Japan’s Nihon Keizai Shimbun reports that Toyota Motor has agreed to develop hybrid systems jointly with Fuji Heavy Industries (FHI), the parent of Subaru, with the aim of using the technology in Subaru Legacy models in two to three years. Executives of both companies will announce details on Monday of a broader Toyota-FHI alliance, including a US manufacturing agreement.
Toyota acquired an 8.7% stake in FHI after GM sold off its stake in the company last year (earlier post).
Toyota originally intended to supply hybrid systems to Fuji Heavy (earlier post), but the companies have decided to work jointly on gasoline-electric hybrid technologies because existing Toyota systems cannot readily be used with the Subaru’s horizontally-opposed engines, according to the report.
Subaru showed its new B5-TPH hybrid concept vehicle at the 2006 North American International Auto Show in January. The B5-TPH concept vehicle applies the company’s Turbo Parallel Hybrid (TPH) powertrain system and lithium-ion battery technology in a two-seat grand touring car that offers fuel economy of 40 mpg. (Earlier post.)
The TPH engine is based on the standard Legacy 2.0-liter Boxer (horizontally-opposed) engine, with modifications to the cams and engine management software to implement the Miller cycle. A Miller-cycle engine (similar to the Atkinson cycle) leaves the intake valve open during part of the compression stroke.
The late closing of the intake valve eliminates the substantial amount of energy normally required to overcome friction (as well as pumping losses) in the process of completing a normal compression stroke. The result is increased engine efficiency, at around 10%–15%, although with a loss of power.
To compensate for the power loss, the prototypic Miller engine uses a supercharger. Subaru instead applies a turbocharger to make up for the power loss in the mid-range. The additional assistance provided by a 10 kW electric motor compensates for low-end power loss.
The result is a high-powered mild-hybrid system that is quite different in design that the Toyota Hybrid Synergy Drive technology.