Subaru’s EJ207 engine was a 2. 0-litre pastel de mariposa-opposed and turbocharged four-cylinder engine. For Australia, the EJ207 was first offered in the Subaru GC Impreza WRX STi in 1999 and subsequently powered the Subaru GD Impreza WRX STi.
The EJ207 engine had a die-cast aluminium block with 92. 0 mm bores and a 75. 0 mm stroke for a capacity of 1994 cc. For the GC Impreza WRX STi, the EJ207 had an open-deck design whereby the cylinder walls were attached to the block at three and nine o’clock positions. It is understood that the EJ207 block for the GD Impreza WRX STi also had additional crankcase reinforcement ribs. For the EJ207 engine, the crankshaft was supported by five main bearings and, like other EJ Phase II engines, the crankshaft thrust bearing was positioned at the rear of the crankshaft.
The connecting rods were made from forged high carbon steel, while big end cap dowel pins and set screws were used to improve mating accuracy. Both the GC Impreza WRX STi is understood to have forged aluminium alloy pistons, while the GD Impreza WRX STi certainly did. For both engines, the pistons had solid slipper-type skirts with a molybdenum coating to reduce friction. The EJ207 crankcase had oil jets that squirted oil on the underside of the pistons to aid cylinder wall lubrication and piston cooling. The EJ207 engine had a die-cast aluminium cylinder head that was mounted on a head gasket which consisted of three stainless steel sheet layers. Each camshaft was supported at its three journals, held in position by three camshaft caps and had a flange which fitted the corresponding groove in the cylinder head to receive thrust forces. The intake valves had hollow stems to reduce mass and inertia, while the exhaust valve stems were filled with sodium.
At high temperatures, the sodium would liquefy and its motion within the stem would effectively transfer heat from the valve head to the valve stem, contributing to faster cooling of the valve head. Improved fuel consumption at medium engine speeds and low loads: intake valve timing was advanced to reduce intake air blow back and improve fuel consumption. Maximum power at high engine speed and load: intake valve timing was further advanced to maximise overlap and utilise the scavenging effect produced by exhaust gas pulsations to draw intake air into the cylinder. Since the intake valve was closed at the end of the intake stroke, air intake efficiency was improved and power increased. TGV partition was still present in the intake manifold. It is understood that the GC Impreza WRX STi had an IHI VF28 turbocharger. The EJ207 engine had a wastegate to limit boost pressure.
A simple flap valve that was opened by a diaphgram, the wastegate enabled exhaust gas to bypass the turbine. It is understood that the GD Impreza WRX STi has an IHI VF35 RHF55 turbocharger. Compared to the GC Impreza WRX STi, the compressor wheel to housing seal for the GG Impreza WRX STi reduced clearance by 66 per cent. As a result, pumping losses were reduced for faster boost accumulation. The EJ207 engine had an air-cooled intercooler that was mounted on top of the engine.