Tuned Port Injection in General Motors Vehicles

2043 Words5 Pages

Tuned Port Injection in General Motors Vehicles

The first production Tuned Port Injection (TPI) systems appeared on General Motors' vehicles in 1985. The GM vehicles built with these systems were the Corvette, Pontiac Firebird, Pontiac Trans AM, and the Chevrolet Camaro. Upon their introduction, these systems achieved a 35 % improvement over carbureted systems and a 20% improvement over available forms of fuel injection in horsepower, torque and economy.

The 1985-1988 TPI system utilized the following sensors and devices to control the engine: Mass Air Flow Sensor and Module, Manifold Air Temperature Sensor, Coolant Temperature Sensor, Oxygen Sensor, Throttle Position Sensor, Cold Start Switch, Cold Start Injector, Fuel Injectors, Idle Air Control Valve, Vehicle Speed Sensor, Electronic Spark Timing Sensor and Module, and Knock Sensor.

When the key is in the "on" position the Electronic Control Module (ECM), the main computer that controls all sensors and engine functions, powers up and readies the engine for start-up. When the starter is engaged and the coolant temperature is less than 100 degrees Fahrenheit, determined by the Coolant Temperature Sensor (CTS), the Cold Start Injector provides a spray of fuel to each cylinder via an air distribution system built into the intake manifold. If the engine temperature is greater than 100 degrees Fahrenheit, the Cold Start Injector is disabled by the cold start switch. Upon startup the ECM utilizes information in the Erasable Programmable Read Only Memory (EPROM) to establish the initial pulse rate for the fuel injectors. The ECM pulses, or opens and closes, the remaining 8 fuel injectors in sequence and the engine starts. During this, the Idle Air Control (IAC) valve is com...

... middle of paper ...

...eaning functions for the MAFS. In 1986 two relays replaced the MAFS module and the ECM was changed. In 1989 the cold start injector was deleted. The EPROM provided a wider pulse width on startup to provide a richer mixture for a cold engine. For those years, all other features are the same. In 1990 the MAF was replaced with the MAP sensor. The1990-92 TPI system still operated the same except that manifold air pressure is used to calculate injector pulse width as opposed to airflow.

Tuned Port Injection saw continued use on General Motors' performance cars from 1992 through 1994. During that period, the TPI system changed greatly but the basic concept behind its operation remained the same. In 1994, GM killed the TPI system and made the switch to a more modern and efficient Sequential Port Fuel Injection (SEFI) system, which is now used all their performance cars.

More about Tuned Port Injection in General Motors Vehicles

Open Document