Failed vanos test post Beisan

[sapote]

I honestly payed zero attention to this, I was so focused on following the Beisan instructions this didn't cross my mind.
I do remember that the pistons did not stick and I did turn the disc by hand CCW and heard a distinct "suction/pumping" noise. I wish I would have payed more attention to fitment, I will be looking over this carefully once I have a different disc and everything is apart on the bench.

A good piston/disc fit will act like a good vacuum damper glass pot: block the piston small hole and without the spring, pushing the piston will compress the air with no leak and piston bounces back smoothly.

[sapote]

So is the suggestion that the disc/hub tangs could be pressed together too tightly causing binding OR maybe pushing pump disc off its "oil grooves" on shaft as a result?

No, the disc/hub tangs tightness has nothing to do with the oil pumping, but it can put a lot of stress on the delicate roller bearing and stress on the hub tangs.
The pistons are riding on the roller bearing inner race.

[Cubieman]

A good piston/disc fit will act like a good vacuum damper glass pot: block the piston small hole and washout the spring, pushing the piston will compress the air with no leak and piston bounces back smoothly.

Should piston go in the full length the side holes? I would assume there is zero taper or anything, just a straight drilled hole. I wonder about the transition space between the inner small holes and the larger side holes, if there is some difference (Beisan vs. OE) that would not let the pistons have full/necessary length of travel in order to produce sufficient oil pressure. That's really getting into the weeds I know.

It would seem that the main known complaints about the beisan disc is sticking pistons, I don't think I have that issue and if Besian disc side holes are indeed tighter than OE I would think that would result in a increase in pressure, so if side cylinders are OK we are left with inner hole/shaft interface and maybe how Beisan disc is machined in regards to inner holes transitioning into the larger side holes.
I would imagine this "transition" is just little on the inside of disc >bigger hole on outside of disc.

[sapote]

Everyone, when you have a chance to have the used disc on your hand, look carefully in the disc center hole and you should see a "cleaned bright" circular line by the 115 bar oil jet: Is the circle cut the 4 small piston hole at their centers or off set from the centers? I believe a perfect installation should have the circular line cuts the 4 holes dead centers.

[sapote]

Should piston go in the full length the side holes? I would assume there is zero taper or anything, just a straight drilled hole. I wonder about the transition space between the inner small holes and the larger side holes, if there is some difference (Beisan vs. OE) that would not let the pistons have full/necessary length of travel in order to produce sufficient oil pressure. That's really getting into the weeds I know.

It would seem that the main known complaints about the beisan disc is sticking pistons, I don't think I have that issue and if Besian disc side holes are indeed tighter than OE I would think that would result in a increase in pressure, so if side cylinders are OK we are left with inner hole/shaft interface and maybe how Beisan disc is machined in regards to inner holes transitioning into the larger side holes.
I would imagine this "transition" is just little on the inside of disc >bigger hole on outside of disc.

The transition from small hole to larger piston hole does not affect anything. The piston will have its full pumping stroke, defined by the eccentric distance from the disc center to the roller bearing center. If the disc hole transition section interferes with the piston then bad thing happens: either the piston open end collapsed or the roller bearing broke.

[sapote]

One crude way to tell if the disc holes are interfering with the hub tangs is after completely torqued down the vanos to the head, remove it and look closely at the disc holes to see any indentation on the holes by the tang corners. The disc made of very hard steel and it takes great force to cut into.

[Cubieman]

Everyone, when you have a chance to have the used disc on your hand, look carefully in the disc center hole and you should see a "cleaned bright" circular line by the 115 bar oil jet: Is the circle cut the 4 small piston hole at their centers or off set from the centers? I believe a perfect installation should have the circular line cuts the 4 holes dead centers.

Does this photo illustrate the "cleaned bright line"? I know it is hard to see, this is a photo I found online. Will inspect mine in due time.

[sapote]

Yep, that’s the cleaned circle and it seems a little offset below the piston holes.

[sapote]

This pic shows the cleaned circle is near perfect to the holes centers. This proves some Vanos might need a shim under the big circular lock to center the cleaned circle.

[sapote]

This one from the internet shows the cleaned circle almost miss the the pistons holes and so it restricted the oil flow into and out of the pistons. The cause: too much clearance between the roller inner race and the circular locking ring, allowing the escaped oil on the front side of the disc (driver vu) to push the disc rearward until stopped by the lock ring/washer. It needs to be shimmed forward. What were the factory boys doing?

Edited: As we can see the wear marks by the hub tabs on the disc holes, and so the disc moved rearward until it touched the tabs, not the washer/C-clip as I first thought. I optimized the disc position and maximize the oil flow, 2 proper thickness washer added between the disc holes and the tabs.

[Cubieman]

It amazes me how pitted some of these disc's look, I don't remember mine being pitted at all.

[sapote]

The holes being hammered by the tangs with 1mm clearance. This car must have higher mileage than yours. I think the new holes should not have less than 0.1mm clearance. Even at 0.1mm one should be careful to center the EX hub on the cam to avoid problem.

[Shonky]

Based on this video it should take about 2 minutes to drop from 40bar to 20 bar. Too short time could mean big leak from the disc (center hole has too much clearance), or bad accumulator. If it is a known good ACC then we can say the leaking disc is the cause.
https://nam3forum.com/forums/forum/m...pressure-tests

Another data point on this. I managed to rig up a pressure guage on mine. DIS VANOS tests are showing the generally expected 200-220ms range.



VANOS pressure from cold ramps up in about 20 seconds to about 105 bar (don't have video of warm up but will definitely do again). As the engine warms up it drops to closer to 100bar at idle and at 2000 or 3000rpm stays basically the same. At shutdown, it drops much quicker than that other thread's video initially and and 40-20 bar takes about 1 minute. Otherwise the VANOS seems to be working pretty well. Either way, a faster pressure drop in my case does not result in slow VANOS advance/retard times. From this video it appears an accumulator may fix that: https://www.youtube.com/watch?v=rGqweBmz4bg

My vehicle:

I am about to do a full Beisan install. Glad I have the before pressure tests.

I see references to 100 bar and to 115 bar. Do we know which it is for sure? I can't find a value anywhere in TIS. Some of the official documentation of the system refers to 100 bar so where did 115 come from?

[heinzboehmer]

I see references to 100 bar and to 115 bar. Do we know which it is for sure? I can't find a value anywhere in TIS. Some of the official documentation of the system refers to 100 bar so where did 115 come from?

100 bar is for the S50. S54 is 115. See page 49 in the attached doc.

[Shonky]

100 bar is for the S50. S54 is 115. See page 49 in the attached doc.

Thanks, right so I'm down at 100 bar then. Took about 10 seconds from cold to 105 bar. I also recorded another video and watched the pressure during the VANOS test and saw fluctuations down to 90-95 bar as the VANOS was actuating.

Either way I still get passing VANOS results with the right numbers.

Edit: This MS54B32 document I have says 100 bar conflicting with the one you posted (attached).