Is this why Vanos oil pump fails?

[poss]

Well I guess there we have it, cobra has singlehandedly solved this riddle.

Mods, lock the thread.

I'm convinced. Graphs never lie.

[simonnim]

Infinite life. Let me vibrate at that rate and have infinite life. Better yet, let me shake my Pringles can at that rate also, maybe I'll have infinite Pringles.

[jet_dogg]

Well I guess there we have it, cobra has singlehandedly solved this riddle.

Mods, lock the thread.

[cobra]

This is what my friend and I always talk about. People on forums debate for years about stuff like this and every once in awhile an engineer comes along and proves everyone has been wrong for the past ten years.

The fact that some cars have no issues and some have broken tabs tells me there's more going on than sheer luck. It's not like the subframe where it is a function of time x abuse.

It has nothing to do with abuse, and everything to do with resonance. You will hear about guys saying "I thrash the hell out of my car and my tabs were fine with 200k track miles!". Well the resonance on this engine is right around 2500-3000RPM, which is where the engine sits at highway speeds or gentle city driving speeds. That's where the rattle is the worst. If you constantly vary the RPM or run at high RPM's, the tabs probably last forever because it doesn't spend a lot of time banging back and forth. Every time the tab smacks the oil pump disk you get a sudden spike of force due to the rapid deceleration. This is a classic high cycle fatigue failure.

This is further substantiated by the S50 using the same oil pump drive design but smaller holes from the factory. No history of failures.

By reducing the stress on the tabs we can bring the hub into the "infinite life" portion of the S-N curve.

[jet_dogg]

Most things are. Just like rod bearings and clearances. I would like a race engine engineer from a prominent team to speak on it, but I highly doubt they're driving around an E46 M3 and poking around on a forum of all places.

However, I had contributed to the M5board by developing a solution for a mirror problem. https://www.m5board.com/threads/side...ng-fix.453370/ . If you're up for a read!

This is what my friend and I always talk about. People on forums debate for years about stuff like this and every once in awhile an engineer comes along and proves everyone has been wrong for the past ten years.

The fact that some cars have no issues and some have broken tabs tells me there's more going on than sheer luck. It's not like the subframe where it is a function of time x abuse.

[Tbonem3]

Wrong

[cobra]

I'm not sure this is even worth discussing anymore. The large holes cause banging at certain resonant rpms which causes the tabs to fatigue. Reducing the clearance reduces the stress so we won't see any more wear or tab failure.

[sapote]

That said, once moving I would not expect the free play to be much issue. The disc will "drag" as it's pumping and the tabs should always be pushing it around. I don't see how the disc would ever get ahead of the tabs and then end up being hit again.

My disc doesn't look as bad as the OP's disc, but I did see the indentation marks on both leading and trailing, which means at times the disc is ahead of the tabs. The engine is a reciprocating in nature and so in every cycle, then crank and driven cams are speeding up and slowing down as the pistons changing direction. With excessive plays in the original disc holes, this caused the hammering effect , and it got worst with more wears in the holes. The same for piston slapping noise if there is too much clearance between piston and cylinder. I don't see any negative effect for a tighter clearance, except it needs more careful when bolting down the vanos to the head with a tighter holes.

[poss]

Mine also had no deformation at 120,000 miles (all of which were driven like I stole it, I might add-- so any notion that going easy on the car causes this to not happen is misguided).

That said, after a decade of people installing the smaller hole Beisan disk, with not a single known failure, I feel like the solution is reasonably proven out at this point.

Interesting...

The dude who drilled my pump disc said the metal was quite soft and drilled easily. There's a noticeable amount of play between the tabs and holes (at least there was in mine). The original holes in mine were measured to be 10.5mm not counting the indents resulting in around .8mm of play originally (the indents probably increased this to 1mm of play). It stands to reason that a hardened straight-faced tab hitting on a curved piece of soft metal is going to leave some kind of an indent.

Perhaps your disc was different?

In any case, all the close ups of broken tabs I've seen appear to be classic examples of stress cracking, and the only thing that can cause stress to the tab is the disc. The more play between disc and tab the higher the impact force will be.

[simonnim]

I don't think the disc issue is fully understood and everything is just conjecture on the internet.

Most things are. Just like rod bearings and clearances. I would like a race engine engineer from a prominent team to speak on it, but I highly doubt they're driving around an E46 M3 and poking around on a forum of all places.

However, I had contributed to the M5board by developing a solution for a mirror problem. https://www.m5board.com/threads/side...ng-fix.453370/ . If you're up for a read!

[Obioban]

There's more to it than just the dimensions of the disk's holes. My 124k 02/2002 s54 had zero, I mean zero, markings whatsoever. Literally looked brand new.

Mine also had no deformation at 120,000 miles (all of which were driven like I stole it, I might add-- so any notion that going easy on the car causes this to not happen is misguided).

That said, after a decade of people installing the smaller hole Beisan disk, with not a single known failure, I feel like the solution is reasonably proven out at this point.

[bloung5]

Just had my vanos overhauled at 156k miles, from the original factory setup. To my surprise, no damage was present. Guess I got lucky.

[jet_dogg]

I don't think the disc issue is fully understood and everything is just conjecture on the internet.

[Tbonem3]

There's more to it than just the dimensions of the disk's holes. My 124k 02/2002 s54 had zero, I mean zero, markings whatsoever. Literally looked brand new.

[poss]

Mine had hardly any wear after about 100k kms. Nothing like that photo.

...once moving I would not expect the free play to be much issue. The disc will "drag" as it's pumping and the tabs should always be pushing it around. I don't see how the disc would ever get ahead of the tabs and then end up being hit again...

It's called 'momentum'. The disc is quite weighty and wants to keep its momentum (same RPM) when the camshafts decelerate because of an aggressive down gear change - causing the tabs to smash into the rear of the oil pump drive holes, and the opposite occurs for aggressive acceleration - the pump disc wants to stay at the same speed but the camshaft says otherwise by slamming the tabs onto the opposite side of the drive holes.

Although they're quite different parts of the car, it's the same fundamental metal fatigue equation that cause both the oil pump tabs and the RACP to fail (at least in terms of the subframe rubber bushings deteriorating and causing them to hammer the RACP) - Number of stress impact cycles and the force of the impacts. If you drive the car hard regularly you are more likely to experience stress fractures in both the RACP and the Vanos oil pump tabs.