2025 Q3 Review - Hillclimb Car

Following the hillclimb car's surprise class win at the Abingdon Carnival Sprint, the results benchmark was set for the rest of the season! The main task before the next sprint (held by Bristol Motor Club at Castle Combe) was to send away the Xona Rotor 6564s for a refresh, and reinstall the turbo ready for the sprint. As ever, AET Turbos were quick to get the turbo refreshed, and with the turbo reinstalled, the was car checked over and we were ready to race. The open capacity class looked to be very competitive, with over 10 cars competing (including two high performance electric cars), and some quick drivers, it was time to see how the Impreza would get on. After walking the track to remind ourselves of where the apexes were (!), the morning's practice runs were started.

For this event the Impreza was double driven and seemed to be going well during the morning sessions, although the intake air temperatures and the brakes were suffering slightly due to the hot weather. With the first timed run completed before lunch, hopes were high to go even faster in the afternoon.

During the lunch break, the front brakes were bled with AP 600 brake fluid to make sure that there was no air in the system, and the Link G4X's datalogs were inspected to make sure that the engine was being fuelled correctly and that no knock was present. With some minor adjustments made to the launch control RPM, it was time to head out for the afternoon's runs.

With the temperature still climbing in the afternoon, the car was having a tough time of it with the intake air temperatures still staying at around 50 degrees Celsius even when using the front mount intercooler's water spray system, and the brake pedal getting slightly less effective when braking after the track's "Hammerdown" straight. With a few counts of knock shown in the datalog, the map's ignition timing values were double checked, and with this seeming sensible, these knock counts were attributed to the high intake temperatures. The intercooler water spray was used for a longer period for a flat out final run for the day to try and counteract the heat, but to no avail, as the intake air temperatures were still too high.

Despite these issues, team Pleiades were 4th and 8th at the event, with the car otherwise performing well against some tough competition! Some suspension setup changes were noted before we return to Castle Combe again. Following the event, a more detailed inspection of the front brake pads revealed that the Carbon Lorraine R5 pads had glazed over, potentially due to the brake disc's high temperature. It was then time to call by Godspeed Brakes in Bridgend, who provided some invaluable guidance on how to improve the front brakes. A set of Brembo four pot calipers and larger front discs were purchased and installed on the car, with a change in front brake pads to a set of Carbon Lorraine R6 pads.

Next on the agenda is to call by the brilliant ProFab exhausts in Swansea to modify the exhaust so that the turbo's position is changed to a less vertical position, as this will help to lubricate the bearings in the turbo. A pre-turbo water spray system is also considered as a means by which to reduce the high intake air temperatures. Hopefully we'll be able to return to Castle Combe in October to see if the changes have helped things. We will provide another update at the end of the year regarding the hillclimb car's continued development!