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Introduction

The FA20D engine was a 2.0-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 before adopting the FA20 name.

Fundamental features of the FA20D engine included it:

• Open up deck design (i.east. 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 exhaust valve timing;
• Directly and port fuel injection systems;
• Compression ratio of 12.5:i; and,
• 7450 rpm redline.

FA20D block

The FA20D engine had an aluminium alloy cake 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 head with concatenation-driven double overhead camshafts. The four valves per cylinder – two intake and two exhaust – were actuated past 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 brawl and check ball 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 use exhaust pulsation to enhance cylinder filling at high engine speeds, the FA20D engine had variable intake and exhaust valve timing, known as Subaru'south '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,
• Exhaust elapsing was 252 degrees.

The camshaft timing gear associates contained advance and retard oil passages, every bit 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 comprehend to make the variable valve timing mechanism more compact. The cam timing oil control valve assembly operated co-ordinate 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 chamber of the camshaft timing gear associates.

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 motility 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 apply force per unit area to the advance/retard hydraulic sleeping accommodation through the advance/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 chain – and accelerate/retard valve timing. Pressed past hydraulic pressure level from the oil pump, the detent oil passage would become blocked and 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 jump power, and maximum accelerate state 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 rubber tube to transmit intake pulsations to the cabin. When the intake pulsations reached the sound creator, the damper resonated at certain frequencies. Co-ordinate to Toyota, this design enhanced the engine induction noise heard in the cabin, producing a 'linear intake sound' in response to throttle application.

In contrast to a conventional throttle which used accelerator pedal attempt 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 command functions.

Port and direct injection

The FA20D engine had:

• A directly injection organisation which included a loftier-pressure fuel pump, fuel commitment piping and fuel injector assembly; and,
• A port injection system which consisted of a fuel suction tube with pump and gauge assembly, 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 conditions. Co-ordinate to Toyota, port and directly injection increased performance across the revolution range compared with a port-only injection engine, increasing power by up to 10 kW and torque by up to twenty Nm.

Every bit 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 bedchamber, though the mixture around the spark plugs was stratified by pinch stroke injection from the straight injectors. Furthermore, ignition timing was retarded to raise exhaust gas temperatures and so that the catalytic converter could attain 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: straight injection only to employ the cooling effect of the fuel evaporating as information technology entered the combustion chamber to increase intake air volume and charging efficiency; and,
• High engine speeds and loads: port injection and direct injection for high fuel flow book.

The FA20D engine used a hot-wire, slot-in type air menses meter to measure intake mass – this meter allowed a portion of intake air to flow through the detection expanse so that the air mass and flow charge per unit could exist measured directly. The mass air flow meter besides had a congenital-in intake air temperature sensor.

The FA20D engine had a pinch 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 virtually the combustion chamber to raise cooling performance. The triple ground electrode type iridium-tipped spark plugs had lx,000 mile (96,000 km) maintenance intervals.

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

Exhaust and emissions

The FA20D engine had a 4-ii-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 beingness released into the temper by catching them in an activated charcoal canister.

Uneven idle and stalling

For the Subaru BRZ and Toyota 86, in that location 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 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 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 rest and the ECU has issued mistake codes P0016 or P0017 – these symptoms have been attributed to a faulty cam sprocket which could crusade oil pressure loss. Equally 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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