Subaru CB18 1.8L Engine Specs, Problems, Reliability, Info

Subaru 1.8 CB18 Turbo Engine Overview

The CB18 is a 1.8-liter four cylinder turbocharged boxer engine with direct fuel injection. This new engine was first introduced with the second-generation JDM Subaru Levorg in 2020, replacing the 1.6-liter FB16DIT engine. A little later, Subaru began to install this engine in other models sold in Japan, such as the Subaru Forester and the Subaru Legacy Outback. The CB18 has multiple design changes compared to FB and FA engines. It also has 40% thermal efficiency, which is a big improvement over previous models.

CB18 Engine Features

First of all, the CB18 is 40 mm (1.57 in) shorter than FB16. The CB engine is still built around an aluminum open-deck cylinder block with cast-in iron sleeves. But the distance between the centers of the cylinders is 98.6 mm (3.88 in) instead of 113 mm (4.45 in). The overall crankshaft length has decreased from 350.5 mm to 315.9 mm (13.80 in to 12.44 in). The engine block is equipped with new, so-called horizontally split connecting rods (FB series has diagonally split rods) and even more compact pistons with low-friction polymer coating on skirts. In addition, there is an 8 mm (0.31 in) crank offset, which reduces friction during the piston downstroke. The lubricant system has been upgraded with a variable capacity oil pump. This oil pump is now located underneath and driven by an additional chain.

The design of cylinder heads has changed significantly. They are aluminum DOHC heads with integrated exhaust manifolds and dual AVCS system. Each camshaft has its own plastic valve cover. As before, there are two single-row roller timing chains and no hydraulic lash adjusters. Like the previous FB16DIT, the CB18 features a direct fuel injection system. Now, direct injectors are positioned closer to the center of the combustion chamber in order to achieve vertical injection. The high-pressure fuel pump has been relocated from the left cylinder head to the right. Max fuel pressure is up to 32 MPa. The new fuel system has two modes: normal mode and LeanBurn mode.

The CB18 comes with an air-to-air intercooler and the Garrett M12 single-scroll turbocharger, which has an electronically controlled wastegate. The piping and intake manifold are made from plastic. The TGV system has been removed but the EGR is still here, and now it additionally comes with EGR temperature sensor and EGR pressure sensor. Another significant change is the replacement of the traditional thermostat with a Thermo Control Valve (TCV). The coolant pump is mechanical, not electric.

The End Result

The new Subaru 1.8-liter turbo boxer engine shows improvements in both power and fuel efficiency. Compared to the FB16DIT, the maximum power has increased by only 5 horsepower, but the torque has raised from 250 Nm (184 lb-ft) to 300 Nm (221 lb-ft). The fuel consumption did not change a lot. It rated at 16.6 km/L or 39 MPG. By the way, this engine runs on regular gasoline (RON 91).

Engine Specs

The Most Common CB18 Problems

Keep in mind, this engine is still a new product on the market. But at the moment, CB18 appears to be a well-built and reliable engine with no major flaws. Of course, no engine is perfect, and the CB18 is no exception.

• This engine has direct fuel injection only. In this case, a carbon build-up in the intake ports is highly potential.
• The engine requires high-quality engine oil. Moreover, it is very thin (0W-16 or 0W-20), which is good for engine efficiency, but not for longevity.
• The CB18 engine does not have hydraulic lash adjusters. You may need to check and adjust the valve clearances from time to time.
• The TCV system still faces reliability issues.
• In 2022, Subaru issued a recall for the Forester, Outback, and Levorg models equipped with the CB18 engine due to a problem with the EGR pressure sensor.

CB18 Overall Reliability and Longevity

To summarize, is the Subaru 1.8L CB18 engine reliable? Yes, it is a durable and reliable engine with adequate power. Unfortunately, like all modern engines, it is filled with electronics, which adds more reliability issues. To avoid any unnecessary problems, follow the maintenance schedule, use the recommended oil and high-quality fuel. Estimated lifespan of the engine is around 150,000 miles (250,000 km).