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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.

Key features of the FA20D engine included it:

• Open deck pattern (i.e. the space between the cylinder bores at the top of the cylinder block was open);
• Aluminium alloy block and cylinder caput;
• Double overhead camshafts;
• Four valves per cylinder with variable inlet and exhaust valve timing;
• Direct and port fuel injection systems;
• Compression ratio of 12.5:1; 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 chapters of 1998 cc. Inside 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 concatenation-driven double overhead camshafts. The four valves per cylinder – two intake and two frazzle – were actuated past roller rocker artillery 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 spring, check ball and cheque ball leap. Through the apply of oil pressure and bound force, the lash adjuster maintained a constant nil 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 frazzle valve timing, known every bit Subaru'south 'Dual Agile Valve Control System' (D-AVCS).

For the FA20D engine, the intake camshaft had a 60 caste 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 assembly contained accelerate and retard oil passages, as well equally a detent oil passage to make intermediate locking possible. Furthermore, a thin cam timing oil command valve assembly was installed on the front surface side of the timing chain cover to make the variable valve timing mechanism more than meaty. The cam timing oil command valve associates 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 chamber of the camshaft timing gear associates.

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 pressure in the advance chamber from negative or positive cam torque (for accelerate or retard, respectively) would apply 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 associates – which was driven by the timing concatenation – 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 accelerate state on the frazzle side, to ready for the next activation.

Intake and throttle

The intake arrangement for the Toyota ZN6 86 and Subaru Z1 BRZ included a 'audio creator', damper and a thin rubber tube to transmit intake pulsations to the motel. When the intake pulsations reached the sound creator, the damper resonated at certain frequencies. According to Toyota, this blueprint enhanced the engine induction racket heard in the cabin, producing a 'linear intake sound' in response to throttle application.

In dissimilarity 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 bending and a throttle command motor to control the angle. Furthermore, the electronically controlled throttle regulated idle speed, traction control, stability control and cruise control functions.

Port and straight injection

The FA20D engine had:

• A directly injection organization which included a high-pressure fuel pump, fuel commitment pipe and fuel injector assembly; and,
• A port injection system which consisted of a fuel suction tube with pump and gauge assembly, fuel pipe sub-assembly and fuel injector associates.

Based on inputs from sensors, the ECM controlled the injection book 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-simply injection engine, increasing power past up to x kW and torque by up to twenty Nm.

Every bit per the tabular array below, the injection arrangement had the post-obit 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 past compression stroke injection from the direct injectors. Furthermore, ignition timing was retarded to raise exhaust gas temperatures and so that the catalytic converter could accomplish operating temperature more quickly;
• Depression 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 simply to utilise the cooling effect of the fuel evaporating equally information technology entered the combustion bedchamber to increase intake air book and charging efficiency; and,
• High engine speeds and loads: port injection and direct injection for loftier fuel flow volume.

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 surface area then that the air mass and flow rate could be measured directly. The mass air menses meter also had a built-in intake air temperature sensor.

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

Ignition

The FA20D engine had a directly ignition organisation 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 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 h2o jacket could be extended near the combustion chamber to enhance cooling performance. The triple basis electrode blazon iridium-tipped spark plugs had 60,000 mile (96,000 km) maintenance intervals.

The FA20D engine had apartment blazon knock control sensors (not-resonant blazon) 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 arrangement with evaporative emissions control that prevented fuel vapours created in the fuel tank from existence released into the temper by 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;
• rough idling;
• shuddering; or,
• stalling

that were accompanied by

• the 'check engine' lite 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 discover an abnormality in the cam actuator duty cycle and restrict the operation of the controller. To set, 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, however, where the vehicle has stalled when coming to balance and the ECU has issued error codes P0016 or P0017 – these symptoms have been attributed to a faulty cam sprocket which could cause oil force per unit area loss. Equally a result, the hydraulically-controlled camshaft could non 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