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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 institute in Ota, Gunma. The FA20D engine was introduced in the Subaru BRZ and Toyota ZN6 86; for the latter, Toyota initially referred to it every bit the 4U-GSE before adopting the FA20 name.

Cardinal features of the FA20D engine included it:

• Open deck pattern (i.e. the infinite between the cylinder bores at the top of the cylinder block was open);
• Aluminium alloy cake and cylinder head;
• Double overhead camshafts;
• Four valves per cylinder with variable inlet and frazzle valve timing;
• Direct and port fuel injection systems;
• Pinch ratio of 12.5:1; and,
• 7450 rpm redline.

FA20D block

The FA20D engine had an aluminium blend 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 bandage iron 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 two exhaust – were actuated by 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 bank check ball jump. Through the apply of oil pressure and bound forcefulness, the lash adjuster maintained a abiding zero valve clearance.

Valve timing: D-AVCS

To optimise valve overlap and use frazzle 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 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,
• Frazzle 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 associates was installed on the front surface side of the timing concatenation cover 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 advance hydraulic sleeping room or retard hydraulic bedchamber 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 force per unit area in the advance chamber from negative or positive cam torque (for advance or retard, respectively) would use pressure level to the advance/retard hydraulic sleeping accommodation 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 associates – which was driven by the timing chain – and advance/retard valve timing. Pressed by hydraulic pressure level from the oil pump, the detent oil passage would go blocked then that information technology did non 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 adjacent activation.

Intake and throttle

The intake organisation 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 cabin. When the intake pulsations reached the sound creator, the damper resonated at certain frequencies. According to Toyota, this design enhanced the engine induction racket heard in the cabin, producing a 'linear intake audio' in response to throttle application.

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

Port and directly injection

The FA20D engine had:

• A direct injection system which included a loftier-force per unit area fuel pump, fuel delivery piping and fuel injector assembly; and,
• A port injection system which consisted of a fuel suction tube with pump and gauge assembly, fuel piping sub-assembly and fuel injector associates.

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 upwardly to 10 kW and torque by upward to 20 Nm.

As per the tabular array below, the injection arrangement had the post-obit operating conditions:

• Cold start: the port injectors provided a homogeneous air:fuel mixture in the combustion chamber, though the mixture effectually the spark plugs was stratified past compression 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 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 only to employ the cooling effect of the fuel evaporating as it entered the combustion chamber to increase intake air book and charging efficiency; and,
• High engine speeds and loads: port injection and directly injection for loftier fuel flow volume.

The FA20D engine used a hot-wire, slot-in type air catamenia meter to measure intake mass – this meter allowed a portion of intake air to flow through the detection area so that the air mass and flow rate could be measured directly. The mass air period meter besides 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 head sub-assembly that received the spark plugs to be increased. Furthermore, the water jacket could exist extended near the combustion sleeping room to heighten cooling functioning. 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 correct 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 command that prevented fuel vapours created in the fuel tank from beingness released into the atmosphere by communicable them in an activated charcoal canister.

Uneven idle and stalling

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

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

that were accompanied by

• the 'cheque engine' calorie-free illuminating; and,
• the ECU issuing mistake 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 detect an abnormality in the cam actuator duty bike and restrict the performance of the controller. To fix, Subaru and Toyota adult new software mapping that relaxed the ECU'south tolerances and the VVT-i/AVCS controllers were subsequently manufactured to a 'tighter specification'.

In that location take been cases, all the same, where the vehicle has stalled when coming to rest and the ECU has issued error codes P0016 or P0017 – these symptoms take been attributed to a faulty cam sprocket which could cause oil pressure level 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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