Another Rod Bearing Story

[BMWZ4MC]

Great information, thanks GuidoK
Premature cam lobe wear seems to be a direct consequence of follower wear. I know of several S54 cars that have had new cams and followers, including a couple of people who exchanged the worn OEM followers for new OEM followers and then had to replace those too when the case hardening failed. I've yet to hear of anyone who has encountered premature wear when they've fitted Schrick followers, but I accept that the sample size is pretty small! I suspect that a lack of oil supply to the head contributes to the problem in some instances, especially if the car is used hard without any mechanical sympathy.

[GuidoK]

I suspect that a lack of oil supply to the head contributes to the problem in some instances, especially if the car is used hard without any mechanical sympathy.

Yeah could be. Could also be a temperature problem. Most reports of worn cam follwers come from the US; lots of people track the cars there in intense desert heat. Maybe the head gets warmer there and the oil film of 10w60 is less effective there.

An oil pressure gage/sensor in the back of the head is a good mod if you track the car (I believe these engines only have an oil pressue switch so there's also no logging on oil pressure).

[Vanne]

There is logging of oil px,at least on mine there is.

[Polarbert]

I’d agree that the vanos issue is overstated on these but bearing wear is real and worth taking in to account imo.

Both the breaking of a tab on the exhaust hub as well as those little bolts starting to shear are real problems.
I know of people who had both and are quite mellow drivers (not tracking their cars). So I don't think it's an abuse problem, it can just 'happen'.

I can't remember if I stated in the original post but the tab on my exhaust hub had snapped. I've never tracked the car.

[GuidoK]

I can't remember if I stated in the original post but the tab on my exhaust hub had snapped. I've never tracked the car.

My opinion is that it's more common than most people think.
And it's becoming a very expensive BMW part, like so many parts from older models now. (dealerprice: €920,-- incl VAT).

Beisan and VAC motorsports both have a reinforced one (also still expenisve), and in the past there was a very nice version from "turbo toy" (I think a user on m3cutters), that had tabs made from C300 steel (a maraging steel), which is a very expensive and exotic steel (mainly used in aircraft landing carriages, so suitable for extreme forces). But that last one isn't being made anymore I think.

There is logging of oil px,at least on mine there is.

But then you have either an aftermarket ecu with extra sensor, or auxillary monitoring/logging equipment
What kind of oil pressure do you get when your engine is hot? (at low revs and at high revs?)

[PDJ]

What kind of oil pressure do you get when your engine is hot? (at low revs and at high revs?)


I my car from the oil pressure gauge i get between 15 and 20psi when hot at tick over and 55 to 60psi at revs over 4000rpm when hot

The pressure on a cold start up can be as high as 120psi at tick over for a short time

[GuidoK]

I my car from the oil pressure gauge i get between 15 and 20psi when hot at tick over and 55 to 60psi at revs over 4000rpm when hot

Interesting. The reason I ask, is that I saw in another topic (I think on zpost) that there are also s54 rodbearings available with larger clearance (so larger gap). From ACL bearings (HX bearings so 6b1569hx for the s54)
It took some digging but the enlarged gap is 0,001", so 0,025mm

And on the one side that makes sense. The stock rodbearing clearance for the s54 is 0,030mm to 0.070mm (in comparison, for the m54, which has a slightly smaller bearing it's 0,020mm to 0,050mm)
And there are lists with data regarding oil thickness and bearing clearance.
So for instance this article:
https://k1technologies.com/blog/bearing ... -explained
and this one:
https://www.enginelabs.com/news/what-i- ... scosities/
Mind you, all american articles, so measurements in inch.
And for thick oil, like 10w60 they advice quite the bearing clearance. Roughly between 0.0028" and 0.0033", so between 0,071mm and 0,083mm.
Considerably larger and adding 0,025mm clearance makes sense. (based on my experience, the clearance that you measure is pretty much inbetween the min and max value, so for the s54 that would make for a typical 0,050mm)
But again, US articles, US engines (usually a far cry away from european and japanese engines...)
And if I look at the low rev oil pressure, that is already pretty low. Rule of thumb is 20psi at idle (ok, also mainly based on US engines).
And enlarging rodbearing clearance typically gives lower oil pressure in low revs (there is more time inbetween strokes to refresh the oil film as the hole is pushed shut it's a pulsating feature unlike main bearings where the flow is continuous, which lower the oil pressure equally no matter what the revs as bearing clearance stays the same).

So I wonder if fitting rodbearings with larger clearance would be good or bad. If oil pressure at idle was higher maybe yes.