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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's engine institute 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 earlier adopting the FA20 name.

Key features of the FA20D engine included it:

• Open up deck design (i.e. the space between the cylinder bores at the top of the cylinder cake was open);
• Aluminium alloy block and cylinder head;
• Double overhead camshafts;
• Iv valves per cylinder with variable inlet and exhaust valve timing;
• Direct and port fuel injection systems;
• Pinch ratio of 12.5:1; and,
• 7450 rpm redline.

FA20D block

The FA20D engine had an aluminium alloy cake 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 chain-driven double overhead camshafts. The four valves per cylinder – two intake and ii frazzle – 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 spring, check brawl and check brawl jump. Through the utilize of oil pressure and leap forcefulness, the lash adjuster maintained a abiding zip 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 equally Subaru's 'Dual Active Valve Control System' (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 elapsing was 252 degrees.

The camshaft timing gear associates independent accelerate and retard oil passages, as well as a detent oil passage to make intermediate locking possible. Furthermore, a sparse cam timing oil control valve assembly was installed on the front end surface side of the timing concatenation encompass to brand the variable valve timing mechanism more meaty. 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 chamber or retard hydraulic chamber of the camshaft timing gear assembly.

To alter cam timing, the spool valve would be activated by the cam timing oil control 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 in the accelerate chamber from negative or positive cam torque (for advance or retard, respectively) would apply pressure to the advance/retard hydraulic chamber through the accelerate/retard check valve. The rotor vane, which was coupled with the camshaft, would and then rotate in the advance/retard direction confronting the rotation of the camshaft timing gear associates – which was driven by the timing chain – and advance/retard valve timing. Pressed past hydraulic pressure from the oil pump, the detent oil passage would become 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 jump power, and maximum advance state 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 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 dissonance heard in the cabin, producing a 'linear intake audio' in response to throttle application.

In dissimilarity to a conventional throttle which used accelerator pedal effort to determine throttle bending, 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 command, stability command and cruise control functions.

Port and direct injection

The FA20D engine had:

• A straight injection system which included a high-pressure level 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-associates and fuel injector associates.

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 weather. According to Toyota, port and direct injection increased functioning across the revolution range compared with a port-only injection engine, increasing power by up to 10 kW and torque by up to 20 Nm.

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

• Cold outset: 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 raise exhaust gas temperatures so that the catalytic converter could achieve operating temperature more quickly;
• Low engine speeds: port injection and straight injection for a homogenous air:fuel mixture to stabilise combustion, amend fuel efficiency and reduce emissions;
• Medium engine speeds and loads: direct injection only to utilise the cooling effect of the fuel evaporating as it entered the combustion chamber to increment intake air volume and charging efficiency; and,
• Loftier engine speeds and loads: port injection and direct injection for loftier fuel flow volume.

The FA20D engine used a hot-wire, slot-in type air flow meter to measure out intake mass – this meter allowed a portion of intake air to flow through the detection expanse then that the air mass and flow 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.v:ane.

Ignition

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

The FA20D engine had long-accomplish, 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 be extended about the combustion chamber to enhance cooling performance. The triple ground electrode type iridium-tipped spark plugs had sixty,000 mile (96,000 km) maintenance intervals.

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

Exhaust and emissions

The FA20D engine had a iv-2-1 exhaust manifold and dual tailpipe outlets. To reduce emissions, the FA20D engine had a returnless fuel arrangement 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 take 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 not coming together manufacturing tolerances which caused the ECU to detect an abnormality in the cam actuator duty cycle and restrict the operation of the controller. To fix, Subaru and Toyota adult new software mapping that relaxed the ECU'southward tolerances and the VVT-i/AVCS controllers were subsequently manufactured to a 'tighter specification'.

At that place have been cases, however, where the vehicle has stalled when coming to rest and the ECU has issued fault codes P0016 or P0017 – these symptoms have been attributed to a faulty cam sprocket which could cause oil pressure loss. As a effect, 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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