Guide To Your Vehicle’s Fuel Injection System

In 1990, the last model to roll out of the factory with a carburetor installed was the Subaru Justy. Since then, all cars have been designed with fuel injection systems (FIS). While carburetors were an impressive piece of machinery, they could not keep pace with the rapid evolution of automotive engines. Moreover, as emission standards rose, catalytic converters were installed into vehicles to reduce the harmful gases present in the exhaust. Because catalytic converters require a precise air-fuel mixture in order to do their job, the carburetor’s days were numbered.

Today, fuel injection systems carefully control the amount of gasoline that enters the combustion chamber of each cylinder. Below, you’ll learn how your vehicle’s FIS works and the process by which fuel is metered and controlled.

Basics Behind The System’s Operation

When you press down on your accelerator, a throttle valve opens and allows air to flow in toward the cylinders. Your vehicle’s computer (called the engine control unit, or ECU) takes note of the open throttle valve and sends fuel toward the injectors. This happens almost instantly to ensure the right air-fuel blend ends up inside the combustion chambers.

Each injector is a valve that opens to allow gasoline to shoot directly through the intake valve into its corresponding combustion chamber. It opens and closes quickly based on instructions received from the ECU. When the fuel flows through the injector, it comes out as a mist in order to burn more cleanly. The amount of fuel sent into the chamber is regulated by the amount of time the valve remains open. This period is called the pulse width.

How The Amount Of Gasoline Is Metered

Because the ECU is responsible for sending pulse width directions to the injectors, it must have a way to monitor the amount of fuel needed for specific driving conditions. It uses data from several sensors.

Oxygen sensors monitor the level of oxygen present in the exhaust coming from the combustion chambers. This data helps the engine control unit to identify a too-lean or too-rich mix and make the appropriate adjustments. An engine speed sensor is used by the ECU to regulate the injectors’ pulse width. A mass airflow sensor sends data to the ECU regarding the amount of air coming into the engine.

Other sensors monitor the throttle position, voltage level, operating temperature, and how much pressure exists in the intake manifold. All of this data is used to carefully meter the amount of fuel that flows through the injectors.

Your fuel injection system can develop a number of problems that will affect your engine’s performance. For example, your injectors can clog. Or, one or more sensors might fail, leading to a too-lean or too-rich air-fuel mix. These issues (and others) can cause a hard start, misfire, hesitation, or stall. If you notice any of these problems, visit a repair shop to have your car’s fuel injection system tested. Otherwise, you might eventually find yourself stranded at the side of the road.

The Value Of Vehicle Computer Chip Adjustments

For a modern automobile, computer-controlled goes hand in hand with horsepower. In earlier years, a few carburetor adjustments would translate into a performance boost. However, since the advent of electronic fuel injection and other technological advancements, systems under the hood of your vehicle are increasingly controlled by computers. As a result, aftermarket computer chips have been developed that enable even a technophobe to modify their vehicle.

Upgrades: How and Why

While there may be a variety of upgrade manufacturers, including JET Performance, Superchips, etc., they all work on the same principles. First, a programmer module, otherwise known as a tuner, is connected to the car computer via the ALDA connector. Note that this connector type is only present on vehicles manufactured on or after 1996. After the connection is made, the tuner pulls in the VIN and all other configuration data. Once that data is analyzed, the tuner presents the user with a settings menu.

Upgrades are not necessary for motorists, but the activity isn’t limited to the car junkie or performance enthusiast. When the car leaves the factory, the control unit is programmed according to an “average driver” profile. For drivers who need the acceleration and power to successfully tackle a freeway on-ramp day after day, or those faced with steep inclines on a routine basis, module tuning can be valuable.

Common Adjustments

There are literally dozens of parameters available on a typical computer tuner, but among them, five settings can significantly change your vehicle’s driving performance. First, the “top speed limiter” determines your car’s maximum speed. When using high-performance tires, this should be adjusted in order to match the specified ratings.

The “rev limiter” determines the maximum rpm (revolutions per minute) value the engine can withstand. By increasing this setting, also known as widening the powerband, your car can deliver more emergency power. This is especially helpful when you’re trying to avoid an erratic driver or claim your spot on the freeway.

“Shift points” are speed and rpm markers that determine when an automatic transmission switches gears. By tweaking these points it is possible to improve acceleration, which is vital for quick passing or avoiding accidents.

Speedometer and odometer corrections are useful for tire size compensation. Cars are programmed at the factory for stock tire sizes, but for those who have installed larger tires or changed 4×4 gear ratios, the speedometer and odometer are no longer accurate.

The most important setting on a tuner concerns the gas and air mixture. These adjustments can result in additional horsepower, torque, and better fuel economy, but drastic changes can be harmful to your engine. In addition, personal driving habits can play a big role in the fuel mix configuration.