Tried searching for this subject for a while and didn't find it so I got a couple of questions about boost gauges. First one is, is the stock boost gauge on the S4 TII mechanical or electronic? I plan on upgrading my exhaust and since I'll need to use a FCD I know my gauge will be lying about what it will read since I wil be lying to my car . So the second question is I plan on getting a GReddy boost gauge, but don't know which to get, electronic or mechanical Which would be easier to install, or could I only use one type instead of either? Thanks for your time sorry for the barrage of questions.

 

Stock is electric and receives the signal from the boost sensor. I believe the mechanical is a little quicker to respond, and both similar in installation, either running a hose to the gauge, or running wiring with a sender installed under the hood.
Choice is yours.

 

More specifically:
The stock dash gauge gets is electrical signal from the ECU which interprets the signal from the pressure sensor.
The pressure sensor has a restrictor pill in the line, so it’s not as quick to respond as a mechanical gauge with a line straight off the LIM.

As the dash ages, the electrical connections to the gauge get weak, so the dash gauge will sometimes will be inaccurate.
In my experience, the pressure sensor has always worked perfectly.

 

*******The stock dash gauge gets is electrical signal from the ECU which interprets the signal from the pressure sensor.**********

Sorry, not so at all. There is a splice in the brown/red wire from the boost sensor, and that spliced wire goes to plug X-15 (FEM-01 on 88) and goes to the boost gauge. The ground for the boost gauge on a BL wire back to X-15 where it interfaces with the brown/black common ground for all the sensors in the engine bay.

You can unplug the brown/red wire at the ECU (pin 2B) and the boost gauge will work as well as it did before extracting the wire from 2B.

See page Bb-2 of the 87FSM (the GOOD FSM).

 

[QUOTE=HAILERS There is a splice in the brown/red wire from the boost sensor, and that spliced wire goes to plug X-15 (FEM-01 on 88) and goes to the boost gauge. The ground for the boost gauge on a BL wire back to X-15 where it interfaces with the brown/black common ground for all the sensors in the engine bay.
You can unplug the brown/red wire at the ECU (pin 2B) and the boost gauge will work as well as it did before extracting the wire from 2B.

See page Bb-2 of the 87FSM (the GOOD FSM).[/QUOTE]

You are correct.
I see it now, it's also in the JPG of the S5 turbo ECU wiring diagram.
The S5 fuel & emissions sections skips that detail.

Anyway, you can trust the pressure sensor, but not always the dash gauge.

 

Thanks for all the help guys. I think for simplicity, I'll go with the mechanical type.