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Introduction

The FA20D engine was a 2.0-litre horizontally-opposed (or 'boxer') 4-cylinder petrol engine that was manufactured at Subaru's engine constitute in Ota, Gunma. The FA20D engine was introduced in the Subaru BRZ and Toyota ZN6 86; for the latter, Toyota initially referred to it as the 4U-GSE earlier adopting the FA20 proper noun.

Key features of the FA20D engine included it:

Open deck design (i.e. the space between the cylinder bores at the top of the cylinder block was open);
Aluminium alloy block and cylinder head;
Double overhead camshafts;
Four valves per cylinder with variable inlet and frazzle valve timing;
Direct and port fuel injection systems;
Compression ratio of 12.five:1; and,
7450 rpm redline.

FA20D block

The FA20D engine had an aluminium alloy block with 86.0 mm bores and an 86.0 mm stroke for a chapters of 1998 cc. Within the cylinder bores, the FA20D engine had cast fe liners.

Cylinder head: camshaft and valves

The FA20D engine had an aluminium alloy cylinder head with chain-driven double overhead camshafts. The four valves per cylinder – two intake and 2 exhaust – were actuated past roller rocker arms which had built-in needle bearings that reduced the friction that occurred between the camshafts and the roller rocker artillery (which actuated the valves). The hydraulic lash adjuster – located at the fulcrum of the roller rocker arm – consisted primarily of a plunger, plunger spring, check ball and check ball spring. Through the use of oil pressure and spring force, the lash adjuster maintained a constant nil valve clearance.

Valve timing: D-AVCS

To optimise valve overlap and utilize exhaust pulsation to heighten cylinder filling at high engine speeds, the FA20D engine had variable intake and exhaust valve timing, known every bit Subaru's 'Dual Active Valve Control System' (D-AVCS).

For the FA20D engine, the intake camshaft had a 60 degree range of adjustment (relative to crankshaft bending), while the exhaust camshaft had a 54 degree range. For the FA20D engine,

Valve overlap ranged from -33 degrees to 89 degrees (a range of 122 degrees);
Intake duration was 255 degrees; and,
Exhaust elapsing was 252 degrees.

The camshaft timing gear assembly contained advance and retard oil passages, likewise every bit a detent oil passage to make intermediate locking possible. Furthermore, a thin cam timing oil control valve assembly was installed on the forepart surface side of the timing chain cover to brand the variable valve timing mechanism more compact. The cam timing oil control valve assembly operated co-ordinate to signals from the ECM, decision-making the position of the spool valve and supplying engine oil to the advance hydraulic sleeping room or retard hydraulic chamber of the camshaft timing gear associates.

To change cam timing, the spool valve would be activated by the cam timing oil control valve associates via a signal from the ECM and move to either the right (to advance timing) or the left (to retard timing). Hydraulic pressure in the accelerate sleeping room from negative or positive cam torque (for advance or retard, respectively) would utilise pressure to the accelerate/retard hydraulic bedroom through the accelerate/retard cheque valve. The rotor vane, which was coupled with the camshaft, would and so rotate in the advance/retard direction against the rotation of the camshaft timing gear associates – which was driven by the timing concatenation – and advance/retard valve timing. Pressed by hydraulic pressure from the oil pump, the detent oil passage would become blocked and so that it did not operate.

When the engine was stopped, the spool valve was put into an intermediate locking position on the intake side past jump ability, and maximum advance state on the exhaust side, to prepare for the side by side activation.

Intake and throttle

The intake system for the Toyota ZN6 86 and Subaru Z1 BRZ included a 'audio creator', damper and a thin rubber tube to transmit intake pulsations to the motel. When the intake pulsations reached the sound creator, the damper resonated at certain frequencies. According to Toyota, this blueprint enhanced the engine induction noise heard in the cabin, producing a 'linear intake sound' in response to throttle application.

In dissimilarity to a conventional throttle which used accelerator pedal effort to determine throttle angle, the FA20D engine had electronic throttle control which used the ECM to summate the optimal throttle valve angle and a throttle control motor to control the bending. Furthermore, the electronically controlled throttle regulated idle speed, traction control, stability command and cruise control functions.

Port and direct injection

The FA20D engine had:

A direct injection system which included a high-pressure fuel pump, fuel delivery pipe and fuel injector associates; and,
A port injection system which consisted of a fuel suction tube with pump and approximate assembly, fuel piping sub-assembly and fuel injector assembly.

Based on inputs from sensors, the ECM controlled the injection book and timing of each type of fuel injector, according to engine load and engine speed, to optimise the fuel:air mixture for engine conditions. According to Toyota, port and straight injection increased functioning across the revolution range compared with a port-only injection engine, increasing power by up to 10 kW and torque past up to 20 Nm.

As per the table beneath, the injection arrangement had the post-obit operating weather condition:

Common cold start: the port injectors provided a homogeneous air:fuel mixture in the combustion chamber, though the mixture effectually the spark plugs was stratified by pinch stroke injection from the directly injectors. Furthermore, ignition timing was retarded to raise frazzle gas temperatures and so that the catalytic converter could reach operating temperature more than quickly;
Low engine speeds: port injection and directly injection for a homogenous air:fuel mixture to stabilise combustion, improve fuel efficiency and reduce emissions;
Medium engine speeds and loads: direct injection only to utilise the cooling effect of the fuel evaporating as information technology entered the combustion chamber to increase intake air volume and charging efficiency; and,
High engine speeds and loads: port injection and direct injection for high fuel flow volume.

FA20/4U-GSE direct and port injection at various engine speeds and loads
The FA20D engine used a hot-wire, slot-in blazon air flow meter to mensurate intake mass – this meter allowed a portion of intake air to flow through the detection area so that the air mass and menstruation rate could be measured directly. The mass air flow meter also had a congenital-in intake air temperature sensor.

The FA20D engine had a pinch ratio of 12.five:one.

Ignition

The FA20D engine had a directly ignition system whereby an ignition coil with an integrated igniter was used for each cylinder. The spark plug caps, which provided contact to the spark plugs, were integrated with the ignition whorl associates.

The FA20D engine had long-reach, iridium-tipped spark plugs which enabled the thickness of the cylinder head sub-assembly that received the spark plugs to exist increased. Furthermore, the h2o jacket could be extended near the combustion chamber to heighten cooling performance. The triple basis electrode type iridium-tipped spark plugs had threescore,000 mile (96,000 km) maintenance intervals.

The FA20D engine had flat type knock control sensors (non-resonant type) attached to the left and correct cylinder blocks.

Exhaust and emissions

The FA20D engine had a 4-2-one exhaust manifold and dual tailpipe outlets. To reduce emissions, the FA20D engine had a returnless fuel system with evaporative emissions control that prevented fuel vapours created in the fuel tank from being released into the atmosphere by catching them in an activated charcoal canister.

Uneven idle and stalling

For the Subaru BRZ and Toyota 86, there have been reports of

varying idle speed;
rough idling;
shuddering; or,
stalling

that were accompanied by

the 'check engine' low-cal illuminating; and,
the ECU issuing fault codes P0016, P0017, P0018 and P0019.

Initially, Subaru and Toyota attributed these symptoms to the VVT-i/AVCS controllers not meeting manufacturing tolerances which caused the ECU to discover an abnormality in the cam actuator duty cycle and restrict the operation of the controller. To prepare, Subaru and Toyota adult new software mapping that relaxed the ECU's tolerances and the VVT-i/AVCS controllers were after manufactured to a 'tighter specification'.

At that place have been cases, however, where the vehicle has stalled when coming to rest and the ECU has issued error codes P0016 or P0017 – these symptoms have been attributed to a faulty cam sprocket which could crusade oil pressure loss. As a issue, the hydraulically-controlled camshaft could not respond to ECU signals. If this occurred, the cam sprocket needed to be replaced.