Understanding The Differences In PFI and GDI Engines

Understanding The Differences In PFI and GDI Engines

GDI Engine Impact on Fuel Injection Technology.

Gasoline combustion engines have come a long way since Luigi De Cristoforis first invented the carburetor in 1876. However, mixing fuel with air in the carburetor before it entered the combustion chamber was still the main technology being used in gasoline vehicles right through to the 1980s.

It was only in this decade that Original Equipment Manufacturers (OEMs) started the transition from carburetor engines to single point fuel injection to overcome some drivability issues and increasing concern over exhaust emissions. The technology was moving quickly though.

When PFI engines emerged at the end of the 1980s, it was a major leap forward in fuel injection design. It overcame many of the performance issues connected with single point injection and the earlier carburetor engines. In Port Fuel Injection (PFI) or Multi Port Fuel Injection (MPFI) fuel is injected into the intake port of each combustion chamber via a dedicated injector.

What are PFI engines?

PFI engines use a three-way catalytic converter, exhaust sensors, and computer-controlled engine management to constantly adjust the fuel-to-air ratio injected into each cylinder.

Cars with GDI engines and PFI engines are dependent on fuel injection technology. This technology is fast evolving, and compared to the current Gasoline Direct Injection, also known as GDI engine technology, PFI engines are not as fuel efficient or capable of meeting today’s ever more stringent emission standards.

Take a look at our PFI engine diagram here, or if you’d like to find out more, contact us here.

PFI Engine

Copyright 2021. Innospec Inc.

What are GDI engines? 

With a GDI gasoline (petrol) engine, fuel is injected directly into the combustion chamber, not the intake port. The benefit of this system of fuel injection technology is that fuel is used more efficiently. Without the need to pump fuel into the intake port, mechanical and pumping losses are reduced significantly.

In GDI engines, fuel is also injected at higher pressures so that fuel droplet sizes are smaller. Injection pressures are in excess of 100 bar compared to a PFI injection pressure of 3 to 5 bar. Fuel droplet sizes with GDI engines are <20μm compared to a PFI engine droplet size of 120 to 200μm.

Take a look at our GDI engine diagram here, or if you’d like to find out more, contact us here.

GDI Engine

Copyright 2021. Innospec Inc.

As a result, GDI engines deliver a higher power output for the same amount of fuel. Onboard management systems keep the whole process in balance and accurately control regulated emissions. The engine management system fires the injectors at the optimum moment for a specific duration based on the demand and driving conditions at that moment. At the same time, the vehicle computer calculates if the engine is running too rich (too much fuel) or too lean (too little fuel) and immediately adjusts the injector pulse width (IPW) accordingly.

The latest generation of GDI petrol engines are sophisticated machines that operate to very tight tolerances. To deliver improved fuel economy and lower emissions, GDI fuel injection technology uses precision components in a high-pressure environment.

A tip for GDI engine cleaning?
Keeping the injector system clean is critical to engine performance.

Fuel additive chemistry is built on an understanding of how the various kinds of GDI engines and PFI engines work. For many years, Innospec has adapted and developed its fuel additive packages to meet the demands of the latest engine fuel injection technology. Understanding the engineering that underpins different engine designs is key to this process.

We hope this clarifies everything you need to know about PFI engines, GDI engines and fuel injection technology. Don’t hesitate to contact us to find out more. We’ll be happy to help.

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