Block and crankcase
Like its EJ20 predecessor, the Subaru EJ201 and EJ202 engines had an
aluminium alloy block with 92.0 mm bores – with cast iron dry-type cylinder
liners – and a 75.0 mm stroke for a capacity of 1994 cc. The cylinder block
for the EJ201 and EJ202 engines had an open-deck design whereby the cylinder
walls were supported at the three and nine o’clock positions.
crankcase for the EJ201 and EJ202 engines had five main bearings and the
flywheel housing was cast with the crankcase for increased rigidity. For the
EJ201 and EJ202 engines, the crankshaft thrust bearing was relocated to the
rear of the crankshaft – this reduced the transfer of natural engine
frequencies to the transmission and driveline.
While the pistons for the EJ201 and EJ202 engines continued to be produced
from cast aluminium, the pistons were lighter than those in its EJ20
predecessor. To reduce friction, the pistons for the EJ201 and EJ202 engines
had reduced piston pin offset and a molybdenum coating. Other features of
the pistons included solid-type piston skirts, flat top combustion surfaces
and reduced top land to cylinder clearance.
The air intake system for the EJ201 and EJ202 engines was tuned to achieve
high torque in the low to medium engine speed range. For lower intake air
temperature, the air inlet duct received air from outside the under bonnet
area. Furthermore, two resonators were incorporated in the air duct to
‘smooth’ the air flow and a large still air box - mounted on the throttle
chamber - improved engine response and quietness.
The EJ201 and EJ202 engines had an aluminium alloy cylinder head with
cross-flow cooling. Unlike the EJ20 engine, the intake ports for the EJ201
and EJ202 engines created a ‘tumble swirl’ motion for air as it entered the
cylinder for better mixing of the air and fuel for more uniform flame travel
and faster combustion. According to Subaru, the tumble swirl action allowed
for maximum gas pressure (downward force) to be applied to the piston 10-15
degrees ATDC (after top dead centre) when the maximum turning moment on the
crankshaft occurred, thereby increasing power output.
Camshaft and valves
The EJ201 and EJ202 engines had a hollow-type single overhead camshaft
(SOHC) per cylinder bank. Due to the cylinder head offset, the left camshaft
was longer than the right camshaft to align the cam belt sprockets. Both
camshafts were driven by a single belt which had round profile teeth for
quiet operation and was constructed of wear-resistant double canvas and heat
resistant rubber materials with a wire core. Furthermore, the timing belt
had an automatic tensioner which allowed for thermal expansion and
contraction. The recommended replacement interval for the cam belt was
100,000 kilometres or four years, whichever occurred first.
EJ201 and EJ202 engines had four valves per cylinder that were actuated by
roller rocker arms. Valve clearance checking/adjustment was only necessary
every 150,000 kms.
Injection and ignition
The EJ201 and EJ202 engines had multi-point sequential fuel injection and
centrally located spark plugs. The EJ201 and EJ202 engines had two ignition
coils (one for each pair of cylinders, i.e. 1-2 and 3-4) which fired the
spark plugs directly twice per cycle. The ignition knock control system had
‘fuzzy logic’ that enabled the maximum ignition advanced angle to be used
without detonation since the programme continually adapted to changes in
environmental conditions and fuel quality.
The EJ201 and EJ202
engines had a compression ratio of 10.1:1, compared to 9.7:1 for its EJ20J
predecessor. According to Subaru, the better air/fuel mixing provided by the
tumble swirl intake ports made the EJ201 and EJ202 engines less susceptible
to detonation or pinging, enabling a higher compression ratio.
the EJ201 and EJ202 engines, the injection and firing order was 1-3-2-4.
2003 Subaru BL/BP Liberty: EJ202 changes
Subaru BL/BP Liberty
which was introduced in 2003, a number of
changes were introduced for the EJ202 engine:
- A lighter cylinder block and head;
- Thinner and lighter cylinder liners;
- A sintered crankshaft journal;
- A re-shaped intake manifold; and,
- A new 4-2-1 exhaust system with equal length header pipes.