Electric motor assist frequency and duration questions

sorry, what was the actual question?

 

Sounds like mostly normal behavior.

The electric motors are there to help you accelerate, and to harvest kinetic energy when you brake. The gas engine is there to maintain headway at whatever speed. The gas engine is configured to have excellent economy at steady RPM, but relatively little torque for acceleration authority. Thus the electric provides the real shove to get you going.

If you try to drive all-electric, you're technically abusing the system, but only mildly. It can't be sustained very long unless you recharge the battery, and to do that you either run the engine or stay on the brake pedal without dropping below 6mph.

The way the car is geared, the gas engine must turn at speeds above 37mph.* It doesn't necessarily burn fuel, but it must physically spin to keep the MG1 motor from going over redline according to the permanent gear ratio those two are locked at.

So... speeds in the mid 30s are ideal for long electric glides, and that works out pretty well for saving fuel. At highway speed you pretty much need to burn gas.

Your stated MPG is a bit low, you may want to check that out, but apart from that it sounds like the car is doing what it is supposed to.

*it's 37mph for some, slightly higher for other model years. I don't have that detail in my head but it's always at a locked ratio to MG1.

 

It's sometimes counterintuitive at first, but unless you have one of the plug-in Prius models, ultimately all the energy the car ever gives you goes in through the fuel tank filler hole.

Driving on electric, you are using that energy over a longer and less efficient path. It either got into the battery by running the engine extra and sending charge back to the battery, or by running the engine to get you up to speed or up a hill, and then reclaiming that energy while you slow or descend, and putting that into the battery. The battery takes a cut for itself both when accepting your energy to store and when giving it back again.

So when you're tooling down the road and the gas engine can handle the load without assistance, that's exactly what you want it to do.

 

If your hybrid battery is weak, the gasoline motor will have to work harder and more often, and thus return noticeably lower fuel economy.

Short trips, high speeds (65+ mph), and AC use all hurt fuel economy.

 

In Gen 1 and Gen 2, it is not possible to go above about 44 MPH without spinning the engine. (it may or may not use gas)

In later transaxles, much higher speeds are possible without spinning the engine. There is a new gear, called the motor speed reduction gear, that allows the computers much more discretion in how to best generate power.

 

At the risk of rehashing #5, what you want for HWY cruising mpg efficiency is the least possible contribution from the battery: helping you with acceleration and deceleration, yes, but just staying out of the way during cruise. Which is pretty much what the car does. Anything else will be less efficient.

(I said 'battery' there because there really isn't ever a time when you're moving the car and the electric motors aren't contributing; they're an indispensable part of the power path from the engine to the wheels, and without them, you have neutral. But the simplified dash display will show them 'not contributing' when they are not making a net credit or debit to the battery.)

 

I’m still enjoying 43mpg with my 550,000 Gen 2 Prius Bridgestone Ecopias from Costco.
Commuting 266 miles twice a week at average speeds of 70mph actually lowers my mileage,the 50 mile commute four days a week has a higher often over 50mpg
I say all this to let you know that the electric motors MG1 and MG2 do quite a bit to keep the RPMs of the ICE in its sweet spot 1500rpm 3200 rpm at heart highway speeds. Specifically using the 3200 knotch for periods of acceleration followed by gradual slowing takes best advantage of the Hybrid drive. Avoiding the 5,000 rpm Max reduces oil consumption and avoids higher fuel cost.
Additionally your Prius is collecting data on your driving patterns,reset each time the 12 V battery is disconnected, for several tanks of gas, It feeds this data into its algorithm-your acceleration patterns, Breaking patterns and optimizes how MG1 and MG2 the ICE and the 600volt battery are used to augment accelerations
and regenerative breaking.
The system operates with considerable synergy.
Pay attention to the two sweet spots of 1500 and 3200 rpm use your ear and your foot on the accelerator. You will feel MG1 and MG2 working with the ICE to maximize the torque to the tires. If you push too hard on the pedal the ICE will increase RPM in an effort to sacrifice its efficiency for added torque you requested. It’s the same when starting from a stop depressing the accelerator (that is actually not connected to a throttle plate rather a computer controlling the hybrid system) more than a third engages MG1 MG2 and the ICE at 3200 RPM as you accelerate add another 5% you can feel increased torque though the engine rpm will hold at 3200. Do this consistently for a tank or two and your Prius will learn that you know what you’re doing. Accelerate with this intention hit your speed then use MG1 and MG2 to push that energy back into the battery very efficiently.
Finally the battery loves to be used, and once or twice a week it likes to be over used, say climb 4144 feet at 70mph and then completely recharged coming back down the other side of the Tejón Pass. I’d say your Prius gets to know you in three tanks of gas though it took me more than that to understand all it was doing for me and how I could be a better synergy driver.


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