Turbo: STi/WRX VF Series Turbocharger breakdown:
(435cfm at 18psi, 250-325whp, Bolt-On)
The VF30 delivers a very wide increase in torque over the standard TD-series turbos. It is important to note that the VF30 is not a roller bearing turbo. The VF30 is commonly considered the best bang for the buck turbo in the IHI VF series line. A relatively new model the VF30 features the same exhaust housing as the VF24, P18, but a larger compressor side similar to the VF22. The combination of these two parts results in increased output potential without the lag associated with the VF22.
Although it doesn’t offer the top end supremacy of the VF22, the VF30 is a great compromise between these unit and the quicker spooling models. The VF30’s compressor wheel is rated at 35 lbs/minute, because the P18 turbine is used to help spool up the VF30’s turbine creates a lot of back pressure which hurt top-end performance.
The VF30 was designed with the EJ20 in mind and will not have the same performance on an EJ25. The VF30 is good for around a realistic 290 to 305 WHP on a 2.0L. The VF30 is not ball-bearing. It uses much more advanced aerodynamics than the VF22/23/24. It should spool much faster than the VF22/23/24, but flow less than the VF22, closer to a VF23.
(435cfm, 250-325whp, Bolt-On)
The VF39 is a single scroll turbo used on USDM STI and latest 2.5L STIs released internationally. Smaller in output capacity than VF30, VF34 and VF22, the VF39’s compressor is rated at the same 35 lbs/minute but the very small P18 turbine really chokes the 2.5L engine. In stock form the EJ25 with the VF39 has very little lag and that was the goal Subaru was looking for with the base package.
Brand new VF39 for sale from Subaru:
Subaru 14411aa5729L Turbocharger
The VF39 is good for around a realistic 285 to 300 WHP installed on a 2.0L. I would not recommend a VF series turbo to anyone looking to upgrade their STI but if you plan on keeping the VF39 you can expect to make between 300 to 330 WHP. If you are considering the VF39, we highly suggest checking out the VF43 as it is a better setup in the same class.
(435cfm, 250-325whp, Bolt-On)
The IHI VF43 comes stock on the 2007 STi. It has almost identical features of the VF39 with a thrust bearing and a P18 exhaust housing, but the wastegate opening is larger to relieve boost creep issues. . It can be found on both base STI’s and STI Limited’s. The VF43 utilizes a thrust bearing design and the P18 exhaust housing. The difference between the VF43 and the VF39 used previously on STI’s is the size of the wastegate.
Brand new VF43’s from Subaru:
Subaru 14411aa620 Turbocharger
The VF43 has a larger wastegate designed to reduce boost creep issues.
Expect to achieve full boost with the proper mods and a quality tune between 3000-3500rpms. 2002-2005 WRX owners will need fuel upgrades for this turbocharger and proper engine management is highly recommended for all vehicles that utilize this turbo aftermarket.
(430cfm, 250-325whp, Modification Required)
This is the standard equipment turbocharger used on the JDM V8-V9 Subaru Impreza WRX STI Spec-C Type RA. The VF36 is a twin-scroll turbocharger that utilizes a ball bearing design, a P25 exhaust housing, and Titanium (possibly TiAl?) compressor wheel for improved spool. It is essentially a fast spooling VF34.
Expect to achieve full boost with the proper mods and a quality tune between 2800-3300rpms. 2002-2005 WRX owners will need fuel upgrades for this turbocharger and proper engine management is highly recommended for all vehicles.