which makes the fuel-air mixture somewhat coolerChecked 2026-08-12
Gasoline direct injection (GDI)
A fuel system that sprays petrol straight into the cylinder instead of into the intake port.
Also called: GDI · direct injection · DI · TSI · SkyActiv-G
What it means
Definition
In direct injection, high-pressure injectors spray fuel into the combustion chamber itself rather than into the port ahead of the intake valve. The DOE notes that injecting into the cylinder makes the fuel-air mixture somewhat cooler. Direct injection describes fuel delivery only — it is a separate thing from turbocharging, though the two are frequently combined.
Why a buyer cares
What it changes
Because the fuel never passes over the back of the intake valve, that surface is no longer washed by fuel. SAE research treats the resulting valve deposits as a property of the design rather than evidence of neglect.
In practice
Where you meet it
In the engine line of a listing or window sticker, written as GDI, DI, TSI or a brand name, and on invoices mentioning intake cleaning.
Two things that look alike
Not the same as
A turbocharger forces air in; direct injection changes where fuel goes. An engine can have either, both or neither.
Read next
Related terms
Port fuel injection (PFI)
A fuel system that sprays petrol into the intake port, upstream of the cylinder.
Intake valve carbon buildup
Deposits that accumulate on the back of the intake valves, most associated with direct-injection engines.
Turbocharger
An exhaust-driven compressor that forces extra air into the engine.
Where it shows up
Related problem files
Where this comes from
Sources
The DOE sentence is a clause within a longer sentence. No OE injection-system maker page with a quotable GDI definition was confirmed.