EG 33 Specification

General

The Subaru EG 33 is a 3300cc horizontally opposed 6-cylinders engine made from an aluminium alloy. It is a 4-stroke cycle, water-cooled, DOHC 24-valve engine. The fuel system utilizes an MPFI (multi port fuel injection) design. A summary of the major construction and function of the features is given below.

The cylinder head is a centre-plug type that utilizes pent-roof combustion chambers. The four valve design is provided with two intake valves and two exhaust valves per cylinder. The intake and exhaust ports are arranged in a cross-flow design.
The exhaust camshafts on the left and right banks are driven by a single timing belt. An anti-backlash gear arrangement, on the exhaust camshaft, engages with a gear on the intake camshaft to provide rotational drive.
A single timing belt drives the two camshafts on both banks whilst also providing drive to the water pump on the right hand bank. An automatic belt tensioner provides constant tension through hydraulic means to eliminate maintenance.
The crankshaft is supported by seven bearings to provide high rigidity and strength.
The cylinder block is constructed from die cast aluminium with integrated cast-iron cylinder liners.

Timing Belt

A single timing belt drives two exhaust camshafts (one in the left and one on the right bank). The back of the belt is also used to drive the water pump. The timing belt teeth have a specially designed round profile to provide quiet operation. The timing belt is constructed from a strong and inflexible core wire, a wear-resistant canvas and heat-resistant rubber material. A hydraulic belt-tension adjuster constantly maintains specified belt tension to correctly drive the camshafts, as well as to provide a "maintenance-free" advantage.

Camshaft

The DOHC engine uses four camshafts in all; intake and exhaust camshafts on the RH bank and intake and exhaust camshafts on the LH bank. Each camshaft has a gear which allows the exhaust camshaft to drive the intake camshaft. The intake camshaft also has a sub gear for eliminating gear backlash thereby reducing gear noise. The cam lobe is finished with "chill" treatment to increase wear resistance and anti-scuffing properties. Each camshaft is supported by four journals with three camshaft caps and a front camshaft cap. Each camshaft flange is supported by a groove provided in the cylinder head to receive thrust force.

Hydraulic Lash Adjuster

The hydraulic lash adjuster is located between the camshaft and valve stem. The top surface of the hydraulic-lash adjuster is always in contact with the cam face. The cam directly pushes the lash adjuster to open or close the valve. The engine oil flows through the cylinder head and into the lash adjuster so as to always maintain zero valve clearance.

Action when the valve starts to lift When the cam begins to push the lash adjuster, the bucket and plunger are pushed down. At the same time, the body is pushed up by the reaction from the valve stem. This causes the high pressure chamber to compress, increasing the oil pressure in the high pressure chamber.
Action while the valve is lifted As long as the cam is pushed by the lash adjuster, the oil pressure in the high pressure chamber is held high. The oil in the high pressure chamber leaks through a very small clearance between the plunger and body. Since the high pressure chamber is compressed in a very short time, almost no change occurs in the oil quantity inside the high pressure chamber. Accordingly, the bucket, plunger and adjuster body work as an integral unit to push down the valve stem to open the valve. The passage for supplying oil from the cylinder head to the lash adjuster is closed during this period, and no oil flows into the lash adjuster.
Action when the valve stops lifting When the cam completes its lash adjuster pressing stroke, the passage for supplying oil from the cylinder head to the lash adjuster opens, allowing oil to flow from the cylinder head into reservoir II of the lash adjuster. Since the pressure in the high pressure chamber is lower than the pressure in reservoir II, the check ball is pushed down by the oil pressure in reservoir II. Accordingly, oil flows into the pressure chamber until the oil pressure becomes equal between the high pressure chamber and reservoir II. Under the action of this oil pressure, the body is pressed against the valve stem and the bucket against the camshaft.

Cylinder Head

Combustion chambers in the cylinder head are compact, centre plug, pent-roof types which feature a wide 'squish" area for increased combustion efficiency. Four valves (two intake and two exhaust), which are arranged in a cross-flow design. are used per cylinder. The cylinder head gasket is made from carbon material (not asbestos). Its core is metal provided with metal hooks to increase resistance to both heat and wear. The inner side of grommets used in the cylinder bore are reinforced with wire to withstand both high combustion pressure and temperature.

Cylinder Block

The cylinder block is manufactured form die cast aluminium. The

The cylinder liners are made from cast iron and are dry types which are totally cast with the aluminium cylinder block. Seven main journal block designs are employed to increase stiffness and quiet operation. The oil pump is located in the front centre of the cylinder block and the water pump is located at the front of the left-cylinder bank. At the rear of the right-cylinder block is a separator which eliminates oil mist contained in the blow-by gas.

Crankshaft

The crankshaft is supported by seven bearings to provide high rigidity and strength. The corners of the crankshaft journals and webs, as well as the crank pins and webs, are finished with fillet-rolled work to increase strength. The seven crankshaft bearings are made from aluminium alloy and the No. 5 bearing is provided with a flanged metal to receive thrust force.

Piston

The piston skirt has a "slipper" design to reduce weight and sliding. The oil control ring groove utilizes a slit design. The piston pin is located in an offset position. The Nos, 1, 3 and 5 pistons are offset in the lower direction while the Nos. 2, 4 and 6 pistons are offset in the upper direction. The piston head is recessed for both the intake and exhaust valves. It also has symbols used to identify the location and the direction of installation. Three piston rings are used for each piston-two compression rings and one oil ring. The top piston ring has an inner-bevel design and the second piston ring has an interrupt design to reduce oil consumption.

Last Updated: Thursday August 31, 2006

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