Subaru develops boxer with 50 percent target
Subaru is working on a new generation of boxer engine intended to achieve thermal efficiency of 50 percent.
Target: 50 percent thermal efficiency
According to a Japanese report, Subaru is working on a new generation of its boxer engine. The development target is thermal efficiency of 50 percent. That would put the engine well above the level of today’s good gasoline engines, which reach just under 40 percent. Dongfeng and Chery recently presented gasoline engines with stated efficiencies of 45.5 and 48 percent respectively.
Efficiency work on the combustion process
The boxer engine remains important for Subaru both technically and as part of the brand, but it also presents developers with its own limits: the flat, wide layout restricts the possible piston stroke and makes conventional efficiency-improvement measures more difficult. Subaru is therefore focusing on mixture formation and combustion. Straighter and narrower intake ports are intended to make the air flow in faster and create a more uniform air-fuel mixture. A turbocharger is meant to compensate for the resulting pressure loss.
The combustion itself is being examined with 3D analyses. These are intended to make knock tendency easier to predict and allow flame propagation to be influenced more precisely. Subaru is also evaluating several technologies that could help improve efficiency:
- Variable-geometry turbocharger
- Miller combustion cycle
- Pre-chamber combustion
In Europe, Subaru will rely only on electric drivetrains in the future. In other markets, however, the company still sees potential for combustion engines. Whether the targeted efficiency will be achieved and when a new boxer generation could enter series production remain open.