05: GDI vs PFI (Pros and Cons)

Let’s discuss GDI vs PFI…

What’s all this GDI magic introduced to us petrolheads? Why would/should I even bother looking at this stuf? Why would I even want to fiddle around with it?

These questions and more we aim to answer with the next few posts. Why? Because we, VPR-Engineering, care for the latest in tech and how we can make it faster!

Check out this youtube clip by EngineeringExplained about the topic, or click below. Do bear in mind that we don’t agree with all of EngineeringExplained’s youtube-content, in fact… a bunch of it is simply wrong.

Little side-note concerning GDI, there are two types of injectors, Solenoid or Piezo. This is why we offer the Delta Solenoid and the Delta Piezo IDMs, which allows us to drive either injector type.

Further to the nice clip, by EngineeringExplained, explaining some basic differences between PFI and GDI.

Here are some more pros and cons:

  1. Pro, GDI: Higher VE (trapped air mass) possible with GDI, due to the fuel vaporisation not occurring in the intake runner, but partly after the intake valve has closed. One of the major downsides of PFI is that it effectively decreases VE.
  2. Con, GDI: Currently there are not many “uprated” DI-injectors on the market. There are a few allowing DI-platforms to have enough fuel delivery up to 150 HP/cylinder.
  3. Pro, PFI: Virtually every aftermarket ECU can drive PFI injectors.
  4. Con, PFI: Relatively inaccurate in terms of fuel dosage delivery.
  5. Con, PFI: requires fuel film modelling/transient fueling.
  6. Pro, GDI: doesn’t require fuel film modelling/ transient fueling except for temp corrections.
  7. Pro, GDI: can quench knock with fuel.
  8. Pro, GDI: Cold starting is a lot easier.

These are just some of the Pros and Cons. We’re not even talking about converting a GDI engine to PFI, which would be┬ástaggering in terms of costs as a lot of parts would have to be custom built in order to mount the PFI-injectors, fuel rail and other required parts.

If one would require more fuel than 150 HP/cylinder, we would advise maintaining the GDI and adding additional injectors in the charge pipes for example. This would be a lot cheaper and just as effective.