slipping clutch in 2005 second generation Prius

[max_frontal_area]

of course it does not have a clutch or even a belt in the CVT tranny...

@ freeway speed, under high loads (2 passengers, considerable amount of cargo all while simultaneously climbing a grade) it sounds and acts just like a slipping clutch. past a certain point more throttle causes engine revs to increase substantially without corresponding increase in speed. additional throttle intensifies problem only. where does the excess power from the additional rpms go?
does it feed into the generator to charge the traction battery?

[RedDevil]

This is normal behavior for a relatively heavy car with a small engine and a CVT of any kind.
You have reached the point where all its power is needed.
At first the hybrid battery will aid, but its resource is not unlimited and will deplete quickly going uphill. From there the ICE is on its own.
A conventional auto would kick down once or twice and run out of revs at some point. A manual would force you to shift down.

The good thing about the CVT is that it will use all the power the engine can provide no matter what speed you go. If the speed drops when the grade gets too steep, the revs remain optimal while the gear ratio matches the speed and the force on the wheels rises, until that matches the steeper grade.

Every once in a while in the mountains you'll have situations where you cannot maintain or get to the speed you'd like, but that is the price you pay for having a car that gets great FE in luxury and safety.
Just keep your foot down. You will get there even if it takes a few seconds extra.

[vskid3]

I haven't climbed any grades at freeway speed in my Prius yet. In my Escape Hybrid (similar hybrid setup), the engine will rev up to 4-5000RPMs to maintain speed going up steep hills using cruise control. Its just the way it is when you have a low-torque atkinson engine.

[max_frontal_area]

so it is simply shifting down for us just like an automatic tranny would do but in an infinitely variable sorta way..

TY!!

[RedDevil]

Yup.
When the revs go up beyond 4000 it is not misbehaving; the poor little thing is pulling its weight.

The engine can produce say 66 kW (on mine). It could theoretically climb 5 meters per second by that, if no power gets wasted to other things like air resistance and such.
On a hot day on the highway, thin mountain air, heavily loaded maybe 2 meter per second rise capacity remains. That is like a 7% incline at highway speed.
The climb rate is indifferent of speed (except for air resistance). At city speed you will still be able to climb at least 2 meter per second, a 15% incline. At jogging speed you could go straight up, if your tires are grippy enough. The CVT won' t budge.
You could climb Mount Everest in little over an hour at that rate. Honk when you reach the top

[bwilson4web]

My recommendation is when climbing, you want to set your speed so there is little or no traction battery draw. Whatever that speed is, you'll maintain it as high as the mountain goes and your climb will be efficient.

Although your 2005 and my 2003 have very similar 1.5L engines, yours can spin up to 5,200 rpm and mine is clamped at 4,500. However, I typically look for a semi-trailer truck and use them as my pacing vehicle. This keeps the engine in a power range where it does not have to use 'fuel enrichment' to avoid overheating the catalytic converter. The fuel trim remains optimum and you'll add altitude about as efficiently as possible at the highest practical speed. Going slower is more efficient but . . . going slower???

Call this the fastest, fuel efficient speed and have a happy.

Bob Wilson