Does the electric motor help hwy mpg ?

Yes, by allowing infinite gearing so that the engine can run at an efficient speed. At high speed it can act as an overdrive.

Even if it didn't, there is no way for a Prius to run without using at least one of the motors to lock the sun gear. In that respect, the electrical system is always involved in moving a Prius.

Tom

 

I belive so. I always see people posting in here that if they removed the hybrid parts of the prius it would do alot better on the highway cause of the weight difference. My question is why are there no other cars that get 49+ mpg on the highway????? It must help alot. Most of my driving is at either 55mph+ or 65mph+.

 

I suspect that a big part of the reason you don't see non-hybrid vehicles that get Prius MPG on the highway is that manufacturers believe (and they may be right) that consumers wouldn't buy a vehicle that has the acceleration of a 3000+ lb vehicle with a power output of 98 hp @ 5200 rpm.

The aerodynamics of the Pruis also help significantly with the hwy MPG.

So for a non-hybrid vehicle with Prius MPG, you'd need a vehicle that looks like a Prius, but has significantly less peak power output (since it woudn't have the power output of the electric motors).

 

From my observations, it does help with Highway MPG's. When I manage to have a 7th bar lit up, my highway mileage increases by about 10 - 15 mpg until the bars return to their normal state of 6 bars. This tells me that if I have an excess of battery power saved up, the car will either use more electrical power to assist highway driving OR it diverts less ICE energy to maintain the 6 bar charge (and probably both are occuring).

 

Yes.

The abillity to add motor power to the engine power allows the engine to run more efficiently, both in terms of how it runs and the rate at which it runs at any time.

Even on the highway there are times of very low and negative power demand.

 

If battery always supplies power on the highway, you will lose battery charge level very quickly.
The real story is Prius tries to maintain 60% SOC battery level by small ampere charging and discharging.

Anyway, the ICE torque is always split 72% to wheels and 28% to generator.
When no torque is consumed by the generator, the wheel torque by ICE is also zero, you can't move your Prius.
Therefore, the series hybrid operation (generator->motor) is always done on the highway.

Ken@Japan

 

Sure, it does. Just look at what the Corolla and Matrix with 1.8 liter Otto cycle engines get.

Electric motors allow Prius to run on Atkinson cycle without compromising passing ability. In fact it works so well that Prius' can accelerate and pass easier than a comparable non-hybrid with an automatic transmission.

 

This page will explain how the Prius uses both MG1, MG2 and the ICE at high MPH's.

Toyota Prius - Power Split Device

On the highway the Prius will use MG2 to get better MPG's.

 

I noticed that after coming down a long big hill with HV fully charged at 8 bars, at 65mph the ICE shuts off and EV powers the car until HV pack drains down to low 7 bars. ICE then fires back up but gets over 90mpg until the HV drains down to 6 bars. Then it returns to 60mpg.

 

Yes but constant speed on the highway does not mean a constant power load. Slight grades would increase or decrease speed, wind and turblence from other traffic would also change the amount of power needed to maintain a constant speed.

Yes:

• smaller engine - this means the engine can run with the throttle more open and less pumping losses. It also means lower internal friction overhead compared to a larger engine.
• peak power - passing and hill climb energy can come from the traction battery
• regenerative speed control - descending hills and slowing down converts potential and kinetic energy into battery power for the next peak power demand
• optimum ICE rpm regardless of speed - the motors, there are two of them, can keep the ICE rpm in the sweet-spot so it runs at maximum or near maximum efficiency

The last point is especially important as our dual-motor, transmission provides manual transmission efficiency yet works like an automatic. There are electronicly shifted, manual transmissions coming on the market but they have no energy storage and release capability. So those cars wear out their brakes in contrast to our Prius that effectively have life-time brake pads.

Bob Wilson