Re: [T3] Full flow to Go?

["Jim Adney" <jadney@vwtype3.org>]

On 6 May 2001, at 20:22, Keith Park wrote:

> Jim...  what kind of pressure did your 100K full flow motors have at
> that mileage?  were you measuring it at the oil cooler output? I know
> your not as worried about the flickering light as I am but...
> 
> I hear what your saying and it does make sense but if pressure isnt
> really all that important why do the performance engines go to such
> extent to run such high oil pressures... I think they have a rule of
> around 15psi of pressure  for every 1000 RPM.

I ran a pressure gauge many years ago, until the line broke and 
flooded my floor with oil. Since then I have just lived with the idiot 
light. I admit to being curious, but none of the engines I have had 
built with full flow have ever had any problems, so I have just 
learned to forget about it. I've had a couple of chances to take such 
engines apart after significant miles (30-60k mi) and the bearings 
were sometimes good enough to just reuse.

The case is supposed to pressure limit at about 28 psi, so I think 
your rule of thumb is grossly exaggerated. The fact is that the 
pressure needed really doesn't go up that much with RPM, 
although it goes up slightly with load. The rate that oil leaks out the 
side of the journal really doesn't go up with RPM, and all the oil 
pump has to do is keep the journal full which allows the journal to 
develop its own internal pressures as needed.

Even Berg admits that it's not pressure which is important but 
rather flow.

OTOH, the power consumed by the oil pump is equal to the 
pressure x the flow rate, so there is good reason to keep a lid on 
the pressure. Power wasted here is simply lost and turns into heat 
in the oil.

-
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Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA
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