That all sounds great right? While this technology is becoming more and more common in performance vehicles giving us a number of benefits, it also has several drawbacks. The injectors are more expensive than PI injectors, because of the materials that are designed to withstand the heat and pressure inside of a motor during the combustion cycle, and fuel components such as fuel lines, and pumps have to be able to hold and deliver fuel at higher pressures. The last drawback that is often overlooked is the added maintenance which is required for vehicles with Direct Injection, called carbon cleaning.
Since Direct Injection motors have the fuel being injected directly into the cylinder, fuel doesn’t flow over the vehicles valves. This means that deposits can settle on the back of the valves and over time will build up causing issues with the valves being able to seal properly, turbulent the air coming into the cylinder, in turn, causing issues with air/fuel ratios, rough idling, cold start issues, and misfires if the carbon buildup is bad enough. This is a service that requires you to remove the intake manifold to gain access to the intake valves for cleaning. Depending on the vehicle and driving conditions the car could require carbon cleaning every 30k-60k miles.
These pictures for example are from a Mazdaspeed3 we had with a little over 30,000 miles that was being used for testing. Prior to valve cleaning we had noticed on the dyno that this vehicle was unable to reach timing levels that we knew from previous experience were attainable on the vehicle, so it was losing power. Post valve cleaning we immediately saw the vehicle have a better idle and the vehicle was making less fueling corrections.