2.8 M52TUB28 Vanos Rev Changeover Point

[Disca]

Something I have always wanted to know but cannot find anywhere so figured why not ask someone who may know!

At what rev points do the vanos switch over on the TU 2.8?
I would have to hazard a guess that one is around 3.5k because my car starts pulling like a train then.
I could be wrong though, just a useless fact I would like to know about the car

 

[NZ00Z3]

The twin VANOS on a M52TU is infinitely variable all of the time. The single VANOS M52 engine switches the VANOS at about 3,500 rpm.

If you have a M52TU engine, then you are detecting the switching of the DISA valve and yes you have correctly identified the switching point at about 3,500 rpm. The DISA valve changes the length of the inlet manifolds. There is a lot of air flow engineering that goes into the manifold design.

Have you replaced your twin VANOS seals? Usually needed if you have >80,000 miles on the clock.

 

[Disca]

Oh thats interesting!
So I presume the VANOS adjust depending upon what is going on within the engine to maintain optimum performance?
As far as I know the VANOS seals have not been changed on the car, the trail of paperwork from the previous owner is very extensive but does not mention their replacement.
I may have to look into doing so!

 

[Brian H]

The twin VANOS on a M52TU is infinitely variable all of the time. The single VANOS M52 engine switches the VANOS at about 3,500 rpm.

If you have a M52TU engine, then you are detecting the switching of the DISA valve and yes you have correctly identified the switching point at about 3,500 rpm. The DISA valve changes the length of the inlet manifolds. There is a lot of air flow engineering that goes into the manifold design.

Have you replaced your twin VANOS seals? Usually needed if you have >80,000 miles on the clock.

Top Info

 

[Alan W]

The DISA valve changes the length of the inlet manifolds. There is a lot of air flow engineering that goes into the manifold design.

Are DISA valves reliable and are there any symptoms associated to a tired or broken one?

 

[NZ00Z3]

I haven't experienced a DISA failure. Forum information suggests that there is a rattle at idle and a loss of performance at the switching rev's.

They are easy enough to test:
- run the engine so the diaphragm has a vacuum charge in it.
- turn off engine and remove DISA, two torx screws
- carefully apply 12V to the DISA and it will activate.
- Inspect the flap to ensure that it is not loose, rattling etc. Take care with the pin that holds the flap onto the shaft as apparently it will drop out on worn units.
-Ensure a tight fit of the O ring when reinstalling. The O ring can be a source of vacuum leak and let in unmetered air that effect cold idle and take off performance.

 

[Pingu]

The twin VANOS on a M52TU is infinitely variable all of the time.

What is your source for this? My experience with the S50 double vanos is that although the inlet and exhaust operate independently, they are either on or they are off.

 

[NZ00Z3]

What is your source for this? My experience with the S50 double vanos is that although the inlet and exhaust operate independently, they are either on or they are off.

Lots of reading on how the VANOS works both in the Bentley Z3 manual and on various forums.

 

[Pingu]

Lots of reading on how the VANOS works both in the Bentley Z3 manual and on various forums.

Plus testing of my own to determine if the VANOS seals in my own Z3 need changing. Below are a couple of charts from my VANOS testing and the VANOS tables from a M54 engine. The M52TU was the prototype for the M54.

Cracking stuff Every day's a school day!!

How did you measure the crank and cam angles while the engine was running?

 

[NZ00Z3]

There is this neat little program call Testo that runs on the same communication platform as INPA. Do your data logging then run it though a spread sheet.

https://www.bimmerforums.com/forum/...0-Diagnostic-program-with-realtime-graph-view

There are also a number of "activation" functions within INPA for the VANOS. You can do lots of testing to see if the VANOS is any good and test that it will hold a setpoint etc without the need to do the logging.

There are some very good tools out there.

 

[Pingu]

There is this neat little program call Testo that runs on the same communication platform as INPA. Do your data logging then run it though a spread sheet.

https://www.bimmerforums.com/forum/...0-Diagnostic-program-with-realtime-graph-view

There are also a number of "activation" functions within INPA for the VANOS. You can do lots of testing to see if the VANOS is any good and test that it will hold a setpoint etc without the need to do the logging.

There are some very good tools out there.

Excellent. I shall have a play. I've measured my engine statically (results below to keep you awake or put you to sleep )...