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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'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 equally the 4U-GSE before adopting the FA20 proper noun.

Key features of the FA20D engine included it:

• Open deck design (i.due east. the space betwixt the cylinder bores at the superlative of the cylinder cake was open up);
• 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;
• Pinch ratio of 12.five:one; 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 capacity of 1998 cc. Within the cylinder bores, the FA20D engine had cast atomic number 26 liners.

Cylinder head: camshaft and valves

The FA20D engine had an aluminium alloy cylinder caput with chain-driven double overhead camshafts. The four valves per cylinder – two intake and two 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 cheque ball spring. Through the use of oil pressure and spring forcefulness, the lash adjuster maintained a constant zero valve clearance.

Valve timing: D-AVCS

To optimise valve overlap and employ exhaust pulsation to enhance cylinder filling at high engine speeds, the FA20D engine had variable intake and exhaust valve timing, known every bit Subaru'southward 'Dual Agile 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 frazzle 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,
• Frazzle duration was 252 degrees.

The camshaft timing gear assembly contained advance and retard oil passages, as well as a detent oil passage to brand intermediate locking possible. Furthermore, a thin cam timing oil control valve assembly was installed on the front surface side of the timing chain encompass to make the variable valve timing mechanism more meaty. 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 advance hydraulic bedchamber or retard hydraulic bedroom of the camshaft timing gear assembly.

To alter cam timing, the spool valve would exist activated by the cam timing oil control valve associates 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 accelerate chamber from negative or positive cam torque (for advance or retard, respectively) would utilise force per unit area to the advance/retard hydraulic chamber through the accelerate/retard check valve. The rotor vane, which was coupled with the camshaft, would then rotate in the advance/retard direction against the rotation of the camshaft timing gear assembly – which was driven by the timing chain – and advance/retard valve timing. Pressed by hydraulic pressure from the oil pump, the detent oil passage would get blocked then 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 spring power, and maximum advance state on the frazzle side, to prepare for the next activation.

Intake and throttle

The intake organization for the Toyota ZN6 86 and Subaru Z1 BRZ included a 'audio 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. 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 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 command the angle. Furthermore, the electronically controlled throttle regulated idle speed, traction command, stability control and cruise control functions.

Port and direct injection

The FA20D engine had:

• A direct injection system which included a high-pressure level 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-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 straight injection increased performance across the revolution range compared with a port-only injection engine, increasing power by up to ten kW and torque by upward to 20 Nm.

Equally per the table below, the injection system had the following operating conditions:

• Cold start: the port injectors provided a homogeneous air:fuel mixture in the combustion chamber, though the mixture around 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 chop-chop;
• Depression engine speeds: port injection and straight injection for a homogenous air:fuel mixture to stabilise combustion, improve fuel efficiency and reduce emissions;
• Medium engine speeds and loads: directly injection only to utilise the cooling issue of the fuel evaporating as it entered the combustion chamber to increase intake air volume and charging efficiency; and,
• High 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 period meter to mensurate intake mass – this meter allowed a portion of intake air to catamenia through the detection surface area then that the air mass and flow rate could be measured directly. The mass air period meter also had a built-in intake air temperature sensor.

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

Ignition

The FA20D engine had a direct ignition organisation whereby an ignition curlicue 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 exist extended near the combustion bedchamber to enhance 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 type) attached to the left and right cylinder blocks.

Frazzle 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 existence released into the temper 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;
• rough idling;
• shuddering; or,
• stalling

that were accompanied by

• the 'check engine' calorie-free 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'southward 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 error codes P0016 or P0017 – these symptoms have been attributed to a faulty cam sprocket which could cause oil pressure 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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