Over the course of the last 8 or 9 years there has been a new method of fuel injection brought to the market with the aim of improving both the performance and fuel efficiency of gasoline engines. This technology goes by the name of Gasoline Direct Injection or Direct Injection (GDI or DI for short. You’ll see both). What this system does is allow for a more precise metering and timing of fuel injection. GDI permits a much leaner fuel mixture at low load/no load situations and a more precise fuel mixture and better atomization of fuel when more power is required. Like most things, GDI has advantages and disadvantages.
In the most common type of injection, usually referred to as port injection, fuel is squirted in to the intake air directly upstream of the intake valves as they open and air is moving in to the engine. With the GDI system fuel is injected directly in to the combustion chamber at considerably higher pressure at just the right moment to insure the best possible combustion efficiency. GDI works particularly well with turbocharged engines. Since turbocharging gets more power from smaller displacement engines that get better fuel economy to begin with, GDI lets manufacturers place smaller engines with more power in to more vehicles. A great example of this is Fords’ V6 3.5L EcoBoost engine that has more power and towing capacity than their 5L V8 engine.
Here are the downsides. It appears as though these engines are going to be spending more time in the shop than the older port injected engines. Two reasons for this. The first and biggest issue is that the intake valves are no longer being washed by the incoming fuel charge. This leads to deposits on the valves that can lead to poor performance and check engine lights. A few engines are equipped with both GDI and port injection in order to mitigate the problem of fouling intake valves but then you have the issue and expense of two separate injection systems. Some carmakers, including BMW and Kia, have issued technical service bulletins to their dealers recommending that drivers use only top tier detergent gasoline without ethanol additives (Good luck with that) and that they periodically use a fuel-system cleaner.
The second potential problem is the high-pressure fuel pump needed to run GDI. Higher pressure = higher stresses and an increased possibility failure.
It’s unlikely that the problem related to GDI won’t be resolved and resolved fairly soon at that. The advantages are huge, the disadvantages surmountable. With customers demanding better performance along with governments requiring increased fuel efficiency and cleaner burning engines, GDI plus variable valve timing and all the other advancements in gasoline engine design are here to stay.
Your Local Mechanic, All Tune and Lube Total Car Care, Tempe Arizona.