BMW rod bearings: What is the real story here?

The M5 V10 version also has the same trouble.  Search up the M539 video where he did his.  There is a chunk he does in the middle that is particularly amusing, while wearing a fake mustache and doing a bad German accent.

Interesting.

Can you bump up the oil pressure a bit to increase the life of the rod bearings?

Noddaz said:

Interesting.

Can you bump up the oil pressure a bit to increase the life of the rod bearings?

Generally the oil pressure in the system had little to no relation to the film pressure on the bearings. If it's an oil supply issue then it might help a bit, but if it's the bearings themselves, then no amount of oil pressure will help.

Just... how is it that anyone finds it acceptable that any car built in the last 20 years wears out rod bearings faster than most cars wear out timing belts?

Berck said:

Just... how is it that anyone finds it acceptable that any car built in the last 20 years wears out rod bearings faster than most cars wear out timing belts?

Have you driven one?  They're worth it.  How many 20-year-old naturally aspirated engines make over 100 hp per liter at the wheels with nothing more than a header, exhaust, and a tune?

In reply to David S. Wallens :

Race cars need dry sumps.  Oil once it is hot is going to go away from the pick up and leave it sucking  air.  ( air is a lousy lubricant) Especially now that brakes are so excellent.  
Baffles and accusumps. Simply delay but don't eliminate the running dry problem.  
    Back in 1954 Jaguar figured  that out and every racing Jaguar since then has had dry sumps. It's also why they won LeMans  so often.    Where dry sumps were banned tricks like putting oil coolers  in the rear of the car to counteract running dry under hard braking. 

codrus (Forum Supporter) said:

Berck said:

Just... how is it that anyone finds it acceptable that any car built in the last 20 years wears out rod bearings faster than most cars wear out timing belts?

Have you driven one?  They're worth it.  How many 20-year-old naturally aspirated engines make over 100 hp per liter at the wheels with nothing more than a header, exhaust, and a tune?

Unless it's a plot by Big Rod Bearing, it's just a fact of ownership. On a new car purchase, I can see that fact stinging. Now, we know so going in.

Berck said:

Just... how is it that anyone finds it acceptable that any car built in the last 20 years wears out rod bearings faster than most cars wear out timing belts?

What he said.

Defenders of the Sacred Roundel seem to accept this as part of life but to me it's simply piss poor design. Couple this to all of the other things that fail on the E46 platform and you can keep 'em for yourself. 

ddavidv said:

Berck said:

Just... how is it that anyone finds it acceptable that any car built in the last 20 years wears out rod bearings faster than most cars wear out timing belts?

What he said.

Defenders of the Sacred Roundel seem to accept this as part of life but to me it's simply piss poor design. Couple this to all of the other things that fail on the E46 platform and you can keep 'em for yourself. 

Lol

In reply to codrus (Forum Supporter) :

Actually, Honda has reduced rod bearing widths over the years.
That goes for the higher output motors as well as grocery getters.
The L15B7 for example have ridiculously small and narrow rod bearings,
yet in stock form can deliver 200+ HP & 200 ft-lb from 1.5L.
Two main kinds of rod bearing loads:
1) Gas loads from combustion, roughly proportional to BMEP or torque, which drops off at higher RPM
2) Inertia loads from reciprocating parts mass, roughly proportional to the SQUARE of RPM.
For auto engines, type 1 loads dominate below 4500-5500 RPM, then type 2 loads grow exponentially.
Lighter pistons & rods help a lot (thus aluminum & titanium), but with modern turbo & controllers,
you can limit the RPM, and just raise boost to increase BMEP and make same or more power.
This permits smaller and lighter components.

It's just poor engineering.  Rod bearings shouldn't be considered wear items like that.  I consider the IMS issue that Porsche M96/7 motors have the same kind of thing, that sort of failure simply shouldn't happen.

Parker with too many Projects said:

Slightly off- topic: Has there ever been an explanation on why this seems to affect the high-output BMW engines more than the Japanese manufacturers, or is it just in how it's reported?

Can't speak for all Japanese engines, but my 1jz had bearings that after ~80k use in all climates, and ran hard after warm up, and raced often, those bearings looked brand new. If I recall they are about an inch in width, but Toyotas are pretty well known for building things on the beefy side.

docwyte said:

It's just poor engineering.  Rod bearings shouldn't be considered wear items like that.  I consider the IMS issue that Porsche M96/7 motors have the same kind of thing, that sort of failure simply shouldn't happen.

They seem to last longer than K24 timing chains, and those are a bigger pain to replace, yet teh internet loves them some K24 engines.

I'd be willing to replace the rod bearings every two years if it meant 8000rpm every day.  Hell I was willing in the put up or shut up sense, but the only E46 M3s I could find that were not stupid expensive were all convertibles.  Maybe things have changed since 2017.

Slippery said:

In reply to z31maniac :

On the flip side, you can say that the M20 is overbuilt   

I am using an M54B30 crank on my M20 stroker. Need to check the bearing widths on that crank to see if they are the same as the S54. 

They are. All those cranks can be used for a stroker M20. M/S50/52, the eta cranks, etc. 

I think the largest displacement you can end up making with a longer throw crank and larger pistons is a 3.1 L M20. 

David S. Wallens said:

codrus (Forum Supporter) said:

Berck said:

Just... how is it that anyone finds it acceptable that any car built in the last 20 years wears out rod bearings faster than most cars wear out timing belts?

Have you driven one?  They're worth it.  How many 20-year-old naturally aspirated engines make over 100 hp per liter at the wheels with nothing more than a header, exhaust, and a tune?

Unless it's a plot by Big Rod Bearing, it's just a fact of ownership. On a new car purchase, I can see that fact stinging. Now, we know so going in.

It's $680 in parts for a job (bimmerworld OEM parts kit) that will probably only need to be done once in the time someone owns the car, assuming normal usage.  It's a DIYable job, can be done with the engine still in the car using an engine support brace and pulling the oil pan.

Yes it's unusual, but it's hardly the fatal flaw that some people make it out to be.

In reply to codrus (Forum Supporter) :

I was under the impression that the rod bearings only lasted about 60k miles.  (Which is also about as long as the rod bearings lasted in G60 Corrados)

...perhaps it is weird to assume that it is normal to drive a funcar 30k miles a year?

Pete. (l33t FS) said:

I was under the impression that the rod bearings only lasted about 60k miles.  (Which is also about as long as the rod bearings lasted in G60 Corrados)

My impression is more like 100K?  60K sounds more like a internet scare number to me.  Average usage is 15K miles/year, and most people are going to get bored of a car before they do 200K on it.

Mine is a caged race car, so it's on a totally different schedule. :)

The Yamaha 3.0/3.2L V6 in the Taurus SHO was another high RPM screamer that had marginal rod bearings.  Basically it came down to when you were doing the 2nd 60K maintenance, it was best to replace the rod bearings.  One thing that a lot of folks learned was that 5w-30 was not the right oil for longevity.  Most of us switched to a 5w-40 or 10w-40 oil to help those bearings last.  More than one engine was saved to see another day after a HPDE event by stopping at a fast oil change place with the owner requesting 20w-50 and then short shifting all the way home.

An interview with Erik Wensberg about the E36-chassis M3–at the time he served as BMW M Brand Manager–might also add some historical perspective:

One small problem: BMW North America simply saw the Euro-spec M3 as too expensive, too complicated for the American market, Wensberg explains. BMW wanted to position the M3 against the Nissan 300ZX, Mazda RX-7 and various pony cars. If sold here in European trim, the M3 would have retailed for about $55,000–about $20,000 too high, Wensberg adds. 

There were other expenses to consider, too. The solid lifters would have required regular adjustments, while the M3 was expensive to insure in its home market. “It was simply a car carrying too big of a penalty,” he continues. 

Pete. (l33t FS) said:

In reply to codrus (Forum Supporter) :

I was under the impression that the rod bearings only lasted about 60k miles.  (Which is also about as long as the rod bearings lasted in G60 Corrados)

 

...perhaps it is weird to assume that it is normal to drive a funcar 30k miles a year?

That sounds like a lot to drive any car. Even when I had my sport bike, I think it took almost 3 years to put 35k miles on it. And that included lots of 300+ mile days. 

codrus (Forum Supporter) said:

How many 20-year-old naturally aspirated engines make over 100 hp per liter at the wheels with nothing more than a header, exhaust, and a tune?

Honda B16a (CRX SiR) in 1988 was right around 100 hp/liter

Honda f20C (S2000) in the 1999 was about 120 hp/liter

Honda b18c5 (Integra type R) in 1997  was about 110hp/liter

All those numbers are with no modifications.  Honestly don't know if they are at the crank or wheel though.

In reply to Pete. (l33t FS) :

Something tells me that there is a proper fix to the K24 timing chain issue you describe, but I haven't looked into it. First I'm hearing of it, honestly.

That, and if you lunch a K24, it costs how much to replace? As opposed to whatever BMW engine we're talking about is how many thousands of dollars these days?

In reply to CrustyRedXpress :

All great engines. All four-cylinder engines, too. 

I have heard that the length of the S54’s crank doesn’t help things here. 

S54 bearing life depends on use If you are driving it as a street car and using maybe  6K once in awhile, they are good for 100K plus, but if you do track events with it (quite a few do get used that way) the life shortens and the 60K estimate is probably about when you should start worrying (and testing). 

I have an after market exhaust on mine and although I rarely really wind it up, when you do, the sound is glorious. I can see why some owners just can't resist that 7900 rpm level (plus even the stock suspension is good enough to put on a good show on the track, given suitable rubber).

In reply to David S. Wallens :

Agreed!