Differences in Cruise Control function

[Easy Rider]

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?

It should. It does in mine.

If it didn't, why have it there at all ??

 

Any chance you can go down that same "hill" again ?

[md13ffhguy]

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.

[...]

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?

I had a chance to log some highway miles on a recent day trip in my wife's car - the one that has exhibited the "run away" effect while the cruise control is set. I concluded that the effect does not seem nearly as significant at highway speeds, as your experience also suggests. Of course, this all depends on the grade of any downhill stretch. I suspect, as ER suggested, that enabling Grade Assist near the top may have kept you closer to your set speed better than the "default." I'd also be interested in your observations if you get the chance to run that downhill again.

[Texasota]

It should. It does in mine.

If it didn't, why have it there at all ??

 

Any chance you can go down that same "hill" again ?

Unfortunately, I won't be back to that hill anytime soon. Maybe again next year. What would you want me to try when and if I return?

[corncobs]

Unfortunately, I won't be back to that hill anytime soon. Maybe again next year. What would you want me to try when and if I return?

Next year? ;)

[Texasota]

I had a chance to log some highway miles on a recent day trip in my wife's car - the one that has exhibited the "run away" effect while the cruise control is set. I concluded that the effect does not seem nearly as significant at highway speeds, as your experience also suggests. Of course, this all depends on the grade of any downhill stretch. I suspect, as ER suggested, that enabling Grade Assist near the top may have kept you closer to your set speed better than the "default." I'd also be interested in your observations if you get the chance to run that downhill again.

 

Maybe there is a speed threshold at which the HVB charging and ICE compression braking behaves the same as if you flipped the GA button on. In other words, at slower speeds you have to flip on the GA button to achieve aggresive charging and ICE compression braking and at higher speeds it occurs regardless of the GA button state.

[Easy Rider]

Unfortunately, I won't be back to that hill anytime soon. Maybe again next year. What would you want me to try when and if I return?

Repeating the test with Grade Assist enabled at the top of the hill.

 

(Now to go back and read the original story; I don't remember it being used the first time.)

[acdii]

My F150 EB that I had would keep the speed within 5 MPH going down a mountain in Denver, and it had regular CC. Seems odd to runaway in the FFH.

[hybridbear]

From my post here:

 

I tried descending steep grades with only ACC and with ACC & Hill Assist. Both methods yielded the exact same results for regen & vehicle speed. When using ACC only the spinning regen circle would appear and the brake lights would illuminate. When using ACC & Hill Assist the regen circle did not appear and the brake lights did not illuminate. I mostly used the Hill Assist button, but in some situations where I wanted the brake lights to illuminate based on traffic around us I did not activate the hill assist button so that the brake lights would be on.

 

I used the cruise control to speed up slightly on the downhills where appropriate and it worked great. The ACC is very smooth at controlling vehicle speed during regen.

[md13ffhguy]

From my post here:

What speeds were you traveling downhill?

[hybridbear]

What speeds were you traveling downhill?

Most stretches had a speed limit of 65 so 65 MPH mostly. Some stretches had a speed limit of only 55 MPH so then I set the cruise to 55 MPH.

[md13ffhguy]

Most stretches had a speed limit of 65 so 65 MPH mostly. Some stretches had a speed limit of only 55 MPH so then I set the cruise to 55 MPH.

Not surprising then. In my most recent testing, noted a few posts above, the runaway effect was not significant when starting a descent at highway speed. It is, however, surprising to start a descent at 30 mph, only to realize the car is eventually traveling at 50+ mph.

[hybridbear]

Not surprising then. In my most recent testing, noted a few posts above, the runaway effect was not significant when starting a descent at highway speed. It is, however, surprising to start a descent at 30 mph, only to realize the car is eventually traveling at 50+ mph.

In the old FFH we had runaway on these exact same roads.

[md13ffhguy]

In the old FFH we had runaway on these exact same roads.

That was without ACC, right?

 

Gotta like how you can recoup so much energy in that Energi, though!

[hybridbear]

That was without ACC, right?

 

Gotta like how you can recoup so much energy in that Energi, though!

Correct, no ACC in the old one. I do like recovering so much energy in the Energi. It's really nice and contributed to that tank showing as 50+ MPGe on Fuelly going from Albuquerque to Phoenix. It involved climbing from about 5000 feet in ABQ up too 7700 feet at the peak in Arizona and then descending to about 1000 feet above sea level in Phoenix.

[Texasota]

Based on all of the interesting posts here it seems like at higher speeds the standard cruise control operates as if the Grade Assist button was turned on. At lower speeds it seems like you will get the runaway effect unless the Grade Assist button is pressed.

 

In other words, it seems like the GA button only affects the CC behavior at lower speeds. It would be interesting to know what that threshold speed is where the CC slows the car down through HVB charging and compression braking.

[nv rick]

From my post here:

I understand that ACC, both with and without grade assist should maintain the set speed, but wouldn't not using GA have a negative impact on the brake pads and rotors? GA uses engine braking which reduces the need for the brakes to maintain downhill speed.

[hybridbear]

I understand that ACC, both with and without grade assist should maintain the set speed, but wouldn't not using GA have a negative impact on the brake pads and rotors? GA uses engine braking which reduces the need for the brakes to maintain downhill speed.

I believe you are correct for the FFH. Since our Fusion is an Energi we never filled the HVB where we needed engine braking. All our braking was done with regen, no brake pads & no engine braking.

[mwr]

Is there an easy way to tell ahead of time when braking (with the pedal) will use friction braking instead of regen? Just observe the state of charge indicator and if it looks full to the top, then friction braking?

[hybridbear]

Is there an easy way to tell ahead of time when braking (with the pedal) will use friction braking instead of regen? Just observe the state of charge indicator and if it looks full to the top, then friction braking?

If your battery is completely full that you will not get any regenerative braking. Otherwise, it's just a matter of braking gently to not exceed the 35 kW limit. The spinning regen circle on the dash does spin faster when you are getting more regen, but nothing indicates when you hit the limit.

[Texasota]

If your battery is completely full that you will not get any regenerative braking. Otherwise, it's just a matter of braking gently to not exceed the 35 kW limit. The spinning regen circle on the dash does spin faster when you are getting more regen, but nothing indicates when you hit the limit.

The empower display is very effective at letting you know where the threshold is between EV and ICE. It would be nice if there was something similar to make us aware of the friction braking threshold. But, I can easily see that as being distracting/dangerous if we are focusing on that during braking instead of focusing on your driving during braking.

[acdii]

The MKT doesnt have grade assist, and going down the hill of TN the rotors warped using ACC. Thankfully there wasnt much trafic so I was able to maintain speed and have them cool down. They trued up once cooled, but I thought for sure I was replacing rotors that night.

[hybridbear]

The empower display is very effective at letting you know where the threshold is between EV and ICE. It would be nice if there was something similar to make us aware of the friction braking threshold. But, I can easily see that as being distracting/dangerous if we are focusing on that during braking instead of focusing on your driving during braking.

The Prius does have this. The BRK display shows how close you are to exceeding the regen limit.

[Texasota]

The Prius does have this. The BRK display shows how close you are to exceeding the regen limit.

Dang. Now I want it! ;)

[acdii]

you want a PRIUS? Your expelled for the day!

[Texasota]

you want a PRIUS? Your expelled for the day!

 

 

Only the brake threshold inidcator, not the entire Prius. I can't drive an egg with wheels.