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Introduction

The FA20D engine was a 2.0-litre horizontally-opposed (or 'boxer') 4-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 earlier adopting the FA20 name.

Cardinal features of the FA20D engine included it:

• Open deck blueprint (i.e. the space between the cylinder bores at the top of the cylinder block was open);
• Aluminium blend cake and cylinder caput;
• Double overhead camshafts;
• Four valves per cylinder with variable inlet and exhaust 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 chapters of 1998 cc. Inside the cylinder bores, the FA20D engine had cast atomic number 26 liners.

Cylinder caput: camshaft and valves

The FA20D engine had an aluminium alloy cylinder head with chain-driven double overhead camshafts. The 4 valves per cylinder – two intake and two exhaust – 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 jump, bank check brawl and check ball spring. Through the use of oil force per unit area 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 loftier engine speeds, the FA20D engine had variable intake and exhaust valve timing, known every bit Subaru'due south 'Dual Active Valve Control System' (D-AVCS).

For the FA20D engine, the intake camshaft had a sixty degree range of aligning (relative to crankshaft angle), while the frazzle 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 independent 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 encompass to brand the variable valve timing mechanism more meaty. 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 chamber or retard hydraulic sleeping accommodation of the camshaft timing gear assembly.

To alter cam timing, the spool valve would exist activated by the cam timing oil control valve assembly via a point from the ECM and motion to either the right (to advance timing) or the left (to retard timing). Hydraulic pressure level in the accelerate chamber from negative or positive cam torque (for advance or retard, respectively) would apply pressure to the accelerate/retard hydraulic bedroom through the advance/retard check valve. The rotor vane, which was coupled with the camshaft, would and then rotate in the advance/retard direction confronting the rotation of the camshaft timing gear assembly – which was driven by the timing chain – and advance/retard valve timing. Pressed past 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 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 'audio creator', damper and a sparse condom 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 blueprint enhanced the engine induction racket heard in the cabin, producing a 'linear intake sound' in response to throttle awarding.

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

Port and straight injection

The FA20D engine had:

• A direct injection system which included a high-force per unit area fuel pump, fuel delivery pipage and fuel injector assembly; and,
• A port injection system which consisted of a fuel suction tube with pump and guess assembly, fuel pipe 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 functioning across the revolution range compared with a port-only injection engine, increasing power by upward to 10 kW and torque past up to 20 Nm.

As per the tabular array 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 effectually the spark plugs was stratified by compression stroke injection from the direct injectors. Furthermore, ignition timing was retarded to raise frazzle 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, improve fuel efficiency and reduce emissions;
• Medium engine speeds and loads: directly injection merely to utilise the cooling outcome of the fuel evaporating as it entered the combustion bedroom to increment intake air book and charging efficiency; and,
• Loftier engine speeds and loads: port injection and direct injection for high fuel flow book.

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

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

Ignition

The FA20D engine had a direct ignition organization 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 coil assembly.

The FA20D engine had long-accomplish, 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 near the combustion chamber to heighten cooling performance. The triple ground electrode type iridium-tipped spark plugs had 60,000 mile (96,000 km) maintenance intervals.

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

Exhaust and emissions

The FA20D engine had a 4-2-one 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 atmosphere past 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;
• crude 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 non coming together manufacturing tolerances which caused the ECU to detect an abnormality in the cam actuator duty cycle and restrict the performance 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 later on manufactured to a 'tighter specification'.

There take been cases, however, where the vehicle has stalled when coming to residue 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. Equally a result, the hydraulically-controlled camshaft could non answer to ECU signals. If this occurred, the cam sprocket needed to exist replaced.

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Source: http://www.australiancar.reviews/Subaru_FA20D_Engine.php

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