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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's 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 equally the 4U-GSE before adopting the FA20 proper name.

Cardinal features of the FA20D engine included it:

• Open up deck design (i.due east. the space between the cylinder bores at the peak of the cylinder cake was open);
• Aluminium alloy cake and cylinder caput;
• Double overhead camshafts;
• Four valves per cylinder with variable inlet and exhaust 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. 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 – ii intake and 2 frazzle – were actuated past roller rocker artillery 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 use of oil pressure and spring force, the lash adjuster maintained a constant zero valve clearance.

Valve timing: D-AVCS

To optimise valve overlap and utilise frazzle pulsation to enhance cylinder filling at high engine speeds, the FA20D engine had variable intake and exhaust valve timing, known as Subaru's 'Dual Active Valve Command Organization' (D-AVCS).

For the FA20D engine, the intake camshaft had a 60 degree range of adjustment (relative to crankshaft angle), while the exhaust camshaft had a 54 caste 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 assembly contained advance and retard oil passages, also as a detent oil passage to make intermediate locking possible. Furthermore, a sparse cam timing oil control valve assembly was installed on the front surface side of the timing chain cover to brand the variable valve timing machinery more compact. The cam timing oil control valve assembly operated according to signals from the ECM, decision-making the position of the spool valve and supplying engine oil to the advance hydraulic bedroom or retard hydraulic chamber of the camshaft timing gear assembly.

To alter cam timing, the spool valve would be activated by the cam timing oil control valve assembly via a signal from the ECM and move to either the right (to advance timing) or the left (to retard timing). Hydraulic pressure level in the advance sleeping accommodation from negative or positive cam torque (for advance or retard, respectively) would apply force per unit area to the advance/retard hydraulic bedroom through the advance/retard check valve. The rotor vane, which was coupled with the camshaft, would then rotate in the advance/retard direction against the rotation of the camshaft timing gear assembly – which was driven by the timing chain – and advance/retard valve timing. Pressed by hydraulic pressure from the oil pump, the detent oil passage would become blocked and 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 spring power, and maximum advance land on the exhaust side, to prepare for the next activation.

Intake and throttle

The intake system for the Toyota ZN6 86 and Subaru Z1 BRZ included a 'sound creator', damper and a thin safe 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 design enhanced the engine induction noise heard in the motel, producing a 'linear intake audio' in response to throttle awarding.

In contrast 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 angle and a throttle control motor to control the angle. Furthermore, the electronically controlled throttle regulated idle speed, traction control, stability control and cruise command functions.

Port and direct injection

The FA20D engine had:

• A directly injection system which included a high-pressure fuel pump, fuel delivery pipe and fuel injector associates; and,
• A port injection organization which consisted of a fuel suction tube with pump and gauge 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 directly injection increased operation across the revolution range compared with a port-but injection engine, increasing power by up to 10 kW and torque by upwards to xx Nm.

As per the tabular array below, the injection arrangement had the following operating weather condition:

• Cold showtime: the port injectors provided a homogeneous air:fuel mixture in the combustion sleeping accommodation, though the mixture effectually the spark plugs was stratified by pinch stroke injection from the directly injectors. Furthermore, ignition timing was retarded to raise exhaust gas temperatures so that the catalytic converter could reach operating temperature more quickly;
• Depression engine speeds: port injection and direct injection for a homogenous air:fuel mixture to stabilise combustion, amend fuel efficiency and reduce emissions;
• Medium engine speeds and loads: straight injection simply to use the cooling effect of the fuel evaporating as information technology entered the combustion chamber to increment intake air volume and charging efficiency; and,
• High engine speeds and loads: port injection and straight injection for high fuel flow volume.

The FA20D engine used a hot-wire, slot-in type air catamenia 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 period rate could be measured directly. The mass air flow meter too had a built-in intake air temperature sensor.

The FA20D engine had a compression ratio of 12.5:1.

Ignition

The FA20D engine had a direct 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 assembly.

The FA20D engine had long-reach, 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 most the combustion chamber to raise cooling performance. The triple ground electrode blazon iridium-tipped spark plugs had 60,000 mile (96,000 km) maintenance intervals.

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

Exhaust and emissions

The FA20D engine had a 4-2-1 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 existence released into the atmosphere by communicable them in an activated charcoal canister.

Uneven idle and stalling

For the Subaru BRZ and Toyota 86, at that place have been reports of

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

that were accompanied by

• the '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 not coming together manufacturing tolerances which acquired the ECU to detect an abnormality in the cam actuator duty cycle and restrict the operation of the controller. To fix, Subaru and Toyota developed new software mapping that relaxed the ECU's tolerances and the VVT-i/AVCS controllers were subsequently manufactured to a 'tighter specification'.

There accept been cases, notwithstanding, where the vehicle has stalled when coming to residue and the ECU has issued error codes P0016 or P0017 – these symptoms have been attributed to a faulty cam sprocket which could cause oil force per unit area loss. As a result, the hydraulically-controlled camshaft could not 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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