Greetings from another happy Prius driver

ICE always power the wheels whenever it is running but only 28% of the torque gets there. The amount of power to the wheels varies between 0% to 100%. Remember, hp = torque * rpm * constant.

0% of the power get to the wheels when the car is at full stop and all the power go to the generator (used to charge battery). The ICE will continue to try to turn the wheels but no power gets transmitted because the wheels are at 0 rpm.

100% of the ICE gets to the wheel when the generator is at 0 rpm. This normally happens on the highway cruising where the torque and power from the ICE is sufficient to keep Prius moving. This mode can be reached around 50 MPH.

I don't think Prius has a timing belt or chain.

 

See the below animation done by one of our member. It is easy to see (at least for me) the two scenarios. I will try my best to describe them.

A simulation of Prius's Planetary Gear

1) Click on THS to activate HSD.
2) Use the mouse to scroll the bars at motor=0, engine=2500 and the generator will be spinning at 9,000 RPM.
3) Click on km/h to see in mph.

You will notice that as you rev up the gas engine, the generator will rev up proportional as well. You can draw a straight line from motor to engine to generator. This is how the PSD is geared and this ratio never changes. If you want to slow down the generator, you need to rev up the motor.

In plain English, the gas engine is making 38 hp which is turning the generator. The output electricity must be charging the battery because the motor is not turning. How do I know the gas engine is making 38 hp? I know the peak power of the gas engine is 76 hp at 5,000 RPM per the spec. I simply divided by 2. This scenario demonstrates 0% of the gas power going to the wheel but 100% is going to the generator.

Set the motor=1800, engine=1300 and the generator will be at 0 RPM. Note that the motor=wheels because they are connected thru reduction gears. Since the generator is not turning, all the power from the gas engine is going to the wheels. In the PSD animation, you can see the motor (blue) at rest. Because the gas engine (red) is turning, it forces the motor=wheels (green) to turn.

In this scenario, 100% of the gas power is going to the wheel and 0% is going to the generator. It is possible that the motor can be consuming battery power to assist if the torque is not sufficient. Let's assume the battery is not assisting due to the slope of the road.

My previous statement about cruising at 50 mph is not accurate because the gas engine needs to rev at 2,100 rpm in order for the generator to be around 0 rpm. The gas engine can rev lower say at 1,400 rpm just enough to maintain 50 mph, the generator needs to rev backward at 2,500 rpm. This is the H-mode where the generator becomes the motor. The motor can become the generator if the HV battery pack is low in juice.