This weekend’s British Touring Car Championship season-opener at Donington Park heralds the first race for a more potent hybrid boost system that delivers twice the power compared to last year.
BTCC series organiser TOCA introduced the spec 48V hybrid-electric system in 2022. The Cosworth spec unit replaced success ballast, which saw the most successful drivers get handed additional weight to slow them down in races and balance out the field. A similar sliding scale approach has been used after the switch to hybrids, whereby more successful drivers are given fewer laps on which they can deploy power from the motor generator unit (MGU).
BTCC teams and viewers soon got accustomed to the new technology, which was a world-first in touring cars. However, they soon recognised that it tended to produce long trains of cars without much overtaking. In response, the BTCC has increased turbo boost pressure by 200mb and factored that into the hybrid system boost. This is designed to increase the difference (or delta) between a car that is using hybrid boost and one that isn’t. The change, which does not add to the MGU’s output, equates to a doubling of the power that a driver has when they push the boost button, from 30bhp to 60bhp.
The BTCC has been continually reviewing its hybrid deployment rules since the technology was introduced. Last year, it added a minimum speed at which drivers could use the boost, with those who were higher in the championship standings (applicable to Race 1) or coming off the back of a strong preceding race (Races 2 and 3) both getting a higher threshold. Lower-ranked drivers received a lower threshold, meaning they could attack sooner out of corners.
But now, drivers will have double the amount of boost available. How will it affect the racing? Alliance Racing Ford engineer Tony Carrozza, who won the 2023 BTCC title working with driver Ashley Sutton, reckons it will have a noticeable impact.
‘Part of the rules that changed for last year was, cars outside the top 10 didn’t have it for every lap,’ he tells Racecar Engineering. ‘The previous year, there was this hybrid train where all of the cars were pushing hybrid at the same point. It didn’t make a delta to the racing.
‘The biggest difference this year is the overlap that you can get between someone not deploying versus someone deploying. Down the start-finish straight at Donington, there is a 16-metre delta. Cars are typically 4.4 to 5 metres long. That’s four car lengths. If you come off the chicane on the bumper of the car in front, you’ve got enough deployment to get alongside, pull in front and have a car length in the braking zone, which is significant.
‘The sheer overlap is the powerful bit. We also ran [simulations] for Silverstone which is the most powerful circuit for the hybrid. It was 28 metres down the back straight where you’re pushing [the hybrid boost button] for 8-9 seconds. The 28-metre overlap is enough to do two or three cars.’
Alliance sampled the increased turbo boost during a Goodyear tyre test at Donington last year, making it one of the first teams to try out the update. By contrast, the West Surrey Racing BMW squad, for example, only used the 2024 levels of boost for the first time at the second of three pre-season tests in April.
‘We know that 200mb is about 30bhp,’ says Carrozza. ‘I ran a load of lap time simulations to work out the optimal deployment zones. It’s very easy to dump it all down one straight, but over the course of the lap you’ve got to trigger it slowly. Last year, at Donington, we were 0.45s [quicker] per lap. This year, it’s just over 0.7s per lap. It’s quite a substantial delta. Brands Hatch Indy was only 0.55s [quicker].’
Given that he won last year’s BTCC title, Sutton often received the short end of the stick when it came to hybrid deployment allocations. Adding to the challenge was the introduction of minimum hybrid deployment speeds, and fewer laps available to deploy. For example, points leader Sutton had five laps on which he could boost in Race 1 at Silverstone last year, compared with nine boost laps for points leader Colin Turkington at the same round in 2022. Nonetheless, Alliance thought of a way to offset that difference.
‘Ash wouldn’t push hybrid on the lap when the person in front was pushing hybrid,’ Carrozza explains. ‘He would just wait until I’d given him the go-ahead that whoever he was fighting against wasn’t pushing. There was his chance to get the overlap.
‘You almost waste the hybrid if you’re using it when the person in front is using it, because you just negate the delta. If you’re in a faster car, you can make up some of that lap time in another way. You don’t need to be pushing the hybrid button.’
The number of hybrid boost laps that each driver gets is unchanged for this year, but the power will be higher. Therefore, expect to see more drivers making overtakes when they are boosting against a driver who isn’t. The scenario shouldn’t be any different to last year when two drivers are on the boost, although Carrozza and other engineers are constantly on the radio informing their drivers about when rivals are pushing the button to get that all-important delta down a straight.
The uprated boost is not only set to have an impact on acceleration out of corners: Carrozza anticipates that it will increase braking distances by between five and 10 metres.
‘The person who is on the hybrid is braking slightly earlier,’ he says. ‘I think there will be some interesting racing. There will probably be some massive closing speeds.’
The BTCC’s move to hybrids in 2022 resulted in a fixed minimum weight being introduced in 2022. This is 1355kg for rear-wheel-drive cars and 1325kg for front-wheel-drive. Having got used to adapting to success ballast for several years, BTCC engineers can now get a clearer picture of car set up.
‘Every session the car balance was changing, because almost every time you went out, you had to change the ballast,’ Carrozza recalls. ‘We would go into a meeting leading the championship, so we would have 75kg in qualifying for Race 1. We’d almost never win Race 1 because we’d qualify sixth or seventh. Then you take ballast out for Race 2 and you’d win a lot. Then you’d have ballast on for Race 3 with reverse grid, so you’re in the middle of the pack with all the ballast on.
‘Typically, you were changing the car constantly over the weekend. Now, we have a fixed base weight. You can really home in on a set up that is really crisp for that weekend and know that the only changes are going to be track conditions, which is quite nice.’
This weekend’s Donington season-opener will be the first time the increased hybrid boost is deployed in anger, although it may take a few rounds for its effectiveness to become clear. For instance, will a car that has fewer 60bhp hybrid system power deployments be as hamstrung as a car that carried the maximum 75kg extra weight during the success ballast era? They will, at least, be more pegged back compared to last year. The early signs are that the increased boost should provide more overtakes and less predictable racing which has been a hallmark of the BTCC for so long.
‘The year that stands out for me is 2018, when you had 17 different winners,’ says Carrozza. ‘Colin [Turkington] won the championship and won only one race. That’s what you’re going to get this year, I think.’
