Vanos a la playa

[buze]

So, exactly, how is it supposed to behave? On my 2.8 facelift (last of the 2.8's) I have at least one of them...

And it behaves more or less like a more 'linear' turbo, at pretty much exactly 2500rpm. You accelerate gently, and at 2500rpm, noise, and pull, changes (for the better).

Is it how it's supposed to behave? googling seems to return me 4k rpm values for M3's etc -- no mention anywhere of such low RPM for vanos to kick in. I mean, i LIKE it, but I just want to check that I'm not playing with a semi knackered unit?

 

[miller1098]

No idea how it works but our in the2.8 comes in much later 4000 or there about.1999 year

 

[NZ00Z3]

Hi

There are two different engines with the 2.8 L label. I'm going to get into a little bit on engine history to hopefully stop this thread getting confused between the two 2.8 L engines.

The first and most common engine was the M52B28 and it had single VANOS on the inlet cam only, see photo, look at the front of the valve cover to see the differences. This was a on/off valve timing change at around 3,000 to 3,500 rpm. Worn VANOS seal leaves the car sluggish when driving above that rev range when it should have switched over.

Your Engine
Then came the M52TUB28 in the face lift model cars. It is a technical upgrade (TU) engine that was the beta tester for the M54. It has VANOS on both the inlet and exhaust cams. They work all of the time and are varied by use of lookup tables in the DME. The engine was also the first to have the DISA valve that changed the inlet manifold length. It switches over at 3,500 rpm. Symptoms of poor VANOS seals is sluggish performance from idle to when the DIAS Valve switch at 3,500 rpm. There is usually a cackle in the exhaust tone at about 2,000 rpm when you put your foot down. Be prepared to loose this cackle as its a sign that the exhaust VANOS is not working. There is a spring in the exhaust VANOS system that pushes the VANOS piston back to the start position. When the seals are worn, the spring overrides the VANOS hydraulics and you get the exhaust tone. See photo of M52TUB20 with 94,000 miles, where the red line is the exhaust VANOS position..

If your car has done over 80,000 mile, sluggish performance under 3,500 rpm and you have the cackle in the exhaust tone, then do the seals. You'll enjoy your cars performance afterwards.

Regards

Murray

 

[buze]

Well, I'm still as confused as before really... I'll have to make a video with my mobile phone and see if someone can make up what's going on. the engine has 61k -- and seems to be working pretty well to my amateur ears... It's just that there is a /clear/ change at 2500 rpm. Not 2000, not 3500.
Would the engine have been remapped somehow to tweak the lookup tables? On lower revs it's loud, seems to resonate, then gets quieter UNTIL 2.5k where power kicks in.

I have to say, the car goes fantastic, but I have nothing to compare it with. If I get the fourth gear, or better the third when overtaking, it'll do 40 to 80 in.... a breath; as long as I keep the revs over 2500 it just purrs and powers away...

 

[NZ00Z3]

Check out the source of all things VANOS

http://www.beisansystems.com/

 

[buze]

So, I looked at 2 videos on youtube on how to replace the seals, and it doesn't appear to be a 'big job'. Am I wrong, am I completely delusional?
I mean, it looks like a big job, but it appears it's doable by a normal human... ?

 

[Eddie Zedder]

In the right hand exhaust tip there is a flap that is controlled by a vacuum system. This keeps the exhaust noise down at low revs and opens up at 2500rpm and produces that wonderful tune. This will be what you are experiencing.

 

[NZ00Z3]

VANOS seal replacement is a straight forward job, follow the instructions and take your time and it will all fit back together OK.

In the right hand exhaust tip there is a flap that is controlled by a vacuum system. This keeps the exhaust noise down at low revs and opens up at 2500rpm and produces that wonderful tune. This will be what you are experiencing.

Among the Z3's around here, both a 2.0L and 2.2L Z3 have had new VANOS seals and the cackle in the exhaust tone disappeared. This Cackle is different to the tone change of the exhaust flap.

 

[Cooper]

So, I looked at 2 videos on youtube on how to replace the seals, and it doesn't appear to be a 'big job'. Am I wrong, am I completely delusional?
I mean, it looks like a big job, but it appears it's doable by a normal human... ?

It is a big job. Not real hard but time consuming, I did my double vanos not long ago. Watch as many Youtube vids as possible and be prepared as this will save you a lot of time. Be careful not to break off the small screw that attaches the vanos to the cam like I did. It was panic stations defcom 5 red alert when I did it and it took another hour to carefully back thread it out.

I think you have a single vanos so just get the right kit......
Get a full replacement kit which has the sets of rings, cap, new small screw, metal gasket for the vanos, metal gasket for the vanos housing, small O ring for the cap.

You might find you need to replace the rocker cover gasket, the spark plug well seals and the 15 or so screw seals for the rocker cover. Have plenty of rags on hand and cover the garage floor with plastic, and the front of the engine so you don't get oil on the belts. Have a bench prepared to do the vanos rebuild. Have hot water ready to heat up the 2 x vanos seals to assist getting them on. Unless you have different specs to my double vanos M54 you can look up my thread on this and see the picture of the torque settings for all the bits and pieces. I can't think of anything else to say atm. Have fun