Boost trigger

[sebdut]

What is the fonction of the boost trigger wire on an Audi s4 wiring diagram?

If you hook the blue wire up as shown, you can change a jumper on the control board, on the left side, from IDC to MPS. This allows you to trigger the system at a specific boost point instead of an IDC point. For example, you can set the system to start spraying at 5psi, then inject on IDC after. The trip/trigger pot is now used to set the boost point at which you want to inject.

[EvoX612]

Please explain where to adjust, is it the THRES Trimmer?
If yes what is the trigger point in 12 o clock position? Bar or psi value ?

When the MPS is linked, the THRES pot is used to set the boost point at which the system is activated.

The pot works on 0-5V signal and the range of the pot is 12% to 72%, same as the IDC. I don't remember if some of the vacuum range is clipped or not. If not, take the range of your MAP sensor, for example 3 bar, and calculate it over the range of the pot. So if 12 o'clock on the pot is 44%, then it would represent 4.7 psi of boost.

[EvoX612]

Thanks it works! Perfect

[ek9max]

What is it's a 2.5 bar sensor? What position would I want if I want to start spraying at 4psi?

My tuner recommended me an AEM kit and start spraying at 4psi and full at 16psi.

Can you do that on an aquamist?