Chevy TPI Fuel Injection Swapper's Guide: How To Install & Modify GM Tuned Port Injection Systems

Tuned Port Injection is surprisingly simple, once you understand the basics. In subsequent chapters we will look at the various components in detail, including ECMs, sensors, and all the attending hardware. Here we will briefly examine the basic concept of tuned port injection and how it works.

When you take the jump from carburetors to fuel injection, you're still utilizing many of the same functions. Carburetors are required to provide appropriate fuel metering for a broad range of engine operating requirements, including engine startup enrichment, cold-running enrichment, idle speed and air/fuel ratio control. cruise air/fuel ratio control, moderate load enrichment, and acceleration enrichment.

To perform these functions, the carburetor provides choke operation, an idle circuit, main circuit, power valve, and accelerator pump circuit.

Fuel injection tackles the same tasks with different tools. Cold startup is handled by either a cold start injector or main injector enrichment based on coolant temperature sensor input.

Cold running enrichment is maintained by coolant sensor input while idle sensor and air/fuel ratio is controlled by an idle air control valve and the mass air flow (MAF) sensor or a manifold absolute pressure (MAP) sensor.

Cruise air/fuel ratio is controlled by the MAP or MAF and the oxygen sensor with the oxygen sensor having priority over fuel management decisions. Load enrichment is handled by the throttle position switch (TPS) and either the MAP or MAF. Acceleration enrighment is controlled by the TPS and the fuel pressure regulator.

Once incoming air flows past the air filters, it can be handled in two ways depending on the year of the engine and the type of engine management being used. Mass air flow-equipped engines actually measure the air flow into the engine and calculate settings to accommodate current conditions.

Speed density-equipped systems only know engine speed and load. They calculate air flow based on known values or a map of the engine's performance characteristics.

• Electronic Carburetors
• Electronic Fuel Injection
• Electromechanical Fuel Injection
• How TPI Works
• Mass Flow Versus Speed Density
• Closed Loop Operation
• Tuned Port Sensor Guide
• Injector Selection and Tuning
• Troubleshooting Guide
• Modifying TPI Systems
• TPI Buyers Guide
• TPI Sources