2: Subaru IHI VF series
IHI is known for producing high-quality turbochargers for both automotive and commercial applications. Subaru released its world-beating WRX STI with IHI turbos, and to this day they are still in high demand.
Several different VF-series turbos have been released throughout the years, but some are more potent than others. The early-shape Version 3 STI was released with the VF22 turbo, which has the largest potential for peak power of any VF turbo. The VF22 has a very large (for an OEM turbo) P20 exhaust housing, and it’s also ball bearing, which allows this compact unit to flow upwards of 20–24psi depending on the application. A few Subaru tuners have seen as much as 298kW at the flywheel on these turbos. If you’re after something a bit more modern, the VF36 turbo released on the JDM STI Spec C from 2003 onwards is the best option, it features a twin-scroll exhaust housing, ball bearings and a titanium turbine wheel and shaft. This will flow around 298kW at the flywheel, and be a lot more responsive compared with the older VF22. These turbos have different turbo flanges, so make sure to check when retrofitting one to your vehicle. The VF36 features a four-bolt twin-scroll flange, whereas the VF22 has a three-bolt single-port flange.
Although a fairly small turbocharger, the VF22 supports big numbers with quick response. Some Subaru tuners have seen upwards of 290kW on race fuel with the VF22