The Focus RS low-inertia turbo system has been upgraded from the previous model and uses the basis of the 2015 Mustang engine to deliver a better performance. Enhanced features include a bigger compressor wheel to encourage more airflow to the engine and increased power throughout the revs, and a greater front-mounted intercooler which boosts air consumption and optimises charge density. The intercooler plays a key role in making sure that the RS turbo system can handle all the extra power the vehicle brings.
Updated versions of the Mustang cylinder pads and cylinder lining (made of high-tensile cast iron) have also been added to the RS MK3 to increase the vehicles durability. The turbo-four does share some of the basic features of the Mustang turbo, including the complete aluminum mill used on the model. The head gasket has been advanced to deal with the extra heat that the engine produces under heavy load.
To further improve the twin-scroll turbo performance, engine breathing is increased due to a modified design, featuring a large-bore exhaust and a low-restriction intake manifold. The exhaust links in to electronically-operated valves in the tailpipe which balance vehicle pressure and increase sound output.
Twin-scroll turbo’s copy the effect of a pair of turbochargers, and the connecting exhaust manifold separates the cylinder channels so exhaust gases that might interfere with each other flow through separate tubes.
The engine firing order from a single-scroll turbocharger would be 1-3-4-2, but the twin-scroll emits 1-4 and 3-2 to make sure that there is no overlap between the cylinders firing on each scroll.
Twin-scroll turbo produces more pressure, reduces turbo lag so the time in between the throttle being opened and intake being delivered is significantly reduced. The turbocharger also sends an increased amount of improved-quality air into the cylinders.
The Ford Focus RS turbo uses an overboost feature to allow the engine to run at increased pressure. The RS overboost lasts for up to 20 seconds, and if the throttle is moved or raised, the overboost timer resets, giving drivers the same boost and increased performance all over again.
It’s rare that the overboost figures are included in the official power rating, but because the overboost is pretty much on demand, the Ecoboost 2.3-litre engine has an official Society of Automotive Engineers rating of 350bhp and 350lb/ft of torque. When the specification for the MK3 was first revealed, the EcoBoost engine used in the Mustang was anticipated to produce around 315hp (235 kW) and 475Nm. The engineering team upgraded the boost pressure on the RS from 18 to 23.1 psi.
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