Greetings,

In the stock S5, is the VDI either fully open or fully closed - or does it smoothly start opening at 5200rpm, and become fully opened at some other rpm? I have the same question with the aux ports; are they fully open above 3600rpm and fully close below, or is the opening smooth over some range?

I have what might be an answer for the aux ports, according the S5 FSM:
begin opening at 0.85psi
fully opened at 1.4psi

Do the actuators actually see a range of psi like that, or is that range only for testing? If this is their operating range, what does that equate to in RPM?

As for the VDI, the FSM says:
fully opened at 2.8psi

But, does it ever see anything below 2.8psi? What does that mean for rpms?

Thanks!

 

On a S5, the air pump pressure is about 3-4 psi at around 4000 rpm, so regardless of when the ECU activates the solenoids for the aux ports or the VDI, the valves pop right open.

 

Interesting, so both the aux and VDI ports are either on or off. I wonder if there would be any benefit to a gradual opening. With the way the aux sleeves rotate to uncover their ports, I'm curious if the power band through the transition could be made more smooth - i.e. if the port starts opening at 3400 and is fully opened by 3800, the lower end of the transition could benefit from a bit more port, while the high end of the range would see the full port opening.

I guess the VDI wouldn't benefit from gradual opening, because the runner lengths don't change.

 

On the S4 models, they do open slowly. I am assuming that there is better control activating them through the air pump, that they changed that on the S5 models and FE

 

Thanks icemark, check your PM!