You might remember Steve Prior’s Prodrive edition WRX STi from a previous feature all the way back in April 2021.   Those with fantastic memories will recall that we carried out a complete nut and bolt re-shell for Steve.  However, the missing part of the jigsaw was a set of Active Valve Control System (AVCS) cylinder heads for Steve’s engine.  This left Steve with the dilemma of having a set installed on his 2.1L EJ20 stroker engine, or starting from scratch to build the holy grail of Subaru engines – an EJ22 block stroked to 2.35L.

Naturally, Steve opted for the EJ22 stroked to 2.35L – an excellent choice (you can read all about the EJ22 and what makes it so special on our website).  Steve tells us that by opting for the EJ22 he has future-proofed himself should he wish to add more power later down the line.

Starting with a bare EJ22 block, our engineers began by machining it to take a 2.5L crank and larger 14mm head studs.  Once complete, they were able to re-bore the block to suit some new RCM Omega forged pistons.  The block faces were re-surfaced and the bottom end assembled in preparation for RCM Stopper head gaskets and the previously-mentioned AVCS cylinder heads.  Leaving no stone unturned with this build, Steve opted to have the heads fully CNC ported and gas flowed. To make the most of the head work, we specified a set of Kelford camshafts to drop in for good measure.

Steve chose to have everything he could in the engine bay painted black, which looks incredible and should make light work of keeping it clean and show worthy.

With car shows in mind, we relocated the battery and screen wash bottle to the spare wheel well so that Steve can still use the boot when family days out require a lot of horsepower.  Doing this meant we were able to rotate the inlet manifold and fabricate some intercooler pipes which aid in flow as well as aesthetics.

Providing the boost, Steve opted for the brand new RCM600 Precision hybrid billet turbo which sits in the stock location. After running this car in and mapping it, we’re all really pleased with the results of this set up.  Just as we expect from a Precision turbo.  To feed the engine with the fuel it needs, we installed a larger fuel pump and some 1600cc injectors ready for when the meth calls!

The results? 555BHP and 438LBFT using 99RON pump fuel and 601BHP and 490LBFT thanks to the addition of some methanol.

When asking Steve what he has in store in the future for his Impreza, he enthusiastically tells us he has just purchased a WRC rear wing, a set of WRC headlights and is hoping to have a big brake kit soon.  The brakes are a must given that his car now sits very high in the Enginetuner power clubs rankings!

New for 2023, Steve has also signed up to the Enginetuner Drivers Club (ETDC) and is very much looking forward to joining us at our events and European road trips and to taking advantage of all the other benefits of membership. We are hosting our next track day on Saturday 18th February at Llandow circuit and we have an epic trip to the Nurburgring planned for July.   

If you are looking to breathe life into your Impreza or other performance car, please don’t hesitate to get in touch for a chat.   Should you wish to know more about the ETDC you can find lots of information and apply via our website.

Catch there dyno video here!

Sign up to the drivers club here!

Enginetuner.  Performance engineering at its finest.