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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 constitute in Ota, Gunma. The FA20D engine was introduced in the Subaru BRZ and Toyota ZN6 86; for the latter, Toyota initially referred to it as the 4U-GSE before adopting the FA20 name.
Primal features of the FA20D engine included it:
- Open deck design (i.east. the infinite between the cylinder bores at the pinnacle of the cylinder cake was open);
- Aluminium alloy block and cylinder caput;
- Double overhead camshafts;
- Four valves per cylinder with variable inlet and frazzle valve timing;
- Direct 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. Inside the cylinder bores, the FA20D engine had bandage 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 – ii 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 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, check ball and check brawl spring. Through the use of oil pressure level 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 sixty caste 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,
- Frazzle elapsing was 252 degrees.
The camshaft timing gear assembly contained accelerate 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 cover to make the variable valve timing mechanism more than meaty. 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 accommodation 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 movement to either the right (to advance timing) or the left (to retard timing). Hydraulic pressure in the accelerate sleeping room from negative or positive cam torque (for advance or retard, respectively) would utilise pressure level to the advance/retard hydraulic chamber through the advance/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 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 get 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 by leap power, and maximum advance state on the frazzle side, to set for the next activation.
Intake and throttle
The intake system 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 sure frequencies. According to Toyota, this blueprint enhanced the engine induction dissonance heard in the cabin, producing a 'linear intake sound' in response to throttle application.
In contrast to a conventional throttle which used accelerator pedal effort to determine throttle bending, 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 command, stability control and prowl command functions.
Port and direct injection
The FA20D engine had:
- A direct injection system which included a high-pressure fuel pump, fuel delivery piping and fuel injector associates; and,
- A port injection system which consisted of a fuel suction tube with pump and approximate associates, fuel pipe sub-assembly and fuel injector associates.
Based on inputs from sensors, the ECM controlled the injection volume and timing of each blazon of fuel injector, according to engine load and engine speed, to optimise the fuel:air mixture for engine conditions. Co-ordinate to Toyota, port and directly injection increased performance beyond the revolution range compared with a port-only injection engine, increasing ability by upward to 10 kW and torque by up to 20 Nm.
As per the table beneath, the injection arrangement had the post-obit operating conditions:
- Cold beginning: 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 directly injectors. Furthermore, ignition timing was retarded to raise frazzle gas temperatures so that the catalytic converter could reach operating temperature more apace;
- Low 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: direct injection only to apply the cooling issue 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 directly injection for high fuel flow volume.
The FA20D engine used a hot-wire, slot-in type air menstruation meter to measure out intake mass – this meter immune a portion of intake air to flow through the detection area so that the air mass and catamenia rate could be measured direct. The mass air flow meter also had a congenital-in intake air temperature sensor.
The FA20D engine had a pinch ratio of 12.v: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-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 exist extended near the combustion chamber to enhance cooling performance. The triple basis electrode type iridium-tipped spark plugs had lx,000 mile (96,000 km) maintenance intervals.
The FA20D engine had flat type knock command sensors (not-resonant type) fastened to the left and right cylinder blocks.
Frazzle and emissions
The FA20D engine had a 4-2-i exhaust manifold and dual tailpipe outlets. To reduce emissions, the FA20D engine had a returnless fuel organization with evaporative emissions command that prevented fuel vapours created in the fuel tank from existence released into the atmosphere by communicable 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 '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 meeting manufacturing tolerances which caused the ECU to detect an abnormality in the cam actuator duty cycle and restrict the functioning 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 afterwards manufactured to a 'tighter specification'.
In that location 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 force per unit area loss. Every bit a result, the hydraulically-controlled camshaft could non 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