Hilborn Injection - Old-School Injection

Hilborn mechanical fuel injection has been a boon to racing over the years. Unfortunately, not so for street-driven vehicles that must operate throughout the rpm range for extended periods rather than full-throttle blasts. That is until recently with the advent of modern computer controls and EFI, or electronic fuel injection. The idea behind EFI goes kinda like this: When you step on the gas pedal, the throttle valve opens up more, letting in more air. The electronic control unit (ECU) senses that the throttle valve has opened and increases the fuel rate in anticipation of more air entering the engine. Sensors monitor the mass of air entering the engine, as well as the amount of oxygen in the exhaust. The ECU uses this information to fine-tune the fuel delivery so the air/fuel ratio is just right.

A fuel injector itself is really nothing more than an electronically controlled valve. It is supplied with pressurized fuel by the fuel pump in your car, and it is capable of opening and closing numerous times per second. When the injector is energized, an electromagnet moves a plunger that opens the valve, allowing the pressurized fuel to squirt out through a tiny nozzle. The nozzle is designed to atomize the fuel to make as fine a mist as possible so it can burn easily and completely.

The amount of fuel supplied to the engine is determined by the amount of time the fuel injector stays open (this is called the pulse width, and it is also controlled by the ECU). Electronic injectors are mounted in the intake manifold so they spray fuel directly at the intake valves. A pipe called a fuel rail supplies pressurized fuel to all of the injectors.

Operational benefits of a street-driven, fuel-injected engine include smoother and more dependable engine response, easier and more dependable engine starting, better operation at extremely high- or low-ambient temperatures, reduced maintenance, and increased fuel efficiency.

An engine's air/fuel ratio must be accurately controlled under all operating conditions to achieve the desired engine performance, emissions, driveability, and fuel economy. Modern Hilborn electronic fuel-injection systems meter fuel accurately and precisely, and let fuel-injected engines run considerably cleaner than comparable carbureted engines. Properly designed fuel-injection systems can react faster and more precisely to rapidly changing inputs, such as rapid throttle movements, and can tailor fuel distribution to closely match the engine's needs across a wider range of operating conditions, such as load, ambient temperature, operating temperature, fuel quality, and altitude (i.e., barometric pressure). You got that?

Carburetors Vs. Eight-Stack InjectionHilborn EFI specialist Andrew Star has written extensively on electronic fuel injection and he's given me permission to quote a bit of technical info that will hopefully be of interest-especially to those with a more technologically adept psyche than I.

"The carburetor can best be described as an air/fuel mixer that uses a differential in pressure to provide fuel at an established metered amount. Although easy to define, the actual workings of a carburetor are complicated, enough so that very few people are able to maximize its potential.

"With air movement toward the intake valve in the intake manifold, a result of piston movement and valve timing, the main venturi of the carburetor has air flowing past the booster, creating a pressure drop. This pressure drop causes fuel to be pushed into the booster supplied by the fuel bowl via the main well of the carburetor. The shearing of the fuel as it enters the air stream out of the booster causes the fuel to separate into smaller particles, where it is picked up by the air and carried into the intake manifold.