The first opposition 4-cylinder engine was patented by Karl Benz in 1896. In 1971, engineers of Fuji Heavy Industries, which owns the automaker Subaru, “fell ill” with the idea of opposition engines.
In 1989, Japanese engineers introduced a new family of EJ engines, with a working volume of 1.5 to 2.5 liters. These engines were the main driving force of Subaru cars literally until 2010. There were created 23 modifications of EJ engines, the most powerful of which produces 305 hp.
In 1998, Fuji engineers modernized and lightened the engine block: liners became “wet”. Pistons were also lightened, the intake system and block heads were optimized.
This is an EJ202 engine removed from a 2000 Subaru Forester with 285,000 miles. This motor differs from the original version “open” aluminum block, cast iron liners and single-shaft 8-valve heads (4 valves per cylinder). Adjustment of thermal valve clearances is made by screws mounted in the rocker arms. This engine does not have timing controllers.
The timing drive uses a toothed belt, which must be changed every 100,000 km. The belt drives not only the camshafts, but also the pump.
Technical characteristics
| Characteristics | Value |
|---|---|
| Exact volume | 1994 cm³ |
| Power System | Injector |
| Power | 130 – 140 hp |
| Torque | 180 – 190 Nm |
| Cylinder block | Aluminum, opposition 4-cylinder (H4) |
| Cylinder head | Aluminum, 16 valves |
| Cylinder diameter | 92 mm |
| Piston stroke | 75 mm |
| Compression ratio | 10.1 |
| Engine (internal combustion engine) | SOHC |
| Hydrocompensators | No |
| Transmission timing | Belt |
| Fasoregulator | No |
| Turbocharger | No |
| What oil to use | 4.0 liter, 5W-30 |
| Ecological class | Euro 2/3 |
| Example service life | 270,000 km |
| Weight of complete engine | 135 kg |
Typical EJ20 engine problems and weaknesses
With its rather legendary history, Subaru’s 2-liter EJ20 opposition engine has a rather controversial reputation. Some people have this engine running more than 400,000 kilometers, while others have it constantly breaking down and being a source of high costs. We can safely say that the most survivable are atmospheric versions, such as EJ20, late EJ201 and EJ202 – relatively simple, with a single camshaft in the cylinder head, designed for 92 gasoline. Nevertheless, these engines are demanding to the quality of fuel and the quality of oil, which should be changed every 7500 km – so experience shows.
Miscellaneous trivia
The sensors of the Japanese engine are very reliable and usually do not present surprises. If the engine Subaru EJ202 suddenly began to stall at idle or keep high idle speeds, then you should inspect and clean the idle speed regulator flap. It is jammed, which causes a disturbance in the idle speed adjustment.
If the Subaru EJ202 engine won’t start at all, you should check the ignition switch or the fuel pump located in the tank, which fails when driving frequently on leftover fuel. The high voltage wires should be replaced every 50,000 miles. The ignition coils are double and very durable.
Jerky acceleration, increased fuel consumption – these are signs of failure of the mass flow sensor of the Subaru EJ202 engine.
Crankcase Ventilation
At the slightest problems with crankcase ventilation, the Subaru EJ202 engine very quickly squeezes out crankshaft and camshaft oil seals and oil together with them. Valve cover gaskets, camshaft plugs also start leaking. Valve system valve on Subaru EJ202 engine should be replaced, and the tubes should be cleaned from clots accumulated in them or also replaced with new ones. If the tubes dry out, air inflow occurs, which leads to improper mixture formation and engine power reduction.
Oil burn
Oil consumption of a liter and a half from change to change with frequent annealing is a normal phenomenon for EJ202 engine. But if oil consumption is also present during measured driving, it is almost certain that either the oil rings are lodged, or the engine has a worn cylinder-piston group. Usually at a mileage of 200,000 – 250,000 km the EJ202 engine needs to replace all piston rings.
In addition, the horizontal location of cylinders is a prerequisite for increased oil consumption, which is not able to independently flow down the cylinder walls. And here it is important not to miss the moment – the engine can “eat” almost all the oil, and the control lamp will light up only when there is only 700 grams of lubricant left in the oil pan.
Fourth Cylinder Knocking
A well-known design flaw of Subaru EJ engines is poor cooling of the 4th cylinder: the piston overheats, expands and begins to “scuff” its skirts and cylinder walls. And usually it is the piston skirts that wear out, and the cylinder surface does not suffer. When running cold, the engine knocks, and after warming up it stops. Many people drive like this. If this problem progresses, the engine starts to knock constantly and there is wear of the surface of the 4th and sometimes also of the 2nd cylinder. The cylinders become oval.
Overheating
But critical overheating of the Subaru EJ202 engine occurs with clogged radiators, engine operation on poor-quality or old antifreeze. At short-term overheating can jam the thermostat. If it jams in the closed position, the engine cooling will actually stop. In this case, various troubles occur, from deformation of the cylinder head, its cracking to jamming of the engine with damage to the engine block.
Signs of overheating, in addition to high coolant temperature on the thermometer: antifreeze leaks through the cylinder-head gaskets, bubbles in the expansion tank at the throttle on a hot engine, steam from the exhaust pipe.
Crankshaft
The crankshaft of the Subaru EJ opposition engine is sandwiched between half-blocks. Each of the connecting rods is connected to the crankshaft by its own journal – as on a 4-cylinder engine. However, neighboring pistons 1 and 2, 3 and 4 on the opposition do not move in counter-phase, but always occupy the same position: synchronously occupy the top or bottom dead points. Accordingly, the first and second pair of pistons of a 4-cylinder opposition engine move in antiphase. An opposed four is better balanced than an inline four, does not need balancer shafts, and generally develops more torque at low rpm.
All the journals of the compact crankshaft of the opposition four-cylinder engine are very narrow, hence the high load on them. The risk of rapid wear is very high if engine temperature conditions are not maintained and poor quality oil is used. Subaru turbo engines are particularly sensitive to lubrication quality.