The clever tech of Fordí s new Fiesta ST

When price is important, improving a performance car while minimising added cost becomes the engineering challenge

FIESTA ST UNCOVERED

YOUíVE READ the review (p50) but now itís time to dig a little deeper to find out what the new Ford Fiesta ST is all about. Itís a car thatís had heavy involvement from the Ford Performance division to make sure it maintains its high esteem among the hot-hatch fraternity.

First off, the ST gets a proper mechanical LSD Ė a Quaife unit that will be found on the options list. The mechanical system limits torque to the wheel with reduced grip, therefore limiting wheelspin and pulling the ST out of tight bends, fully exploiting the three-potís newfound extra grunt.

The LSD is designed to work in conjunction with the enhanced torque vectoring tech which, like any other system, electronically applies brake pressure to the inside front wheel if it detects slip, which also reduces understeer. Ford Performance has worked hard to make the mechanical LSD and electronic torque vectoring work in harmony.

Ford-patented force-vectoring springs bolster stability (and improve ride quality), roadholding and responsiveness of the new twist-beam rear suspension. Essentially it keeps the feel and fun-to-drive experience of old with sharp turn-in and keen direction changes, but adds in needed compliance. Itís also 10kg lighter compared to a Wattís link setup.

A first for a compact hot hatch, the ST also uses non-uniform, non-interchangeable, directionally wound springs. The idea behind it is that they apply vectoring forces to the rear suspension, which in turn enable cornering forces to go directly into the spring for increased lateral stiffness.

Instead of adaptive dampers, the ST uses sophisticated Tenneco twin-tube front and mono-tube rear dampers with RC1 valve technology, resulting in frequency dependent damping. Overall body control is increased while high-speed driving refinement is retained.

The company stated that buyers expected Ďbig thingsí from the new ST. It seems Ford has well and truly delivered.

THE LSD IS DESIGNED TO WORK WITH THE ENHANCED TORQUE VECTORING, WHICH ELECTRONICALLY BRAKES A SPINNING INSIDE FRONT WHEEL

BIG TECH, SMALL PACKAGE

New engine offers more power, less fuel

THE STís big news is a switch from a 1.6-litre turbocharged four-cylinder to a boosted 1.5litre triple. Despite the pot drop, power is rated at the same 147kW (6000rpm) the old ST made on overboost. Itís matched with a generous 290Nm of torque from 1600-4000rpm.

Itís an all-new, all-aluminium engine and features turbocharging, high-pressure fuel injection and twin-independent variable cam timing. The integrated exhaust manifold also delivers more torque at a faster pace by minimising the distance the exhaust gases have to travel between the cylinders and turbo.

The active exhaust bumps up the volume on the already unique engine sound to enhance the driving experience.

The smartest tech is cylinder deactivation, which allows the engine to drop to two cylinders at engine speeds up to 4500rpm in just 14 milliseconds. Weíve seen this before, but not on a triple due to noise and vibration issues. It works so well on the ST that most drivers wonít even notice it (or, admittedly, the claimed 6 per cent fuel saving).