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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 it as the 4U-GSE earlier adopting the FA20 proper name.

Primal features of the FA20D engine included information technology:

• Open deck design (i.due east. the space between the cylinder bores at the meridian 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;
• Directly and port fuel injection systems;
• Compression ratio of 12.v:one; 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 iron 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 – ii intake and two frazzle – were actuated by roller rocker arms which had congenital-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 leap, check ball and cheque brawl jump. 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 exhaust 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 System' (D-AVCS).

For the FA20D engine, the intake camshaft had a lx 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, 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 surface side of the timing chain embrace to make 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 accelerate hydraulic chamber 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 command valve associates via a signal from the ECM and motion 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 accelerate or retard, respectively) would apply pressure to the accelerate/retard hydraulic chamber through the accelerate/retard check valve. The rotor vane, which was coupled with the camshaft, would then rotate in the accelerate/retard management against the rotation of the camshaft timing gear assembly – which was driven past the timing chain – and advance/retard valve timing. Pressed by hydraulic pressure from the oil pump, the detent oil passage would become 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 past spring ability, and maximum accelerate state on the frazzle side, to gear up 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 sparse rubber tube to transmit intake pulsations to the motel. When the intake pulsations reached the audio creator, the damper resonated at certain frequencies. According to Toyota, this design enhanced the engine induction dissonance heard in the cabin, producing a 'linear intake audio' in response to throttle awarding.

In dissimilarity to a conventional throttle which used accelerator pedal endeavor 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 angle. Furthermore, the electronically controlled throttle regulated idle speed, traction control, stability control and cruise control functions.

Port and direct injection

The FA20D engine had:

• A direct injection arrangement which included a high-pressure fuel pump, fuel delivery pipage and fuel injector assembly; and,
• A port injection organization which consisted of a fuel suction tube with pump and gauge assembly, fuel pipe 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-just injection engine, increasing ability past upwards to 10 kW and torque by up to 20 Nm.

As per the tabular array below, the injection system had the following operating atmospheric condition:

• Cold start: 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 direct injectors. Furthermore, ignition timing was retarded to raise exhaust gas temperatures so that the catalytic converter could reach operating temperature more than apace;
• Low engine speeds: port injection and direct injection for a homogenous air:fuel mixture to stabilise combustion, ameliorate fuel efficiency and reduce emissions;
• Medium engine speeds and loads: direct injection just to utilise the cooling issue of the fuel evaporating as information technology entered the combustion sleeping accommodation to increase intake air book and charging efficiency; and,
• Loftier engine speeds and loads: port injection and directly injection for high fuel flow book.

The FA20D engine used a hot-wire, slot-in blazon air flow meter to measure intake mass – this meter allowed a portion of intake air to flow through the detection area and so that the air mass and flow rate could exist measured directly. The mass air flow meter also had a born intake air temperature sensor.

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

Ignition

The FA20D engine had a direct ignition system whereby an ignition ringlet 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-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 almost the combustion chamber 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 type knock control sensors (not-resonant type) attached 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 organisation with evaporative emissions control that prevented fuel vapours created in the fuel tank from being released into the atmosphere by communicable them in an activated charcoal canister.

Uneven idle and stalling

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

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

that were accompanied by

• the 'bank 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 non coming together manufacturing tolerances which caused the ECU to detect an abnormality in the cam actuator duty bike and restrict the operation of the controller. To fix, Subaru and Toyota developed new software mapping that relaxed the ECU'southward tolerances and the VVT-i/AVCS controllers were subsequently manufactured to a 'tighter specification'.

There have been cases, however, 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 cause oil force per unit area loss. As a effect, 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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