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On 1 Sep 98, at 12:42, Erkson, Toby wrote: > Okay, there's an item out there that you can use to replace the oil > pressure bypass (flywheel end, NOT oil pump end). It has a screw going > through the cap that can be used to increase or decrease (bring back to > stock) the oil pressure from the bearings. > > Like a sucker I bought it (less than $7 so why not?) and installed it in > hopes of increasing the pressure by not allowing oil to flow so readily > into the pump by increasing the necessary load pressure of the spring. This does not affect the flow INTO the pump. It only bleeds excess back into the sump, thus reducing the pressure. Otherwise the pressure would be VERY dependent on RPM since the pump is a positive displacement pump. > Then, I realized after I installed it, how in the heck am I going to see a > pressure increase if the oil has already passed the bearings? Or am I > wrong -- is the bypass in parallel (judging by the Bentley/Haynes it is) > with the bearings so an oil pressure gauge (stock location) would read a > difference or would the excess pressure just pour into the bearings > (doubtful since VW did install the bypass for an overpressure reason)? My > guess would be, if one wanted to measure the oil pressure more accurately > at/by the bearings, the case should be tapped right before the pressure > relief bypass, correct? VW put the sensor point at a perfectly good place, one of many perfectly good places. There is really not too much pressure drop (once the oil is warm) within the large oil galleys, it all drops at the entrance to the bearings, where the clearances get tight. Anyway, none of this is an indication of what the real hydrodynamic pressures (the ones actually doing the lubricating) are inside your bearings. The hydrodynamic pressure is generated by the rotation of the shaft and the fact that the load has forced the shaft off-center. The rotation thus forces oil into a smaller and smaller space, thus upping the pressure and keeping the two pieces of metal apart. All the oil pump has to do is to feed enough oil into a bearing at a low pressure point so it can be forced around to where it is needed. Think about this and draw a picture. All we really need the pump to do is provide ENOUGH oil, and we need the spaces between bearing parts to be small enough that all the oil doesn't all leak out the sides before it gets to where it's needed. Jim - ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ------------------------------------------------------------------- Too much? Digest! mailto:type3-d-request@vwtype3.org Subj=subscribe