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

Key features of the FA20D engine included information technology:

• Open deck blueprint (i.e. the infinite betwixt the cylinder bores at the elevation of the cylinder cake was open);
• Aluminium blend cake and cylinder head;
• Double overhead camshafts;
• 4 valves per cylinder with variable inlet and exhaust valve timing;
• Straight and port fuel injection systems;
• Compression ratio of 12.5:1; and,
• 7450 rpm redline.

FA20D cake

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

Cylinder head: camshaft and valves

The FA20D engine had an aluminium alloy cylinder head with chain-driven double overhead camshafts. The four valves per cylinder – 2 intake and two exhaust – were actuated by roller rocker arms which had built-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 leap, check ball and check ball leap. Through the utilize of oil pressure and spring force, the lash adjuster maintained a constant zero 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's 'Dual Active Valve Control System' (D-AVCS).

For the FA20D engine, the intake camshaft had a 60 degree range of aligning (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 contained advance and retard oil passages, as well equally a detent oil passage to make intermediate locking possible. Furthermore, a thin cam timing oil control valve assembly was installed on the forepart surface side of the timing chain comprehend to brand the variable valve timing machinery more compact. The cam timing oil control valve assembly operated according to signals from the ECM, controlling the position of the spool valve and supplying engine oil to the advance hydraulic bedchamber or retard hydraulic sleeping room of the camshaft timing gear assembly.

To change cam timing, the spool valve would be activated by the cam timing oil control valve assembly via a point from the ECM and move to either the right (to advance timing) or the left (to retard timing). Hydraulic pressure level in the advance sleeping accommodation from negative or positive cam torque (for accelerate 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 so rotate in the accelerate/retard direction against the rotation of the camshaft timing gear assembly – which was driven past 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 information technology did non operate.

When the engine was stopped, the spool valve was put into an intermediate locking position on the intake side by spring ability, and maximum advance land 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 sound creator, the damper resonated at sure frequencies. Co-ordinate to Toyota, this design enhanced the engine induction noise heard in the cabin, producing a 'linear intake audio' in response to throttle awarding.

In dissimilarity to a conventional throttle which used accelerator pedal try 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 control motor to command the angle. Furthermore, the electronically controlled throttle regulated idle speed, traction control, stability command and cruise command functions.

Port and straight injection

The FA20D engine had:

• A straight injection organization which included a high-pressure level fuel pump, fuel delivery pipage and fuel injector assembly; and,
• A port injection system which consisted of a fuel suction tube with pump and approximate 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 performance beyond the revolution range compared with a port-only injection engine, increasing power past upward to 10 kW and torque by upwards to 20 Nm.

Every bit per the table below, the injection organization had the post-obit operating weather:

• Cold start: the port injectors provided a homogeneous air:fuel mixture in the combustion sleeping accommodation, though the mixture around the spark plugs was stratified by compression 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 than quickly;
• Low engine speeds: port injection and straight injection for a homogenous air:fuel mixture to stabilise combustion, meliorate fuel efficiency and reduce emissions;
• Medium engine speeds and loads: straight injection only to utilise the cooling effect of the fuel evaporating every bit it entered the combustion chamber to increment intake air book and charging efficiency; and,
• High engine speeds and loads: port injection and straight injection for high fuel period book.

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 flow through the detection area so that the air mass and period rate could be measured directly. The mass air flow meter likewise 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 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-achieve, 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 most the combustion chamber to enhance cooling performance. The triple basis electrode blazon iridium-tipped spark plugs had sixty,000 mile (96,000 km) maintenance intervals.

The FA20D engine had flat type knock command sensors (non-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 system with evaporative emissions control 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, there accept been reports of

• varying idle speed;
• crude 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 detect an abnormality in the cam actuator duty cycle and restrict the operation of the controller. To set up, Subaru and Toyota developed new software mapping that relaxed the ECU's tolerances and the VVT-i/AVCS controllers were later manufactured to a 'tighter specification'.

There have been cases, however, where the vehicle has stalled when coming to residuum and the ECU has issued error codes P0016 or P0017 – these symptoms take been attributed to a faulty cam sprocket which could cause oil pressure loss. As a upshot, the hydraulically-controlled camshaft could not 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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