Technical information on the Toyota D-4S system
 

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:

http://www.ft86club.com/forums/attac...1&d=1326102067

http://www.ft86club.com/forums/attac...1&d=1326102067

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:

http://www.ft86club.com/forums/attac...1&d=1326102067

http://www.ft86club.com/forums/attac...1&d=1326102067

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:

http://www.ft86club.com/forums/attac...1&d=1326102067

http://www.ft86club.com/forums/attac...1&d=1326102067

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:

http://www.ft86club.com/forums/attac...1&d=1326102067

http://www.ft86club.com/forums/attac...1&d=1326102067

Finally, here is the dual fan-spray type used on the 2GR-FSE Lexus IS350 engine, which uses the D-4S system:

http://www.ft86club.com/forums/attac...1&d=1326102800

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.

Awesome. Thanks!

Is premium 91 or 94 mandatory or can regular gas be used?

well, premium is hardly ever "mandatory" on an unmodified modern engine in the sense that you probably won't do any long term damage from using regular 87 AKI fuel. Subaru EJ255/257 turbo engines don't take kindly to regular gas. That being said, some GDI engines were specifically intended to run ok on regular fuel like the Ford Ecoboost.

Premium is recommended/required for the Toyota GR series GDI engines and I wouldn't be surprised if the FR-S/BRZ engine also requires it. You would probably be noticeably down on power and fuel economy if you didn't use it.

Thanks arghx7! :happy0180::happy0180::happy0180:

Giving the high compression, premium would probably be the recommended gas. Even my Tacoma "requires" premium b/c of the VVTi but with most cars, you can go with lower octane since there are knock sensors. I could feel the difference on my truck when I switch to 89.

So all in all, Should I use 93 or 91? (depends where I go)

In California they don't even sell 93 a lot of the time, so I imagine 91 should be okay?

You can use any. Here in EU we have the choice between E110, 95 and 98.

So Volkswagen is adopting the combined GDI + PFI combustion concept in their new 1.8T

http://www.ft86club.com/forums/attac...1&d=1327718874

It uses multi-hole injectors instead of dual fan-type sprays. You'll also notice that it has a tumble control valve. The port injectors are not used during warm up, but rather the direct injectors fire two to three times per cycle depending on coolant temperature. This engine is boosted and not optimized for high rpm operation.

So they got rid of stratified injection for NOx emissions it seems...sounds like VW group's fuel economy is going to take a hit.

I wasn't aware of any VW stratified charge engines in the North American markets. The 2.0T isn't.

Oh wait really? I remember spending a lot of time looking around because I had trouble believing that VW had stratified charge engines in NA. They advertise "FSI" and "TFSI" and all. I don't think I found conclusive evidence though.

-->arghx7: Do you know when the new VW 1.8T will hit the market...and will it be replacing the current 2.0T TSI? It's fascinating they're following Toyota's footsteps with port & DI