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

 Express Car Care 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 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 and then flows passed 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. Because of this it’s called Gas Direct Injection.
• The pressurized gas and air are ignited by the spark plug, powering the engine.

So why the 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 for an engine.

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 necessary for GDI injectors.  When they become contaminated, the performance ends.  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 won’t reach the backside of those intake valves.  A professional fuel system cleaning process needs to be done on the GDI engines in order to get them clean.

So, GDI will continue to become more prevalent in everything from compact cars to pick-up trucks.  Ask your Express Car Care service adviser if your vehicle could benefit from a fuel system cleaning.