Here is some info on BMW diesel engines.
Swirl flaps.
Swirl flaps are designed to create swirl or tumble of the air to aid better combustion under light load where soot levels tend to be dominant because of the lack of air, they are also there to help with driveability in low load conditions, they are controlled by a vacuum or solenoid actuator and are closed during light-load operations such as when idling at traffic lights, changing gear and deceleration to maximise combustion efficiency, fuel economy and emissions performance. The flaps are fully open during higher load conditions to maximise volumetric efficiency and power output.(more info below)
Swirl flap control DDE 4.0
The controllable swirl flaps are located in the intake pipe and are closed or opened depending on the operating status. The flaps are closed at engine speeds below approx 2000 rpm and injection volume below 30 mm^3.
Function.
The pressure converter connects the vacuum unit with the vacuum supply by means of hoses. When activated by the DDE control unit, the changeover valve switches vacuum to the vacuum unit thus operating the control rod and closing the swirl flaps. The control rod is up against the rear stop when the swirl flaps are open.
Troubleshooting.
Fault code 1A22 "Swirl flaps" is stored if a defect occurs in the activation of the pressure converter.
Effects of faults.
Swirl flaps stick in open position: Deterioration in exhaust gas characteristics in lower speed ranges otherwise no effect.
Swirl flaps stick in closed position: Power loss of approx. 10 % at higher engine speeds.
Electrical swirl flaps DDE5.0/DDE6.3
The adjustable swirl flaps are located in the tangential channels of the intake system and are opened and closed according to the operating status of the engine. The swirl flaps are closed under the following conditions:
at low engine speeds and low injection volumes (map-controlled)
The swirl flaps generally open when
the coolant temperature < 14 °C OR
the amount of fuel > 24 mg OR
engine speed > 2250 rpm OR
the intake temperature < -5 °C.
Function.
In the case of the M57 TU with exhaust emission stage EURO 4 and the M67 TU, an electric motor activates the control rod to close the swirl flaps, the swirl flaps are sealed when closed in the tangential ducts with rubber gaskets. The control rod is up against the rear stop when the swirl flaps are open.
Effects of faults.
If the swirl flaps stick in open position: Deterioration in exhaust gas characteristics in lower speed ranges otherwise no effect.
If the swirl flaps stick in closed position: Loss in power output of approx. 10 % at higher engine speeds, danger of engine overheating.
With no Vacuum applied the flaps are open, so if the vacuum system / solenoid fails the flaps are open.
Swirl flap failure.
Swirl flap failure being reported on BMW diesel engines including later models, less than 10000 miles reported.
When the swirl flaps fail they usually break through the metal shaft where the screw/rivet goes through, these then drops into the inlet port and either jam the valve open and the piston smashes against the valve or they drop into the engine, this can cause the piston bore to become badly scored and the piston top can be damaged from the parts embedding themselves in the piston, it's also known that parts can go back up through the open valve and into another cylinder.
BMW have made the spindle stronger by using 4.5mm rod instead of 4mm rod, as found on around April 2004 manifolds.
Video of broken swirl flap
Engine Info.
M47 engines(136bhp non common rail vp44 injection pump) have no swirl flaps and the turbos last alot longer,
M47N common rail engine(150bhp face lift model August-September 2001 onwards) has flaps and turbo that fails, in late 2004 the manifold was uprated, part number 11617800577 on box and Realoem, old part number on manifold is 11617787318, New design turbo fitted around November 2003 due to common failure of earlier ones on e46 4 cylinder engines.
M57 engines(M57D)(525d & 187bhp 330d) have no swirl flaps on the manual cars BUT AUTOMATICS do.
M57N engines(M57TUD)(525d & 330d 204bhp) have swirl flaps.
Turbo.
There are 2 types of turbochargers for the 320d - a version fitted before 12/2003 with a cast turbine impeller and the later type fitted with a machined impeller, the later ones seems to take the heat and stress much better and fail less.
The newer 320d(EU4) and later models turbo waste gates are electrically operated where as the older ones are vacuum operated up to end 2003 so they are not interchangeable, due to the different operation lots of other parts would need to be changed including software.
Oil separator.
To prolong turbo life the oil breather should be replaced with the new plastic "vortex" type, the old version is a foam filter that resembles a mini paint roller, it's recommended every 3rd or 4th service the new filter is cleaned or replaced, the filter can be found on top of the cylinder head cover(cam cover) under a plastic top that's held down by 4 bolts.
EGR.
The EGR valves can have a restrictor installed, it needs to be no smaller than a 7mm hole otherwise it will flag up a fault light on later models, this feeds enough exhaust gas and seems to keep things cleaner and can help with performance, the downside is the EGR actually reduces the combustion temperature so disconnecting it completely or even restricting it may have consequences later on(premature turbo failure)
Maintenance.
(Owners recommendations)
Oil & Filter recommended every 10k miles(6000-6500 miles)
Oil Breather recommended every 20k miles (12000-13000 miles)
Clean EGR recommended every 20k miles (12000-13000 miles)
These shorter intervals should help prolong the life of your engine and parts.
Fuel system.
The 150bhp diesels are self bleeding, the fuel pump relay is green and lives behind the glovebox, it's the third one over from the left and is common for failing.
The lift pump in the tank keeps the fuel level equal in both halves of the tank and the fuel line full.
The pre-supply pump lives under the passenger floor and when you turn on the ignition if it's working OK you will hear a slight hum for about 30 seconds.
(info courtesy from Tefal at bimmerforums.co.uk
LINK )
