TPI is one of the most popular swaps out there.  The swap is quite simple and the intakes are abundant, making this a fairly economical way to add fuel injection to your older vehicle.   Our quick-reference chart will simplify installation.  We have separate installation information pages for 82-87 Carbureted F-Body & 88-92 TBI Camaro & Firebird owners.

The TPI Low Down:

• What does it stand for : TPI = Tuned Port Injection. 
• How it works : TPI uses several sensors : TPS, CTS, O2, IAT, Knock, MAF & MAP.  Each sensor sends a signal to the ECM, and the ECM's PROM controls the fuel supply and ignition timing.  An idle air control valve (IAC) controls the idle RPM, determined by the ECM.  8 engine size based injectors are used in a batch fire method.  The batch fire method fires 1 side (Cyl 1, 3, 5, 7) of the motor at a time.
  • TPS (Throttle Position Sensor) : Determines the amount the pedal is depressed.  Mounts right on the throttle blade.
  • CTS (Coolant Temperature Sensor) : Lets the ECM know what temperature the coolant is.  Also operates the cooling fan motors on certain ECMs.
  • IAT (Intake Air Temperature Sensor) : Determines the temperature of the air entering the engine.  Warmer air needs less fuel to reach the proper air/fuel ratio.
  • Knock : Determines the amount of "knocking" the motor is having.  When it detects knock, the ECM retards the timing.  The knock sensor is different on MAF & MAP systems.
  • O2 (Oxygen Sensor) : Determines whether the motor is running lean or rich, so the ECM can compensate and run as close to 14.7:1 ratio as possible.  O2 sensors should be changed every 30k miles since they operate on an internal battery.
  • MAF (Mass Air Flow Sensor) : Determines the amount of air that enters the throttle blade.  More air entering means more fuel is required.  This sensor is used on all 85-89 TPI systems.
  • MAP (Manifold Absolute Pressure Sensor) : Determines the load on the motor by reading the engine's vacuum.  Less vacuum means the motor is under load, and will require more fuel.  This sensor replaced the MAF sensor, and is used on all 90-92 TPI systems.
• TPI systems : There are basically 2 types of TPI systems, a MAF system, and a speed density system.  The MAF system, used from 85-89, used a Mass Air Flow sensor to determine the load on the motor.  The speed density system, used from 90-92, used a MAP sensor to determine engine load.  The speed density system is easier to plumb since there is no MAF sensor.  Each system uses a different ECM and harness.  For the most part, each TPI intake unit can be used on either system. The 90-92 system is easier to install and works well on stock applications.  The 85-89 MAF system works better on modified applications.
• Fuel Pressure : TPI runs at 38-47 PSI (+/- 2 PSI), which requires a high pressure fuel pump and high pressure fuel line.  TBI operates at 9-12 PSI, and a carburetor operates at under 9 PSI. 

What you need to convert to TPI

Fuel Injector Size Suggestion

    The size of the fuel injectors plays a major role in the performance and fuel efficiency in a TPI system.  For the most part, stock flow-rating injectors are sufficient for stock applications.  High-flowing injectors are really only necessary and large displacement motors and higher RPM applications. An adjustable fuel pressure regulator can be used to increase the fuel rail pressure, which simulates increasing the injector's flow rating. 

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