2025 Q3 Review - Impreza STI Hatchback

Things progressed steadily for the hatchback for the next quarter of 2025, with the 2.1 litre engine build underway and with the car receiving some much needed TLC whilst the Welsh summer allowed! First on the agenda was the rear subframe, which had seen better days.

At first, the intent was to dismantle, clean, and repaint the subframe, such that it would be as good as new. After inspecting the subframe more closely, however, it was deemed that the best course of action for the long term was to purchase a new rear subframe with the associated arms and new bolts from our friends at DL Motorsport.

The fuel filler pipe was also replaced with a new pipe, and the hatchback's underside was cleaned and painted with a layer of paint to protect against corrosion. Next, a trip was made to ProFab exhausts in Swansea for a custom up pipe, and a turbo back exhaust with twin tailpipes. This exhaust up pipe was a tricky job due to the decision to mount the Xona Rotor turbo in a location as close to the standard turbo position as possible (as opposed to a rotated position), with considerations required regarding the positioning of the turbo intake, exhaust, up pipe, and wastegate.

ProFab exhausts however, did a superb job in accommodating all these requirements, and the new exhaust looks great, and we can't wait to see what it sounds like - hopefully it is a bit quieter than the Invidia exhaust that was previously tried on the car!

In addition, the rear differential was sent away to Geartech LTD for a check over and a new set of seals, and the rear wheel bearings were replaced with new bearings and new heat shields. Whilst it was off the road, the hatchback was also treated to an interior clean and a new cabin filter, which seemed to have been changed a long while ago judging by the amount of leaves that had gathered on top of the filter.

Assembling the 2.1 was going as planned, with the rare ARP L19 11mm stud kit ensuring that the cylinder heads would stay in position when the boost gets turned up!

The only slight delay occurred when it came round to setting the valve clearances. With the Supertech valves and the new seats, the clearances between the valves and the cams turned out to be very small, and since it was very difficult to find the smaller solid shim sizes, it was eventually opted to send the Supertech valves to Roland Alsop Machining to grind back a small amount (approximately 0.3mm) from the top of the valve stems, such that a more common shim size could be used.

This is advantageous for the engine's future owner, as the cylinder heads would not require removing when the valve clearances close up over time, as a more common shim sizes could be used to obtain the correct valve to cam clearance. At the time of writing, we are awaiting the return of the valves, such that the 2.1 litre engine can be completed, and to install the engine in the car to run it in! As ever, please stay tuned for another update on the hatchback later on this year.