Overview of Electronic Fuel Injection Systems

The Brucato Pro Control Unit is a stand-alone, fully-adjustable ECU for Mercury 2.4 and 2.5-Liter EFI V6 engines.

For most people reading this article, an introduction to the Electronic Control Unit (ECU) or Electronic Control Module (ECM) of an electronically fuel injected engine is not necessary. Automobiles have been equipped with these units for over twenty years now, in varying levels of sophistication.

Essentially, the ECU or ECM is an onboard computer system that receives input from various sensors and actuators on and in the engine and delivers the programmed amount of fuel based on this input. As computer technology has increased, so has the ability to more accurately monitor engine operations. The result is more performance from less fuel.

In most applications, these computer systems fall into two basic categories:  "Intelligent" and "Non-Intelligent".  ‘Intelligent’ EFI control systems have the ability to receive input from advanced onboard sensors such as Manifold Absolute Pressure sensors, and adjust themselves based on these constantly changing variables. ‘Non-intelligent’ systems differ in that they are usually not equipped to receive and process complex progressive electronic inputs, and therefore, offer less efficiency and performance potential than their more advanced counterparts.  Mechanical and early analog fuel injection systems would be examples of non-intelligent systems.

Although a ‘non-intelligent’ electronic fuel injection system can meter and deliver fuel much more precisely than carburetors, digital fuel injection systems take this much further. Unlike the early analog EFI systems, digital fuel injection systems operate on a more adaptive global model, with the ability to process more data concurrently from a variety of changing parameters.

The Mercury fuel injection control systems implemented in 2.4 and 2.5-litre V6 outboard engines are somewhat adaptive, although on a very limited scope. They include analog control units and more advanced digital systems. These ECU’s are the basis for the sequential multi-port injection systems designed for these high-performance engines, and are capable of monitoring basic engine functions to a varying degree, depending on the engine model and year.

Any computer system can be programmed and reprogrammed, however, the ease and level of programmability depends on the sophistication of the computer system’s architecture. For most users, the ECU that the 2.4 and 2.5-litre Mercury engines are factory-equipped with offers the reliability and performance they were designed to deliver in most general applications. Most importantly, the factory ECU offers only basic, limited linear fuel enrichment adjustments. If any further adjustments are required, the ECU can indeed be reprogrammed to remove RPM limiters and alter the fuel mixture, however this involves sending the unit to a specialized facility, which involves cost and downtime. Further, with advanced engine modifications and race applications that demand “on the edge” tuning capability, the importance of easily adjusting the fuel delivery process throughout the entire RPM range becomes clear.

Page Two: Brucato Pro Control Unit System Architecture