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

Key features of the FA20D engine included information technology:

• 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;
• Directly 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. Within the cylinder bores, the FA20D engine had cast iron liners.

Cylinder head: camshaft and valves

The FA20D engine had an aluminium blend cylinder head with chain-driven double overhead camshafts. The 4 valves per cylinder – two intake and two frazzle – were actuated past roller rocker artillery which had built-in needle bearings that reduced the friction that occurred between the camshafts and the roller rocker artillery (which actuated the valves). The hydraulic lash adjuster – located at the fulcrum of the roller rocker arm – consisted primarily of a plunger, plunger spring, cheque ball and check ball leap. Through the use of oil pressure level and leap force, the lash adjuster maintained a constant null valve clearance.

Valve timing: D-AVCS

To optimise valve overlap and utilize 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 caste 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 duration was 252 degrees.

The camshaft timing gear assembly contained accelerate 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 comprehend to make the variable valve timing mechanism more compact. The cam timing oil command valve assembly operated according to signals from the ECM, controlling the position of the spool valve and supplying engine oil to the accelerate hydraulic chamber or retard hydraulic sleeping room of the camshaft timing gear assembly.

To modify cam timing, the spool valve would be activated past the cam timing oil command valve assembly via a signal from the ECM and motion to either the right (to advance timing) or the left (to retard timing). Hydraulic pressure level 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 chamber through the advance/retard bank check valve. The rotor vane, which was coupled with the camshaft, would and then rotate in the accelerate/retard direction confronting the rotation of the camshaft timing gear assembly – which was driven by the timing concatenation – and accelerate/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 state on the exhaust side, to gear up 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 audio creator, the damper resonated at certain frequencies. According to Toyota, this pattern enhanced the engine induction noise heard in the cabin, producing a 'linear intake audio' in response to throttle application.

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

Port and direct injection

The FA20D engine had:

• A direct injection system 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 approximate assembly, fuel pipe sub-associates 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 direct injection increased functioning across the revolution range compared with a port-only injection engine, increasing ability by up to 10 kW and torque by upward to 20 Nm.

Every bit per the table below, the injection system had the following operating weather:

• Cold showtime: 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 heighten exhaust gas temperatures so that the catalytic converter could reach operating temperature more than speedily;
• 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 effect of the fuel evaporating as it entered the combustion bedchamber to increase intake air volume and charging efficiency; and,
• Loftier engine speeds and loads: port injection and direct injection for high fuel flow volume.

The FA20D engine used a hot-wire, slot-in type air menstruation meter to measure intake mass – this meter immune a portion of intake air to flow through the detection expanse so that the air mass and catamenia rate could be measured straight. The mass air flow meter also had a congenital-in intake air temperature sensor.

The FA20D engine had a compression ratio of 12.five:1.

Ignition

The FA20D engine had a direct ignition arrangement whereby an ignition roll 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 exist increased. Furthermore, the water jacket could be extended near the combustion chamber to raise cooling functioning. 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 control sensors (not-resonant type) attached to the left and right cylinder blocks.

Frazzle and emissions

The FA20D engine had a four-2-1 frazzle manifold and dual tailpipe outlets. To reduce emissions, the FA20D engine had a returnless fuel system with evaporative emissions command that prevented fuel vapours created in the fuel tank from being released into the atmosphere 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;
• crude 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 non meeting manufacturing tolerances which caused the ECU to detect an aberration 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'south tolerances and the VVT-i/AVCS controllers were afterwards manufactured to a 'tighter specification'.

There have been cases, nevertheless, 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 not respond 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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