3ZR-FE Toyota engine

Introduction

The 3ZR-FE was a 2.0-litre four-cylinder petrol engine that was a member of Toyota’s ‘ZR’ engine family. Key features for the 3ZR-FE engine included its aluminium alloy cylinder block and head, offset crankshaft, double overhead camshafts, four valves per cylinder actuated by roller rocker arms and dual VVT-i.

For Australia, the 3ZR-FE was first introduced in the E150 Corolla Ultima in 2010 and subsequently used for the XA40 RAV4 (see table below).

The 3ZR-FE engine had a service weight of 116 kg.

3ZR-FE block

The 1987 cc 3ZR-FE engine had a die-cast aluminium alloy block with 80.5 mm bores and 97.6 mm stroke; compared to the 1.8-litre 2ZR-FE, bore length was unchanged but stroke was increased by 9.3 mm (from 88.3 mm). For compact dimensions, the 3ZR-FE engine had 7 mm between its cylinder bores for compact dimensions.

The 3ZR-FE engine had spiny-type cast iron liners in which the casting exteriors formed large irregular surfaces to enhance adhesion between the liners and the aluminium cylinder block – this aided heat dissipation, reduced heat deformation of the cylinder bores and lowered operating temperature.

Within the blowby gas passage of the cylinder block, the 3ZR-FE engine had an oil separator which separated engine oil from the blowby gas to reduce oil degradation and the consumption of engine oil.

Crankshaft, connecting rods and pistons

The 3ZR-FE crankshaft had five journals and eight balance weights. To reduce the forces on the side of the cylinder walls, the crankshaft was offset by 8 mm to the intake side of the bore centres. Furthermore, the lining surface of the big-end crankshaft bearings was micro-grooved to optimise oil clearance, improve cold-cranking performance and reduce vibration.

The 3ZR-FE engine had steel connecting rods and, to reduce mass, plastic region tightening bols. Like the crankshaft bearings, the lining surface of the connecting rod bearing was micro-grooved.

The 3ZR-FE engine had aluminium alloy piston with full floating-type piston pins. To reduce friction, the 3ZR-FE engine had low tension piston rings and resin-coated piston skirts. The groove of the top piston ring underwent a hard anodizing treatment for abrasion resistance, while the no.1 compression ring had an inside bevel shape to reduce blowby gas and a Physical Vapor Deposition (PVD) coating for wear resistance. The 3ZR-FE cylinder block contained piston oil jets for cooling and lubrication – these jets contained a check ball to prevent oil from being fed when oil pressure was low.

Intake

The 3ZR-FE engine had a plastic inlet to reduce mass and heat transfer from the cylinder head. The 3ZR-FE engine had a linkless-type throttle body and Toyota’s ‘Electronic Throttle Control System – intelligent’ (ETCS-i) which controlled throttle valve opening according to with the amount of accelerator pedal effort and the condition of the engine. To improve the flow of air within the intake manifold, mesh was used between the throttle body and the intake manifold.

The 3ZR-FE engine had upright, Siamese-type intake ports to increase intake efficiency and reduce the overall surface area of the intake port walls.

Cylinder head

The 3ZR-FE engine had an aluminium cylinder head that was mounted on a triple-layer metal type cylinder head gasket. The die-cast aluminium cylinder head cover contained an oil delivery pipe for lubrication of the sliding parts of the roller rocker arm.

Camshafts

The 3ZR-FE engine had double overhead camshafts – made from cast iron alloy – that were driven by a roller chain that had an 8 mm pitch. To lubricate the chain, the die-cast aluminium timing chain cover contained an oil jet. The ratchet-type chain tensioner had a non-return mechanism and used a spring and oil pressure to maintain chain tensioner; the tensioner also suppressed noise generated by the timing chain.

For the 3ZR-FE engine, the cam profile was designed with an indented R (radius) to increase valve lift when the valves began to open and finished closing.

Valves

The 3ZR-FE engine had four valves per cylinder – two intake and two exhaust – that were actuated by roller rocker arms which had built-in needle bearings to reduce friction between the cams and roller rocker arms.

At the fulcrum of each roller rocker arm there was a hydraulic lash adjuster which consisted of a plunger, plunger spring, check ball and check ball spring. The oil pressure and the spring force that acted on the plunger pushed the roller rocker arm against the cam to adjust the valve clearance that was created during the opening and closing of the valve. As a result, the hydraulic lash adjusters maintained constant zero valve clearance.

The 3ZR-FE engine had an included valve angle of 29 degrees.

Dual ‘Variable Valve Timing – intelligent’ (VVT-i)

The 3ZR-FE engine had a dual VVT-i system that could vary inlet and exhaust valve timing. A VVT-i controller was fitted on the front of the intake and exhaust camshafts and an oil passage in the intake and exhaust camshafts supplied engine oil to the VVT-i system. The ECU controlled camshaft advance and retard via an oil-control valve that was mounted on the cylinder head and vane-type actuators on the ends of the four camshafts.

The dual VVT-i system had four main operating scenarios:

• Low engine temperature, engine start, idling or light load: inlet camshaft on full retard and exhaust camshaft on full advance – this eliminated valve overlap and reduced the volume of exhaust gas blowback into the cylinder and inlet ports;
• Medium-load range: inlet timing was advanced and exhaust timing was retarded (for increased overlap). These settings increased internal exhaust gas recirculation (EGR) to reduce nitrous oxides and reduced pumping losses;
• High-load range, low-to-medium engine speed: inlet timing was advanced to close the intake valve earlier – this reduced the volume of intake air blowback into the inlet ports and improved volumetric efficiency; and,
• High-load range, high engine speed: inlet camshaft timing was retarded and exhaust timing advanced. By retarding inlet timing according to the inertial force of the inlet air, volumetric efficiency and power were improved.

Injection and ignition

The 3ZR-FE engine had sequential fuel injection via long-nozzle, 12-hole injectors. The 3ZR-FE engine had pentroof type combustion chambers and both the cylinder head and the piston crown had taper squish areas around the circumference of the chambers to improve intake efficiency and anti-knocking performance.

The 3ZR-FE engine had Toyota’s ‘Direct Ignition System’ (DIS) in which there was one ignition coil (with igniter) for each cylinder. With Toyota’s ‘Electronic Spark Advance’ (ESA), ignition timing was determined by the ECM based on inputs from sensors and adjusted according to knocking.

The 3ZR-FE engine had long-reach, thin-electrode type iridium tipped spark plugs that were located at the centre of the combustion chamber. The 3ZR-FE engine had a compression ratio of 10.0:1 and firing order of 1-3-4-2.

Exhaust

The 3ZR-FE engine had a stainless steel exhaust manifold with two integrated three-way catalytic converters. Ball joints were used to join the exhaust manifold to the front exhaust pipe and the front pipe to the tailpipe.