Gasoline direct injection (GDI) is a fuel injection system that sprays gas, directly into the combustion chamber.
So, gasoline direct injection (GDI) uses a separate fuel injector, for each cylinder.
As a result, this allows for direct access, to the combustion chamber. So, the only thing going through the intake manifold and the intake valves, is air.
Now, with gasoline direct injection (GDI), the fuel enters each cylinder, as a high pressure mist. Then, uses computer controlled electric injectors, to spray fuel into the cylinders.
Consequently, the computer controls, all aspects of the system. So, with all the different running conditions the computer will decide, when to inject the fuel.
The Benefits, Of Gasoline Direct Injection (GDI)
First, you have better fuel economy, with less overall emissions. As a result, this leads to better engine performance.
So, the engine makes more power, and uses less fuel because of:
- Spraying fuel directly into the combustion chamber, as compression is building.
- As well as, during and after initial combustion.
So, these engines can tolerate, extremely lean fuel mixtures. (up to 40:1). Even under light load, and cruise conditions. The net result, is typically (15 to 20) percent better fuel economy.
So, this new system closely controls the fuel mixture, at just the right moment. Also, gasoline direct injection (GDI) can handle higher compression ratios. As a result, they usually produce more power.
The Disadvantages, Of Gasoline Direct Injection (GDI)
So, the big disadvantage of this system, is carbon building up, on the back of the intake valves. This can throw a computer code, and result in an engine misfire or a ignition failure.
Also, the actual cost of this system, tends to be higher. Because, the fuel pump must be capable of very high pressures.
All this has led to the engine, needing to drive the fuel pump. So, the main reason we are seeing vehicles on the market with gasoline direct injection (GDI), is tighter fuel economy standards.
So, Gasoline Direct Injection (GDI) Requires, Extremely High Operating Pressures. (up to 2200 PSI).
This system needs more fuel pressure, to overcome compression pressure, inside the cylinder. As a result, it needs to deliver a higher volume of fuel, in a shorter period of time.
The higher injection pressure also helps, to atomize the fuel into small droplets. So, it will mix better with air, for more complete combustion.
So, How Does Gasoline Direct Injection (GDI) Create New Problems
Along with many new innovations, comes a new set of problems.
First, higher cylinder temperatures and pressures released into the crankcase, accelerate oil vaporization. Eventually this causes oil droplets, to coat the intake valves. Also, with this system fresh fuel, is not sprayed onto the intake valves.
As a result, the valves are no longer cleaned or cooled by the fuel.
Secondly, it can cause piston rings, to become stuck into their lands. And, if the engine uses low tension rings, the sludge can prevent them from properly sealing. As a result, that can cause sludge and fuel deposits, to bake onto the top of the piston.
Since inception, gasoline direct injection (GDI) has had known problems with, carbon building up. One of the problems is cooked fuel deposits building up and fouling the injectors. As the deposits accrue over time and mileage, the timing can also be altered. Carbon building up on the back of the valves, can alter ignition timing, and the firing order.
The carbon also acts as an insulator, so the valves can heat up and fail. Over time, the carbon can fall off the valves and make its way, to the bottom end of the engine. As a result, causing wear on the moving parts.
Carbon deposits may flake off and pass through the combustion chamber, and into the exhaust. So, if the engine is equipped with a turbocharger, there is a chance the carbon could damage the turbine fins in the turbocharger.
The problem tends to be worse in gasoline direct injection (GDI) engines, that are used mostly for short trips. Because, the intake valves never get hot enough, to burn off the deposits.
How To Clean This New (GDI) System
Some of the choices may include:
- Use a chemical cleaner sprayed into the throttle body or intake manifold, directly into the intake ports.
- Remove the intake manifold and spray solvent, directly into the intake ports in the cylinder head.
- For extremely heavy carbon deposits, it may be necessary to remove the cylinder head to clean the valves.
In Summary
So, port injection, is much better than the old carburetors, and throttle body systems. But, just can’t match the power and economy, produced by gasoline direct injection (GDI). As fuel costs increase, the difference in manufacturing cost between port and direct injection systems will diminish. Can’t wait to see what happens next !!
Thank You !!
