Checking Basic Boost Pressure on the Road
Checking basic boost pressure on the roadTool: Pressure gauge 83 93 514
Important: The engine should be thoroughly warmed up.
1 Mount the pressure gauge vertically to avoid erroneous readings.
2 Connect the pressure gauge hose to the intake manifold.
Important:
The starting point for this check is on cars with a manual gearbox:
3rd gear and engine speed below 1500 rpm
On cars with automatic transmission:
Selector lever in position 2.
3 Manual gearbox:
Accelerate with wide open throttle.
Automatic transmision:
Accelerate with wide open throttle. Depress the accelerator to just before the kickdown point.
4 Make a note of the pressure gauge reading just before 3000 rpm because the ignition is retarded above 3000 rpm on certain versions and this lowers the boost pressure. When engine speed approaches 3000 rpm, depress the brake pedal while holding the accelerator depressed so that full engine load is obtained at 3000 rpm. Note the basic boost pressure reading on the pressure gauge.
For the correct basic boost pressure, see "Specification".
Important:
Basic boost pressure is the starting point for the APC system's pressure control function and directly affects the boost pressure level, that is to say engine performance, which is attained when the APC system is engaged.
Through the adaptive function incorporated in the DI/APC system, continuous compensation of the maximal boost pressure in relation to the prevailing basic boost pressure takes place. Increasing the basic boost pressure above that recommended could damage the engine. Maximal boost pressure, which gives the right engine power, is controlled by the DI/APC system.
5 It the basic pressure is outside the tolerance limits, see "Adjusting basic boost pressure". Adjustments
6 Remove the pressure gauge.
7 Carry out adaptation as described under"Adaptation".
Important:
Checking boost pressure by driving the car on the road must be carried out as quickly as possible (in about 3-5 seconds) to avoid abnormally high brake pad temperatures.
Drive the car at least 1 km between readings and after finishing the test so that the brake pads have time to cool down.