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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 found 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.

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 head;
• Double overhead camshafts;
• Four valves per cylinder with variable inlet and frazzle valve timing;
• Direct and port fuel injection systems;
• Pinch ratio of 12.v:one; 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 capacity of 1998 cc. Inside the cylinder bores, the FA20D engine had cast iron liners.

Cylinder caput: 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 2 exhaust – were actuated by roller rocker arms which had built-in needle bearings that reduced the friction that occurred betwixt 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 use of oil force per unit area and spring force, the lash adjuster maintained a constant nil valve clearance.

Valve timing: D-AVCS

To optimise valve overlap and utilize exhaust pulsation to enhance cylinder filling at loftier engine speeds, the FA20D engine had variable intake and exhaust valve timing, known as Subaru's 'Dual Active Valve Command Arrangement' (D-AVCS).

For the FA20D engine, the intake camshaft had a sixty degree 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 duration was 252 degrees.

The camshaft timing gear assembly independent advance and retard oil passages, as well as a detent oil passage to brand intermediate locking possible. Furthermore, a thin cam timing oil command valve assembly was installed on the front surface side of the timing concatenation cover to make the variable valve timing mechanism more compact. The cam timing oil control valve associates operated co-ordinate 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 assembly.

To modify cam timing, the spool valve would be activated past the cam timing oil control valve assembly via a signal from the ECM and move to either the correct (to advance timing) or the left (to retard timing). Hydraulic pressure in the advance chamber from negative or positive cam torque (for advance or retard, respectively) would apply pressure to the advance/retard hydraulic bedchamber through the advance/retard cheque 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 by the timing chain – and accelerate/retard valve timing. Pressed past hydraulic pressure from the oil pump, the detent oil passage would become blocked then 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 prepare 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 sparse 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 cabin, producing a 'linear intake sound' in response to throttle application.

In dissimilarity to a conventional throttle which used accelerator pedal effort to determine throttle angle, the FA20D engine had electronic throttle control which used the ECM to summate the optimal throttle valve angle and a throttle command motor to control the bending. 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 directly injection organization which included a high-pressure fuel pump, fuel delivery 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 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. According to Toyota, port and direct injection increased functioning across the revolution range compared with a port-but injection engine, increasing power by up to 10 kW and torque past upwards to xx Nm.

As per the table below, the injection organization had the following operating conditions:

• Cold start: the port injectors provided a homogeneous air:fuel mixture in the combustion bedchamber, though the mixture around 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 rapidly;
• Low engine speeds: port injection and direct injection for a homogenous air:fuel mixture to stabilise combustion, amend fuel efficiency and reduce emissions;
• Medium engine speeds and loads: direct injection simply to apply the cooling issue of the fuel evaporating equally information technology entered the combustion chamber to increment intake air volume and charging efficiency; and,
• High engine speeds and loads: port injection and direct injection for high fuel menses volume.

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

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

Ignition

The FA20D engine had a direct ignition arrangement whereby an ignition curl 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 curl associates.

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 exist extended near the combustion chamber to enhance cooling functioning. The triple ground electrode blazon iridium-tipped spark plugs had 60,000 mile (96,000 km) maintenance intervals.

The FA20D engine had flat type knock command sensors (not-resonant type) attached to the left and right cylinder blocks.

Frazzle and emissions

The FA20D engine had a four-ii-1 exhaust manifold and dual tailpipe outlets. To reduce emissions, the FA20D engine had a returnless fuel arrangement with evaporative emissions command that prevented fuel vapours created in the fuel tank from being released into the temper by communicable 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;
• crude idling;
• shuddering; or,
• stalling

that were accompanied by

• the 'bank 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 meeting manufacturing tolerances which caused the ECU to detect an abnormality in the cam actuator duty bicycle and restrict the operation of the controller. To fix, Subaru and Toyota adult 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 rest and the ECU has issued error codes P0016 or P0017 – these symptoms accept been attributed to a faulty cam sprocket which could crusade oil pressure loss. As a event, the hydraulically-controlled camshaft could not answer 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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