5 Ways To Make Your Subaru Impreza STi Better
2. ENGINE TUNING
The EJ20 2.0ltr unit in the STi is a great base for further tuning and has proven itself at the highest levels of motorsport over the years. In terms of building a capable daily driver, there’s no real benefit to be had from upgrading the bottom end at this sort of power level – it comes with forged internals as standard, a higher rev limit than the UK models and will be happy kicking out 400bhp if it’s mapped properly. We’d advise you to fit a higher-flowing RCM oil pump as your first priority, as this is a part that commonly leads to engine failure. To achieve 400bhp, you should be looking at upgrading to a TD05-20G, MD321H or GT2871r turbo, all of which are capable of doing the desired figures. On top of that, you’ll also be looking at bigger injectors, an upgraded fuel pump, adjustable fuel pressure regulator, front-mounted intercooler, tubular headers and a full decat exhaust system from the likes of Hayward & Scott, Scoobysport, HKS or RCM. There are various ECUs and boost controllers on the market, but we’d advise that you take it to a mapping specialist such as Zen Performance to get the car dialled in. The clutch will also need upgrading to handle the power, so check out items from Exedy or OS Giken. Elsewhere, it’s worth fitting a lightweight flywheel while you’re there!