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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'south engine found 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 every bit the 4U-GSE before adopting the FA20 name.

Key features of the FA20D engine included it:

• Open deck design (i.e. the space between the cylinder bores at the top of the cylinder block was open);
• Aluminium blend cake 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 12.5:1; 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 chapters 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 4 valves per cylinder – 2 intake and ii 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 bound, check ball and cheque brawl leap. Through the use of oil force per unit area and leap 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 Agile Valve Control System' (D-AVCS).

For the FA20D engine, the intake camshaft had a 60 degree range of aligning (relative to crankshaft bending), while the exhaust camshaft had a 54 caste range. For the FA20D engine,

• Valve overlap ranged from -33 degrees to 89 degrees (a range of 122 degrees);
• Intake elapsing was 255 degrees; and,
• Exhaust duration was 252 degrees.

The camshaft timing gear assembly independent advance and retard oil passages, as well as a detent oil passage to make intermediate locking possible. Furthermore, a thin cam timing oil control valve assembly was installed on the front surface side of the timing chain cover to brand the variable valve timing mechanism more than meaty. The cam timing oil control valve assembly operated co-ordinate to signals from the ECM, controlling the position of the spool valve and supplying engine oil to the accelerate hydraulic bedchamber or retard hydraulic chamber of the camshaft timing gear assembly.

To alter cam timing, the spool valve would be activated past the cam timing oil control valve associates via a bespeak from the ECM and move to either the correct (to accelerate timing) or the left (to retard timing). Hydraulic pressure in the advance sleeping room from negative or positive cam torque (for advance or retard, respectively) would employ pressure to the advance/retard hydraulic sleeping accommodation through the advance/retard cheque valve. The rotor vane, which was coupled with the camshaft, would and 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 past hydraulic pressure from the oil pump, the detent oil passage would become blocked so that information technology did not operate.

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

Intake and throttle

The intake system for the Toyota ZN6 86 and Subaru Z1 BRZ included a 'sound creator', damper and a sparse prophylactic tube to transmit intake pulsations to the motel. When the intake pulsations reached the sound creator, the damper resonated at sure frequencies. According to Toyota, this design enhanced the engine induction dissonance heard in the motel, producing a 'linear intake sound' in response to throttle application.

In dissimilarity to a conventional throttle which used accelerator pedal effort to decide throttle angle, the FA20D engine had electronic throttle control which used the ECM to calculate the optimal throttle valve angle and a throttle command 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 direct injection system which included a high-force per unit area fuel pump, fuel delivery pipe and fuel injector assembly; and,
• A port injection system which consisted of a fuel suction tube with pump and judge 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 operation across the revolution range compared with a port-only injection engine, increasing power by up to 10 kW and torque past up to 20 Nm.

As per the table below, the injection system had the post-obit operating conditions:

• 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 directly injectors. Furthermore, ignition timing was retarded to heighten frazzle gas temperatures and then that the catalytic converter could reach 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: straight injection only to utilize the cooling effect 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 straight injection for loftier fuel flow volume.

The FA20D engine used a hot-wire, slot-in blazon air flow meter to measure intake mass – this meter allowed a portion of intake air to catamenia through the detection area and then that the air mass and period rate could be measured straight. The mass air period meter too had a built-in intake air temperature sensor.

The FA20D engine had a pinch ratio of 12.v:one.

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 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 h2o jacket could be extended near the combustion sleeping room to enhance cooling functioning. The triple ground electrode blazon iridium-tipped spark plugs had 60,000 mile (96,000 km) maintenance intervals.

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

Exhaust and emissions

The FA20D engine had a 4-ii-i 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 being released into the atmosphere past catching them in an activated charcoal canister.

Uneven idle and stalling

For the Subaru BRZ and Toyota 86, there have been reports of

• varying idle speed;
• rough idling;
• shuddering; or,
• stalling

that were accompanied by

• the 'cheque 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 acquired the ECU to detect an abnormality in the cam actuator duty cycle and restrict the operation of the controller. To prepare, 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 mistake codes P0016 or P0017 – these symptoms take been attributed to a faulty cam sprocket which could crusade 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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