In conventional gasoline internal combustion engines, direct injection is a design that allows an engine to run more efficiently and reduces emission levels by injecting the fuel directly into the combustion chamber. While fuel injection isn’t a recent technology, the system essentially replaced carburetion by the late 1980s. Early forms of fuel injection sprayed a mist of gasoline into the intake manifold, which entered the combustion chamber when the intake valve opened. With this form of fuel injection, the amount of fuel used isn’t always efficiently burned as some remains in the intake manifold unburned. Direct injection ensures that the fuel is delivered directly into the combustion chamber for better fuel efficiency. Another effect of direct injection is increased horsepower from smaller displacement engines.
While many manufacturers currently use direct injection, a perfect example of the advantages of direct injection is found under the hood of the Cadillac CTS. The CTS is available in two models, Both models utilize General Motors’ 3.6-liter aluminum V-6 block with double overhead camshafts (DOHC), four valves per cylinder and variable valve timing (VVT). The only difference is that the CTS Performance sedan uses a direct-injected version, which increases horsepower and torque and achieves almost identical fuel economy. The 3.6L DI gets 304 horsepower, 273 lb-ft of torque and EPA fuel economy estimates of 17 miles per gallon in the city and 26 mpg on the highway. The standard 3.6-liter with sequential fuel injection (SFI) gets 263 horsepower, 253 lb-ft of torque and EPA fuel economy estimates of 18 miles per gallon in the city and 26 mpg on the highway.