The H22A is famous for being one of Honda's highest performing engines, producing anywhere from 190 to 220 horsepower in stock iterations. Turbo systems, however, can add anywhere from 30 to several hundred horsepower to your Honda H22A engine.
A custom turbo kit can be pieced together for the H22A from used parts off stock turbocharged vehicles. Locating parts for a custom kit can be difficult, and used stock parts offer less horsepower gains than a custom aftermarket kit. However it's also much cheaper to build your own H22A turbo kit, and even a system built from inexpensive used parts can yield a gain of 40 or more horsepower on the H22A.
There are numerous custom aftermarket turbo kits available for the H22A. These kits will be easier to bolt up than a custom kit, and will also include some supporting modifications such as fuel pump and injectors allowing the H22A to gain upwards of 100 horsepower. Note that with such high gains, other supporting modifications will be needed as stock parts begin to fail, notably the clutch and other transmission components.
Whatever method used to turbocharge the H22A, ECU tuning is paramount. The stock ECU programming lacks the ability to compensate its fuel curves even for the smallest of turbo systems. Either an ECU reflash program or a fully tunable ECU is needed to reliably add a turbo system to the H22A.
