The throttle isn't used at all actually, it's only used if the valvetronic system fails. It's a fail safe to prevent the engine from going out of control.

In theory, throttle response should be better, because there's no volume between the throttle and cylinders. But I suspect they programmed the ECU to ignore quick throttle inputs so people don't crash themselves or something.

Diesels do it... The new common rail diesels inject fuel into the combustion chamber at full compression under loads of up to 50,000 psi. Gasoline engines do it at less than 3,000 psi because Gasoline motors don't use the introduction of fuel to initiate combustion like a diesel does. We still use spark plugs. That is because diesel is a more stable fuel...

Now as far as tuning goes I would like to add another topic for discussion... I'll start with my "hypothesis" as it were... the D-4S system is going to be epic for Ethanol and forced induction here is why...

In my engine, direct injection only, it is very difficult to control fuel delivery under boost at WOT through the mid range. Take a look at the attachments I have include, they deal with Ethanol fueling. Due to ethanol's properties it is difficult for the HPFP of my motor to keep up. The D-S4 engine should be able to take care of any fuel issues because it has secondary port injectors. If the ECU can be unlocked, and a turbo added... the possibilities are quite extraordinary.

On the log pick titled e85logpic2 you see the desired fuel pressure vs. actual in the second row of figures blue (FP Des psi)and orange (FP Rail psi) graph lines. Notice the RPM, 4400, just after at initial tip in on a 3rd gear pull 60-100mph. With the port injection You could run alot more fuel and use Ethanol more effectively. Oh by the way due to the efficiency of airflow, I have to mix my E85 with 91 octane at a ratio of 50/50. I would not be able to feed the motor with even close to enough fuel with straight E85. That is the downfall of direct injection, bigger injectors are big bux and hard to come by. With the port system on here, the extra fuel will just get thrown in, no problem.

On e85logpic1 you can see how, on the same pull, the fuel easily catches up in the upper ranges. This is due in large part to the cam driven HPFP that is used in my car. Other DI systems may or may not run into this problem, just something to think about I guess.

just want to bring this back to light as we know more about the engine and cars are being delivered soon.

Sorry if I missed something. Could you explain this? What more do we know?

Many thanks. :)

Holy necro batman! He was referring to knowing about the D4S system after the first batches of cars were delivered... in 2012.

I think they were debating if the D4S system was superior or necessary and not just designed to clean off the direct injectors, so they don’t build up carbon. The implication was that a catch can or air/oil separator would be better and easier than a complex direct and port system.

For some reason, I got a thread subscription update notice in my e-mail today. But I didn't notice the date on the post. I assumed this thread was active today.