Description and operating principle of the Duratec ST 2.0 l engine (Focus 1)

The 2.0L Duratec ST engine is based on the 2.0L Zetec-E engine. Compared to the 2.0L Zetec-E engine, the following changes have been made to the design of this engine:

• Cylinder Block - Modified to include piston injectors.
• Cylinder Head - Inlet Port: High flow design with new manifold feed. Exhaust Port: - Standard port but with secondary air feed to the back of the exhaust valve. Water Jacket: Flow change in the port area. Variable valve timing (VCT) oil supply circuit. VCT (Variable Timing) solenoid valve integrated into the front camshaft bearing cap.
• Intake Valves - Have a 33.5mm diameter with revised clearance to retain bridge and longer length for the new port.
• Exhaust valves - These are standard diameter but are longer to accommodate the tappet on the intake side.
• Intake camshaft - Increased lift and duration with variable valve timing. Pulse wheel to indicate camshaft position.
• Exhaust camshaft - Increased lift and duration.
• Tappet - A series of sizes that are specially graded to accommodate the new valve length and revised cam shape.
• Valve Springs - Special for intake and exhaust valves to match new valve lengths and revised cam shape.
• Piston group - Piston with 20 mm piston pin. Connecting rod: Forged design with broken parting line. Upper piston ring: Inward slope to reduce combustion gas bypass and negative ring end ovality to reduce wear.
• Camshaft Cover Assembly - Design modification to accommodate new VCT solenoid valve. Camshaft Cover Assembly with Gasket.
• Upper Timing Belt Cover Assembly - Design modification to include VCT pulley.
• Front Engine Mount - Repositioned mounting studs to accommodate VCT pulley.
• Generator bracket - Design change due to design change of engine mount.
• Intake Manifold - Made of two parts, replacing the one-piece manifold with fixed channel length. Accumulator chamber assembly. Housing assembly - Manifold - Injectors. Design with adjustable intake channel length. The unit has short channels when the engine is off and then, after the engine is started, switches to the long channel position. At a frequency of more than 6000 rpm, the channels again switch to the short position.
• Throttle Body - Diameter change to 63mm.
• Injectors - Increased flow, 224.8 g/min at 2.7 bar (normal fuel rail pressure)
• Fuel Rail - Revised design with integral damper and no fuel return line. Changed fuel rail inlet port location, requiring new fuel feed hose.
• Flywheel assembly - Double weight flywheel.
• Clutch assembly - Large diameter friction disc. Large diameter pressure disc.
• Oil cooler - Modine type.
• Variable Valve Timing System - Variable Valve Timing Block Assembly. Solenoid Valve Assembly
• Oil Separator Assembly - Internal changes to improve high load cornering performance - to be incorporated into the base engine.
• Exhaust system - Tuned 4-2-1 system with catalytic converter located under the oil pan.