It may be small, but this snarling, stripped-out Fiesta ST Mk6 track car loves a tear-up on the street or circuit.

Feature from Fast Ford. Words: Ben Birch. Photos: Ade Brannan.

In the modern age of big-power turbos, huge Brembos from the factory and more electronic aids than Apollo 13, some might lead you to believe a naturally-aspirated Fiesta ST150 is dead meat.

But if you’ve ever watched the Fiesta Championship or Fiesta Challenge race cars, you’ll know that when they’re built and driven correctly, these little buzz boxes are seriously rapid – and what you see here is as close as you will get to a Fiesta Challenge car on the road.

AJ Stewart was massively inspired by the racers when turning his once-docile Fiesta into the hardcore animal it is today, and you can see the influence flowing throughout the build.

Fiesta ST Mk6 track car

He bought the car in 2010, having previously owned various Mk4 and Mk5s – which were modified with 1.7 Puma engine swaps and tons of go-faster parts – but this Fiesta has remained in his ownership longer than any other. But why?

AJ explains, “The Mk6 was a natural progression for me, and I think the ultimate naturally-aspirated Fiesta. The others were good but the engines were a bit small, whereas the ST came with the 2.0-litre Duratec, along with a really good chassis. They’re a great package as standard, but just need waking up a bit.”

As is usually the case, his first mods were a performance exhaust and air filter, but things escalated quickly when he met and became friends with the guys at Jamsport.

“Because of their involvement with the racing Fiestas and track days, my interest in taking my car on track exploded, and the whole focus of the build became more hardcore. We went deep,” he laughs.

Uprated cams, a Cosworth inlet and various suspension kits came and went as AJ dipped his toe into learning the UK circuits and honing his driving skills, gradually working towards the ultimate specification he had in mind for the ST.

“The ethos was to build a clean, simple car in the Clubsport style, and retain its naturally-aspirated character.”

The barking, rev-loving, naturally aspirated engine sets the tone for the whole car – no frills, no complications, just good old, analogue fun. The centrepiece of the powerplant is a massive air filter covering a set of Jenvey throttle bodies, which not only sound delicious but endow the Fiesta with a huge increase in aggression, throttle response and, of course, horsepower.

Fiesta ST Mk6 track car

AJ says, “The throttle bodies were a huge game-changer; the car made 207bhp with them on the standard ECU, but the next game-changer was fitting an ECU Master engine management system.”

Between Jamsport and RRR Engineering, the ECU was fitted and mapped with functional launch control and flat-shift and gave an extra 10bhp alongside much better driveability. Luckily for AJ, he was able to finance it all by selling his old Cosworth inlet and single throttle body, along with various wheels he had accumulated over the years.

He remembers, “I bought the Cosworth inlet at £400 and sold it for more than three times that. The prices they’re fetching is madness really, but I’m not complaining.”

Talking of madness, the wheels he sold were his 33rd different set on the car.

“I’m now on my 34th,” he laughs. “I always have two sets of wheels and tyres – one for the road and one for the track. I end up getting bored and selling whichever set is sat in the shed at the time.”

Thankfully, the Team Dynamics are staying put, as they suit the junior BTCC car vibe perfectly, as well as being ultra-lightweight.

“You can feel a dramatic difference between these 15in wheels and bigger ones; the steering is more responsive, and the car handles much better,” enthuses AJ.

Fiesta race cars run 15s too, so these improved dynamics with a smaller wheel makes sense; a bonus being that track day tyres are more readily available and cheaper than those in larger diameters.

The only issue with small wheels can be brake clearance, and with AJ adamant about having four-pot callipers, he had to search a fair bit before he found a solution. Wilwood has a knack of developing brake kits for tight spaces, in this case the slimline Midilite callipers offering the right profile to fit behind the spokes, and along with 300mm discs giving a massive improvement in bite and resistance against brake fade on track.

Fiesta ST Mk6 track car

When it came to suspension, AJ had tried out quite a few cheap brands over the years, many of which developed issues. So, with the rest of the car now being raised to a higher level, he bit the bullet and decided the suspension needed to be raised too – his days of scrimping on what is surely one of the most important areas were over.

AJ explains, “I’ve got a few mates into fast Renaults – Meganes, Clios, that sort of thing – and in that scene BC Racing and Meister R are very well regarded.” In the end he plumped for Meister Rs, and more specifically the Zeta CRD kit, which is aimed at offering a compromise between road use and occasional track-day use.

With a Jamsport fast-road geometry setup, the Fiesta ST Mk6 track car really does hang on through the corners without being too edgy, erring on the sensible side of camber and toe. It’s a perfect balance for those of us who don’t profess to be Senna incarnate and means elaborate and expensive adjustable suspension components aren’t required to have fun and go fast in safety.

Fiesta ST Mk6 track car

This keep-it-simple approach has been applied to every modification on AJ’s ST, which is why the overall result is such an absolute success. No silly body kits adorn the exterior, and no garish items ruin the interior. The only changes to the outside are purely functional, such as the drilled front bumper to funnel air into the throttle bodies, fog-light air ducts to cool the brakes, bonnet pins to prevent a disaster on the main straight and an open front grille to accommodate an oil cooler.

AJ adds, “Oil temperatures were a bit high on track and oil changes were getting dirtier. I had taken the grille out to de-badge it, and after fitting the oil cooler had some trouble refitting the grille – so I left it off, and quite like it, to be honest.”

On the inside is the classic Clubsport style, a blend of race car and road car, which always works. “Roll cages and buckets go so well with a carpeted front cockpit and interior trim. The car weighs just 1080kg with me in it, but I can still drive it to the Nürburgring in relative comfort,” says AJ.

The Fiesta ST Mk6 track car does okay at the Green Hell, but AJ admits the famous track is slightly too big for a little Fiesta.

He says, “Cadwell Park is my favourite circuit. It’s the perfect place for the Fiesta as it’s quite twisty, which levels the playing field a bit against cars with more power.”

In fact, this naturally-aspirated, almost-15-year-old Ford scalps Renaultsport Meganes and 350bhp Focuses – no mean feat and goes to show how Fiestas can be turned into an amazing all-round package.

“I love it. I’ve had people on track days come up to me afterwards, and they are convinced it must be supercharged or turbocharged, and they’re shocked when I tell them it isn’t,” laughs AJ.

Fiesta ST Mk6 track car

Thankfully, he has no plans to do so either, nor is he going to trade into an ST180. “They’re mega cars, but I love naturally-aspirated,” he says with a shrug, “I think for a track car N/A is better, and now I’ve got power with reliability, I won’t do anything else other than enjoy it”.

That definitely has the Fast Ford seal of approval – we love the modern turbo stuff with all the fancy bells and whistles, but now and again it’s heart-warming to see a proper analogue, no-nonsense older Ford still doing the business and embarrassing unsuspecting big-power machines.

Tech Spec: Fiesta ST Mk6 Track Car


1999cc Duratec, Milltek 4-1 exhaust manifold, Milltek de-cat, Longlife custom exhaust system with 3in down turned tailpipe, Cosworth 220-spec cams, Newman valve springs and retainers, K1 forged rods, Supertec pistons, ARP bolts throughout, Torques custom PCV breather system, APS oil cooler with braided lines, Cosworth high-pressure oil pump, Cosworth thermostat, JS Performance coolant hoses, Jenvey drive-by-wire throttle bodies, ECU Master EMU Black engine management system with Bluetooth adaptor, DC Innovations custom ECU holder, painted rocker cover and coolant cover, 395cc injectors, baffled sump plate


217bhp and 164lb.ft


Rebuilt Durashift five-speed gearbox, Quaife ATB LSD, Helix organic clutch, TTV lightweight flywheel, ARP flywheel bolts, Vibra-Technics torque mount


Meister R Zeta CRD coilovers, Vibra-Technics mount kit, Powerflex bushes throughout, front and rear strut braces


Front: Wilwood Midilite four-piston callipers, Hi-Spec calliper brackets, RTS Performance 300mm C-hook discs, EBC Yellowstuff pads, Torques custom braided lines; rear: standard callipers, RTS Performance C-hook discs, EBC Yellowstuff pads, HEL braided lines, Dot 5.1 fluid

Wheels & Tyres:

Front: 7x15in ET38 Team Dynamics Pro Race 1.2; rear: 7x15in ET35 Team Dynamics Pro Race 1.2, 195/50R15 Michelin Pilot Sport 3/Nankang NS2R tyres


Aerocatches bonnet pins, carbon mirrors, Triple R splitter, drilled front bumper, cold air feed fog-light ducts


Weld-in SHP Engineering rear roll cage, Corbeau Clubsport XL seats, OMP subframes and mounts, Turn One four-point harnesses, SiCo battery relocation, Quaife nylon gearknob, safety net, Stack oil pressure gauge in Airtec surround, Turn One steering wheel with Momo boss, Track Car Door Cards rear panels, Samsung tablet for ECU readout