Subaru FB16 Specifications
| Engine Model: Subaru FB16 |
| Engine Type: 4-cycle 4-cylinder DOHC 16-valve liquid-cooled gasoline |
| Total Displacement: 97.6 cu.in (1.59 L) |
| Rated Engine Power: 113-115 Hp (84-86 kW) at 5600 rpm |
| Fuel System Type: Multi-point fuel injection |
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The Subaru FB16 is a 1.6-liter, naturally aspirated
flat-four engine introduced in 2010. It belongs to the FB engine family, which
represented Subaru's first major clean-sheet Boxer design in over 20 years,
replacing the long-running EJ series in smaller displacement applications.
The FB16 was engineered with a singular focus
on maximizing fuel efficiency and reducing internal friction while
maintaining the inherent balance and low center of gravity advantages of
the horizontally opposed configuration. This engine introduced numerous
technological advancements over its predecessor, including a timing
chain in place of a belt, dual active valve control systems (AVCS), and
a long-stroke architecture optimized for low-end torque.
The FB16 engine is recognized for its refined operation, improved fuel
economy, and reduced maintenance requirements compared to the EJ series
it replaced. Its long-stroke design delivers responsive low-end torque
well-suited for urban driving environments, while the all-aluminum
construction contributes to reduced vehicle mass. The adoption of a
timing chain eliminates scheduled replacement intervals, a significant
departure from the belt-driven EJ engines.
Dual AVCS on both intake and exhaust camshafts enables precise valve
timing control, improving combustion efficiency and reducing emissions.
However, early production units (2011-2014) experienced oil consumption
issues related to piston ring design, a condition addressed in later
revisions. The engine's reliance on low-viscosity 0W-20 oil is critical
for proper operation of the variable valve timing system and timing
chain tensioners.
Engine Type: Horizontally opposed 4-cylinder (boxer), 4-cycle, naturally
aspirated gasoline.
Displacement: 1,599 cc (97.6 cu.in), equivalent to 1.6 L.
Bore: 78.8 mm (3.10 in).
Stroke: 82.0 mm (3.23 in).
Compression Ratio: 10.5:1 to 11.0:1.
Firing Order: 1-3-2-4.
Maximum Power: 113-115 hp (84-86 kW) @ 5,600 rpm.
Maximum Torque: 150 Nm (111 lb-ft) @ 4,000 rpm.
Maximum Engine Speed: 6,500 rpm (electronically governed).
Fuel System: Multi-point fuel injection (MPFI).
Valvetrain: DOHC, 16 valves (4 valves per cylinder) with dual AVCS
(Active Valve Control System) on intake and exhaust camshafts.
The cylinder block is constructed from cast aluminum
alloy, a departure from the cast-iron blocks used in earlier EJ series engines.
This material selection significantly reduces overall engine mass while
maintaining adequate structural rigidity for a naturally aspirated application.
The open-deck design incorporates cast-iron cylinder liners pressed into the
aluminum casting to provide a durable wear surface for the piston rings.
The crankcase features a split construction with a separate aluminum bedplate
reinforcing the main bearing caps, contributing to crankshaft stability and
reduced noise, vibration, and harshness (NVH). The block integrates piston
cooling oil jets directed at the underside of each piston crown. Asymmetrical
connecting rods are utilized, allowing pistons and rods to be removed through
the top of the cylinder block without splitting the crankcase halves,
simplifying service procedures.
The cylinder heads are manufactured from aluminum
alloy, with separate castings for the left and right banks. Each head houses the
DOHC arrangement with four valves per cylinder. The combustion chambers feature
a compact pent-roof design optimized for high compression ratios and efficient
flame propagation. Intake valves measure 33.0 mm (1.30 in) in diameter, while
exhaust valves measure 28.0 mm (1.10 in).
The valvetrain utilizes bucket-type tappets with shim-under-bucket design,
requiring periodic valve clearance inspection. Dual AVCS (Active Valve Control
System) is present on both intake and exhaust camshafts, with hydraulic
actuators mounted to each camshaft sprocket providing continuous variable valve
timing. This system enables the ECU to adjust valve overlap for internal exhaust
gas recirculation (EGR) effects, improving fuel economy and reducing emissions.
The fuel system employs a multi-point sequential fuel
injection architecture with returnless fuel delivery. Fuel pressure is regulated
at 3.5 bar (51 psi) and delivered to four injectors per bank positioned in the
intake ports. The intake manifold is constructed from plastic composite material
to reduce weight and thermal conductivity. The sequential injection timing is
controlled by the Engine Control Unit (ECU) based on crankshaft position,
camshaft position, and engine load.
The system incorporates a fuel evaporative emissions control system that purges
fuel vapors from the charcoal canister into the intake manifold under
appropriate operating conditions. The ECU utilizes a mass airflow sensor for
load calculation and maintains closed-loop fuel control through oxygen sensor
feedback.
The lubrication system is a forced-feed, wet-sump type
utilizing a high-efficiency rotor-type oil pump mounted to the front of the
crankshaft. The pump is driven directly by the crankshaft, ensuring immediate
oil pressure upon startup. Oil is drawn from a stamped steel oil pan through a
baffled strainer before pressurization. A full-flow cartridge-type oil filter is
mounted externally on the cylinder block.
The system supplies lubricant to the crankshaft main bearings, connecting rod
bearings, camshaft bearings, bucket tappets, dual AVCS actuators, timing chain
tensioners, and timing chain guides. The high-efficiency oil pump design reduces
parasitic losses compared to earlier EJ series pumps. The specified
low-viscosity 0W-20 oil is essential for proper AVCS actuator response and
timing chain tensioner function.
The cooling system is a pressurized, water-cooled setup
utilizing a centrifugal water pump driven by the engine's timing chain. A
wax-type thermostat with a rated opening temperature of 82°C (180°F) regulates
the engine operating temperature. Coolant circulates through the aluminum
cylinder blocks and cylinder heads before passing through a cross-flow radiator
equipped with an electric cooling fan controlled by the ECU.
The system incorporates a pressurized expansion tank with a coolant level sensor
that alerts the driver to low coolant conditions. The electric cooling fan
operates at multiple speeds based on coolant temperature, air conditioning
system demand, and vehicle speed. The cylinder heads incorporate integrated
exhaust passages that require specific cooling channel routing for thermal
management.
| Intake and Exhaust Systems |
Intake System: The intake manifold features a plastic
composite construction with integrated intake air control valves that alter
effective runner length based on engine speed to optimize torque
characteristics. An electronically controlled throttle body (drive-by-wire)
eliminates mechanical cable linkage, integrating with the vehicle's stability
control, cruise control, and idle speed management systems.
Exhaust System: The exhaust system incorporates stainless-steel exhaust
manifolds for each cylinder bank, converging into a single downpipe. A
close-coupled catalytic converter reduces light-off time and lowers cold-start
emissions. The system includes upstream and downstream oxygen sensors for
closed-loop fuel control and catalyst monitoring.
The engine utilizes a direct ignition system with
individual pencil-type ignition coils mounted directly over each spark plug. The
coil-on-plug design eliminates high-tension spark plug wires. The ignition
system is fully integrated with the ECU, which controls spark timing based on
engine speed, load, coolant temperature, and knock sensor input.
Timing System: The camshafts are driven by a single-row
silent timing chain. The chain routes around the crankshaft sprocket, left and
right bank camshaft sprockets (which incorporate the AVCS actuators), and an
automatic hydraulic chain tensioner. The timing chain is designed as a lifetime
component, eliminating the scheduled replacement intervals required for
belt-driven EJ series engines. The system includes chain guides and a tensioner
supplied with oil pressure from the lubrication system.
Piston and Connecting Rod Assembly: The FB16 utilizes lighter pistons with
shorter skirts and low-tension piston rings compared to earlier EJ engines,
reducing reciprocating mass and internal friction. The connecting rods feature
an asymmetrical design that permits removal through the top of the cylinder bore
without crankcase splitting. Early production units (2011-2014) experienced oil
consumption issues attributed to piston ring design; revised ring packs were
introduced for models produced after 2015.
Overall Engine Length: 580 mm (22.83 in).
Overall Engine Width: 680 mm (26.77 in) measured across the cylinder heads.
Overall Engine Height: 620 mm (24.41 in).
Dry Weight: The complete engine assembly weighs 110 kg (243 lb), inclusive of
the intake manifold, exhaust manifolds, and all ancillary components.
Engine Oil Capacity (with Filter): 4.8 liters (5.1 qt).
Engine Oil Specification: SAE 0W-20 full synthetic oil meeting API SN or ILSAC
GF-5 specification. The use of 0W-20 oil is mandatory for proper AVCS actuator
operation and timing chain tensioner function. Fuel Filter: Integrated with the
fuel pump assembly in the fuel tank; no scheduled replacement interval under
normal operating conditions. Air Filter Replacement Interval: 40,000 km (25,000
mi).
Coolant Capacity: 6.0 liters (6.3 qt) inclusive of the radiator and heater
circuit. Spark Plug Type: NGK SILZKAR7B11 or equivalent iridium-tipped plug.
Spark Plug Gap: 1.0-1.1 mm (0.039-0.043 in). Spark Plug Replacement Interval:
100,000 km (62,000 mi). Timing Chain: No scheduled replacement interval;
inspection of chain tensioner and guides is recommended if engine noise is
evident.
Valve Clearance (Cold): Intake: 0.20-0.26 mm (0.008-0.010 in); Exhaust:
0.25-0.31 mm (0.010-0.012 in). Adjustment requires shim replacement under the
bucket tappets. Valve Clearance Inspection Interval: 100,000 km (62,000 mi). Oil
Consumption Monitoring: Early production units (2011-2014) should be monitored
for oil consumption exceeding 0.5 liters per 1,600 km (0.5 qt per 1,000 mi);
revised piston ring designs in later production address this condition.
Cylinder Head Bolts: 30.0 Nm (3.1 kgf-m, 22 lb-ft).
Main Bearing Cap Bolts (Bedplate), Step 1: 20.0 Nm (2.0 kgf-m, 15 lb-ft).
Main Bearing Cap Bolts (Bedplate), Step 2: 45.0 Nm (4.6 kgf-m, 33 lb-ft).
Connecting Rod Cap Bolts, Step 1: 15.0 Nm (1.5 kgf-m, 11 lb-ft).
Connecting Rod Cap Bolts, Step 2: 45.0 Nm (4.6 kgf-m, 33 lb-ft).
Camshaft Bearing Cap Bolts: 12.0 Nm (1.2 kgf-m, 9 lb-ft).
Intake Manifold Bolts: 20.0-25.0 Nm (2.0-2.5 kgf-m, 15-18 lb-ft).
Exhaust Manifold Nuts: 25.0-30.0 Nm (2.5-3.1 kgf-m, 18-22 lb-ft).
Crankshaft Pulley Bolt: 150.0 Nm (15.3 kgf-m, 111 lb-ft).
Spark Plugs: 20.0-25.0 Nm (2.0-2.5 kgf-m, 15-18 lb-ft).
Oil Filter Cartridge Housing: 18.0 Nm (1.8 kgf-m, 13 lb-ft).
AVCS Camshaft Sprocket Bolts: 90.0 Nm (9.2 kgf-m, 66 lb-ft).
Flywheel / Drive Plate Bolts: 55.0 Nm (5.6 kgf-m, 41 lb-ft).
Timing Chain Tensioner Bolt: 25.0 Nm (2.5 kgf-m, 18 lb-ft).
The Subaru FB16 engine was primarily utilized in
European and Japanese markets where small-displacement engines are favored for
fuel economy, taxation structures, and emissions compliance. Applications
include:
Subaru Impreza (GP2/GP3/GJ2/GJ3 Generation): 2011-2016, in sedan and hatchback
body styles across European and Asian markets.
Subaru Impreza (GT2/GT3/GK2/GK3 Generation): 2016-2023, continuing the 1.6-liter
engine as a base powertrain in markets where smaller displacement was preferred.
Subaru XV / Crosstrek (GP/GT Generation): 2012-2023, in base model
configurations across European and Asian markets, offering the FB16 as a
fuel-efficient alternative to the larger FB20 engine.
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