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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 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 equally the 4U-GSE before adopting the FA20 name.

Cardinal features of the FA20D engine included it:

• Open deck design (i.e. the infinite betwixt the cylinder bores at the top of the cylinder block was open up);
• 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.five:1; and,
• 7450 rpm redline.

FA20D block

The FA20D engine had an aluminium blend 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 fe liners.

Cylinder caput: camshaft and valves

The FA20D engine had an aluminium blend cylinder head with chain-driven double overhead camshafts. The four valves per cylinder – 2 intake and 2 exhaust – were actuated past roller rocker arms which had built-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 spring, bank check brawl and check brawl spring. Through the utilize of oil pressure and spring forcefulness, the lash adjuster maintained a abiding nothing 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 every bit Subaru'south 'Dual Agile Valve Command Organisation' (D-AVCS).

For the FA20D engine, the intake camshaft had a lx 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 associates contained advance and retard oil passages, likewise equally a detent oil passage to make intermediate locking possible. Furthermore, a thin cam timing oil command valve assembly was installed on the front surface side of the timing chain cover to brand the variable valve timing mechanism more than compact. The cam timing oil control valve associates operated according to signals from the ECM, decision-making the position of the spool valve and supplying engine oil to the advance hydraulic chamber 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 command valve associates via a indicate from the ECM and move to either the right (to accelerate timing) or the left (to retard timing). Hydraulic force per unit area in the advance sleeping room from negative or positive cam torque (for advance or retard, respectively) would utilize pressure to the advance/retard hydraulic chamber through the advance/retard cheque valve. The rotor vane, which was coupled with the camshaft, would and so rotate in the advance/retard direction against the rotation of the camshaft timing gear associates – which was driven by the timing chain – and advance/retard valve timing. Pressed by hydraulic pressure level 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 past bound ability, and maximum advance state on the frazzle side, to prepare for the adjacent activation.

Intake and throttle

The intake organization 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 motel. When the intake pulsations reached the sound creator, the damper resonated at certain frequencies. Co-ordinate to Toyota, this design enhanced the engine consecration noise heard in the cabin, producing a 'linear intake audio' 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 control 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 command and cruise control functions.

Port and direct injection

The FA20D engine had:

• A straight injection organisation which included a loftier-pressure level fuel pump, fuel delivery piping 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 atmospheric condition. According to Toyota, port and directly injection increased performance across the revolution range compared with a port-but injection engine, increasing power by up to 10 kW and torque by upwardly to 20 Nm.

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

• Common cold start: the port injectors provided a homogeneous air:fuel mixture in the combustion bedroom, though the mixture around the spark plugs was stratified by pinch stroke injection from the direct injectors. Furthermore, ignition timing was retarded to enhance exhaust gas temperatures then that the catalytic converter could achieve operating temperature more than quickly;
• Low engine speeds: port injection and direct injection for a homogenous air:fuel mixture to stabilise combustion, meliorate fuel efficiency and reduce emissions;
• Medium engine speeds and loads: direct injection merely to apply the cooling outcome of the fuel evaporating as it entered the combustion chamber to increment intake air volume and charging efficiency; and,
• High engine speeds and loads: port injection and direct injection for loftier fuel menstruum 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 flow rate could be measured directly. The mass air catamenia meter also had a built-in intake air temperature sensor.

The FA20D engine had a compression ratio of 12.v:1.

Ignition

The FA20D engine had a direct ignition system whereby an ignition whorl 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 roll assembly.

The FA20D engine had long-reach, iridium-tipped spark plugs which enabled the thickness of the cylinder head sub-associates that received the spark plugs to be increased. Furthermore, the water jacket could be extended nigh the combustion chamber to enhance cooling performance. The triple footing electrode blazon iridium-tipped spark plugs had 60,000 mile (96,000 km) maintenance intervals.

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

Exhaust and emissions

The FA20D engine had a 4-ii-1 exhaust manifold and dual tailpipe outlets. To reduce emissions, the FA20D engine had a returnless fuel organisation with evaporative emissions control 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 past

• the 'bank 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 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 developed 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 have been attributed to a faulty cam sprocket which could cause oil pressure loss. Equally a outcome, 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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