Ford Motor Company calls its direct injection system “EcoBoost.” General Motors uses the term “Ecotec.” The Maza term is “DISI.” Volkswagen prefers “GDI.” Makers of direct ignition engines try to increase power and fuel economy while reducing emissions.
Direct injection systems use precise control of the volume and delivery timing of fuel. These systems spray precise amounts of fuel under extremely high pressure directly into the combustion chamber. pPrevious types of fuel injection systems were different. Fuel was delivered “upstream” of the engine’s intake valve. Because, with direct infection, fuel sprays directly into the combustion chamber at various points in the cycle, and it can be delivered whether the intake valve is open or not.
Previous types of fuel injection, throttle body and multi-port, for example, mixed fuel with air before it entered the combustion chamber. The goal in all circumstances was to achieve an air/fuel ratio of 14.7-1. (Nerds and technicians call this “the stoichiometric air fuel ratio” which, by definition, is the ratio of air and fuel required to produce a chemically complete combustion event.)
A companion technology is variable valve timing. With variable valve timing, an engine’s intake and exhaust valves open and close at different points of the camshaft’s rotation. In engines without variable valve timing, valves always open and close at the same point in the crankshaft rotation. With variable valve timing, a vehicle’s electronic ignition control operates in one of three different combustion modes: ultra lean burn, stoichiometric, or full power, depending on required load. Amazingly, some vehicles in the ultra-lean mode can use air/fuel ratios as high as 65:1 for brief periods.
The downside of direct injection engines is soot buildup. When fuel sprays injected directly into the combustion chamber, there is no fuel to clean the intake valves. EGR systems introduce exhaust gas into the intake manifold upstream of the combustion chamber to reduce combustion temperature. Unfortunately, the re-circulated exhaust gas contains small amounts of soot, a by-product of combustion. Soot builds up in the intake valves, on the intake valve stems, on top of the pistons, and on the cylinder walls. With older systems where fuel was introduced above the intake valves, the fuel would help remove carbon deposits. With direct injection, fuel no longer flows over the intake valves. Carbon buildup resulst. Because direct injection system deliver a precise amount of fuel, there is not enough excess fuel to wash a vehicle’s cylinder walls. Carbon buildups up there and on top of the pistons. Carbon buildup will rob performance. In severe cases, carbon deposits can break off and ruin catalytic converters.
“How do I prevent carbon buildup in my direct injection engine,”you ask? Thanks for asking. The best way to avoid carbon buildup is to maintain proper oil change intervals. Also, change air filters and PCV valves as needed. Use high quality fuel with the octane rating suggested by your vehicle’s manufacturer. Be sure to use the correct viscosity motor oil.
The best way to remove any carbon buildup in your fuel system is to have an induction service performed. Sant Automotive utilizes a three step system to perform this service. One chemical is atomized and sprayed through the air intake, usually through the throttle body. This process cleans the throttle body, air intake, and the intake valves, and intake valve stems. Then, it enters the combustion chamber. Once the chemical has entered the combustion chamber, it cleans the cylinder walls and the top of the pistons. It is then expelled out the exhaust valves which it cleans en route to the catalytic converter which can benefit from cleaning as well. This is one hard working chemical.
Introducing a second chemical through the fuel system cleans the high pressure fuel pump, fuel rails, and fuel injectors are cleaned. Adding a detergent to the engine oil completes the process. The detergent cleans the cylinder walls that were not cleaned by the other two chemicals. Additionally, the detergent helps remove carbon, dirt, and debris from all lubricated areas of the engine.
Direct injection technology holds the promise to increase fuel economy and help the environment, but there are still some drawback. Enjoy the increased performance and fuel economy, but be aware of the maintenance needs.
If you have any questions, please call Sant Automotive at 314-849-2900.