BSFC: Brake Specific Fuel Consumption. A measure of how efficiently fuel is consumed in the engine, or how many pounds of fuel is being used per horsepower produced in an hour.
Detonation: Also called "pinging" or "spark knock." A too-rapid release of energy that creates excessive combustion-chamber pressure and temperature. The result is engine damage.
ECM (Engine Control Module. a.k.a. "ECU"): The electronic "brain" of the fuel-injection system. Controls fuel delivery and often spark.
Fuel Enrichment Mode: The warmup period when the engine is in open-loop mode and following a predetermined program rather than being controlled by oxygen sensor inputs.
Group Fired Injectors: The injectors are actuated in groups. A V-8 is typically fired in banks of four.
IAC (Idle Air Control): A motor-operated air-bleed valve controlled by the ECM to adjust idle speed.
Injector Duty Cycle: The amount of time the injector is open versus the time it is closed.
Knock Sensor: Essentially a very sensitive "microphone" mounted on the engine that's tuned to the sound frequencies typically found during detonation (pinging). When they are detected, it converts this to a signal that the ECM can read so the timing can be adjusted.
MAF EFI (Mass Air Flow Fuel Injection): The two main reference signals are the MAF sensor, which measures actual airflow, and engine temp. Finer adjustments are influenced by any other sensors that are present.
MAP (Manifold Absolute Pressure) Sensor): A device that reads manifold pressure (vacuum). The ECM uses this signal as a reference to measure airflow.
Oxygen Sensor, a.k.a "Lambda" sensor: A device inserted into the exhaust system that measures oxygen content in the exhaust. The ECM uses this as a reference to adjust fuel mixture
PCM (Powertrain Control Module): Controls and integrates the engine with the transmission and transfer case. May also connect to an Electronic Traction Control system.
Pulse Width: The amount of time, in milliseconds, the injectors are open.
SFI (Sequential Fuel Injection): The injectors are opened sequentially according to the firing order.
Speed Density EFI: The engine has three primary reference sensors, the MAP sensor, engine temp, and engine speed. Airflow is calculated from these inputs and basic fuel delivery is adjusted to match.
TCM (Transmission Control Module): Some rigs use a separate transmission-control module to control the shift on an electronically controlled transmission. It will react to inputs from the engine or ECM.
TPS (Throttle Position Sensor): A device that converts the angle of the throttle butterfly into an electronic signal
VCM (Vehicle Control Module): Essentially a PCM with another name. It may integrate some other non-engine/drivetrain systems into the mix.
Building and Tuning Electronic Fuel Injection
By Ben Strader
(Cartech, 2004; 128 pp.)
Ben Strader has been firmly established as one of the gurus of the performance fuel-injection realm. Up to now, his vast knowledge has only been dispensed in the seminars he does in various parts of the country. Now you can learn those EFI performance secrets at home. Strader's book is not light reading, but the mental effort is worth the time. The book is broken down to cover the basics of electronic useful injection and individual chapters on the setup and tuning tricks for the various popular aftermarket EFI systems. That includes bolt-on systems to convert a carbureted engine, or tunable stand-alone ECMs for modified fuel-injected engines. Some of the systems covered include ACCEL, AEM, Autronic, Edelbrock, EFI Technology, Electromotive, F.A.S.T., Haltech, Holley Commander 950, MoTeC, and SDS. If you have an unanswered EFI performance question or an unfulfilled project, this book is the latest and greatest on the topic.
Precision Automotive Technical Services Engineering Section