2JZ-GE Toyota engine

Introduction

The Toyota 2JZ-GE was a 3.0-litre inline six-cylinder engine that replaced the 7M-GE engine. Designed to run best at medium to high engine speeds, key features of the 2JZ-GE included its cast iron block, aluminium alloy cylinder head, double overhead camshafts and wide-angled valves. In 1997, the 2JZ-GE engine was upgraded and variable intake valve timing (‘VVT-i’) was introduced.

2JZ-GE block

The 2JZ-GE engine had a cast iron cylinder block with a skeleton structure that included eleven oil return and blow-by gas passages and two main oil holes. With 86.0 mm bores and an 86.0 mm stroke, the 2JZ-GE engine had a capacity of 2997 cc. To reduce noise and enhance rigidity the external walls were curved. Furthermore, the air conditioning compressor, alternator and other ancillary components were attached directly to the cylinder block.

Crankshaft, connecting rods and pistons

The crankshaft for the 2JZ-GE engine had seven journals and twelve counterweights; both pins and journals were induction-hardened to increase rigidity. The crankshaft operated on aluminium alloy bearings, while the bearing caps were fitted using plastic region tightening bolts. The 2JZ-GE engine had a dual-mode crankshaft damper pulley which combined a torsional damper and bending damper to reduce both torsional and bending vibration.

The 2JZ-GE engine had hot-forged connecting rods, while each connecting rod and connecting rod cap were joined with knock pins and plastic region tightening bolts. At the small end of the connecting rod, a bimetal bushing was press-fitted into the piston pin hole. At the big end of the connecting rod, an oil jet sprayed oil onto the underside of the pistons for cooling.

For the 2JZ-GE VVT-i engine, the connecting rods were made of high-strength vanadium steel for mass reduction and due to the higher output of the engine.

The aluminium alloy pistons for the 2JZ-GE engine had slotless type oil return holes in the oil ring grooves to lower the temperature in the top ring groove. To reduce friction,

• The side rails of the oil ring were treated with a gas nitriding process;
• The surface of the no.1 compression ring was chromium plated; and,
• The piston skirt areas were coated with resin.

For the 2JZ-GE VVT-i engine, the valve recess in the piston was reduced to improve combustion efficiency and the skirt portion was reduced for weight reduction.

Cylinder head

The 2JZ-GE engine had an aluminium alloy cylinder head that was mounted on a single-layered metal gasket and used plastic region tightening bolts. The cylinder head had upright and small-diameter intake ports and sub-water jackets for cooling the intake ports – these design features contributed to torque production at low to medium engine speeds.

For the 2JZ-GE VVT-i engine, the cylinder head jacket was modified to improve cooling around the spark plugs so that the compression ratio could be increased. Furthermore, the cylinder head intake port adopted a smaller diameter to improve intake airflow velocity, increasing torque at low to medium engine speeds.

The 2JZ-GE engine had a three-part cylinder head cover in which the no.1 and no.2 cylinder head covers were made of magnesium to reduce weight; the cylinder head cover gaskets were made of acrylic rubber.

Camshafts

The 2JZ-GE engine had double overhead camshafts – made from cast steel – and heat-treated bearing caps. The camshafts had seven journals, six of which were located between two cams. To maintain tension, the belt-driven camshafts had an automatic tensioner that consisted of a spring and oil damper.

For the 2JZ-GE VVT-i engine, the intake camshaft had an oil passage to supply engine to the VVT-i system.

Valves

The 2JZ-GE engine had four valves per cylinder – two intake and two exhaust – that were made of heat-resistant steel and had an included valve angle of 45 degrees (i.e. the angle between the intake and exhaust valves). For wear resistance, the valve stem underwent a soft nitriding process and cobalt alloy was bound to the valve face. Valve dimensions were as follows:

• Intake valve diameter: 33.5 mm;
• Exhaust valve diameter: 29.0 mm;
• Intake valve lift: 8.26 mm; and,
• Exhaust valve lift: 8.41 mm.

To adjust the clearance between the back side of the cam-lobe and the valve on which it operated directly (i.e. without an intermediate rocker arm), the 2JZ-GE engine had outer shim type valve adjusting shims. For the 2JZ-GE VVT-i engine, valve spring tension was reduced.

2JZ-GE valve timing: without VVT-i

As per the table below, the 2JZ-GE engine without VVT-i had valve overlap of 6 degrees, intake duration of 233 degrees and exhaust duration of 236 degrees

2JZ-GE valve timing: VVT-i (Variable Valve Timing – intelligent)

For the 2JZ-GE VVT-i engine, the intake camshaft was controlled over a range of 60- from 12 degrees ATDC to 48 degrees BTDC – to provide inlet valve timing according to engine speed, intake air volume, throttle position and coolant temperature, the ECU determined optimal valve timing. For the 2JZ-GE VVT-i engine, intake duration was 233 degrees and exhaust duration was 226 degrees.

• An outer gear that was driven by the timing belt;
• An inner gear that was affixed to the camshaft; and,
• A movable piston that was placed between the outer gear and inner gear.

The piston had helical splines (twisted, vertical grooves) and moved in the axial direction to shift the phase of the outer gear and inner gear, thus causing valve timing to change continuously.

The camshaft timing oil control valve controlled the position of the spool valve in response to the ECU, applying hydraulic pressure to the intake camshaft timing pulley to the advance or retard side. The ECU used signals from the camshaft position sensor and the crankshaft position sensor to detect the actual valve timing, thus providing feedback control to achieve the targeted valve timing.

When the engine was stopped, the camshaft timing oil control valve was in its mode retarded state.

Intake and throttle

Initially, the 2JZ-GE engine had a conventional throttle body whereby the throttle valve opening was determined by the amount of accelerator pedal effort. Furthermore, the throttle body and Idle Air Control (IAC) were integrated into a single unit to reduce weight and the number of component parts.

For the 2JZ-GE VVT-i engine, the ‘Electronic Throttle Control System – intelligent’ (ETCS-i) was introduced. For ETCS-i, the ECU calculated the optimal throttle valve opening according to driving conditions and used a control motor for the throttle valve opening. ETCS-i controlled the Idle Speed Control (ISC) system, traction (TRC) system and cruise control; as a result, the ISC valve and sub-throttle valve were discontinued. Furthermore, the 2JZ-GE VVT-i engine had a thermostat in its throttle body. The thermostat used the thermal expansion of wax to close a valve and stop the flow of warm coolant when coolant temperature was high in the throttle body’s warm coolant passage – this prevented throttle body temperature from rising more than needed.

The intake air which passed through the throttle body was directed to the cylinders via an air connector, intake air chamber and intake manifold. The intake air chamber was fitted to the air connector via a re-usable, three-layered stainless steel gasket which had a silicone rubber coating. For the original 2JZ-GE engine, the intake manifold was fitted to the intake air chamber and the cylinder head via a gasket which had a metallic coating. For the 2JZ-GE VVT-i engine, however, a heat-barrier gasket made of phenol resin was used between the cylinder head and the intake manifold to reduce intake air temperatures and improve charging efficiency.

The 2JZ-GE intake included an Acoustic Control Induction System (ACIS) which varied the length of the intake pipe to harness the effect of inlet pulsations to improve engine performance. ACIS consisted of:

• A bulkhead to divide the intake manifold into stages; and,
• An intake air control valve in the bulkhead which opened and closed to vary the effective length of the intake manifold according to engine speed and throttle valve opening angle.

Injection and ignition

The 2JZ-GE had L-type electronically-controlled, multiport sequential fuel injection (SFI). In this system, air introduced from the throttle body, air pipe and air gallery flowed through the air chamber – formed by the O-ring and insulator – under the fuel injector and was then mixed with the fuel. The air-fuel mixture was introduced into each cylinder every time the engine completed two revolutions. While the 2JZ-GE engine had two-hole fuel injectors, compact four-hole injectors were introduced for the 2JZ-GE VVT-i.

For the 2JZ-GE VVT-i engine, a returnless fuel system was introduced to reduce evaporative emissions.

For Europe (but not Australia or the USA), the 2JZ-GE VVT-i engine had an Air Assist Fuel Injection System that was designed to regulate air intake (atmospheric side) using the throttle valve and direct it to the nozzle of the fuel injector inside the intake manifold (negative pressure side) – this promoted atomisation of the fuel while reducing emissions.

The 2JZ-GE engine used Karman-Vortex air flow meter which measured the intake air volume electrically: as air flowed past the vortex generator, vortices were generated at a frequency proportional to the velocity of the air flow. The vortices were detected by subjecting the surface of a thin metal foil (mirror) to the pressure of the vortices and optically detecting the vibrations in the mirror by means of a luminous diode and a photo transistor. A calculation of the frequency could then determine the amount of air flow.

The Direct Ignition System (DIS) for the 2JZ-GE VVT-i engine was a two-cylinder simultaneous ignition system which ignited two cylinders simultaneously with one ignition coil. As such, the DIS system consisted of three sets of ignition coils that were integrated with plug caps and with high-tension cords attached directly onto the ignition coil.

The 2JZ-GE engine also had ‘Electronic Spark Advance’ (ESA) whereby ignition timing was determined by the ECM based on inputs from sensors and adjusted according to knocking. Furthermore, the 2JZ-GE engine had two piezo-electric type knock sensors.

The 2JZ-GE engine had pentroof type combustion chambers with spark plugs located near the centre of the chamber to improve anti-knocking performance. While the 2JZ-GE engine had a compression ratio of 10.0:1, the 2JZ-GE VVT-i engine had a compression ratio of 10.5:1. For Australia and Europe, the 2JZ-GE VVT-i engine introduced platinum-tipped spark plugs; the USA, however, had twin-ground electrode spark plugs.

The firing order for the 2JZ-GE engine was 1-5-3-6-2-4.

Exhaust

The original 2JZ-GE had dual exhaust manifolds – made from cast iron – that were connected to the cylinder block via stainless steel gaskets which had a laminated structure.

For the 2JZ-GE VVT-i engine, however, the exhaust manifold was made from stainless steel and the branch portion of the exhaust manifold was extended to utilise exhaust pulsations and improve exhaust gas flow, thereby improving torque at low to medium engine speeds.

The original 2JZ-GE engine had an exhaust gas recirculation (EGR) system which recirculated a portion of the exhaust gas back into the intake air-fuel mixture to slow down combustion in the cylinder and lower the combustion temperature – this, in turn, reduced the amount of NOx emissions. For the 2JZ-GE VVT-i engine, EGR was discontinued.

The 2JZ-GE engine had stainless steel exhaust pipes: the centre exhaust pipe separated into a ‘Y’ at the middle and each pipe after the ‘Y’ had its own sub-muffler. For the 2JZ-GE VVT-i engine,

• The front exhaust pipe adopted dual pipe construction to improve engine performance;
• The centre exhaust pipe had a larger diameter and a straight muffler to reduce exhaust pressure; and,
• The main muffler adopted a long tail pipe for quieter idle.

For emissions control, the 2JZ-GE had two monolithic type, three-way catalaytic converters. In the 2JZ-GE VVT-i engine for Europe and Australia, three-way catalytic converters were integrated with the exhaust manifold and the three-way catalytic converter under the floor was discontinued.