Starting with that controversial Quaife Torque Biasing Differential, it sat at the heart of the Focus RS’s approach and appeal. It meant Ford didn’t have to use a heavier four-wheel drive system and in turn meant the three-door Focus shell did not need reworking to make it fit. The differential works by sensing a loss of traction and then sending power to the opposite front wheel to prevent wheel spin. It does this without completely cutting power to the front wheel that has lost traction.
RS is generally tough and reliable
When launched, the Quaife differential had an aggressive set-up that let the steering wheel wriggle and writhe in the driver’s hands as it did its work. It could cause the Focus RS to move around on the road more than a Subaru Impreza, but the benefits came in the corners where the Focus offered far more grip than seemed possible. For the final 1,000 Focus RS models, Quaife refined the differential’s behaviour so the steering wheel doesn’t move so much under hard acceleration. A rework of the ECU by Ford also helped finesse this perceived problem and brought a smoother engine tickover.
The Quaife differential is very tough and can handle tuning of up to 400bhp without any problems. Ford fitted uprated driveshafts as standard to the RS, while an AP Racing clutch sits between the engine and gearbox. Based on Ford’s MT75 five-speed manual gearbox, the Focus RS’s transmission has a unique set of close ratio gears designed to make the most of the engine’s turbocharged performance. A short-throw gear shift mechanism is also standard.
Despite the 2.0-litre turbo engine developing its peak 212hp at 5500rpm, it also has 229lb ft of torque at 3500rpm, so the RS is surprisingly flexible in more mundane driving situations. It can also return an official average of 27.9mpg that, coupled to a 55-litre fuel tank, gives a useful touring range of around 300 miles per fill.
Front mounted intercooler a worthy upgrade
The 2.0-litre Duratec engine was built in Bridgend, Wales and is based on an uprated Zetec motor with iron block and aluminium cylinder head. Sodium-filled exhaust valves help cope with the heat generated by the Garret GT2560LS turbo. One of the few areas to watch for with a Mk1 Focus RS is the cambelt, which can snap, so it’s best to replace it every 60,000 miles rather than the Ford-recommended 100,000-mile intervals. While changing the cambelt, it’s also wise to replace the idler pulley and water pump as is common practice with most cambelt changes.
The other big concern in the Focus RS engine bay is the air-to-water chargecooler for the turbo. Its design dictated a shorter intake pipe than an air-to-air cooler would use and this can lead to very high temperature. If the coolant in the chargecooler reaches boiling point it can lead to a complete failure and also allow super-heated air into the engine that can melt pistons and spark plugs.
To eliminate any potential chargecooler issues, a popular modification is to fit a front-mounted intercooler, such as the kit offered by JW Racing for around £1,100. While originality is desirable, this kit removes one of the RS’s few weak spots and also makes the radiator more efficient by improving air flow.
A stainless steel exhaust was standard from the factory with a 65mm bore and it works well with aftermarket ECU chips to release another 25hp from the engine. Upgrades are available to take the 2.0-litre engine to 300hp and 400hp is possible, but for road use the engine is fine.