Boost Pressure Regulation, Checking

Charge Pressure Regulation, Checking

Recommended special tools and equipment e.g.:




- V.A.G 1397 A Turbocharger Tester

Test requirements
- No leaks on intake or exhaust side.
- Coolant temperature must be at least 80°C

Test sequence
Charge pressure is measured under Wide Open Throttle (WOT) while driving or on the roller type test stand.






- Disconnect connection hose between intake manifold and deceleration shut-off valve at intake manifold and connect to T-piece of VAG1397A turbocharger tester.
- Switch on measurement range 1.

NOTE:
Using turbocharger tester, see operating instructions.
The hoses must be connected absolutely free of leaks.
When charge pressure is measured during the drive, a second person is necessary to operate the turbocharger tester for safety reasons.
Make sure that the pressure hose is not pinched between engine hood and chassis.

- Measure charge pressure at Wide Open Throttle (WOT):

On dynamometer
In 3rd gear or in 2nd drive mode

While driving

Vehicles with manual transmission
- Accelerate vehicle at Wide Open Throttle (WOT) in 2nd gear

Vehicles with automatic transmission
- Manually (Tiptronic) shift vehicle in 4th gear and accelerate vehicle from low speed at Wide Open Throttle (without kick down, transmission does not downshift any more).
- Between 1800 to 2300 RPM, press the "M" memory button on turbocharger tester and read out the test value.
Specified value: (absolute pressure) 1.350 to 1.750 bar

NOTE: Repeat measurement if full charge pressure has not yet built up.

If boost pressure is exceeded:
- Check Wastegate Bypass Regulator Valve -N75-. (Throughput in hose from turbocharger via valve to vacuum diaphragm with connector disconnected).
- Check for proper seating of vacuum diaphragm for wastegate bypass regulator valve at turbocharger.
- Check vacuum diaphragm.
- Check bearing for shaft of wastegate bypass regulator valve in turbocharger for ease of movement. If rusted solid, replace turbocharger.
- Replace turbocharger

If charge pressure is not reached:
- Check Wastegate Bypass Regulator Valve -N75-.
- Check bearing for shaft of wastegate bypass regulator valve in turbocharger for ease of movement. If rusted solid, replace turbocharger.

- Turbocharger faulty, replace.