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This weekend I took my one-year old Prius up to the mountains for the first time. It wasn't until I got to the first steep grade that I remembered that there was no second or third gear to shift into.

While ascending the mountain, the engine seemed to be working hard, and when we got to our destination, I turned the car off and smelled that burning smell that you smell in an overheated car. No indicator lights came on, and the car was fine once it cooled off, but it did have me worried.

I couldn't find any advice on driving a Prius up or down steep grades. Does anyone here have experience or links? Was I headed for trouble if I needed to go further up the mountain? Should I have left the engine on when I stopped so the coolant had a chance to cool it down?

Thanks,
 

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There's plenty of monitoring and checking of critical items, such as coolant temp, flow, engine temp, inverter temp, MG temps, oil pressure (granted that is a go/no go). I wouln't worry about it. If you recently had your oil changed, it could be spilt oil on the engine or manifold. A slipping tire could cause that smell too, though you should be well aware if that was the case, considering the sensitivity of TC.
 

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I've driven over the Rockies several times (I-80 and I-70) and got to the point where the battery was depleted and it had to go on ICE alone. All that happened was that I dipped below the speed limit for a few seconds once or twice but nothing else.

On the way down, I just drove it like any other car. I kept it in cruise control and only "touched" the brake when I got over 85. I didn't even need to use the "B" mode to do that since the "drag" from whatever cruise control was trying to do kept me from going much faster than that. I'm not sure if that was al regen or if it used the brakes too but I never smelled any brake overheating or anything like that. If I disengaged cruise control, the car sped up noticeably.
 

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Interesting... sounds like cruise control will try to slow down the car. Do other cruise controls (in other cars) do that? I've never had cruise control... but when renting I thought they just applied gas, not brakes.
 

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CCs in conventional cars just let go of the throttle when vehicle speed exceeds set speed and relies on the car's normal drag to slow it down. In a conventional automatic, that would include drag from tranny and ICE.

The Prius emulates the conventional automatic drag by applying some regen. You can see and feel this regen even though you are not pressing any pedals. The Prius CC simply emulates letting go of the accelerator and relies on the programmed 'default' regen drag. If CC were allowed in B, you would see more drag by regen, slowing the car down faster if a hill were to cause the vehicle speed to run away from the set speed.
 

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Mountain Driving

I drove on an extended downhill stretch coming out of Sequoia National Park yesterday and used regenerative braking for the whole stretch, instead of shifting into "B" like I usually do. At the bottom of the run, I experienced the battery running the ICE to discharge the excess energy from the regenerative braking. I have seen this mentioned on this board, but never experienced it. It's odd, but logical. I will go back to using "B" and cruise control on the rest of this trip (headed for Yosemite, now). Besides, it is easier to let the CC due all the work.
 

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I live on the top of a mountian so I know the feeling of the engine working hard. I have never had a smell though. The engine does rev a lot and the battery depleates, but no smell.
 

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DanMan32 said:
The Prius emulates the conventional automatic drag by applying some regen. You can see and feel this regen even though you are not pressing any pedals. The Prius CC simply emulates letting go of the accelerator and relies on the programmed 'default' regen drag. If CC were allowed in B, you would see more drag by regen, slowing the car down faster if a hill were to cause the vehicle speed to run away from the set speed.
The part this doesn't explain is why when you disengage the CC, the car speeds up noticeably. Without CC, you still ordinarily get the "drag" feeling but it seems to drag more to at least attempt to keep the speed. If what you are saying is all that is going on, you would expect CC and non-CC to act the same. Maybe it has something to do with how full the battery is.
 

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I personaly have not experienced the car going faster with CC disengaged than when it was engaged, but then my encounter with steep hills while in CC is limited. I thought perhaps CC could increase regen past the coast drag default, but everybody's observations indicate that the car can accelerate past the CC setpoint on a sufficiently steep hill, thus requiring pressure on the brake pedal to get the car to slow down, or tolerate the unrequested increase in speed. However, based on your observation, perhaps CC is given access to more regen than coasting, but still has a limit.
 

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Your description matches my observation. The CC can only maintain the speed on a hill to a certain point. Then the speed increases, but not as much as with it disengaged. The only thing I don't know is if it uses regen only, or if it uses some friction braking as well. I know my Sienna with the special laser cruise control distance monitoring thingy applies brakes if needed when it comes up on a car so I know it is possible.
 

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Mine does make a lot of noise, but I figure if it won't go--it won't go. I don't get a weird smell though, but usually I have about 300 miles to go so 300 miles later (no smell). It actually does pretty well compared to most cars going up an incline, to that I'm quite surprised..
 

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First off, there is nothing to worry about with high RPM sounds. The engine is governered at 5k and that is where it stops, no more. On a Japanese 4-cylinder 5k is actually a rather low RPM limit. Most Japanese 4 cylinders actually redline in the mid-6s 7s and even 8ks.

The Prius engine block is 1NZ-FXE. Its parent block is 1NZ-FE (???) which is the block in the now departed Echo, not sure if it was carried over to the Yaris. There is no real significant difference in the blocks other than the valve timing which allows the Prius block to run as an Atkinson cycle engine. I'm not sure about the offset crank (it has been a while since I've seen a schematic, is the crank slightly offset, is it carried over from the 1NZ-FE - Danman???).

Anyway smells can be decieving. I have found strange smells coming out of the engine compartment of just about every car I have owned at one time or another that never returned again. That is the key issue. If the smell is recuring, then you have a problem. If the smell is not recuring, then don't worry.
 
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