The Evolution and Potential of the PHEV

Today, the plug-in hybrid electric vehicle (PHEV) model of the Outlander has become the flagship model of Mitsubishi Motors. When originally released in 2013, it established the new category of a PHEV crossed with an SUV, which was unlike anything before in the automotive world.

How did the development team eventually arrive at the PHEV? Together with Kazunori Handa, a member of the EV and Powertrain Advanced Engineering Development Department and the development team of EVs at Mitsubishi Motors since 1994, this series looks back on the development of the PHEV. Part 3 is “The Evolution and Potential of the PHEV.”

Created through pursuit of the perfect vehicle, the Outlander PHEV finally shipped out to the market. While it was well-received by many customers, the response was not what the development team had anticipated. Looking back on that time, “We were surprised at how many people were saying they were disappointed when the engine kicks in," Handa recalls.

"With the Outlander PHEV, we had adjusted the timing of when the engine starts so that drivers could accelerate exactly as they want. In making these adjustments, the operation of the driver's foot on the accelerator is the only factor other than its traveling speed that the vehicle can use to judge the intentions of the driver. Electric motor driving can handle the work for normal acceleration on its own, but we made adjustments so when the driver steps hard on the accelerator, the vehicle judges that more acceleration is needed and starts the engine to supplement the accelerative force. Smooth acceleration is not compromised even when the engine kicks in. It delivers the accelerative force that the driver wants. What differs are the sound and vibration of the engine. However, our customers found the sound and vibration a bit uncomfortable."

For example, imagine a busy intersection in the city. If the driver steps hard on the accelerator while trying to turn right, the PHEV system's controller determines that lots of output is needed and starts the engine. Some drivers found it uncomfortable that the engine suddenly started vibrating and making noise.

"Once people experience the quiet and smooth acceleration of an electric vehicle, they want to enjoy it even more. As a result, the demand from those who want to drive only in EV mode exceeded our expectations."

Due to comments such as these, the developers needed to work out a mechanism to keep the engine from starting even when the accelerator is pressed hard. What they configured in response was EV Priority Mode. "We set it up to intentionally keep the engine from starting even when pressing hard on the accelerator, so the engine activates only when the battery runs out. Drivers can now decide for themselves something that the car had previously decided."

Outlander PHEVs equipped with EV Priority Mode were released in Japan in February 2017. Then in August 2018, the PHEV system was significantly improved to allow drivers to enjoy the unique driving experience of EVs even more.

"We were also getting more requests from people who wanted to keep the engine off not only in city driving but also on expressways. In response, we aimed to evolve the PHEV by creating a car that makes it as unnoticeable as possible that the engine is doing any of the driving. However, the motors would need more power to be able to handle expressways and winding roads on their own. We also wanted to increase the range and boost the power generation efficiency of the engine. These were accomplished by evolving the main components of the PHEV system – the battery, motors, and engine."

Increasing the capacity of the drive battery from 12.0 to 13.8 kWh also extended the Outlander PHEV's EV driving range from 60.8¹ to 65.0 kilometers. In addition to the battery's capacity, its maximum output was increased by 10% while output of the rear motor was raised by around 12%, and output of the generator that supplies power to the motors was also upped by around 10% to deliver powerful road performance. Even the engine was upgraded, with displacement enlarged from 2.0 to 2.4 L, and a high expansion ratio cycle (Atkinson cycle) was adopted to enable high-efficiency power generation in the lower rev range.

"When the engine is powering the car, its engine speed vary significantly from idling to driving at full power. Thermal efficiency also differs at different engine speed, but you have to think about efficiency at all rpms when developing the engine. However, with a PHEV which is centered on electric power generation, the number of speeds to power the engine can be narrowed down. We made it possible to generate power efficiently at low rpms by enlarging the displacement and narrowing down the operation range of the engine."

The new Eclipse Cross PHEV model released in Japan in December 2020 also has Tarmac mode, which delivers a high level of cornering and stability on dry, paved surfaces.

"Tarmac mode quickens acceleration response by starting the engine sooner and putting it on standby, allowing for exhilarating driving experiences even on winding roads."

Mitsubishi Motors' PHEVs have earned good reviews by customers, and the Outlander PHEV led global sales in the SUV-type PHEV category from January 2013 through September 2020. Subsequently, the PHEV model of the all-new Outlander loaded with all of Mitsubishi Motors' refined PHEV technologies was released in December 2021.

"In developing the all-new Outlander PHEV model, we first adjusted its motor output. Many customers are surprised at how well EVs accelerate, but their absolute acceleration is not particularly high and is inferior to that of internal combustion engines. To overcome this, we had to increase both the torque and the output of the motors."

Improving the output of the motors made it possible to drive only with the motors at a wider range of speeds, allowing the invigorating acceleration of an EV continue uninterrupted. Battery performance was also upgraded, allowing a range of approximately 87 kilometers² with the electric motors alone and a total of around 1,000 kilometers or more with a full tank of gas.

"Even when pressing the accelerator and reaching a certain level of speed, there is no fearful feeling of losing any control. Also when turning, it makes no odd movements. This comprehensively crafted road performance delivers the feeling of 'I-Fu-Do-Do' or authentic and majestic in Japanese, that is precisely what our car concept is about. It was designed with the essence of a Mitsubishi car for an exhilarating ride with precise handling and peace of mind on any type of road."

What is appealing about PHEVs? Handa emphasizes the versatile ways they can be used.

"PHEVs are not only good for the environment. They are also the same as our familiar gasoline engine cars in that they require no charging, nor any concern about range. PHEVs can reduce our impact on the environment without sacrificing any of the appeal of fun, high-convenience mobility. I think that is why people will choose PHEVs. Another appealing point of Mitsubishi Motors' PHEVs is that they come equipped with on-board outlets capable of supplying AC 100V power. Customers can utilize them in a variety of ways, including using them to cook with electric pots at campsites, or even powering their equipment to play music at outdoor events. Unlike a power generator, this power source makes no noise, so this makes it user-friendly. PHEVs offer broad-ranging appeal according to each person's usage style and lifestyle."

On a full tank of gas, the PHEV model of the all-new Outlander can supply around 12 days' worth of power³ to the typical home. In 2019 when Typhoon Faxai caused large-scale power outages in Chiba Prefecture, Japan, that dragged on for long hours, Mitsubishi Motors' PHEVs came to the rescue by serving as a key power source for elder care centers and other facilities. Whether as a mode of transportation or as an emergency power source, the unique features of these vehicles come in handy when the unexpected happens.

"I have heard people say they had a power generator in case of emergencies, but since they hadn't used it regularly it didn't activate during an actual emergency. PHEVs are always in use as cars, plus they can serve as a power source in an emergency. Mitsubishi Motors has entered into disaster cooperation agreements⁴ with around 180⁵ local governments in Japan, and I believe this is because they realize how advantageous the Outlander PHEV's power supply capability is."

The dedication to create the perfect vehicle with the PHEV still permeates the minds of Mitsubishi Motors' engineers even now.

"High-powered yet highly operable, with a compact body - I want to offer a PHEV that incorporates all of these strong points of the Lancer Evolution at a reasonable price. That is my goal right now. Just how close can we get to the perfect car in terms of range, price, interior space, and other aspects? Personally, I believe that the future evolution of the PHEV will be cars like the Lancer Evolution that have outstanding environmental performance. The cars that are truly fun to drive really are Mitsubishi Motors' cars."

The Mitsubishi Motors' PHEV quest is far from over.