1NZ-FE Toyota engine

Introduction

Toyota’s 1NZ-FE was a 1.5-litre four-cylinder petrol engine that was first introduced in theXP10 Echo. A member of Toyota’s ‘NZ’ engine family, the 1NZ-FE was related to the Atkinson-cycle 1NZ-FXE that was introduced in the XW10 Prius, but differed in that had:

• A conventional Otto cycle;
• A compression ratio of 10.5:1; and,
• A 6400 rpm redline.

The 1NZ-FE engine was subsequently used in the XP90 Yaris and XP130 Yaris models.

For models with manual transmissions, the 1NZ-FE engine had a service weight of 94.2 kg.

1NZ-FE block

The 1497 cc 1NZ-FE engine had an aluminium alloy cylinder block with 75.0 mm bores and an 84.7 mm stroke. The 1NZ-FE engine had thin-walled cast iron liners – which enabled a distance between the bores of 8 mm – with ‘spiny type’ construction in that their casting exteriors formed large, irregular surfaces for better adhesion with the cylinder block. This enhanced adhesion improved heat dissipation and reduced heat deformation of the cylinder bores.

The 1NZ-FE block contained a water pump swirl chamber and an inlet passage, while the rear portion of the block had a conical shape to improve coupling rigidity with the transaxle. Since the rear oil seal was pressed into the 1NZ-FE block, the rear oil seal retainer was omitted for compact packaging.

Crankshaft, connecting rods and pistons

The 1NZ-FE engine had an offset crankshaft that shifted the bore centre 12 mm towards the intake (relative to the crankshaft centre). As a result, the side force when maximum pressure was applied was reduced and, according to Toyota, fuel economy was improved by between one and three per cent. Furthermore, the crankshaft had five journals, four balance weights and an integrated crankshaft position sensor.

The steel connecting rods for the 1NZ-FE engine had caps that were held by plastic region tightening bolts. The aluminium alloy pistons had semi-floating type piston pins and low-tension rings. Furthermore, the piston head had a taper squish shape to improve combustion performance.

Cylinder head and camshafts

The 1NZ-FE engine had an aluminium alloy cylinder head. To maintain uniform temperature for the combustion chamber wall, the cylinder head contained a water jacket that was positioned between the exhaust port and spark plug boss.

The 1NZ-FE engine had double overhead camshafts (DOHC or Toyota’s ‘Twin Cam’) that were driven by a roller timing chain which had an 8.0 mm pitch; the timing chain was lubricated by engine oil from an oil jet. To reduce engine noise and frictional losses, the chain drive included a chain tensioner, chain tension arm and chain guide. The chain tensioner used a spring and oil pressure to maintain chain tension and had a ratchet type non-return mechanism.

A single-piece, aluminium die-cast timing chain cover sealed the front portion of the cylinder block and the cylinder head. For servicing of the chain tensioner, the timing chain cover included an access hole.

Valves

The 1NZ-FE engine had four valves per cylinder – two intake and two exhaust – that had a 33.5 degree included valve angle and were actuated directly by the camshafts. The valve lifters had shimless valve adjustment such that adjustment of valve clearance required the appropriate valve lifters to be replaced.

The dimensions of the 1NZ-FE valves were as follows –

• Intake valve face diameter: 30.5 mm;
• Intake valve stem diameter: 5.0 mm;
• Exhaust valve face diameter: 25.5 mm; and,
• Exhaust valve stem diameter: 5.0 mm.

VVT-i

For the 1NZ-FE engine, the ECU could calculate optimal valve timing from engine speed, vehicle speed, mass air flow, throttle position and water temperature inputs, and control the intake camshaft within a range of 60 degrees (of crankshaft angle).

As per the table below, valve overlap for the 1NZ-FE engine ranged from -5 degrees to 55 degrees (a range of 60 degrees). Furthermore, the 1NZ-FE engine had intake duration of 225 degrees and exhaust duration of 224 degrees.

• A housing driven from the timing chain; and,
• A vane coupled with the intake camshaft.

The camshaft timing oil control valve controlled the position of the spool valve according to signals from the ECU – this enabled hydraulic pressure to be applied to the VVT-i controller advance or retard side and cause rotation in the VVT-i controller vane circumferential direction. The ECU used signals from the camshaft position sensor and crankshaft position sensor to detect actual valve timing, thus providing feedback control to achieve the intended timing.

When the engine was stopped, the intake camshaft would be in its most retarded pressure for easy starting. When hydraulic pressure was not applied to the VVT-i controller immediately after the engine was started, the lock pin prevented movement of the VVT-i controller.

Injection and ignition

The 1NZ-FE engine had sequential fuel injection via 12-hole injectors that were fitted in the intake port in the cylinder head. The 1NZ-FE engine had pentroof-type combustion chambers with a taper squish shape and operated at a compression ratio of 10.5:1.

The 1NZ-FE engine featured Toyota’s distributorless ‘Direct Ignition System’ in which there was one ignition coil for each cylinder and the spark plug caps were integrated with an ignition coil. The 1NZ-FE engine used long-reach iridium-tipped spark plugs to increase the thickness of the surrounding cylinder head and so that the water jacket could be extended near the combustion chamber. The iridium-tipped spark plugs had 100,000 kilometre replacement intervals.

Exhaust and emissions

The 1NZ-FE engine had a long branch-type stainless steel exhaust manifold to improve torque at low to medium engine speeds. Furthermore, the 1NZ-FE engine had a rearward exhaust layout and double-wall construction for the exhaust pipe which connected to the three-way catalytic converter (TWC) – this contributed to faster warm-up of the TWC.

Ball joints were used for coupling the exhaust manifold to the front pipe and the exhaust pipe to the main muffler. The muffler included a spring control valve that could vary the length and resistance of exhaust gas flow. The valve opened steplessly when exhaust gas pressure overcame spring pressure. As a result, the valve would be closed at lower engine speeds to reduce exhaust noise and open at higher engine speeds to reduce back pressure and increase power output.

To reduce emissions, the 1NZ-FE engine had a returnless fuel system to reduce evaporative emissions. To reduce emissions,

• TheToyotaXP10 Echo had three vacuum switching valves (VSVs) and a vapor pressure sensor that were used to detect any evaporative emission leakage between the fuel tank and charcoal canister by measuring changes in fuel tank pressure; and,
• For theXP90 Yaris andXP130 Yaris, five hours after the ignition switch had been turned off, the ECM operated the canister pump module to detect evaporative emission leakages via changes in reference orifice pressure.

1NZ-FE: 2003 revisions

The 1NZ-FE engine was revised in 2003 due to the introduction of European STEP IV emissions regulations. As a result,

• Piston shape was changed;
• The shape of the exhaust manifold was modified;
• Construction of the three-way catalytic converter was changed;
• An additional three-way catalytic converter was fitted;
• Cooling fan control was added; and,
• A 32 bit ECU was introduced (previously 16 bit).