FPV F6 270 Turbo engine

Variable Cam Timing (VCT)

The F6 270 Turbo engine had a vane-type VCT phaser – produced by Aisin – on each camshaft that provided continual variable adjustment within a 60 degree range (10 degrees advanced or 50 degrees retarded from the initial pin lock position). Each camshaft phaser was hydraulically controlled via an oil control valve that was mounted on top of it. However, the BA F6 270 Turbo engine had Ford’s ‘Dual Equal Phase Shifting’ (DEPS) VCT system whereby the intake and exhaust camshafts could only be controlled synchronously. As such, intake and exhaust camshaft timing could only be advanced or retarded by the same degree simultaneously, and not independently.

Valve timing for the initial, advanced and retarded camshaft settings are understood to be the same as the Barra 182 and BA F6 270 Turbo engine engines and are given in the tables below. Based on these timings, valve overlap was 25 degrees, intake duration was 251 degrees and exhaust duration was 246 degrees.

At idle, the camshaft timing could be advanced by 10 degrees from the pin lock position for smoother running. On low throttle openings, however, the system could retard timing by as much as 50 degrees from the pin lock position to reduce fuel consumption and lower exhaust emissions via internal exhaust gas recirculation.

Dual Independent Variable Cam Timing (VCT): BF F6 270 Turbo

Significantly, the variable cam timing system for the BF F6 270 Turbo engine was Ford’s ‘Dual Independent Phase Shifting’ (DIPS) which enabled the intake and exhaust camshafts to be varied independently of each other.

Valve timing for the BF F6 270 Turbo engine is understood to be the same as the Barra 190 and Barra 245T engines and is given in the tables below. From these, valve overlap could be varied from -35 degrees to 85 degrees, intake duration was 256 degrees and exhaust duration was 256 degrees. Furthermore,

• On low throttle openings, timing would be retarded by up to 50 degrees to improve fuel economy;
• At idle, the intake camshaft was retarded by 18 degrees for improved combustion and a stable idle; and,
• At higher loads, timing would be advanced for greater power.

Injection and ignition

The F6 270 Turbo engine had an electronically-controlled sequential fuel injection system with peak fuel delivery pressure of 4.0 bar. The ‘speed density’ fuel injection system used the engine speed, intake air temperature and manifold absolute pressure sensors to calculate intake air mass and therefore the fuel required to be injected for combustion. This quantity of fuel was then adjusted according to feedback information from the Heated Oxygen (HEGO) sensor, providing close loop control of fuel injection.

The F6 270 Turbo engine had distributorless, coil-on-plug ignition with individual coils mounted above the spark plug. The long-life spark plug was positioned in the centre of the combustion chamber roof between the four valves. For the BF F6 270 Turbo engine, upgraded spark plugs were introduced which had a 0.5 mm finewire centre electrode (the smallest then available) and platinum pad ground electrodes. According to Ford, the spark plugs were optimised for idle stability and helped prevent misfire.

The F6 270 Turbo engine had a 1-5-3-6-2-4 injection and firing order.

For the BF F6 270 Turbo engine, the ignition system featured adaptive and variable dwell (the time required to charge the ignition coil) for more efficient ignition control. Specifically,

• Adaptive dwell accounted for battery voltage and the temperature of the coil windings in the ignition system to provide a more reliable, consistent charge; and,
• Variable dwell provided maximum coil energy when high voltages were required (e.g. wide open throttle) and minimum coil energy when cruising or at idle.

Internal Exhaust Gas Recirculation (EGR)

The F6 270 Turbo engine complied with Euro II emission standards upon its release and had an internal exhaust gas recirculation system whereby late closing of the exhaust valves – during the downward induction stroke – would cause some of the unburned exhaust gas in the extractors to return to the intake.

Knock sensing and spark correction

The BF F6 270 Turbo engine introduced an additional knock sensor which, according to Ford, enabled a change in ignition timing strategy for more accurate spark control, improved fuel economy and greater refinement. Specifically, the Powertrain Control Module had four forms of spark control:

• Individual/averaged spark correction: a performance mode which used 50 per cent of the individual cylinder correction and 50 per cent of engine average spark correction for more consistent performance at higher engine speeds and under heavy loads;
• Individual ‘fast only’ spark correction: reacted to detonation noise and retarded the spark for the next firing event on the same cylinder. This method provided optimum fuel efficiency because spark was only retarded when detonation was detected by the system;
• Individual slow/fast spark correction: applied in addition to the ‘fast only’ mode, slow correction recorded the spark advance used on previous combustion cycles and gradually reduced spark advance if knock was not detected for a few seconds, providing greater refinement; and,
• No spark correction: used at low engine loads when detonation was not possible. As a result, optimum spark timing was applied.

Stephen Tomlinson

http://AustralianCar.Reviews

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