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Introduction

The FA20D engine was a two.0-litre horizontally-opposed (or 'boxer') four-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 information technology as the 4U-GSE before adopting the FA20 proper name.

Key features of the FA20D engine included it:

• Open deck pattern (i.e. the space between the cylinder bores at the elevation of the cylinder block was open up);
• Aluminium alloy block and cylinder head;
• Double overhead camshafts;
• Iv valves per cylinder with variable inlet and exhaust valve timing;
• Directly and port fuel injection systems;
• Compression ratio of 12.five:ane; 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 caput with chain-driven double overhead camshafts. The four valves per cylinder – two intake and two frazzle – 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, bank check ball and check ball bound. Through the utilize of oil pressure and spring forcefulness, the lash adjuster maintained a abiding zero valve clearance.

Valve timing: D-AVCS

To optimise valve overlap and use exhaust pulsation to enhance cylinder filling at high engine speeds, the FA20D engine had variable intake and exhaust valve timing, known as Subaru'due south 'Dual Active Valve Control Organisation' (D-AVCS).

For the FA20D engine, the intake camshaft had a lx degree range of aligning (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 assembly contained advance and retard oil passages, also as a detent oil passage to make intermediate locking possible. Furthermore, a thin 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 than 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 chamber or retard hydraulic chamber of the camshaft timing gear assembly.

To change 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 accelerate timing) or the left (to retard timing). Hydraulic pressure level in the advance chamber from negative or positive cam torque (for advance or retard, respectively) would apply pressure level to the advance/retard hydraulic bedroom through the accelerate/retard cheque valve. The rotor vane, which was coupled with the camshaft, would then rotate in the advance/retard management against the rotation of the camshaft timing gear assembly – which was driven by the timing concatenation – and accelerate/retard valve timing. Pressed by hydraulic force per unit area from the oil pump, the detent oil passage would go blocked 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 by bound power, and maximum advance state on the frazzle side, to prepare for the next 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 cabin. 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 sound' in response to throttle application.

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 command, stability control and cruise control functions.

Port and straight injection

The FA20D engine had:

• A direct injection system which included a high-pressure fuel pump, fuel delivery pipe and fuel injector assembly; and,
• A port injection system which consisted of a fuel suction tube with pump and gauge associates, fuel pipage sub-assembly 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 weather. According to Toyota, port and direct injection increased performance across the revolution range compared with a port-just injection engine, increasing power past up to 10 kW and torque past upward to 20 Nm.

As per the table beneath, the injection system had the following operating conditions:

• Cold start: the port injectors provided a homogeneous air:fuel mixture in the combustion chamber, though the mixture around the spark plugs was stratified past compression stroke injection from the direct injectors. Furthermore, ignition timing was retarded to enhance exhaust gas temperatures and then that the catalytic converter could reach operating temperature more quickly;
• Low engine speeds: port injection and direct injection for a homogenous air:fuel mixture to stabilise combustion, improve fuel efficiency and reduce emissions;
• Medium engine speeds and loads: direct injection merely to utilise the cooling effect of the fuel evaporating every bit information technology entered the combustion bedroom to increase intake air volume and charging efficiency; and,
• High engine speeds and loads: port injection and directly injection for loftier fuel menstruation volume.

The FA20D engine used a hot-wire, slot-in type air flow meter to measure out intake mass – this meter immune a portion of intake air to flow through the detection area and then that the air mass and catamenia rate could be measured straight. The mass air catamenia meter likewise 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 gyre 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 curl assembly.

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 water jacket could be extended near the combustion sleeping room to enhance 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 blazon knock control sensors (non-resonant type) attached to the left and right cylinder blocks.

Frazzle and emissions

The FA20D engine had a 4-two-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 being released into the temper by catching 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 '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 not meeting manufacturing tolerances which acquired the ECU to observe an aberration 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 have been cases, notwithstanding, where the vehicle has stalled when coming to remainder and the ECU has issued error codes P0016 or P0017 – these symptoms accept been attributed to a faulty cam sprocket which could crusade oil pressure loss. As a result, the hydraulically-controlled camshaft could not reply 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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