It’s hard to think of any changes you could make to a Ford Fiesta ST that might make it better. Few performance cars are so well sorted straight out of the box, and so long as you don’t need something bigger, it’s the hot hatch of choice. The idea of a modified one, then, fills us with concern rather than excitement.
It helps that this particular tweaked ST comes from Mountune, whose Stage 1 upgrades show some sign of restraint, and indeed we dug the Essex firm’s M320 kit for the Focus ST. But that’s a car which never quite hit the mark in standard guise - the Fiesta ST, on the other hand, is practicality a deity in car form. And this isn’t a no-brainer upgrade as before - unlike this kit’s Ford-sanctioned predecessor, the ‘M235’ pack isn’t warranty-safe.
That doesn’t seem to have stopped people - the M235 was completely sold out for a little while. So have those owners made the right call, and is it worth taking the plunge? To find out, we had a go ourselves.
The upgrade doesn’t include any aesthetic treatments, but Mountune’s demo car does include some visual hints to the under-bonnet changes. These include side stripes, a wrapped roof, branded mudguards and a part-carbon fibre rear wing. To extract the extra power, you get a new airbox and panel filter (which is helpful if you want to unlock even more power further down the line if you wish), a Bluetooth ‘Smartflash’ device, and a corresponding Android/iOS app. Remaps and tuning boxes are so last year.
Set to the ‘performance’ mode as the ST was for our drive (there are also ‘stock’ and ‘anti-theft’ modes), the standard power figure of 197bhp rises to 232bhp. Arguably the more important stat is the torque figure, which goes up to 258lb ft from 214.
It’s this that explains the Fiesta’s little 1.5-litre inline-three serious mid-range clout. From the factory, the triple is already punchy, but in this tweaked state, the ST is a hilarious little rocketship. That extra shove makes it even more playful, too - the car’s propensity to lift-off oversteer seems to have been enhanced, although there are other factors at play which may have affected this. Mountune has a set of stiffer development springs fitted to the car, and yes, the weird banana shape of the ‘directionally-wound’ coils at the rear is retained.
With the factory Performance Pack fitted, which includes a mechanical limited-slip differential, the ST’s front end is more than capable of coping with the standard power and torque levels. Here, though, it’s being taxed a whole lot more. The LSD mostly stays on top of things, but you will occasionally feel a little slip on the inside wheel, and there is a noticeable - but not outrageous - increase in torque steer. I’d be reluctant to get this kit for an ST with the standard open diff.
To go with the livened-up driving experience, there’s also a more dramatic soundtrack, which is achieved without swapping out any pipes. The new airbox gives a noticeably gnarlier intake growl, while at the other end, the exhaust lets out more pops and crackles thanks to the software fiddling done by the Smartflash app. It injects a little more fun into proceedings, without ever being excessive.
That sums up the M235 Fiesta nicely. The winning Fiesta ST formula hasn’t been ruined, simply because this kit doesn’t take things too far. It enhances what’s already there, rather than trying to turn the ST into something different and cocking it up in the process. For £795 (£575 without the airbox), you can’t go far wrong, even if you also want to splash out on Mountune’s £1295 brake kit post-conversion.
The only question is whether or not you’re happy with the warranty implications. Alternatively, if you’re reading this in a few year’s time after yours has lapsed, you know what to do.