Subaru EZ30R Engine

Introduction

Subaru’s EZ30R was a 3.0-litre horizontally-opposed (or ‘boxer’) six-cylinder petrol engine. Replacing Subaru’s EZ30D, the EZ30R engine was first introduced in the Subaru BP Outback 3.0R in 2003 and subsequently offered in the Subaru BL/BP Liberty 3.0R and Subaru Tribeca. Compared to the EZ30D engine, changes for the EZ30R included:

• A lighter cylinder head and block by ‘eliminating excessive reinforcement’;
• Rounder cylinder liners;
• Variable intake valve timing and variable valve lift (AVCS+);
• A revised cylinder head with three independent exhaust ports;
• The introduction of electronic throttle control; and,
• Twin mufflers.

The EZ30R engine was 816.4 mm wide, 438.4 mm long, 643.5 mm high and weighed 180 kg.

This article considers the EZ30R engine as it was supplied in Australian-delivered vehicles market; specifications for other markets may differ. For easier identification, AustralianCar.Reviews has adopted the convention of referring to the pre-2003 Subaru H6 engine as the EZ30D and the post-2003 H6 engine as the EZ30R.

EZ30R block

The EZ30R engine had a die-cast aluminium cylinder block with 89.2 mm bores and an 80.0 mm stroke for a capacity of 2999 cc. Within the bores, the EZ30R engine had monoblock cast iron cylinder liners.

For the EZ30R engine, the water jackets were independent for the right and left halves of the block. The block halves were bolted together with 19 bolts (all located on the right bank of the engine), while the cylinder block and transmission cased were attached with 11 bolts.

The crankshaft for the EZ30R engine was supported by seven main bearings.

Cylinder head and camshafts

The EZ30R engine had an aluminium cylinder head with chain-driven double overhead camshafts (DOHC) per cylinder bank. The camshafts were made from carbon steel pipes and had sintered metal lobes. During construction, the lobes were affixed to the steel pipes using a sintered metal paste; the camshafts were then baked until the paste hardened. For the EZ30R engine, the lobes of the camshafts were offset by 1 mm to rotate the camshaft bucket and shim to reduce wear.

The EZ30R engine had two timing chains – the left timing chain had 148 links and the right timing chain had 134 links. The timing chains were sprayed with oil from a jet located on the oil pump relief valve housing and did not require maintenance since oil pressure and spring tension maintained chain tension.

AVCS and Variable Valve Lift

The EZ30R engine was fitted with Subaru’s ‘Active Valve Control System’ (AVCS) with Variable Valve Lift, a combination sometimes referred to as AVCS+. Subaru’s AVCS+ system was developed by Porsche and based on its own VarioCam Plus.
 

AVCS

The Active Valve Control System (AVCS) provided variable intake valve timing by rotating the intake camshaft relative to the camshaft sprocket, within a maximum range of 50 crankshaft degrees. The Engine Control Module (ECM) calculated the optimum valve timing based on intake airflow, engine coolant temperature, throttle position and camshaft position sensors. The ECM would then send a signal to an Oil Control Valve (OCV) – positioned at each intake camshaft sprocket – which controlled the oil pressure that was supplied to the advance and retard chambers within the AVCS actuator.

As per the table below, the EZ30R engine had intake duration of 250 degrees and exhaust duration of 232 degrees; valve overlap ranged from -3 to 47 degrees.

VVL

The intake camshaft was machined with a split lobe for each intake valve – the centre of the lobe was the low-speed lobe, while the outer lobes were the high-speed lobes. The lobes could be engaged in response to a signal from the ECM to an oil switching valve (OSV) in each cylinder head which supplied oil pressure to a switchable tappet. The inputs for Variable Valve Lift are understood to be the same as for AVCS.

The variable valve lift system only changed the lift of one of the intake valves for each cylinder since the other intake valve always provided high lift. The operation of the variable valve lift system may be summarised as follows:

• At engine speeds below 2000 rpm, valve lift for one of the intake valves was reduced to increase intake air speed and to create a swirl effect within the combustion chamber (since the lift of the two intake valves differed). As a result of the faster intake air speed and better mixture formation, a higher torque output was achieved;
• At engine speeds between 2000-4000 rpm and with high loads, valve lift for the variable intake valve would be increased to reduce intake resistance for greater power; and,
• At engine speeds above 4000 rpm, high valve lift would be provided regardless of load.

Injection and ignition

The EZ30R engine had sequential, multipoint fuel injection via ‘air assist’ fuel injectors; the injection and firing order were 1-6-3-2-5-4. Dual air/fuel sensors were used to monitor fuel mixture after combustion and continual adjustments were made to reduce exhaust gas emissions.

The EZ30R had a direct ignition system with an individual ignition coil for each cylinder (i.e. ‘coil-on-plug’), eliminating the need for a distributor and spark plug wires. Dual knock sensors enabled the ECU to adjust ignition timing in response to combustion noise feedback.

The EZ30R engine had a compression ratio of 10.7:1; 95 RON premium unleaded petrol was specified so that the maximum possible ignition angle could be utilised.

Exhaust

The EZ30R engine had three exhaust ports per cylinder head, i.e. independent and equal length exhaust pipes for each cylinder. Relative to the EZ30D engine, the length of the pipes to the joint collection point was increased by 300 mm relative to the EZ30D engine for improved gas flow. The exhaust pipes were doubled skinned and had an air gap to maintain gas temperature for more rapid activation of the catalytic converter.