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Introduction

The FA20D engine was a 2.0-litre horizontally-opposed (or 'boxer') iv-cylinder petrol engine that was manufactured at Subaru'south engine plant 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 before adopting the FA20 name.

Fundamental features of the FA20D engine included information technology:

• Open deck design (i.east. the space betwixt the cylinder bores at the summit of the cylinder block was open);
• Aluminium alloy block and cylinder caput;
• Double overhead camshafts;
• Iv valves per cylinder with variable inlet and frazzle valve timing;
• Direct and port fuel injection systems;
• Compression ratio of 12.5:1; 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 capacity of 1998 cc. Inside the cylinder bores, the FA20D engine had cast iron liners.

Cylinder head: camshaft and valves

The FA20D engine had an aluminium alloy cylinder head with chain-driven double overhead camshafts. The iv valves per cylinder – two intake and ii 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 arms (which actuated the valves). The hydraulic lash adjuster – located at the fulcrum of the roller rocker arm – consisted primarily of a plunger, plunger spring, cheque ball and check ball spring. Through the employ of oil pressure and leap force, the lash adjuster maintained a constant nothing valve clearance.

Valve timing: D-AVCS

To optimise valve overlap and utilise exhaust pulsation to enhance cylinder filling at loftier engine speeds, the FA20D engine had variable intake and exhaust valve timing, known as Subaru's 'Dual Agile Valve Control System' (D-AVCS).

For the FA20D engine, the intake camshaft had a sixty caste range of adjustment (relative to crankshaft angle), 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 duration was 252 degrees.

The camshaft timing gear associates independent advance and retard oil passages, as well as a detent oil passage to make intermediate locking possible. Furthermore, a thin cam timing oil control valve assembly was installed on the front end surface side of the timing chain embrace to brand the variable valve timing mechanism more compact. The cam timing oil control valve assembly operated according to signals from the ECM, controlling the position of the spool valve and supplying engine oil to the advance hydraulic chamber or retard hydraulic sleeping accommodation of the camshaft timing gear associates.

To alter cam timing, the spool valve would be activated by the cam timing oil command 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 advance chamber from negative or positive cam torque (for advance or retard, respectively) would utilize pressure level to the advance/retard hydraulic chamber through the advance/retard check valve. The rotor vane, which was coupled with the camshaft, would and so rotate in the advance/retard direction confronting the rotation of the camshaft timing gear assembly – which was driven by the timing chain – and advance/retard valve timing. Pressed past hydraulic force per unit area from the oil pump, the detent oil passage would go blocked then that information technology did not operate.

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

Intake and throttle

The intake system for the Toyota ZN6 86 and Subaru Z1 BRZ included a 'sound creator', damper and a sparse 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 pattern enhanced the engine consecration racket heard in the motel, 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 calculate the optimal throttle valve bending and a throttle command motor to command the angle. Furthermore, the electronically controlled throttle regulated idle speed, traction control, stability command and cruise command functions.

Port and direct injection

The FA20D engine had:

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

Based on inputs from sensors, the ECM controlled the injection volume 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 direct injection increased performance across the revolution range compared with a port-but injection engine, increasing power by upwards to 10 kW and torque by upwardly to 20 Nm.

Every bit per the table below, the injection system had the following operating conditions:

• Cold get-go: the port injectors provided a homogeneous air:fuel mixture in the combustion chamber, though the mixture around the spark plugs was stratified by pinch stroke injection from the directly injectors. Furthermore, ignition timing was retarded to raise exhaust gas temperatures then that the catalytic converter could reach operating temperature more speedily;
• Low engine speeds: port injection and straight injection for a homogenous air:fuel mixture to stabilise combustion, amend fuel efficiency and reduce emissions;
• Medium engine speeds and loads: direct injection only to utilise the cooling effect of the fuel evaporating as it entered the combustion sleeping accommodation to increase intake air volume and charging efficiency; and,
• High engine speeds and loads: port injection and direct injection for high fuel catamenia book.

The FA20D engine used a hot-wire, slot-in type air flow meter to measure intake mass – this meter allowed a portion of intake air to menstruum through the detection area so that the air mass and flow rate could be measured directly. The mass air menstruation meter besides had a built-in intake air temperature sensor.

The FA20D engine had a compression ratio of 12.5:ane.

Ignition

The FA20D engine had a straight 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 coil associates.

The FA20D engine had long-achieve, iridium-tipped spark plugs which enabled the thickness of the cylinder caput sub-assembly that received the spark plugs to be increased. Furthermore, the water jacket could be extended near the combustion chamber to enhance cooling functioning. The triple footing electrode blazon iridium-tipped spark plugs had sixty,000 mile (96,000 km) maintenance intervals.

The FA20D engine had apartment blazon knock command sensors (non-resonant type) attached to the left and right cylinder blocks.

Exhaust and emissions

The FA20D engine had a four-2-one exhaust manifold and dual tailpipe outlets. To reduce emissions, the FA20D engine had a returnless fuel arrangement 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;
• crude idling;
• shuddering; or,
• stalling

that were accompanied by

• the 'bank check engine' light 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 non meeting manufacturing tolerances which caused the ECU to detect an abnormality in the cam actuator duty cycle and restrict the operation of the controller. To set, Subaru and Toyota developed new software mapping that relaxed the ECU'due south tolerances and the VVT-i/AVCS controllers were subsequently manufactured to a 'tighter specification'.

There accept been cases, still, where the vehicle has stalled when coming to rest and the ECU has issued fault codes P0016 or P0017 – these symptoms have been attributed to a faulty cam sprocket which could crusade oil pressure loss. As a result, the hydraulically-controlled camshaft could non respond to ECU signals. If this occurred, the cam sprocket needed to be replaced.

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Source: http://www.australiancar.reviews/Subaru_FA20D_Engine.php

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