The tricky diff that helps the Ford Focus ST fight torque steer

In some ways the Ford Focus ST is the anti-hot hatch, hot hatch. It was the highest placed front-drive contender at MOTOR’s Sports Car of the Year award in 2022, in part as a result of the way it cleverly side steps so many of the old, tired, and frankly irrelevant cliches people throw at hot hatches.

One of the major and now outdated criticisms of modern hot hatches is that they are woeful torque steering monsters relegated to an eternity of understeer, while oversteer is an impossible task never to be achieved.

Yeah, give the Focus ST a try and report back to us on that one.

Part of what makes the Focus ST so sure-footed in the way it sidesteps these cliches is the front differential.

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Instead of going with a traditional mechanical limited-slip diff, Ford opted to splash some of the development budget on a Borg Warner supplied FXD unit. This expensive bit of kit is what is commonly referred to as an electronic limited diff, or eLSD.

Now, instead of traditional electronic diffs, the Borg Warner still has most the componentry of a traditional mechanical LSD, but with an additional clutch pack with electronically controlled actuation that allows it to have a locking state that can vary from completely open to entirely locked.

Simpler eLSD applications shirk the mechanical diff componentry and simply try to apportion the power via ESC-driven intervention from the brakes – cutting power when wheelspin is detected on the unloaded side.

The Borg Warner eLSD with its hybrid mechanical and electronic parts allows Ford to proactively fight torque steer and wheelspin, moving the power as required before you starting spinning wheels.

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Information such as steering angle, throttle input, speed, and drive modes are all part of the systems calculations of how much the diff should be locked at any given moment.

In practice, it works wonderfully. Yes, you do get the odd tug of the wheel, but it’s few and far between, and the power-down ability of the 2.3-litre four-pot is mightily impressive mid-corner. The eLSD just gripping up and pulling the nose out of the turn.

Instead of having to pull power, the eLSD afford the ST the ability to use more of its generous outputs, more of the time, staying ahead of the curve of torque steer and wheelspin.

If you have your doubts about how much fun it can be to chuck a front-drive hatch around, we heartily recommend getting behind the wheel of a Focus ST and ridding yourself off all those tired old cliches.