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Introduction

The FA20D engine was a 2.0-litre horizontally-opposed (or 'boxer') iv-cylinder petrol engine that was manufactured at Subaru'due south 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 proper name.

Key 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 alloy block and cylinder head;
• Double overhead camshafts;
• Four valves per cylinder with variable inlet and exhaust valve timing;
• Straight and port fuel injection systems;
• Compression ratio of 12.5:1; and,
• 7450 rpm redline.

FA20D cake

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. 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 born 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 spring, check ball and bank check ball leap. Through the utilize of oil pressure level and jump force, the lash adjuster maintained a constant zippo valve clearance.

Valve timing: D-AVCS

To optimise valve overlap and employ exhaust pulsation to enhance 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 threescore degree range of aligning (relative to crankshaft bending), 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 elapsing 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 cover to make the variable valve timing mechanism more meaty. The cam timing oil command 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 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 indicate from the ECM and motility to either the right (to accelerate timing) or the left (to retard timing). Hydraulic pressure in the advance sleeping accommodation from negative or positive cam torque (for advance or retard, respectively) would use pressure to the advance/retard hydraulic chamber through the advance/retard check 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 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 by spring power, and maximum advance land on the exhaust side, to set for the next activation.

Intake and throttle

The intake organisation for the Toyota ZN6 86 and Subaru Z1 BRZ included a 'audio creator', damper and a sparse rubber tube to transmit intake pulsations to the cabin. When the intake pulsations reached the audio creator, the damper resonated at certain frequencies. According to Toyota, this design enhanced the engine consecration 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 attempt to determine throttle angle, the FA20D engine had electronic throttle control which used the ECM to summate the optimal throttle valve bending and a throttle command motor to control the angle. Furthermore, the electronically controlled throttle regulated idle speed, traction control, stability control and cruise command functions.

Port and direct injection

The FA20D engine had:

• A direct injection system which included a high-pressure fuel pump, fuel delivery pipage 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 weather condition. According to Toyota, port and direct injection increased performance across the revolution range compared with a port-only injection engine, increasing power by upwards to ten kW and torque past up to 20 Nm.

As per the table below, 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 by 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 than quickly;
• Low engine speeds: port injection and straight 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 utilise the cooling effect of the fuel evaporating as it 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 menstruation meter to mensurate intake mass – this meter immune a portion of intake air to menses through the detection area so that the air mass and flow rate could be measured straight. The mass air flow meter besides had a born intake air temperature sensor.

The FA20D engine had a compression ratio of 12.v: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 be extended near the combustion chamber to heighten cooling functioning. The triple footing electrode type iridium-tipped spark plugs had sixty,000 mile (96,000 km) maintenance intervals.

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

Frazzle and emissions

The FA20D engine had a iv-2-1 exhaust manifold and dual tailpipe outlets. To reduce emissions, the FA20D engine had a returnless fuel arrangement with evaporative emissions control that prevented fuel vapours created in the fuel tank from beingness released into the atmosphere by catching 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 past

• 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 not meeting 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's tolerances and the VVT-i/AVCS controllers were subsequently manufactured to a 'tighter specification'.

There have been cases, nonetheless, where the vehicle has stalled when coming to rest and the ECU has issued error codes P0016 or P0017 – these symptoms have been attributed to a faulty cam sprocket which could crusade oil force per unit area loss. Every bit a result, the hydraulically-controlled camshaft could not reply 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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