceeded 65 MPH I started applying the brakes to slow down and I presume that was 100% friction brakes since the HVB was fully charged.

The behavior of my 2015 does seem to be very different than what has been described in the above posts. This seems to indicate that the programming has been changed for the 2015 models. It also makes me wonder if the GA button does anything over and above than what I am getting by the default behavior of my 2015 FFH?