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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 every bit the 4U-GSE before adopting the FA20 name.

Key features of the FA20D engine included it:

• Open deck blueprint (i.e. the infinite between the cylinder bores at the top of the cylinder block was open up);
• Aluminium alloy cake and cylinder head;
• 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:one; 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. Inside the cylinder bores, the FA20D engine had cast iron liners.

Cylinder head: camshaft and valves

The FA20D engine had an aluminium blend cylinder caput with chain-driven double overhead camshafts. The four valves per cylinder – ii intake and ii 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 jump, check ball and check brawl spring. Through the use of oil pressure and leap force, the lash adjuster maintained a constant cipher 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 exhaust valve timing, known as Subaru'south 'Dual Active Valve Control System' (D-AVCS).

For the FA20D engine, the intake camshaft had a threescore caste 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,
• Exhaust elapsing was 252 degrees.

The camshaft timing gear associates contained advance and retard oil passages, too as a detent oil passage to make intermediate locking possible. Furthermore, a sparse cam timing oil control valve associates was installed on the front surface side of the timing chain 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, decision-making the position of the spool valve and supplying engine oil to the advance hydraulic bedroom or retard hydraulic chamber of the camshaft timing gear associates.

To change cam timing, the spool valve would be activated past the cam timing oil command valve associates via a bespeak 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 bedchamber from negative or positive cam torque (for advance or retard, respectively) would apply force per unit area 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 accelerate/retard direction against the rotation of the camshaft timing gear assembly – which was driven past the timing chain – and advance/retard valve timing. Pressed by hydraulic force per unit area 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 state on the exhaust side, to set up for the adjacent activation.

Intake and throttle

The intake organization 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. According to Toyota, this pattern enhanced the engine induction noise heard in the motel, producing a 'linear intake audio' in response to throttle awarding.

In dissimilarity to a conventional throttle which used accelerator pedal endeavour to determine throttle angle, the FA20D engine had electronic throttle command which used the ECM to calculate 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 command and cruise control functions.

Port and direct injection

The FA20D engine had:

• A direct injection organization which included a loftier-pressure 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 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. According to Toyota, port and straight injection increased performance across the revolution range compared with a port-but injection engine, increasing ability by upwardly to ten kW and torque by up to twenty Nm.

Every bit per the table beneath, the injection organization had the following operating conditions:

• Common cold get-go: the port injectors provided a homogeneous air:fuel mixture in the combustion bedroom, though the mixture around the spark plugs was stratified past pinch stroke injection from the direct injectors. Furthermore, ignition timing was retarded to enhance exhaust gas temperatures so that the catalytic converter could reach operating temperature more quickly;
• Depression 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 utilise the cooling result 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 high fuel flow volume.

The FA20D engine used a hot-wire, slot-in type air flow meter to measure intake mass – this meter allowed a portion of intake air to period through the detection area so that the air mass and flow rate could exist measured directly. The mass air flow meter as well had a born 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 be extended virtually 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 apartment type knock command sensors (non-resonant blazon) fastened to the left and right cylinder blocks.

Exhaust and emissions

The FA20D engine had a four-two-ane exhaust manifold and dual tailpipe outlets. To reduce emissions, the FA20D engine had a returnless fuel organisation with evaporative emissions control that prevented fuel vapours created in the fuel tank from being released into the temper 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 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 not meeting manufacturing tolerances which acquired the ECU to detect an abnormality in the cam actuator duty cycle 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, however, 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 cause oil pressure loss. As a event, 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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