After the problems encountered during the Time Attack event at Imola earlier in the year I left the car off at a specialist called Preparazioni Soretti. They specialise almost solely on Imprezas and are known in Italy for their skill and expertise on Subarus, but they sometimes work on all sorts of other cars too. I left the car with them because they have some experience with SR20 engines but more importantly because they are familiar with the Apexi PowerFC ECU, which isn’t common in Italy, and they are the ones who mapped my car after the rebuild. The car has been there for a few months as I wasn’t in any rush to get it fixed and didn’t want to spend all summer working on it; I needed to enjoy my summer!
The problems that I had during the super-lap at Imola were that the car would stutter and miss on boost and I’m not sure I would have known where to start. The first thing they did was check the compression, and in the process they found out that the candles were burned and one even lost a tip after arcing. The compression test also showed that 2 cylinders were low so they pulled head to investigate. The low compression was caused by burned valves, which was a result of having incorrectly shimmed valves. An issue I struggled with during the build. They decided to rectify the whole head and rebuild it all with new components. New intake and exhaust valves, valve springs, matched titanium retainers and seats. They also reshimmed the valves with a bespoke tool they built, which I’m sure most people who have worked on an SR are aware of. New shims and rocker guides were installed and then everything was put back together.
The engine now purrs and produces more power at less boost. The previous setup yielded 343hp and 428Nm at 1.3bar and now it produces 355hp and 422Nm at 1.2bar, and they told me the tune should be good up to 1.4bar.
The plan now is get all the small things sorted so I can test the car on track before the year ends, so I can finally understand the potential of the car after the rebuild. The splitter needs to be secured properly so it doesn’t chatter at speed and there are a few wiring issues to be cleaned up and resolved. The car has also been running a fixed manual boost controller for the time being so I need to spend some time setting up the GIZZMO electronic boost controller.