Central Fuel Injection (CFI) and How it Works

March 18, 2013

Central fuel injection has changed the way cars work. At one time, engines would receive their fuel mixture from the carburetor when the car would suck in air. The engine would then disperse the fuel throughout the engine which in turn would keep the engine running. With central fuel injection, the engine still sucks in the air but the distribution of the fuel is done in a different and more fuel saving manner. Here is a brief overview of how this works.

Single Injector Setups

With fuel injection, the car does not rely on the suck of the engine. It has a more accurate system that is activated electronically and the fuel is distributed by injectors. There are single port and multi port injectors, the single port being quite common. This sprays the gas into a central intake. Then it takes the gas and the right amount of air and distributes both into the engine at the same time. This Ford central fuel injection system was never used in the European market.

Multi-Port Setups

The multi-port has an injector for each cylinder that the engine has. These injectors will spray fuel into the intake valve and then into the burning chamber. Each injector is activated by a wire. Newer versions of this type now just use one fuel line that is connected to a fuel rail which is on top of the engine. The injector will get gas from the central fuel rail and spray it into the engine.

The injectors know how much fuel to distribute because the system is designed to be able to measure how much air your engine is sucking in. As soon as the car engine starts, the air measurement begins. There is a wire that will become red hot when the engine starts and as the air is sucked in past it, and once the wire begins to cool, the car will determine how much air is being sucked in by how cool the wire is getting. This tells the car how much air is being sucked in and will spray out the correct amount of fuel.

Related Questions and Answers

Does Injector Cleaner Work?

Many people ask: 'Does injector cleaner work?'. The answer is yes, if the problem was caused by contaminants and/or varnish. Fuel injector cleaner works by dissolving the varnish produced by burning fuel, and releasing collected contaminants that cause faulty injector spraying. A fuel injector is an electrically controlled engine part that sprays fuel into the engine. The fuel is sprayed so that it is better able to mix with air, before it is burned in the engine. Because the spray is produced through a small orifice (hole), any amount of contamination and/or varnish deposits can affect the spray pattern, and therefore the amount of fuel entering the engine.

How Can You Tell if You Have Clogged Fuel Injectors?

Clogged fuel injectors will produce uneven spray patterns and cause the wrong amounts of fuel to enter into the engine. Uneven spray patterns prevent a proper mixture of air and fuel because the fuel is not being atomized. This will cause improper burning of the fuel, and the vehicle's engine will run rough when idling. The injector's operation can be observed, by looking under the breather, on vehicles with central fuel injection. With the engine running, observe the injector's spray pattern. It should be an even, conical spray with no drips. Dripping and/or and un-even spray indicates a clogged injector.

For more info, see Central Fuel Injection (CFI) and How it Works

What is the Best Fuel Injector Additive for Improving Gas Mileage?

Gas mileage can be improved by using a fuel injector additive. However, the additive is not the chemical that is responsible for the increase in gas mileage. The chemical contained in injector cleaner only cleans the injector. The increase in gas mileage comes from a cleaned and properly working fuel injector. In fact, the best way to prevent injector clogs is to use a quality grade of fuel. Moreover, many injector cleaners are comprised of the same chemicals that are added to gasoline, so the best injector cleaner is the one that contains large amounts of solvents, not petroleum distillates.

What is the Best Method for Cleaning Diesel Injectors?

Cleaning diesel injectors is similar to cleaning gasoline injectors. The best way to prevent injector clogs is to use a high quality diesel fuel. However, in the absence of that, regular use of an injector cleaner can keep injectors clean and properly working. The easiest and cheapest way to do this is by using a product that is added to the fuel tank. This type of cleaner works as the vehicle is driven, and requires no specialized equipment or tools. However, if left unchecked, the vehicle may need to go to the shop for a cleaning that requires the use of specialized equipment.

How Many Types of Fuel Injection Additives are there?

There are two types of fuel injection additives on the market today. The most popular and common of these are petroleum distillates. These additives are used in most quality fuels, and are sold in concentrated form. They tend to work in instances where the fuel additives are not strong enough to completely clean the injector(s). The other class of additive is solvent based. These are strong cleaners, and will quickly dissolve varnish. Additionally, they will also clean residue from the entire fuel system. Moreover, some brands take advantage of both types of additive in order to affect a thorough injector cleaning.

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