Overview
The 903 was transformed over the winter. The Paxton supercharger gave way to a Rotrex C38-81, a modern and far more efficient unit that for the first time made an intercooler worthwhile, and a bespoke intercooler with a 4-inch-deep core was built by Alpha Performance Fabrication to go with it. Dave Rowe at EPS mapped the new package on 18th April 2025 on a deliberately conservative 75mm supercharger pulley, producing 0.87 bar of boost and 376bhp in race trim, up from the 306bhp of the Paxton.
The engine's ignition was then brought up to the same standard ahead of Snetterton in June: a Bosch 3x2 coil pack, Bosch Motorsport three-channel amplifiers and Clewett 8mm leads, triggered by an Adapt Motorsport sensor module in place of the distributor. The results followed. The 903 won the Invitation Class in every race it started in 2025, qualified in the top half of the field for the first time, and set new personal bests at Snetterton and on its first visit to the Anglesey Coastal circuit.
After the season the development continued with a WEVO GateShift for the 915 gearbox in September, an FVD 3kg lightweight flywheel and a move to the 70mm supercharger pulley in October, laying the groundwork for the full 0.95 bar and 425bhp of the 2026 car.
Round 1: Donington Park National Circuit, 21st April 2025
Three days after the dyno session, the 903 lined up on Easter Monday at Donington Park among a record grid of 38 cars for qualifying and a 40-minute pit stop race, both run in drizzle on a wet track. The series report singled out the car as "one of the more impressive performances", qualifying "comfortably in the top half of the field for the first time", in 19th with a 1min33.084secs, against the 1min35.526secs managed in similar conditions a year earlier. The 903 finished 21st overall and won the Invitation Class.
Round 2: Brands Hatch Grand Prix Circuit, 17th & 18th May 2025
The 903 did not take part.
Round 3: Snetterton 300 Circuit, 14th & 15th June 2025
With the ignition upgrade completed just in time, Snetterton was the breakthrough weekend of 2025. Across qualifying, two 15-minute sprint races and a 40-minute pit stop race in mixed conditions, the lap time fell at every session: 2mins22.960secs in qualifying, 18th of 32, then 2mins20.898secs, 2mins18.894secs and finally 2mins16.711secs in the 40-minute race. That was almost nineteen seconds a lap quicker than the 2mins35.67secs of the 903's first Snetterton race in August 2023. The car was clocked at 219.4km/h on the Bentley Straight and won the Invitation Class in all three races.
Round 4: Anglesey Coastal Circuit, 5th & 6th July 2025
Anglesey brought the 903's first visit to the short Coastal layout, having prepared on the simulator for the International circuit, and a grid of just 19 cars with the date clashing with the British Grand Prix. Scrutineering found the rear spoiler 30mm too high, and Phil Brough made the fix just in time for the first race. Qualifying last with a 1min26.870secs, the car then improved race by race: 1min23.481secs, 1min22.311secs and 1min21.012secs, almost six seconds quicker than qualifying, finishing 17th, 17th and 13th and winning the Invitation Class in all three. The series report noted that the 903 "was almost 4 seconds per lap quicker than qualifying" in the first race, finally "despatching Hugh Peart's nimble 924 with a blast of power down the back straight".
Round 5: Silverstone International Circuit, 16th & 17th August 2025
The 903 did not take part.
Round 6: Circuit de Spa-Francorchamps, October 2025
The 903 did not take part.