I would like to present here in-depth technical information on the Toyota gasoline direct injection (GDI) systems up through the development of the 2GR-FSE engine found in the Lexus IS350. I am dividing literature on the D-4/D-4S system into four sections, corresponding with what I feel are four different eras in Toyota's development of direct injection.
Note: These files may not always be available, so save your own copy.
Early D-4 System w/ lean stratified charge & swirl injector
This is the earliest production Toyota GDI engine. The combustion concept relied on a swirl control valve and helical intake port to create a stratified mixture.
1AZ-FSE engine with swirl control valve and swirl injectors
D-4 System New Combustion Process w/ lean stratified charge & fan injector
The fan-type injector and shell-shaped piston crown were first developed here, but they were optimized for a lean burn stratified charge combustion concept that the industry has mostly abandoned today.
Development of combustion system with fan injector and shell piston cavity
2JZ-FSE engine with "New Combustion Process"
Fan injector for 2JZ-FSE engine
Detailed specifications on a Fan injector
Late D-4 System w/ stoichiometric homogenous charge operation
This is a transition period in the Toyota GDI systems. This type of engine continues to use a single fan-type injector and shell-shaped piston crown but with variable cam phasers on both the intake and exhaust side. Now the combustion concept is oriented toward stoichiometric air-fuel ratio and homogenous mixture instead of lean stratified charge. Stratified charge is used only during warm up. Around that time the rest of the industry moved in the same basic direction (homogenous, stoichiometric, but stratified warmup), most likely because this combustion concept is easier for meeting tight NOx emissions standards.
Lexus GS300 3GR-FSE engine
Emissions Reduction of 3GR-FSE engine
D-4S System w/ stoichiometric simultaneous port and direct injection
This is the immediate progenitor of the 4 cylinder D-4S boxer engine used in the FR-S/BRZ. Building on the combustion system of the 3GR-FSE engine, this motor uses simultaneous port fuel injection (PFI) and GDI injectors that utilize a dual fan spray. The simultaneous injection during warmup and at certain load points allows improved combustion stability without requiring a restrictive intake port design that increases tumble flow.
Lexus IS350 2GR-FSE engine
At the time of writing these are the most comprehensive documents we have on the development of Toyota's direct injection combustion systems. Hopefully the dissemination of this information will help improve understanding and speed up the process of developing parts for the FR-S/BRZ and any other platform that utilizes this system.
Types of GDI Injectors
For reference purposes, here are the major types of GDI injectors in use. The first and oldest type is the swirl-type solenoid injector:
It has a cone-shaped spray pattern and is side-mounted in the combustion chamber. The early Toyota D-4 system used a swirl injector as well as a lot of other 1st generation GDI designs. I believe the Mazda MZR engine in the Speed3/Speed6/Cx-7 uses this design. Manufacturers have mostly abandoned this design on the latest generation of mass produced GDI engines. The newer injector designs promote better mixing in the combustion chamber.
Next up is the center-mounted (next to spark plug) BMW piezoelectric injector:
This type of combustion system uses a more expensive, higher pressure, and more responsive injector. It does not depend on charge motion (swirl, tumble) for mixture formation. The next type of injector, the multi-hole solenoid type is by far the most common on the latest generation of GDI engines:
Note that the above two images show a 6-hole injector. Many variations of multi-hole injectors are used in production engines, with different numbers of holes and spray patterns. Ford, Hyundai, GM, VW, and others use some kind of multi-hole injector on their current GDI engines. Finally we have the fan-type solenoid injectors used in Toyota GDI systems. Here is the earlier type with a single spray:
Finally, here is the dual fan-spray type used on the 2GR-FSE Lexus IS350 engine, which uses the D-4S system:
You can see that the injectors used in the D-4S 2GR-FSE engines are significantly different from basically everything else out there right now.