Re: Tapping

[Brian M Kennedy <kennedy@xxxxxx>]

> > Okay, we all know the M3 (and a few other Bimmers) have this problem
> > of oil starvation in high-g turns that cause the valves to start tapping. 
> > What I don't understand is why they keep tapping for many minutes after
> > the car has stopped high-g cornering.

Brant M. Miller wrote:

> One source of continuing tapping is foamed oil.  The foaming is caused by
> the same performance driving that can unport the oil pump pickup.  Oil
> manufacturers include anit-foaming agent in the oils (a surfactant, I
> believe, that assists air bubble breakage), but it does not completely
> prevent the problem.  The air component of the foam is compressable and
> does so in the lifters, with tapping the result.

Interesting.  But I thought adding an extra quart to reduce the tapping
would actually increase foaming (since the oil level gets high enough
that it gets churned a bit).  Is that not so?  Or are there some additional
dynamics at work?

Thanks for the info,

Brian

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