This is the engine that was used as the base for the Alfa 4C's new more powerful engine which has an aluminum block instead of cast iron:
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UNDER THE BONNET - TECHNOLOGY IN ACTION
1750 TBi PETROL ENGINE
Scavenging
The enhanced performance of this continuously variable valve timing engine is the result of applying ‘scavenging technology', maximising torque at very low engine speeds.
This is achieved by monitoring and optimising engine parameters such as fuel measurement, injection timing and spark advance. Managed by a new ECU, it is possible to define the angle and times of valve overlap in order to generate airflow from the inlet manifold to the exhaust manifold and therefore activate the turbocharger very quickly.
This new process allows for maximum exploitation of the turbocharger compared to conventional turbocharged petrol engines.
The results are maximum torque at just 1500 rpm - 70% greater than that of a conventional turbo engine - and throttle response times slashed by half.
Direct Injection
Direct injection with an advanced double-injection strategy is essential to reduce emissions. Allowing direct control of fuel metering during the scavenging process, it is possible to prevent unburnt fuel ending up in the exhaust, which affects the catalytic converter. The secondary injection system has a new high-pressure pump and new 7-aperture injectors which guarantee perfect vaporisation.
This allows excellent performance to be achieved even in the presence of relatively high compression, and provides low consumption at cruising speeds.
Dual variable valve timing (VVT)
The two continuous phase variators on both inlet and exhaust camshafts optimise the valve timing at all speeds, minimizing consumption and emissions. In addition, by coupling the two variators to the turbocharger, the ‘scavenging' strategy is accurately controlled.
In response to a sudden torque request from the driver, it is therefore possible to significantly accelerate engine response, even from low RPM.
Turbocharger
This engine incorporates a new generation KKK fixed geometry turbocharger connected to an innovative pulse converter-type exhaust manifold which optimises the use of exhaust pressure waves to increment driving torque at low speeds. Both manifold and turbine are made of microcast steel so that they can withstand very high working temperatures (up to a maximum of 1020 °C). This is important for a reduction in fuel consumption while operating at medium/high speed.
Thermal fluid dynamics
The inlet ports have been designed using new technology allowing the optimal level of turbulence to be created. This results in the correct mixing of air and fuel. The combustion chambers have also been optimised by using ‘squish' areas, minimising the surface-to-volume ratio and therefore benefitting combustion efficiency.
Friction
The entire engine has been designed to reduce losses through friction. Pistons have ‘flexible' rings to limit tangential load and advanced materials have been used to reduce wear. In addition, the aluminium alloy cylinder head design incorporates roller rocker arms that help reduce losses through sliding contact by up to 65 % at 2000 rpm, compared to traditional cylinder heads with hydraulic tappets.
An optimised crankshaft design based on long connecting rods but a comparatively short stroke, has cut to a minimum the high speed vibration normally associated with four-cylinder engines, obviating the need for balancer shafts.
Performance
A new engine management system combined with a scavenging strategy has achieved new ‘benchmark' levels for engine performance.
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