5 Series E34 525td (M51) TOUR
read off the charge air temperature: it should be the same as ambient temperature. If
the temperature display is not plausible, and if there is no fault in the electrical system,
replace the temperature sensor.
C.
Charge pressure measurement
Charge pressure is measured at two defined engine speed points. The first measuring point
is at 3000 rpm where there is a high and stable charge pressure level. The second
measuring point is at 4000 rpm by which time the pressure release valve on the exhaust
turbo-charger (wastegate valve) must have opened.
If measurements are performed at any other engine speeds, this will give rise to incorrect
diagnoses.
Note:
At excessive engine speeds, the M41 and M51 engines exhibit a slight downwards
trend in their charge pressure characteristics.
Preparation:
-
Check air filter insert for contamination and replace if necessary.
-
Assess performance and exhaust smoke characteristic at top speed on road or rolling-
road test rig
=> there may be no need to perform a charge pressure measurement.
-
Connect an overpressure gauge between the intake air manifold and charge pressure
sensor by inserting a T-piece to the charge air measuring hose. The MoDiC is not
suitable for this measurement because its response characteristics are too slow.
-
Measure charge pressure at full throttle (i.e. accelerator pedal fully depressed) at the
aforementioned inspection speeds in a middle gear.
Measurements conducted while the vehicle is stationary with "the accelerator pedal
depressed" do not provide accurate information due to the inertia of the exhaust turbo-
charger as it comes up to speed. For this reason, under load, maintain the prevailing
engine speed by braking with the left foot for at least 3 secs. with a precision of
+/- 200 rpm.
Nominal values for charge(over)pressure at full throttle for 3000 and
4000 rpm:
M51
105 kW
85 kW
950 - 1150 mbar
750 - 900 mbar
M41
66 kW
1000 - 1250 mbar
If pressure is above or below this level, check:
-
Is the wastegate mechanism jammed?
-
Is there a leak in the wastegate pressure hose (between compressor housing and
wastegate diaphragm)?
-
Is the end float on the wastegate actuating rod too high? (> 0.15 mm)
Important:
The actuating rod on the wastegate valve is pre-set and sealed in the factory and
must not be changed under any circumstances. For this reason, no components can
be obtained for the exhaust turbo-charger. If the seal lacquer is damaged, all warranty
applications will be rejected.
If charge pressure is adjusted beyond the tolerance band as a "tuning"measure, the
DDE issues the fault message "range exceeded." This activates a back-up program
which deliberately reduces fuel injection quantity, thereby reducing engine power. This
entails a risk of damage to the engine.
SI Troubleshooting of air supply and exhaust re-circulation (AGR) M41 M51
BMW AG - TIS
23.01.2013 05:52
Issue status (12/2007) Valid only until next DVD is issued
Copyright
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