Posts Tagged ‘Subaru FB20’

The New Subaru FB20 Boxer Naturally Aspirated Engine

Friday, March 11th, 2011

 

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

 

EJ20 (Gasoline)

FB20 (Gasoline)

Engine Displacement

1994cc

1995cc

Bore Pitch

113mm

113mm

Bore x Stroke

92 x 75mm

84 x 90mm

Stroke/Bore

0.82

1.07

Cam Drive System

Direct

Rocker Arm

Valve Angle

41 degrees

27 degrees

Fuel Injection Method

PFI

PFI

 

 

 

 

 

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.