Engine braking when going downhill on highway ?

[avidien]

Has anyone experience engine braking on the highway when going downhill ?

I experienced it today on the highway; there was some traffic at the bottom of a downhill, so I slowed down.

Transmission shifted gear from 6th to 5th , then felt the engine braking when going to 5th to 4th gear,

like the car was braking automatically even when my foot wasn't on the brake pedal, very weird feeling.

Is this normal ?

 

[Reggie Watts]

i've noticed this as well and believe it is normal. in fact, when i use the manual mode, i often downshift as much as two to three gears under heavy braking just to benefit from some engine braking. some on this site have said that this is bad for the transmission.

 

[nsbio]

This sounds like a correct behavior and exactly what I would expect from a good driving vehicle. I do this automatically on my manual (pun intended) Mazda3 and I was pleasantly surprised when my automatic CX-9 did the same on a downhill even in auto mode.

 

[voldsom]

I haven't noticed too much engine braking when if full auto mode, unless the cruise control is on. The thing definitely drops gears if it gets going too fast (i suppose since it also can't control the brakes, as the system is the CX-9 is pretty basic). I'll have to keep an eye out for it though.

Something I HAVE noticed is that when in automatic mode and I'm cursing along in 6th or 5th, if a slight hill comes up and the 9 drops a gear, it doesn't register all the time on the dash (maybe 20% of the time it will register and show the lower gear). I've always wondered if that was normal (sorry, not trying to thread jack you avidien )

 

[avidien]

I haven't noticed too much engine braking when if full auto mode, unless the cruise control is on. The thing definitely drops gears if it gets going too fast (i suppose since it also can't control the brakes, as the system is the CX-9 is pretty basic). I'll have to keep an eye out for it though.

Something I HAVE noticed is that when in automatic mode and I'm cursing along in 6th or 5th, if a slight hill comes up and the 9 drops a gear, it doesn't register all the time on the dash (maybe 20% of the time it will register and show the lower gear). I've always wondered if that was normal (sorry, not trying to thread jack you avidien )

no worries Voldsom, yep, I have the same thing happen to me, you can definitely feel the drop in gear and no registering on the dash

 

[eskimo0101]

Mine definitely downshifts to increase engine braking with the cruise control on. I noticed it the last skiing trip of the year because I had already taken the ski box off my car and took the wife's CX-9. I was pretty impressed to be honest, one more thing protecting me from involuntarily donating to the local police in Ashford who always sit at the bottom of a steep hill running radar.

 

[voldsom]

no worries Voldsom, yep, I have the same thing happen to me, you can definitely feel the drop in gear and no registering on the dash

(thumb) good to know it's not just mine, lol. I'll be keeping an eye out for when I'm just coasting to see if it engine brakes as well (other than on cruise control).

 

[sjg]

Something I HAVE noticed is that when in automatic mode and I'm cursing along in 6th or 5th, if a slight hill comes up and the 9 drops a gear, it doesn't register all the time on the dash (maybe 20% of the time it will register and show the lower gear). I've always wondered if that was normal (sorry, not trying to thread jack you avidien )

I don't think you're noticing a gear change. The dash readout seems to correctly display the gear. I do experience the same thing you do where the gear indicator is reading 6 and you're going uphill and you feel/sense an engine/transmission change but the gear indicator stays at 6. I'm pretty sure that what you feel isn't a gear change but the release of the lock for the torque converter. The torque converter locks in high gears at constant speed in the name of better fuel efficiency. When the transmission thinks it needs to do things differently it releases the lock and the engine may speed up a little bit. This baffled me at first but I'm fairly sure this is what's going on.

As far as engine braking goes I use the manual option to downshift for some long downhill grades. I have also noticed the automatic mode will do this as well. If you're going downhill with your foot off the gas it may downshift. It never seems to do enough to really slow down the car but it will keep things from getting too fast. There must be some pitch sensors and programming for the transmission to do this. Again, I haven't seen it slow me down or even maintain speed but it does keep the speed from increasing a lot.