| Originally, gasoline engines solely used carburetors | | | | dispersal created by the system has a cooling |
| to prepare the air and gas mixture. However, the | | | | effect on the engine that increases power across |
| relative inaccuracy of this method has led to the | | | | the entire RPM band. |
| development of direct fuel injection, resulting in a | | | | When it's running, the computer is continually |
| more efficient burn and lower emissions. Below, | | | | varying between different air-gas ratios to ensure |
| I'm going to explain how the system works as | | | | the best performance. The three modes are "full |
| well as its pros and cons. It is likely that a greater | | | | power," "ultra lean burn," and "stoichiometric." |
| number of vehicles will be built with this type of | | | | During a full power burn, the mixture is richer, |
| engine in the future, so it's worthwhile to | | | | enabling the car to accelerate faster and prevent |
| understand its operation. | | | | knock. "Ultra lean burn" pushes the ratio as high as |
| How Direct Fuel Injection Works | | | | 65:1, providing emission reductions under |
| In most gasoline-fueled cars, the engine operates | | | | low-stress situations. "Stoichometric" mode runs |
| on a four-stroke cycle. In a four-stroke engine, | | | | the engine at a 14.7:1 mixture, the optimum |
| during the first step the intake valve opens and | | | | combination that ensures a 100% burn, used for |
| the cylinder is filled with a mixture of gas and air. | | | | moderate-stress situations. |
| Next, the valves close and the piston moves up, | | | | Disadvantages |
| compressing the mixture. After that happens, | | | | Unfortunately, direct injection systems are more |
| ignition is triggered, sending the piston downwards | | | | expensive and complex to build, resulting in a |
| in what is known as the power stroke. Lastly, the | | | | concentration among high-performance cars and |
| exhaust valve opens and the piston travels | | | | trucks. Another drawback to these systems is |
| upward, forcing out the waste fumes. | | | | the component durability. The assembly must be |
| In a carbureted vehicle, the fuel blend is mixed | | | | able to handle high-pressure gasoline as well as the |
| before entering the cylinder on the first stroke. | | | | heat and pressure in the cylinder for extended |
| With direct injection, the gas is sprayed into the | | | | periods of time. Furthermore, the assembly must |
| cylinder while the air enters via the intake | | | | be very accurate in order to direct the spray |
| manifold. | | | | properly. This tight tolerance can also make the |
| Advantages | | | | assembly unreliable, especially if the engine is |
| There are a number of benefits to a | | | | routinely placed in high-stress situations or driven |
| direct-injected engine. The primary advantages | | | | for long distances. |
| involve improved fuel economy and greater | | | | Even though prices currently remain relatively high |
| power output. Each burst of gasoline is precisely | | | | for these systems, their improved performance |
| measured and timed by the onboard computer, | | | | and fuel efficiency is likely to spur their adoption in |
| translating into greater efficiency and less pollution. | | | | additional car models. Before long, carburetors will |
| In addition, the ultra-fine droplets and even the | | | | be a distant memory. |