Direct Injection Engine (GDI)

Direct Injection Engine (GDI) vs. Port Fuel Injection

GDI isn’t perfect, but it’s become the technology of choice on many newer models.


Gasoline direct injection (GDI) is a more advanced version of multiport systems, where fuel is injected directly into the combustion chamber instead of the intake port. Direct injection improves combustion efficiency, increases fuel economy and lowers emissions.

Both systems use electronic fuel injectors to spray fuel into the engine, but the difference is where they spray the fuel. With port injection systems, fuel is sprayed into the intake ports.

There are four basic types of fuel-injection systems in use today: throttle body injection, port fuel injection, sequential fuel injection and direct injection. With direct-injection technology, the main benefit is better fuel economy for most applications and a bit more power.

One of the problems with GDI engines stems from small particles of oil/dirt that can blow back from the crankcase ventilation system and deposit onto the walls of the intake port and the back of the valve. Carbon sticks to the valve because fuel doesn’t spray down the back of the valves like in a port-injected system. The buildup can become significant enough that a piece can break off and damage the catalytic converter. It also can cause ignition problems.

Some OEMs are utilizing both port and cylinder injection to reduce the carbon buildup, while other suppliers are working on higher-pressure injection pumps that atomize the fuel better to keep the accumulation to a minimum. But there is no magic-bullet formula to prevent this carbon accumulation.

Direct-injected engines also are afflicted by a condition called low-speed pre-ignition (LSPI). LSPI is an abnormal combustion event caused by higher cylinder pressures common in turbocharged GDI engines running in low-speed, high-torque conditions.

With multiport fuel injection, fuel atomizes as it’s sprayed into the intake port and then is pulled into the combustion chamber. It’s not the most efficient method of mixing and igniting the fuel, but it’s still much more efficient than a carburetor.

New computer technology has enabled manufacturers to switch to GDI to allow more precise control of the combustion event and to achieve lower emissions. However, the small particles that don’t atomize cause hot spots in the combustion chamber. OEMs and the aftermarket are aware of the condition, and even oil manufacturers are working to solve the problem.

A computer that tells the injectors when to spray fuel electronically controls both systems, but the main difference is where each one sprays the fuel. Port injection sprays fuel into the intake ports, where it mixes with the incoming air.

The injectors usually are located in the runners of the intake manifold. When the intake valve opens, the fuel mixture is pulled into the engine cylinder.

With direct injection, the injectors are in the cylinder head and spray fuel directly into the combustion chamber, mixing with the air charge. The intake only supplies air to the combustion chamber with direct injection. GDI is the leading technology today and is only going to improve in the coming years. Port fuel injection still might have a place, but as a secondary player for low-speed conditions.

You May Also Like

MEMA Announces Steering Committee for Sustainability Center

Members of the steering committee will provide guidance and oversight for the center’s leadership.

MEMA, The Vehicle Suppliers Association, announced the members of the steering committee of the Center for Sustainability, launched in January.

Committee members were selected to represent the diverse membership of the organization, covering automotive and commercial vehicle, original equipment and aftermarket, large and small companies, and the remanufacturing community.Members of the steering committee will provide guidance and oversight for the center’s leadership. In addition, they will support the programming that will be developed for the benefit of all member companies in the organization.“We are thrilled to have the commitment of these outstanding industry executives as we take the Center for Sustainability from concept to reality,” said John Chalifoux, chief sustainability officer, MEMA, following the inaugural meeting of the steering committee. “I look forward to working with the committee members who will continue to provide their expertise and a balanced perspective for all MEMA members.”The 10 executives serving on the MEMA Center for Sustainability steering committee are: 

Ball Joints: How Much Play Is Too Much?

There’s a common misconception that any play in a ball joint means it’s
wearing out.

Selling Tools for Underhood Repairs

The category is spread across several vehicle systems, and includes a number of specialty tools.

Charging Ahead: Aftermarket Eyes EV Opportunities

We’ve seen a significant uptick in industry activation surrounding vehicle electrification, in a variety of ways.

DIY Oil Changes

Changing the engine oil and filter is right in the sweet spot for your DIY customers.

Other Posts

Arch Auto Parts Double Footprint of Main Distribution Center

Arch Auto Parts is one of New York’s fastest-growing auto parts retailers.

ASE Winter Registration Deadline March 31

Service professionals registering by the deadline will have 90 days to schedule an appointment to take their ASE tests.

Worldpac Celebrates Opening of New Warehouse in Puerto Rico

The 30,000-square-foot facility has the capacity to house more than 400,000 OE and premium-brand auto parts.

Autel, Repairify Announce Agreement for Remote Diagnostics

Repairify will integrate its remote solutions into a revised version of Autel’s Remote Expert platform.