Worldwide Sales of Toyota Hybrids Surpass 9 Million Units

Toyota City, Japan, May 20, 2016―Toyota Motor Corporation is proud to announce that the cumulative figures for global sales of its hybrid vehicles reached 9.014 million units as of April 30, surpassing the 9 million unit mark*. This latest million-unit milestone was achieved in just nine months.

Q. Why do HVs get worse fuel efficiency in winter than in other seasons?

A. Because the HV needs more fuel to warm up the engine and to run the heater in winter, fuel efficiency tends to be worse than in other seasons.

A fuel efficiency comparison by season is shown below. During winter, the HV needs more fuel to warm up the engine and to run the heater, causing fuel efficiency to drop. (The engine coolant is the heat source of the heater.)

The fuel efficiency of conventional vehicles worsens in summer due to the A/C, while the fuel efficiency of Toyota HVs worsens in winter more than summer because of the electric compressor which contributes to longer operation of the engine for heating in winter.

As a way to improve fuel efficiency in winter, the new model Prius incorporates an exhaust heat re-circulation system, which warms up the engine coolant using the engine exhaust heat.

Example fuel efficiency comparison by season (reference)

Exhaust heat recirculation system (ZVW30)

Q. Why do HVs have good fuel efficiency?

A. A reason for the good fuel efficiency of HVs (THS-II) is the combined advantages of the gasoline engine and electric motor.

The motor features the capability of producing maximum torque when started, allowing for effective acceleration. On the other hand, the engine provides remarkable fuel efficiency during constant speed driving. The HV demonstrates its superior fuel efficiency by fully utilizing characteristics of both the engine and motor.

Furthermore, brakes for conventional vehicles convert kinetic energy to heat energy, which is a waste of energy. HVs convert kinetic energy to electric energy using the motor (MG2). This electric energy can be used for driving the HV, improving the fuel efficiency.

Primary features of HVs which contribute to fuel efficiency

Feature	Description
Idling stop	Stops the engine when the HV is stopped
Motor assist	Uses the motor to assist drive power
EV mode	Makes motor driving possible at low speeds
Engine	Controlled optimally
Regenerative braking	Converts energy wasted in braking to electricity
Electric A/C	Enables A/C without operating the engine

Q. Why do the engine and hybrid system need independent cooling systems?

A. Because the target cooling temperature differs for both the engine and hybrid system.

The engine and hybrid system have independent cooling systems

Due to differing target cooling temperatures, the engine’s cooling system is designed to maintain an engine coolant temperature within 80 °C to 100 °C (176 °F to 212 °F) after warming up, the same as conventional engines, and hybrid system is designed to keep less than approximately 65 °C (149 °F), particularly for cooling down the inverter.

Q. Does the frequent use of the EV mode increase fuel efficiency?

A. No. The EV mode runs the HV using only the motor, and not the engine. Fuel efficiency in the EV mode may be worse than that of normal mode (in which the system optimizes fuel efficiency.)

An advantage of driving in the EV mode is quietness, because the HV runs using the motor, and not the engine. Apart from enjoying driving the car as an electric vehicle, the EV mode is effective for driving in environments where people are concerned about car noise, such as early in the morning, late at night, quiet residential areas, and so on. (Refer below for EV mode operational conditions.)

Fuel efficiency is remarkably high during the EV mode, however, after the SOC has decreased to approximately 2 segments, the engine operates continuously to charge the HV battery. The engine operates this way regardless of vehicle driving conditions, which translates to less efficient fuel consumption. Therefore, the EV mode fuel efficiency tends to be worse than normal mode as a whole.

The output distribution between the motor and engine has been optimized to reduce fuel consumption in normal mode. (*Some models allow selection between an Eco mode and Power mode as normal modes in addition to the EV mode (driving with only the motor)).

Comparison of fuel efficiency between the EV mode and normal mode (20 km-drive at the same interval) * This data is reference information, which may vary depending on the driver and driving conditions.

EV mode operational conditions

Q. Can hybrid vehicles run without gasoline? How far can hybrid vehicles run with only the electricity stored in the hybrid vehicle battery?

A. No. hybrid vehicles cannot run without gasoline. hybrid vehicles can run only a very limited distance with only the hybrid vehicle battery.

There are two ways to charge the hybrid vehicle battery:

1) Regenerative braking and

2) The engine power.

The engine cannot operate if it runs out of gasoline, so the hybrid vehicle runs with the motor. In this case, the hybrid vehicle battery is charged with only regenerative braking, leading to low SOC (state of charge), which makes the hybrid vehicle unable to run.

Possible running distance is only a few kilometers. It depends on the SOC and the driving conditions at the time.

State when unable to drive

Hybrid Vehicle System (Q & A)