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Re: [T3] full flow oil filter


On 28 Jan 2005 at 16:50, Mysterious J wrote:

> It does appear that CB Performance has included a bypass valve, should 
> the filter become restricted.  My concern would be the future 
> availability of filters.

Yes, they have a bypass valve, but at what pressure does it relieve? Does this 
happen before the pump cavitates?

The problem is that just a little bit of restriction can cause enough of a 
pressure drop that the pump inlet pressure drops below the vapor pressure of 
some of the more volatile components of the oil (gasoline, for instance.) Once 
this happens the liquid cavitates which stops the pump from working and can 
damage the pump if it continues. 

It can even happen in very small amounts right at the pump rotor and cause 
damage to the pump without your ever knowing that there is a problem.

The problem here is that at the inlet you're working within a pumping pressure 
differential that is something less than 15 psi and less at high altitude. On 
the outlet, there's no such limit, since the positive displacement pump will 
just make up any difference that occurs, at the cost of some HP, of course.

Filters at pump inlets just have to be VERY carefully done.

-- 
Jim Adney
jadney@vwtype3.org
Madison, WI 53711-3054
USA

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