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Technical information wanted for adaptive cruise control.

SteveAZ

Well-Known Member
Joined
July 15, 2011
Messages
261
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42
City, State
Mesa, Arizona
Year, Model & Trim Level
2021 Lincoln Corsair
There's plenty of info on how Adaptive cruise works but I haven't been able to find anything on the technical aspects. What happens in the engine to slow the car down? when I'm going down a hill in my neighborhood about 25 or 30 and the car begins to accelerate something other than braking takes place to slow the car. It almost sounds like a Jake brake but not so loud. It's easy to know when the brakes are applied but the there must be something else going on when the throttle is off and the car is only picking up speed slowly. If I disable the Adaptive Cruise and only use the standard cruise the car will still slow to the set speed, say 65, but it feels like the car is down shifting but theres no increase in rpm. OK, I think you get the idea. What's going on under the hood?


SH
 



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There's plenty of info on how Adaptive cruise works but I haven't been able to find anything on the technical aspects. What happens in the engine to slow the car down? when I'm going down a hill in my neighborhood about 25 or 30 and the car begins to accelerate something other than braking takes place to slow the car. It almost sounds like a Jake brake but not so loud. It's easy to know when the brakes are applied but the there must be something else going on when the throttle is off and the car is only picking up speed slowly. If I disable the Adaptive Cruise and only use the standard cruise the car will still slow to the set speed, say 65, but it feels like the car is down shifting but theres no increase in rpm. OK, I think you get the idea. What's going on under the hood?


SH
I looked into your question Sharin and found that it is engine braking. The transmission does not downshift, but it also does not coast or disconnect from the transmission. So the friction from the engine is slowing the car. I hope that helps! :)

Cory
 






Cory, Thanks for taking time to research the question. We live at the top of a ten mile grade that at times exceeds 6%. From what I sense there is a lot more going on under the hood than just friction. Maybe valve timing? There is an obvious change in engine sound, like a downshift to fifth gear. I'm just a geek curious about what makes my car tick. Even if you find a more detailed explanation it won't help make my driving any more pleasurable.

Thanks
SH
 






On our '10 F150, when the hill descent kicks on, it does downshift...
 






Well, at least there are two of us who think so. :)

SH
 






Cory, Thanks for taking time to research the question. We live at the top of a ten mile grade that at times exceeds 6%. From what I sense there is a lot more going on under the hood than just friction. Maybe valve timing? There is an obvious change in engine sound, like a downshift to fifth gear. I'm just a geek curious about what makes my car tick. Even if you find a more detailed explanation it won't help make my driving any more pleasurable.

Thanks
SH
After more research, I found it is simply a closed throttle, with the transmission connected to the engine, as opposed to coasting. The change in engine noise is similar to downshifting, except that the gear is in 6th. The valve timing is continuously variable, but is unchanged from any other closed throttle event. Is there something I can help with to make your driving experience a better one?

Cory
 






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