Technical information on the Toyota D-4S system

[arghx7]

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.

[Dimman]

Awesome. Thanks!

[Sleeperz]

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

[arghx7]

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.

[RRnold]

Thanks arghx7!

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.

[Snoopyalien24]

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

[serialk11r]

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

[Levi]

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

[arghx7]

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



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.

[serialk11r]

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.

[arghx7]

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

[serialk11r]

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]

[Ryephile]

-->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

[arghx7]

I'm only speculating here because the chart is cryptic, but I wouldn't be surprised if they introduce a 2.0 version with the same basic architecture. That 1.8 is going to be underpowered for an A4 type of segment in the North American market.

[Ryephile]

Ok, just FYI the EA888 1.8T's aren't in US VW/Audi's.

I think the EA888 Mk3 will end up being the powerplants for the forthcoming Audi A3 and Golf MKVII, both of which are due next model year. Who knows if we'll get the 1.8T's here, or if they'll make a EA888 Mk3 2.0T for the US market.

Nevertheless, thanks for sharing the technical documents.

[Tradewind]

All I need to know is how to get control of the system so we can boost the engine with some extra air and in turn some fuel

[Tradewind]

Technical info required on injection system

Are the any specs available on total fuel flow per minute per cylinder for the injection system?

[arghx7]

For the 2.0 boxer engine? No. This thread isn't about that engine specifically. It's about the preceding engines. There are D-4S fuel flow specs if you read through the material in the first post.

[arghx7]

Below are charts out of a very recently published study from the Sloan Automotive Laboratory at MIT. The study examines the cooling effects of direct injection under high load operation. The study took a Pontiac Solstice engine (GM LNF, direct injected 2.0 liter turbo) and equipped it with port injectors. Note that the Solstice uses a multi-hole type injector, not a fan-type like the Toyota D-4S system.

The researchers figured out an average combustion chamber pressure trace at a borderline knocking condition using direct injection only and then port injection only. They kept the rpm, spark timing, and intake air temperature constant.




Then they heated up the intake air and tried to figure out how much hotter the intake air has to be for direct injection to have the same borderline knock combustion chamber pressure trace as port injection. The method was used to calculate "effective charge cooling" of direct injection, especially with ethanol fuels.




The charts display the palpable benefits of direct injection in mitigating knock. You don't have nearly as much of the latent heat of vaporization being wasted.

[Dimman]

@Jeff Lange,

Jeff, I'm curious about the injectors of this car. Are the ports and directs the same parts as on the IS350 2GRFSE?

Reason being that the fueling situation sounds different in this:

Originally Posted by JP

And the Toyota Techinfo doc on the SFI system:
http://www.purcellperformance.com/Te...13%20FR-S).pdf

Than it does in an earlier press release for the IS350: (attached .pdf)

This is a 2nd gen application of the D4-S from what I've heard, and the FA20 sounds like it needs port to supplement the direct at high load/rpm, whereas the 2GRFSE didn't, relying only on direct.

2GRFSE direct injectors may be a higher flow? Possible upgrade?

Thanks,
D

[arghx7]

Here's the chart in question:



At very high rpm the most important thing they are going to do is try and keep the exhaust manifold and especially the cat from overheating. By overheating, I mean exceeding some target temperature--most likely a max catalyst temperature of 900C. It was probably easiest and cheapest to spray the port injectors, after performing tests to verify that there wouldn't be some kind of bad side effect from this strategy.

You have to be careful not to think of a direct injector like it's just a port injector mounted spraying into the cylinder. It's not. It's more complicated than that, because of the shorter time for mixture formation and because fuel pressure is variable. Direct injection tuning/calibration on a modern engine is exponentially more complicated than fuel injection tuning back in the days of say the 2JZ.

Generally speaking a port injection system relies on a constant pressure differential between the fuel and the intake manifold. On the early multi-port injectors, it was about 2.5 bar. Then it went to 3, and 4, maybe up to 5 bar. This pressure differential could be controlled mostly mechanically by a fuel pressure regulator on/near the rail, as in a conventional return fuel system like Mark IV Supra 2JZ engine. For discussion's sake, fuel is solely controlled through injector "ON" time on a 2JZ.

Fuel could also be controlled through an in-tank regulator with injector pulsewidth corrections, as in a conventional returnless system. In both situations, the fuel pressure isn't a major determinent of injector mass flow except in the sense that the injectors run right around whatever base pressure the system was designed for.

With direct injection it's different, in part because you have shorter crank angle duration for mixture formation. Instead of having many crank angle degrees for the fuel to vaporize on the back of a valve (like typical closed-valve port injection), you have a narrow crank angle window. Maximum injector pulsewidth is therefore limited. To increase fuel delivery and appropriately size the injectors, you may have to increase fuel pressure. Since it's a mechanical fuel pump, there could be significant energy consumption involved in that.

The calibration engineers may have decided that they didn't want to crank up the fuel pressure at very high rpm because of energy losses. It could have been easier to just spray the port injectors and then verify that doing this doesn't cause some other kind of problem.

What I'm trying to say here is, it's a bit premature to call the direct injectors "maxed out."