What is Tuned Port Injection (TPI)?
Tuned Port Injection is a type of fuel injection which GM first used in 1985. It was used by some Camaros and Firebirds from 1985 until 1992, and by Corvettes from 1985 until 1991. It provides excellent driveability, throttle response, and great fuel economy. It has a relatively flat powerband, and makes great bottom and midrange power. However, a TPI engine begins to suffer near 4500 RPM, as the intake does not flow well enough to feed the engine’s needs. People often refer to other intakes such as the LT1 intake, the Holley Stealth Ram, or the Miniram as a version of TPI. This is not true. These other intakes are forms of port injection, but not forms of Tuned Port Injection. Tuned Port Injection is so named because of its long tube runner design. The air being drawn into the engine moves in pulses, and the runner length is such that air pulses arrive at the intake valve at convenient moments in the combustion cycle, and can force their way into the combustion chamber on their own.
