Electronic fuel-injection systems fall into two categories: throttle-body injection or multi-point injection. A throttle-body housing has as many as four electronically controlled fuel injectors, depending upon manufacture and engine power requirements. These injectors aspirate outside air into the fuel spray from the computer operated injectors in order to promote thorough mixing of the atomized fuel and combustion air in the intake manifold. A throttle-body is similar in appearance and function to a carburetor only in that it is mounted atop the intake manifold, and serves to introduce a mixture of fuel and air into the manifold for distribution via the intake runners to the intake valves. Simple in design, throttle-body-based fuel-injection systems are much more economical to operate than carburetors and have enjoyed many years of success. However, because they employ the principal we refer to as air/fuel pre-mix-defined as the process of achieving fuel and air mix away from the combustion zone in order to achieve satisfactory performance and efficiency-successful throttle-body injection systems must rely completely upon proper intake manifold design. When fueling through the intake manifold, the internal design of the manifold dictates how well and how evenly atomized fuel and combustion air are mixed, and then introduced into each cylinder for combustion. a poorly designed intake manifold will allow atomized fuel to adhere to and collect along rough internal surfaces, as well as permit the formation of air eddy-currents around sharp turns inside the manifold, both of which can interfere with the combustion process.
Unlike throttle-body systems, multi-point-more commonly called multi-port-electronic fuel-injection systems comprise a single air door and an electronic fuel injector for each cylinder. In a multi-port system, a fuel injector is mounted at the end of each intake runner or port to introduce pressure-atomized fuel directly into the combustion chamber in each cylinder. Air for combustion is introduced through an air-door (similar in appearance and function to the air-handling components of the throttle-body) and is aspirated through the intake manifold into the combustion chamber. In this system, the primary mixing of pressure-atomized fuel and combustion air takes place in the cylinder, rather than in the intake manifold, in a process referred to as air/fuel post-mix. While multi-port injection systems still depend upon a proper intake-manifold design for optimum performance, the elements of intake design peculiar to fuel handling can largely be ignored. The particular advantage of multi-port systems compared to throttle-body systems, is that pressure-atomized fuel is introduced nearer the point of combustion, thereby permitting cleaner, more efficient firing than with a throttle-body system with a minimum of unburned fuel carried into the exhaust. More sophisticated, sequentially fired, multi-port injection systems allow for the precise coincidence of fuel injector opening and intake valve opening, yielding maximum power and minimum waste from each cylinder. While multi-port injection systems are superior in operation and performance to throttle-body systems, they can be substantially more expensive to purchase and install. Thus, they are not necessarily a cost-effective alternative in every electronic fuel-injection application. Performance Injection Equipment employs throttle-body injection systems in small-block applications and uses the more robust multi-port injection systems for big-blocks.
The Idle Air Control (IAC)...
The Idle Air Control (IAC) (arrow) is one of the few devices that do not send information to the microprocessor. Instead, the IAC receives commands from the processor. In order to maintain a constant idle speed, the processor issues commands to the Idle Air Control to modulate its position depending upon engine running conditions.
The Manifold Absolute Pressure...
The Manifold Absolute Pressure sensor (MAP) is a load-sensing device. We mounted ours on the inner fender on the passenger side. The information it sends to the microprocessor is used by the processor to determine the volume of fuel and the degree of timing required for reliable operation. The Electronic Spark Timing module (EST) is the ignition controller. It controls spark well and sends information to and receives information from the microprocessor concerning ignition timing. Computer-controlled ignition timing is different from vacuum-advance or centrifugal-advance timing. With vacuum or centrifugal timing, the timing cannot be varied with engine load. With electronic fuel-injection systems, the microprocessor uses information from the MAP sensor to calculate the load exerted on the engine. Timing information sent from the processor to the EST module varies as the load exerted on the engine varies. For example, when the throttle is snapped into wide open from the closed position, the timing rises to full advance. As the load exerted on the engine increases, the processor retards timing to avoid harmful detonation. This action provides snappy acceleration, yet the timing is so precisely controlled the high initial advance does not damage the engine. When the vehicle achieves cruising speed, and the load exerted on the engine becomes relatively light, the processor advances timing, which improves fuel efficiency and reduces exhaust emissions.
The microprocessor or Electronic...
The microprocessor or Electronic Control Unit (ECU) is the device that governs the operation of an electronically fuel-injected engine. Principally, the ECU collects and processes information from the many sensors and issues commands to various devices in order to control fuel and timing. With the out-of-the-box electronic fuel-injection systems by Performance Injection Equipment, the PROM chip supplied in the ECU comes preprogrammed for superior operation.
Although the processor has...
Although the processor has an AC Delco sticker on it, a processor is a processor, and these are the easiest to modify. We ran the wiring and mounted ours under the dash on the passenger side.
Notice there is only one fuel...
Notice there is only one fuel line into the throttle body. a closed-loop system means there is no fuel-return-line needed to send the unnecessary fuel back to the gas tank. This means with the PIE kit, another line (for fuel return) need not be run. This saves time, work, and expense.
Although the kit comes with...
Although the kit comes with a capable in-line fuel pump to install, you may feel you need more fuel. This fuel trap is available and installs inside your fuel tank. You can then install your in-tank fuel pump for some serious fuel pumping.