The Subaru CB engine is a

gasoline Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic co ...

boxer-4 engine used in

Subaru ( or ; ) is the automaker, automobile manufacturing division of Japanese transportation conglomerate (company), conglomerate Subaru Corporation (formerly known as Fuji Heavy Industries), the Automotive industry#By manufacturer, twenty-first ...

automobiles. It is the fourth generation of Subaru boxer engines, following the first ( EA, 1966–94), second ( EJ, 1989–2021), and third ( FB/ FA, 2010/2012–present) generations.

Overview

The CB engine was first introduced in August 2020 with the second-generation Levorg. According to Subaru, CB stands for Concentration/Compact Boxer. It is the fourth-generation boxer engine family from Subaru. Compared to the preceding FB series, the CB is shorter; the bore pitch (centerline to centerline spacing between adjacent cylinders) has decreased from and the overall crank length has decreased from . For the first time in a Subaru engine, the centerlines of the cylinder bores do not intersect with the crankshaft axis; instead, there is a crank offset of . This offset reduces friction during the piston downstroke. Overall

thermal efficiency In thermodynamics, the thermal efficiency (\eta_) is a dimensionless performance measure of a device that uses thermal energy, such as an internal combustion engine, steam turbine, steam engine, boiler, furnace, refrigerator, ACs etc. For a he ...

is 40% due to the adoption of

lean-burn Lean-burn refers to the burning of fuel with an excess of air in an internal combustion engine. In lean-burn engines the air:fuel ratio may be as lean as 65:1 (by mass). The air / fuel ratio needed to stoichiometrically combust gasoline, by con ...

combustion with an excess air ratio (λ) of 2. The injector is positioned next to the spark plug in the center of the combustion chamber to ensure the lean mixture will ignite reliably. A small single-scroll turbocharger was equipped to maintain charge air volume and improve throttle response. The

connecting rod A connecting rod, also called a 'con rod', is the part of a piston engine which connects the piston to the crankshaft. Together with the crank, the connecting rod converts the reciprocating motion of the piston into the rotation of the cranksh ...

s in the CB engine are split horizontally, like those in the second generation EJ engines. The third generation FB/FA connecting rods are split diagonally (also called an offset or asymmetrical connecting rod) to allow a longer piston stroke without increasing the width of the engine, but the horizontally-split connecting rods are stronger.

CB18

The first engine in the series is designated ''CB18'', a 1.8 litre dual overhead cam 16-valve engine featuring dual

AVCS The active valve control system (AVCS) is an automobile variable valve timing technology used by Subaru. It varies the timing of the valves by using hydraulic oil pressure to rotate the camshaft, known as "phasing", in order to provide optimal val ...

with

gasoline direct injection Gasoline direct injection (GDI), also known as petrol direct injection (PDI), is a mixture formation system for internal combustion engines that run on gasoline (petrol), where fuel is injected into the combustion chamber. This is distinct fro ...

and a turbocharger. Compared to the FB16 used in the previous generation of the Levorg, the CB18 offers decreased fuel consumption ( for the CB18 and for the FB16, both using the JC08 mode) and increased torque ( for the CB18 and for the FB16). In addition, the CB18 achieves its peak torque at a lower engine speed. Engine weight of the CB18 has been reduced by compared with the FB16. In October 2020, Subaru announced the CB18 also would be fitted to the top-of-the-line 'Sport' trim of the 5th generation

Subaru Forester The is a compact crossover SUV that has been manufactured by Subaru since 1997. The first generation was built on the platform of the Impreza in the style of a taller station wagon, a style that continued to the second generation, while the thir ...

in the Japanese market; other models of the Forester are equipped with the mild hybrid FB20D e-BOXER. The CB18 engine is also fitted to the Subaru Legacy Outback for the Japanese market. In April 2022, Subaru had to suspend production of Forester, Outback and Levorg after it discovered a sensor in CB18 engine malfunctioned. ;''CB18'' specifications: *Displacement:

DOHC An overhead camshaft (OHC) engine is a piston engine where the camshaft is located in the cylinder head above the combustion chamber. This contrasts with earlier overhead valve engines (OHV), where the camshaft is located below the combustion c ...

, turbocharged *Bore × stroke: * Compression ratio: 10.4:1 *Power: at 5,200–5,600 RPM *Torque: at 1,600–3,600 RPM ;''CB18'' applications: * 2021–present JDM

Subaru Levorg The is a mid-size car manufactured since 2014 by Subaru. According to the company, the name Levorg is an acronym of three words, LEgacy, reVOlution, touRinG. The Levorg shares its platform with the Impreza, Legacy and WRX. The Levorg was fi ...

(VN5) * 2021–present JDM

(SK5) * 2021–present JDM Subaru Legacy Outback (BT5)

References

External links

( ja, Subaru CB engine) * * {{DEFAULTSORT:Subaru Cb Engine Subaru engines Boxer engines Gasoline engines by model Four-cylinder engines