2ZZ-GE Toyota I4 Engine

Introduction

First offered in Australia in 1999 in the Toyota T230 Celica, the 2ZZ-GE was a 1.8-litre four-cylinder petrol engine. The 2ZZ-GE and related 1ZZ-FE were members of Toyota’s ZZ engine family and featured alloy construction to reduce mass. Whereas the 1ZZ-FE was developed for economy and low-end torque, the 2ZZ-GE was developed for top-end power and had a 7800 rpm redline. The 2ZZ-GE engine had a dry weight of 115 kg.

From 2003 to 2007, the 2ZZ-GE powered the E120 Corolla Sportivo.

2ZZ-GE block

The block of the 1796 cc 2ZZ-GE engine was made of fine ceramic-fibre and grain-reinforced aluminium-silicon alloy. The 2ZZ-GE engine had 82.0 mm bores and an 85.0 mm stroke, with 5.5 mm between adjoining bores (also known as bore to bore wall thickness). Whereas the 1ZZ-FE engine had cast iron cylinder liners, the 2ZZ-GE had Metal Matrix Composite (MMC) cylinder walls for linerless construction. Furthermore, the cylinder block was split at the crankshaft centreline and the cast aluminium lower block carried five main bearing caps.

The 2ZZ-GE block featured external ribbing for added rigidity, while the water-pump swirl chamber and the inlet passage to the pump were integrated into the block for compact packaging and mass reduction.

Crankshaft, connecting rods and pistons

The 2ZZ-GE engine utilised a forged crankshaft that had five journals and eight balance weights. The ladder-type crankshaft bearing caps had chill-fitted cast-iron inserts around the journal position. According to Toyota, these features provided greater strength, reduced noise, greater rigidity for the coupling to the transaxle and resistance from heat deformation. Furthermore, the oil-filter bracket, air conditioner compressor bracket and rear oil-seal retainer were integrated into the bearing cap to reduce the number of parts. Passage holes were provided in the crankshaft bearing area of the cylinder block for better airflow at the bottom of the cylinder and reduced back pressure at the bottom of the piston.

To reduce reciprocating mass and friction, the 2ZZ-GE engine had narrow and lightweight connecting rods which featured nutless-type plastic region tightening bolts. The pistons were made from an aluminium alloy and, to reduce friction, had an iron and tin coating. Furthermore, the pistons were internally cooled by oil jets and used full floating-type piston pins.

Cylinder head

The 2ZZ-GE engine had an all-alloy cylinder head with double overhead camshafts (Toyota’s ‘twin cam’ design) and four valves per cylinder that were actuated by shimless bucket-type tappets. The camshaft was driven by an 8 mm pitch roller chain which featured a lubricating oil jet and auto tensioner.

As denoted by the ‘G’ in its name, the 2ZZ-GE engine had widely-angled valves for freer breathing: the valve included angle was 43 degrees. For the 2ZZ-GE engine, the intake valves had a 34.0 mm diameter and the exhaust valves had a 29.0 mm diameter. To reduce intake resistance and valve train mass, narrow valve stems were used.

Like the1ZZ-FE, the 2ZZ-GE engine featured ‘laser-clad valve seats’ whereby the valve seats were made by welding high-resistance material into the port, with the valve seat then machined into that material. Compared to a conventional shrink-fit valve seat, the thinner laser-clad valve seats provided greater air flow and improved cooling around the valves.

Variable valve timing – intelligent (VVT-i)

For the 2ZZ-GE engine, Toyota’s ‘variable valve timing – intelligence’ (VVT-i) provided continual variations of the intake valve timing according to engine speed, throttle position, inlet camshaft angle, engine coolant temperature and intake air volume.

For both theT230 Celica and E120 Corolla Sportivo, the VVT-i system could vary inlet camshaft timing over a range of 43 degrees relative to crankshaft angle. However, the variable lift system (detailed below), had the effect of increasing valve opening duration such that the full range of inlet timing variation was 68 degrees as measured from the maximum retard intake valve opening in the low-medium engine speed range at minus 10 degrees BTDC (before top dead centre) to the maximum advance intake valve opening in the high engine speed range at 58 degrees BTDC.

VVT-i was controlled by the ECU and implemented via an oil-pressure activated ‘push-push’ type system. Specifically, the hardware for the VVT-i system consisted of:

• A camshaft timing oil control valve – mounted adjacent to the inlet camshaft gear wheel – that was controlled via a coil and plunger by the ECU. When the ECU sought to vary valve timing, it directed a signal to the spool-type oil control valve to provide oil pressure to either the ‘advance’ or ‘retard’ side of the four vane chambers; and,
• A VVT-i controller mechanism that consisted of a housing on the front of the timing wheel – driven via the timing chain – and a four-bladed vane that was coupled with the intake camshaft.

Inlet cam timing was set to the maximum retard position for engine start-up, operation at low engine temperature, idle and engine shut-down. To prevent any knocking noise, a locking pin in the controller locked the camshaft timing in the maximum retard position for engine start-up and immediately thereafter until oil pressure was established.

Intelligent variable valve timing with lift (VVTL-i)

In addition to variable inlet valve timing, the 2ZZ-GE engine had a variable valve lift system operated on the inlet and exhaust valves. At engine speeds above 6000 rpm, high-lift camshaft profiles were engaged and the cam lobes increased intake lift by 54 percent (from 7.25 to 11.2 mm) and exhaust lift by 38 per cent (from 7.25 mm to 10.0 mm). The high-lift cam profiles had the effect of increasing valve-opening duration and therefore the range of inlet timing variation. By increasing the lift of the intake and exhaust valves, a greater volume of air-fuel mixture could form in the combustion chamber for greater power.

For both theT230 Celica and E120 Corolla Sportivo:

• Inlet duration was 228 degrees in the low-to-medium engine-speed range and 292 degrees in the high-speed range (a duration range of 64 degrees); and,
• Exhaust duration was 228 degrees in the low-to-medium engine speed range and 276 degrees in high-speed range.

However,

• For theT230 Celica, valve overlap could vary between 4 degrees (full-retard inlet setting and low-speed lift settings) and 94 degrees (full advance inlet and high-speed lift settings); and,
• For the EE120 Corolla Sportivo, valve overlap could vary between 24 degrees (full-retard inlet setting and low-speed lift settings) and 118 degrees (full advance inlet and high-speed lift settings).

The hydraulically activated variable-lift mechanism was electronically-controlled by the ECU according to throttle position, inlet camshaft angle, coolant temperature (which had to exceed 60 degrees) and intake air volume. The variable-lift mechanism shared some of its hydraulic control hardware with the VVTi system and included:

• Eight rocker arms – one for each pair of valves – which had an integrated needle roller cam follower, a rocker arm pad and hydraulic rocker arm pin;
• Two rocker shafts positioned inboard of the camshafts; and,
• A spool-type oil control valve on the aft end of the inlet camshafts.

At engine speeds below 6000 rpm, the low-to-medium speed camshaft acted on the needle-roller cam follower and the rocker arm actuated its pair of valves. Simultaneously, the rocker arm pad would ride against the high-lift camshaft lobes, but moved freely within the rocker arm. In this state, the rocker pad did not contribute to rocker arm movement and therefore made no contribution to valve activation. When the engine was operating in the low-to-medium speed ranges, the oil control valve was open to the drain side.

When engine speed exceeded 6000 rpm, the oil control valve would close the drain side and hydraulic pressure would flow through the rocker shafts to the hydraulic rocker arm pin. The hydraulic pressure pushed the rocker arm pin out to lock the bottom of the rocker arm pad. With the rocker arm pad locked in its full extended position, the high-lift (high-speed) camshaft lobes would operate the rocker arm and actuate its pair of valves.

When engine speeds fell below 6000 rpm, the oil control valve would open on the drain side to relieve pressure on the cam changeover mechanism and allow the system to return to normal lift conditions.

Intake

For efficient engine breathing, the 2ZZ-GE engine had long and straight intake ports. For the 2ZZ-GE engine, the aluminium intake manifold and die-cast aluminium air intake chamber were welded together. Furthermore, a resonator was used within the intake to optimise mid-range torque and the intake duct had a variable valve which was closed at low engine speeds to reduce noise.

Injection and ignition

The 2ZZ-GE engine had sequential electronic fuel injection (EFI) with four-hole injector nozzles mounted in the inlet ports (to minimise cylinder wall wetting). An L-type hot-wire meter was used to measure air flow. The ‘Toyota Direct Ignition’ system was a distributorless, coil-on-plug system which featured electronic spark advance with a knock control system.

The combustion chambers had a pentroof design, while the piston crowns had a ‘tapered squish’ design to improve thermal efficiency and reduce the likelihood of engine knock (pre-ignition). The squish angle was shaped obliquely along the wall surface of the combustion chamber to improve airflow, promote swirl and enhance flame travel. The 2ZZ-GE engine had flat-topped pistons with valve clearance cut-outs to achieve an 11.5:1 compression ratio.

Exhaust

The 2ZZ-GE engine had a stainless steel exhaust manifold and a four-into-two-into-one extractor-type exhaust system which used a metal separator plate in the exhaust union.