We recently worked on turbo upgrade for 2013 Subaru STi who customer wished to add more power before doing engine internals upgrade. The car arrived with Injector Dynamics 1000cc fuel injectors, AEM Cold Air intake, headers, downpipe and 3-port boost solenoid. The customer chose the latest bolt-on Tomioka Racing Hybrid ball bearing TD05-GT28 turbocharger with Billet compressor wheel for his upgraded turbo.
Tomioka Racing ball bearing turbo uses genuine Garrett Ball Bearing and complemented the CHRA with their proprietary aerodynamic turbo blade design. The size of the hybrid turbo is similar to Garrett GT28. The turbo also came with billet 1.3 bar waste-gate actuator and 8cm turbine housing.
With a conservative tune and peak boost at 18psi, the car hit 339whp and 354 lbs/ft of torque. Target boost was achieved at less than 4500rpm. The next addition for the customer is the front mount intercooler kit, Tial QR Blow-Off Valve and Tomioka Racing temperature controlled Oil cooler kit and VP C16 Race Gas. We’re pushing the envelope on the turbo and stock EJ25 block.
With peak boost at 23psi, the car powered to almost 390whp and 390 lbs/ft of torque. The target boost was hit slightly later at 4650rpm. The peak boost level was held back by the 3-port boost solenoid not able to regulate past peak boost of 23 psi. Otherwise the car could easily push beyond 400whp with the current set-up. We’ll have to see if customer is willing to switch to better 3-port boost solenoid to experience the full potential of his build in the near future. Overall this is a very efficient ball bearing bolt-on turbo for enthusiast who likes quick response and those who aspire to go beyond 400whp.