Fatu’s Sleeper STI GRB

Sleeper WRX STI

Sleeper STI GRB

It all started with a knock.

Anyone familiar with Subaru’s will be familiar with the all-too-common big end bearing failure. Fatu and his 2008 WRX STI learnt about this failure the hard way, when the engine started making a loud knocking noise.

We Proposed a standard engine rebuild, but Fatu had other ideas – he wanted to make the most of this situation, going all out with a high performance build. The plan was to build a setup that makes reliable power and maintains response.



We started the build with a Semi-closed deck EJ207 (Click here to learn about different Subaru blocks) getting the PBMS oil gallery modification treatment. This is a process that ultimately provides improved big end bearing lubrication, safeguarding against the common failure. Additional oil flow to take advantage of this is pushed via a 12mm race-prepped oil pump

Genuine Subaru forged pistons and Eagle connecting rods have been used. For medium powered road and race cars, these pistons are a great option – they can be run with a smaller piston-to-bore clearance resulting in less noise and less oil consumption. To provide adequate clearance, the valve relief pockets were measured and machined out.


PBMS EJ207 Upgrade package

The factory STI heads got the complete PBMS treatment – including a PBMS Stage 2 port and polish, Kelford 272 Cams and Kelford high pressure valve springs. These modifications enhance the flow of the cylinder head without reducing velocity. The result is more power, without sacrificing any response.



To keep the setup simple and reliable Fatu opted to go for a bolt-on turbo. We’ve fitted a prototype (it went well, so we’re soon to put it into production) PBMS/TC GTX3071R. This is similar to factory in it’s external size, however the turbine and compressor are both large enough to support 400hp+. A front mount intercooler was also added to aid turbo cooling on our quest for reliable power.


Link ECU is a go-to for engine management in New Zealand. Using a piggy back system with the factory ECU, we setup and tuned this package to great success. We were even able to use the motorsport functions for launch control and antilag.


GTX3071R PBMS Stage 2 Engine Result E10

Our aim was a responsive 280kw at the wheels. What we got was even better! The vehicle performs superbly – with identical response to a PBMS Stage 2 tuned GRB (Downpipe and reflash tune) whilst making 300kw at the wheels. This result was achieve on 26psi using Gull Force 10 (E10). On 14PSI peak power is 240kw.





About the author, Julius

Julius provides technical support and expertise to Possum Bourne Motorsport. He's been involved with the industry since 2009 and has stamped his mark as an industry leader.

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