I live in the mountains of Colorado - 8500 ft. I regularly drive my 2004 Prius to Denver - 5280 ft. In between there I have to go through Eisenhower tunnel - 11,00 ft. Not too far up the "hill" I use up all the energy in the batteries. However, I have been able to hold almost 60 mph to the tunnel. I am really impressed that the car can even do it with that tiny engine. Besides, ruining my MPG, am I doing any harm to my engine? My dealership said to drive it like I would any normal car and not worry. But, should I? I don't want to!

I'd be interested to see what you more experienced Prius owners have learned about the car's power output. I'd especially like to learn what you know about pushing the engine when the batteries are drained.

From my experience, I think it is one amazing machine!

 

I don't drive in the mountains, nor kow if the engine can be harmed. But, I believe that the computer control of all RPM's, engine and motor/generators alike, tend to ensure that the vehicle won't LET you hurt it.

Re, climbing: Until the battery is nearly drained: Computer won't allow that to happen either. As the battery gets closer to it's lowest voltage limit, more and more of the engine output will be routed to the battery to prevent ever dropping below a predetermined charge state. So when you say you've used up "all the energy in your batteries", it may be more accurate to say the batteries have reached the lowest charge the system will allow.

The hills around where I live are not long, but some are very steep. If one climbs a hill, and notices the amber arrows indicating flow from the batteries to motor, backing off the gas pedal a bit can result in no feed from the battery. No flow to the motor is being demanded. That means all electrical output from the generator is going to the motor, whilst the battery is loafing. Back off a fraction more, and you'll see charging output to the battery, if it's not fully charged. So, there's a fine line between neither drawing power from the battery nor charging the battery. If you can work that fine line the car will be producing as much power as possible w/out battery draw, and a reduced speed will result. How that would play out on a long, hi alt climb... beats me. Surely reduced road speed, but a greater charge state at the crest. Though the reduced road speed might very well be unacceptable, since the subsequent downhill will recover most, if not all of the battery charge anyway.

Denny_A

 

There was a condition in the first generation Prius known as 'Turtle Mode' and that's exactly the situation you would have gotten if you had one of those: battery at the lowest charge level (40% but shows as empty on the screen) and all power coming from the engine. It would limit the amount of acceleration and also the top speed of the vehicle (86 MPH in the Japan version) but the Prius II (2004+) has eliminated the Turtles by increasing the engine power by about 4.5kW and also increasing the maximum RPM of the small motor-generator to 10,000 RPM so that more power can be generated to feed to the big motor-generator. In general you won't be able to 'hurt' the Prius, it simply won't let you, but driving hard will obviously hurt your fuel economy, so if you can it's best to slow down a little.

 

There was a time - many folks here won't remember - when a car with 75 horsies was considered powerful. You could drive it all you wanted: fast, slow, up a mountain and - yes, believe it or not - people even towed caravans and trailers with cars that had 75 or so hp and a manual transmission. Engines back then were less sophisticated than today.
The bottom line: the ICE in the Prius can do lots of work, you'd be surprised, without being 'overworked'.
It's just today we got spoiled by powerful cars - and 95% of the time we don't use that power, and simply pay for that luxury by burning lots of gas.
My first two cars had less than 70hp, and were great!

 

Remember, in a Prius, you don't control anything, the computers control everything. Your ground speed is translated by the throttle. Your throttle communicates to the computers the velocity you want to go and how fast from a current velocity, or dead stop, you want to get to your new velocity.

The Prius is going to do what you tell it to do, up to the predetermined limits, RPM, SOC, etc. which it has been programmed with. I see no way to overwork the vehicle considering the very conservative limits Toyota engineers have set into the computer system.

Pulling hills is always a lot of work for any vehicle, however they are designed for those situations. Toyota knew that for the Prius to be commercially successful in the American market it has to be able to take the driving conditions that you are experiencing. Sure, if you pull a hill at speed you are going to use more fuel, however at the same time, don't slow down so much in the effort of raising your hill climbing MPG that you become a road hazard.

 

Lisa, the only recommendation I have for you is to switch your Prius to synthetic oil at your next oil change. Synthetic oil protects better at the hotter engine temps and higher rpms which you are generating in the mountains.

Other than that, be glad the car can do so well up there !!!

 

I drove up into Montana earlier this year, and crossed the Continental Divide three times. Climbing didnt' hurt my car, but I kept the speed to around 50 mph on the steep climbs, just to cut down on the noise. On the trips down, I used the B setting intermittently on the very steep slopes to help control the speed going downhill. I still managed in the mid to high 30's for mpg.