The Subaru B5-TPH carries a revolutionary powertrain system beneath sporty bodywork. This vehicle’s TPH powertrain is a strategically important technology for the power source of clean-energy vehicles and will be incorporated with the Subaru core technologies including the Subaru Boxer Engine and Symmetrical All-Wheel Drive system.
The Subaru TPH powertrain in the B5-TPH places a thin, 10-kW motor generator between a vehicle’s engine and its automatic transmission. The combination of the motor-generator and the turbocharged Subaru Boxer Engine creates a system that not only provides power in the mid-speed ranges when the turbocharger is active — as with conventional turbo models — but it also delivers excellent acceleration and fuel economy. This superb, all-range performance has been enabled by electric motor-assist, a feature that is designed to boost engine torque at low speeds.
For even greater efficiency, the TPH gasoline engine adopts the Miller Cycle. A Miller-cycle engine leaves the intake valve open during part of the compression stroke, effectively shortening the compression stroke to avoid detonation. However, due to the turbocharger, the cylinder still packs a larger “charge” than would a conventional-cycle engine. In the Subaru B5-TPH, the Miller Cycle turbo boxer engine operates up to 30 percent more efficiently than a conventional gasoline engine.
This provides a low-cost solution to giving driving enthusiasts lively acceleration and a high top speed but with excellent fuel consumption and low exhaust emissions. The four-cylinder horizontally-opposed petrol engine features a Miller Cycle system which improves engine efficiency by reducing pumping losses thanks to a combustion expansion stroke that is longer than the compression stroke. Normally this system makes an engine sluggish at low speeds but thanks to the electric motor, standing-start torque is boosted beyond even an Impreza Turbo’s.
The electric motor itself produces 10 kW and 150 Nm torque while the petrol engine has a 191 kW output with 343 Nm torque. A new type of manganese lithium ion battery charges to 95 per cent capacity in five minutes and operates not just in city driving but also when cruising.
The design of the Subaru B5-TPH itself is a striking one featuring smooth contours and a large tailgate, hinged just behind the B-post. Its ‘crossover’ theme combines the practicality of a hatchback, fun of a coupe and all-terrain ability of a SUV, complete with a 200 mm ground clearance.
Meanwhile, Subaru’s much-admired full-time symmetrical all-wheel drive and low-centre-of-gravity ‘boxer’ engine ensures agile handling. But while the B5-TPH continues the theme of previous concept cars such as the B11S and B9 Scrambler, the concept is not meant to hint at any future Subaru models.