2001 Subaru HM-01 - AllCarIndex

Subaru launches new hybrid concept car at the Frankfurt Auto Show

Fuji Heavy Industries Ltd., a global manufacturer of transportation and aerospace-related products and maker of Subaru automobiles, is bringing a new and exciting Subaru hybrid concept car, the HM-01, to the 59th Frankfurt Auto Show.

Small in size but big in advanced technology, HM-01 debuts a completely new hybrid AWD system which not only improves fuel consumption but also offers Subaru's thinking towards the compact car of tomorrow.

HM-01 is designed around the twin tenets of high running performance and high driving stability. While its compact body provides the promise of fun and sporty driving, HM-01 is at the same time a small personal car: as user-friendly as it is earth-friendly thanks to its lightweight and reduced exhaust emissions. For next generation, eco-aware concepts like the HM-01 also point towards an improved and simplified traffic infrastructure in the future.

Subaru's new concept AWD hybrid system links 658 cc inline 4-cylinder engine to i-CVT. Driving the rear wheels is a 42-volt electric drive unit. This lightweight system offers over 10% improved fuel consumption together with high driving performance and high driving stability.

At the Frankfurt Auto Show, Subaru is also going to exhibit the Impreza WRX STi, the pacesetting 2.0-litre/AWD sports model unveiled in Japan in October 2000. Subaru is gunning for a stronger grip on the European market through the development of this highly charged new Impreza STi.

Key Features

The HM-01, dubbed an 'emotional mini car' by its builder, is a combination of a compact urban 2+2 that is at home in the city, yet with sharp-responses and strong sporting aspirations that make it fun to drive on open roads.

And it is a very safe car, too. Secondary safety is taken care of by a strong and sturdy yet lightweight monocoque body, while primary safety is provided by an all-wheel drive system typical of Subaru, but achieved in a very different and ingenious way.

The little HM-01 doesn't just borrow the concept of the town car from its illustrious 360 predecessor, it also builds on its original character.

As a result, there are visible 360 styling cues all the way through its design. Apart from similar side lines and door trims, stylists of the HM-01 also used more than a little 360 style in the front wings.

But in spite of these glimpses of the past, the overall look is crisply modern with a sporty exterior and a simple and elegant interior.

Apart from the ingenious technology used in the HM-01, the aspects of the car that really stand out are the styling, with its wheel-at-each-corner planted look, and its packaging. And with no propeller shaft to intrude into the passenger compartment of this all-wheel drive car, more room is liberated for the occupants.

Note: Subaru 360

The 360 was the first production car for Fuji Heavy Industries. The company, born out of the Nakajima Aircraft Company, used much of its aero expertise to produce the little town car. The 360 featured a monocoque construction, still very much a novelty back then, and a 356cc, air-cooled, two-stroke engine mounted at the rear. The three-speed car had just 16bhp at its disposal and weighed a scant 385kg.

Technical Highlights

New Concept Hybrid AWD System

The HM-01 is packaged very cleverly. Taking the front-wheel drive minicar Pleo platform, Subaru has adapted its 658cc straight-four engine to drive the front wheels via an i-CVT (Continuously Variable Transmission).

The rear wheels are driven by a 42 volt electrical motor system. Ingeniously, the difference between front and rear wheel speeds is synchronised electrically. Instead of a propeller shaft running to the rear to power the rear wheels, the HM-01 has wires that pass current to a rear-mounted motor that looks after the rear drive.

A central processing unit monitors driving conditions and throttle position and distributes power in the most efficient and environmentally friendly way possible.

For example, when the car stops and idles, the engine is automatically switched off and is restarted by a high-power 2kW starter motor connected to the engine via a belt. This makes for almost silent and vibration-free re-starting.

When the car is cruising on the overrun, the momentum of the car is converted into electrical energy by the motor in the rear drive unit, which also recharges the batteries.

The electrical components consist of a newly developed dual-voltage 42 volt system utilising a readily available, easily recyclable 36 volt sealed lead acid battery. This is used in conjunction with a regular 12 volt unit, a high-power 3kW alternator and a DC-DC converter that takes the power down to 14 volts for the rest of the car's electrical system.

In spite of its innovative design, the HM-01 utilises currently available electrical components and this has two main benefits. As well as reduced purchase and maintenance costs, using existing technology avoids the need for the setting up of a special infrastructure in the production and supply of new specialist components.

Rear Drive Unit

Subaru has almost unrivalled knowledge and experience of all-wheel drive technology so it made sense for the HM-01 to incorporate an all-wheel drive chassis.

The heart of the system is the central control unit that distributes the right amount of power to each wheel for the prevailing conditions. It takes into account the grip available and whether the road is smooth or bumpy.

Careful electrical control also monitors the wheels when the car is coasting off power and recharging the batteries, so that maximum stability is maintained at all times.

Instead of using a set of conventional reduction gears, the HM-01 uses a set of planetary gears. Each element of the drive train has been pared down in weight and size to make the possible intrusion into the HM-01's compact dimensions.

Specification

Dimensions

Body Size: 3,425mm (length) x 1,505mm (width) x 1,475mm (height)

Wheelbase: 2,310mm

Engine Type: In-line four cylinder 658cc

Max Power: 34kw/6000rpm

Max torque: 58Nm/5200rpm

Drive type:All-wheel drive (front: i-CVT; rear: electric)

Tyre Size: 175/60 x 15

Electric Rear Drive Unit

Operating Voltage: 42 volts; maximum torque: 144 Nm. Maximum output: 5kW

High power alternator