How to build a (better) BTCC race car

Good old ‘balance of performance’… It’s a mixed blessing in 21st century motorsport. On the one hand, it giveth many more cars an opportunity to win than otherwise could; on the other, it taketh away advantages gained through technical – and even driving – excellence. 

In the British Touring Car Championship, the regulations are written to ensure as much parity as possible between different models of what are recognisably touring cars. Problem is, the pool of such machinery is ever-diminishing owing to the auto industry’s move to SUVs and electric.

The net needed to be cast wider, and that is why, as you read this, Ash Sutton leads the standings with a Ford Focus Titanium saloon model that cannot be bought for the road in the UK, and which has replaced the fourth-generation ST hatchback of yore.

The primary reason for the move to the saloon for the Alliance Racing team was aerodynamics: that hatchback shape was severely wanting in a straight line. “Ultimately, the reason for picking the saloon is that it [aero] is not part of the balance of performance, so you want to pick the slipperiest car you can,” points out Antonio Carrozza, technical chief of the NAPA-liveried squad and Sutton’s long-time engineer.

“You can add downforce to that car with no real issues, and you can’t shed the drag if you’ve picked the wrong shape of car.”

Most of the grumbling about Excelr8 Motorsport’s Hyundai i30 N Fastback wielded by reigning champion Tom Ingram is centred upon its straightline speed. The hatch struggled to compete with a model whose shape allowed it to keep on accelerating as others maxed out. 

Sutton took two wins at the Donington Park opener and leads the points

Photo by: JEP

“Because BTCC is balance of performance on engines, very well controlled on weight, you’re all running the same subframe, suspension etc, there’s not much to differentiate the cars,” explains Carrozza.

“Once you’ve pulled the outer skin off, underneath they’re all very similar. Even wheelbases – the Hyundai’s the shortest of the front-wheel-drive cars, with the Ford we’re the longest wheelbase of the FWD cars, but there’s only 70mm between them. The road cars that you can pick that meet the criteria – minimum 4.4 metres, has to be four-door – you’re quite limited.

“So the aerodynamics becomes quite key. The amount of parasitic drag – that’s the wording I use, it’s the stuff that you can’t change from shape of the base car that you pick – you can’t change that. You can add quite significant amounts of downforce through lots of features, especially around the front bumper and design of cooling packs and radiators, but you can’t shed that parasitic drag, and a lot of that’s caused by putting a rear wing on a road car – it makes it significantly more draggy. It’s massively highlighted on either an estate or a hatchback.”

“Within a week of we had an answer from the other teams – it was almost unanimous, only one was a no. I won’t say who that was but you can probably guess…” Antonio Carrozza

Carrozza says Alliance was one of the teams that petitioned for the change, introduced for the 2027 BTCC season, allowing in models on sale worldwide – as long as that manufacturer has a non-electric presence in the UK market. With Team BMR, his and Sutton’s old team, he’d worked on a Jaguar X-type project. With Alliance, there were Mercedes and Audi investigations in late 2022, and a bid to go MG for this season. When that went quiet, the team asked for dispensation to bring a 2027 car to the series one year early.

“At the Knockhill weekend [mid-August] I put the proposal to Alan Gow and Sam Riches [boss and technical supremo respectively of BTCC organiser TOCA]: can we bring the regulations forward, because everything had gone quiet on the MG front?” recounts Carrozza. “Within a week of Knockhill we had an answer from the other teams – it was almost unanimous, only one was a no. I won’t say who that was but you can probably guess… 

“By the time we got to Donington [late-August] we’d basically got the green light from TOCA – now we needed to get the finance in place. We were costing the project between Donington and Silverstone [September], still trying to get the support that we could at the top level of Ford Motorsport.

The old Focus had an aero disadvantage against chief rival Hyundai

Photo by: JEP

“As we came back from Brands after the last race of the season [early-October] that first car got pushed into the fab bay and we started chopping parts up. The new parts arrived a week after Brands, and we started from then.”

The result was what Carrozza describes as a ‘cut-and-shut’, grafting the Titanium saloon rear end onto the existing hatchback shells. But this is no dodgy back-street-garage operation. Parts were ordered through the Ford dealer network, with the cars produced in Germany but on sale in Turkey. 

“There was a lot of crossover between the hatchback and the saloon in terms of the inner structures,” says Carrozza. “We’ve got completely custom boot floors and rear crash structure areas. So all of that element on the underside is really straightforward – we’re only talking the inner quarter panels, the roof skin, all of the roof cross members [being different]. I don’t know if it’s widely known, but the doors are the same. But it’s working out how and where we were going to cut the parts, because at that point we didn’t have any CAD.

“The first one, we took our time with it. We made sure it was very methodically done, and then we started making jigs, so that all of the next ones replicated it.”

Two weeks before the first car hit the track at Donington Park in the hands of BTCC newcomer Lewis Selby, Alliance took its ‘new’ baby to Catesby tunnel. It’s not a static facility in the conventional sense; it’s a 1.7-mile former Victorian railway tunnel, through which Sutton and Dan Cammish drove!

“It’s good fun for the first 10 minutes – you get a real sense of speed,” laughs Cammish. “But then it gets quite monotonous when you have to do about 100 runs a day. It’s a cool venue. Me and Ash shared duties – you’ve got to be careful because obviously cars put out a fair amount of CO2 and the tunnel’s not that well ventilated, and we’ve got breathing apparatus that pumps oxygen into your helmet. But we get a lot of good data so it’s well worth it.”

Carrozza believes the saloon shape provides much better aero

Photo by: JEP

These tests, says Carrozza, “completely validated the project for us. We’d done a full CFD programme on the race car as well as the CFD programme that TOCA had run on the road car, so there’s multiple aerodynamic elements that we’d been looking at and working through.”

After Catesby, all four drivers – Sutton, Cammish, Sam Osborne and Selby – had their cars on track at Snetterton before the BTCC’s official pre-season run-outs at Croft and Brands Hatch. What was the feeling before rocking up at Donington for round one?

“The drag numbers we’re talking about [on the hatchback] are an aerodynamic power deficiency of about 20-25bhp compared to where the Hyundai was at 200km/h [120mph],” reports Carrozza.

“TOCA do a very, very good job on the BOP of engines. Therefore if you’ve got a car that’s aerodynamically inefficient, you’re fighting that from the get-go” Antonio Carrozza

“That’s just the aero power requirements. TOCA do a very, very good job on the BOP of engines. Therefore if you’ve got a car that’s aerodynamically inefficient, you’re fighting that from the get-go. As soon as you start to hit 160km/h, the numbers become quite big and then that exponential gain of drag just kills the straightline speed. 

“However, what I would say is that wasn’t the thing that the drivers said is brilliant – it was the mid-corner stability, the high-speed aerodynamics, the wing being more in the free stream than it was on the hatchback. If you look at a lot of the hatchbacks, the rear wing’s actually tucked underneath the rear spoiler.

“The rear spoiler on the road cars – that’s intended to work on its own, not with another aerodynamic feature behind it. So you end up with wings that stall at high speed, at high yaw angles, at certain angles of attack. It becomes a bit of an unpredictable beast.

Drivers have already reported that the new Titanium feels more stable

Photo by: JEP

“And that was actually always one of my bugbears with the hatchback – we didn’t have a tuneable aerodynamic package, because we had to run the rear wing at absolute maximum everywhere, because if you didn’t it was just horrendous.”

Hence the lack of pace on the straightline-heavy Silverstone National Circuit… And the saloon’s aero should also help at tracks such as Thruxton. “It’s all about momentum at Thruxton,” reasons Carrozza. “If you can come off the corner 10km/h quicker, because you’ve got confidence in the car, a good front end, there’s some rear stability, you can attack the high-speed stuff and there’s a lot more to be gained there.”

“We’ve got the pace in the car,” acclaims Sutton, unsurprisingly. “It’s definitely an improvement – it can only be an improvement in theory. In terms of the balance, what we’re experiencing, it doesn’t feel too dissimilar from the car last year. We’re just chasing the straightline performance. I believe we’re ticking that box, which is good.”

Cammish adds: “It’s not like it’s a massive shift but it’s definitely got some more rear grip, and it’s more stable. The fundamentals of the car and how it works are the same. I’ve got no doubt that it will only get stronger.”

Sutton’s qualifying time at Donington – just 0.008 seconds off Ingram’s – along with the two wins and comparable race pace to the Hyundai suggest that Alliance has made a big jump on its basic platform of performance, just as did Carrozza’s rework of the hatchback over the 2022-23 winter that led to his driver’s fourth title.

But that model had pretty much been maximised. And, as Carrozza warns: “The key is, the same as we did in the 2022-23, we haven’t just attacked that one area either. There’s lots of little bits that we’ve done to the car, and all of them have been in the right direction.”

On the basis of Donington, they seem to have worked.

This article is one of many in the monthly Autosport magazine. For more premium content, take a look at the June 2026 issue and subscribe today. 

Catesby tunnel work was monotonous but has provided some useful data

Photo by: NAPA Racing