Gasoline Direct Injection

Question:

My new car has a “GDI” engine. What does that mean to me and other Charlotte vehicles with this new type of engine?

Joey’s Truck Repair Inc. Answer:

GDI stands for Gasoline Direct Injection. It’s a type of fuel injection system that is becoming very popular on modern engines.

Let’s talk about the two most common forms of fuel injection. Port Fuel Injection has been common in Charlotte vehicles for the last several decades. With this type, there is a small port just outside the cylinder on the engine.

• The fuel injector squirts a bit of gas into this area just before the intake valve opens

• When the valve opens, air enters the port and mixes with the gas, then flows past the valve and into the engine

• The gas and air mixture is compressed by the piston

• The spark plug fires, igniting the gas which pushes against the piston, thus powering the engine

With Gasoline Direct Injection the process is a bit different.

• First, there is no port outside the cylinder

• When the intake valve opens, air is drawn into the cylinder

• The air is compressed by the piston

• At the correct time, the engine management computer signals the fuel injector to spray gasoline directly into the cylinder (hence, Gas Direct Injection)

• The pressurized gas and air are ignited by the spark plug, powering the engine

So why move to GDI? Well, by injecting the gas directly into the engine, the management computer is able to time the injection event more precisely. Also the gas sprayed directly into the engine cools the compressed air enough to allow for better combustion. This adds up to more power and better for a given engine size.

Now these two types of fuel delivery systems call for different kinds of fuel injectors. Port fuel injectors squirt their fuel at 40 to 65 pounds per square inch – that’s like the pressure in a bicycle tire.

GDI injectors operate at over 2,000 pounds per square inch. Of course it’s always important to keep your fuel injectors clean – but it’s even more important for GDI injectors. When they become contaminated, the performance and fuel economy diminish.

Speaking of fuel system cleaning, different cleaners and cleaning processes are required for GDI engines. Intake valves get a fair amount of carbon build-up over time. With port injection, some gasoline flows over the valve when it opens to let in the gas and air. This has a cleaning effect which doesn’t occur with GDI. So pouring a bottle of fuel system cleaner in your gas tank will not reach the backside of those intake valves. A professional fuel system cleaning process here will take care of that concern.

So GDI will continue to be more prevalent in NC on everything from compact cars to pick-up trucks. Give us a call & ask if your vehicle could benefit from a fuel system cleaning.

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