Atlantis Speaks Again M M Maier

Introduction

The FA20D engine was a 2.0-litre horizontally-opposed (or 'boxer') four-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 information technology as the 4U-GSE before adopting the FA20 name.

Key features of the FA20D engine included it:

• Open up deck design (i.e. the infinite between the cylinder bores at the superlative of the cylinder cake was open);
• Aluminium alloy block 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.five:i; 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. Within 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 concatenation-driven double overhead camshafts. The four valves per cylinder – two intake and two exhaust – were actuated past roller rocker arms which had congenital-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 leap, check ball and check ball spring. Through the use of oil pressure and spring force, the lash adjuster maintained a constant goose egg valve clearance.

Valve timing: D-AVCS

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

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

The camshaft timing gear assembly independent advance and retard oil passages, besides equally a detent oil passage to make intermediate locking possible. Furthermore, a thin cam timing oil control valve associates 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 according to signals from the ECM, controlling the position of the spool valve and supplying engine oil to the advance hydraulic sleeping accommodation or retard hydraulic bedchamber of the camshaft timing gear associates.

To alter cam timing, the spool valve would be activated by the cam timing oil command valve assembly via a signal from the ECM and movement to either the right (to advance timing) or the left (to retard timing). Hydraulic pressure in the advance bedchamber from negative or positive cam torque (for advance or retard, respectively) would employ pressure to the advance/retard hydraulic sleeping accommodation through the accelerate/retard bank 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 by the timing chain – and accelerate/retard valve timing. Pressed by hydraulic pressure from the oil pump, the detent oil passage would get blocked so that it did non operate.

When the engine was stopped, the spool valve was put into an intermediate locking position on the intake side by bound power, and maximum advance state on the exhaust side, to prepare for the adjacent activation.

Intake and throttle

The intake system for the Toyota ZN6 86 and Subaru Z1 BRZ included a 'sound creator', damper and a thin safety tube to transmit intake pulsations to the cabin. When the intake pulsations reached the sound creator, the damper resonated at sure frequencies. Co-ordinate to Toyota, this blueprint enhanced the engine consecration racket heard in the cabin, producing a 'linear intake sound' in response to throttle application.

In contrast to a conventional throttle which used accelerator pedal effort 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 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 straight injection arrangement which included a high-pressure fuel pump, fuel delivery pipe and fuel injector assembly; and,
• A port injection organisation 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 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-merely injection engine, increasing power by upwardly to ten kW and torque by up to 20 Nm.

As per the table below, the injection system had the following operating atmospheric condition:

• Cold start: 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 raise exhaust gas temperatures and so that the catalytic converter could reach operating temperature more quickly;
• Depression engine speeds: port injection and straight injection for a homogenous air:fuel mixture to stabilise combustion, ameliorate fuel efficiency and reduce emissions;
• Medium engine speeds and loads: straight injection just to utilise the cooling outcome of the fuel evaporating every bit it entered the combustion chamber to increase intake air volume and charging efficiency; and,
• High engine speeds and loads: port injection and directly injection for high fuel period volume.

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

The FA20D engine had a compression ratio of 12.5:1.

Ignition

The FA20D engine had a direct ignition organization whereby an ignition ringlet 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 exist increased. Furthermore, the water jacket could be extended near the combustion chamber to enhance cooling performance. The triple ground electrode type iridium-tipped spark plugs had threescore,000 mile (96,000 km) maintenance intervals.

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

Exhaust and emissions

The FA20D engine had a 4-2-1 frazzle manifold and dual tailpipe outlets. To reduce emissions, the FA20D engine had a returnless fuel system 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, in that location have 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 non meeting manufacturing tolerances which caused the ECU to detect an abnormality in the cam actuator duty cycle and restrict the performance 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 afterward manufactured to a 'tighter specification'.

There have been cases, however, where the vehicle has stalled when coming to remainder and the ECU has issued fault codes P0016 or P0017 – these symptoms have been attributed to a faulty cam sprocket which could cause oil force per unit area loss. As 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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