The New Subaru FB20 Boxer Naturally Aspirated Engine

The New Subaru FB20 Naturally Aspirated Engine

Original Translation from “Proud of Boxer. Technology and passion for Subaru Boxer Engine.”

FB20 has the following specifications

Engine Form: 4-Cylinder DOHC Flat Engine

Engine Type: FB20

Engine Displacement: 1995cc

Bore x Stroke: 84.0 x 90.0mm

Compression Ratio: 10.5

Maximum Output: 109kW/6000rpm

Maximum Torque: 196Nm/4200rpm

FB20 Versus EJ20

The Bore pitch remained at 113mm to keep room for the 2.5L version. The longer stroke improves the fuel Efficiency, and even with longer stroke, the engineers were able to maintain the new FB engine close to the dimension of EJ engine.

The new TGV (Tumble Generator Valve) on the FB20 has a new flap feature to adjust the air flow to the intake chamber. The FB20 also features an in-port fuel injection, a major change from the EJ predecessor. The fuel injectors are located on the cylinder heads to improve fuel efficiency and reduce gas emissions.

In-port injection

Breaking down the internals of FB20

The valve is direct bolt-on with cam angle at 41⁰ with cam distance of 126mm on EJ engine.

FB20 uses roller rocker on the valve to retain the engine width and reduce friction loss. Valve cam angle is reduced to 27⁰ and cam distance to

Smaller bore on FB20 engine

FB20 Cylinder head, separate pieces from the cam carriers, reducing the weight

FB20 Connecting rods shaped to engine width similar to the EJ. FB20 piston is smaller. The crown design is to maintain tumble flow’s momentum.