RS4 15 amp Fuse #9 removed: Brake servo (vacuum pump)

[mid-life RS4]

Recently purchased a 2008 RS4 and noticed today that Fuse #9 has been removed. The brakes work fine but now I wonder why this is missing and what are the downsides?

Hopefully somebody can educate me?

Cheers

[mid-life RS4]

I found a schematic on line but unfortunately can't paste the picture in. From what I see, if Fuse #9 (Brake Servo) is pulled from the fuse box then multiple items would not get power. My brakes work fine but I wonder why this fuse was pulled and things seem to work OK?

• Brake System vacuum Pump V192
• Brake Servo
• Brake Booster Relay J569
• Brake Booster Pressure Sensor G294 with Non-return Valve
• Secondary Air Injection (AIR) Solenoid Valve N112

Audi RS4 Vacuum Hoses
The conventional method of supplying vacuum to the brake servo and the engine components is problematic in
the case of FSI engines. This means that connecting a vacuum line downstream of the throttle valve would not supply the needed vacuum. This is due to the fact that in many engine operating situations, the wide open throttle valve would
result in low mass flow rates and vacuum in the intake manifold. For this reason, in both engine versions, the required
vacuum is produced by a suction jet pump and, if necessary, additionally by an electrical vacuum pump. The suction jet pump is connected in parallel with the throttle valve part upstream and downstream of the throttle valve. The branched air flow drives the suction jet pump. An extreme case is that of cold starting. For example, when the catalytic converter is heating up, the throttle valve is wide open. In this case, the vacuum produced by the suction jet pump is not enough to sufficiently evacuate the brake servo. The Brake Booster Pressure Sensor G294 is connected to the line to the brake booster and transmits its values to the Engine Control Module J623 (ECM). In the ECM (map controlled), the Brake Booster Relay J569 and the Brake System Vacuum Pump V192 are activated until the required vacuum is present.

[koolade9]

FWIW, I removed that booster pump along with the SAI and didn't have any issues. Granted I may not have seen that certain combination of conditions. Didn't cause any problems on the track though.

[mid-life RS4]

Hi koolade9 and thanks for your feedback. If you get a chance, please let me know if your fuse box has the #9 fuse installed or not.

Cheers and HNY