2023 Overview - Hillclimb car

2023 was a year of development and testing for the hillclimb car, with the integration of the 6564S Xona Rotor turbo from AET Turbos with the car's existing engine. Specifically, the engine was a second hand closed deck EJ25 which had been refreshed with new forged internals by CP Autos in Bristol. The decision was made to mount the turbo in a near vertical position, as was done by Prodrive in their record breaking Isle of Man challenge car driven by Mark Higgins. Positioning the turbo in this manner was advantageous when compared to a rotated kit as the exhaust gasses had a straighter flow path from the turbine exit. This choice necessitated a custom made up pipe and both water and oil lines for the turbo. Handily, ProFab exhausts were very accomodating and were able to fabricate an upipe, an external wastegate pipe and a 3.5" turbo back exhaust for the Impreza, which met the noise requirements for Motorsport UK Hillclimbs and sprints. The turbo's oil feed line was provided by Racinglines, who advised that it was advisable to have a heat protection coating on the feed line, a wise precaution! Water lines were sourced from Auto Silicone hoses. With the engine, turbo, and associated ancillaries installed in the car, it was time to begin mapping! During the first pull, it was quickly discovered that the spring installed in the Turbosmart Progate 50 was too strong, as the car was making 1.8 bar of boost with no wastegate duty cycle applied! With the lightest spring installed, the car made a much more manageable 1 bar of boost, with the turbo coming online at approximately 4k rpm which was a very usable power band. It was then time to put the car on the dyno and see what it produced!

The power figures were 400whp when using a pump fuel and VP's octane booster, then the boost was turned up to 1.3 bar on VP RX102 race fuel, where the car made 470whp! The Link G4X's oil protection limiter gave piece of mind when mapping if the oil pressure was not up to scratch. However, on the drive home from the dyno, something felt amiss, with the car seeming to be a bit flat. The cause was to become apparent in 2024, but for now, the car was complete and fully mapped.