KillerBMotorsport написал(а):
From another post my dissertation on oil pumps...
There are many similar versions of "modified" pumps that companies offer, but typically the quick modification is to add a shim to increase the pumps by-pass valve's activation pressure and/or change the by-pass valve's spring to increase the valve activation pressure. Adding a shim or changing the spring in this way means instead of the pressure being regulated to a maximum of 85psi, as designated by the factory, you will now have pressure above that amount because the by-pass valve will require more force to open.
The downside can be decreased efficiency of the by-pass valve because with shims and/or a heavy duty shim it may not be able to open completely causing oil pressure higher than desired. This can be especially disaterous if the pump has been ported to flow more oil without the supporting bearing clearances throught the motor. Oil pressure can exceed the capability of seals causing oil leaks in the motor and turbo. You ever see threads with new turbo/builds with oil leaks? Check out the build list and there is almost always a modified pump installed.
Another modification, although not as common and almost always done with shim/spring changes, is porting. This is when the entrance and/or exit ports and internal passages of the pump have had manufacturing imperfections removed/smoothed and/or passages opened up to increase the flow potential of the pump. The downside here is work being performed without data to back up the porting. It's not difficult to modify a pump to outflow the pressure relief, but I know of few companies that have data to backup thier work. If the pump can outflow the by-pass valve you can get pressure above what the oil seals can handle, again causing oil seals to fail and leak.
The theory with oil pressure and flow is to provide as much unrestricted flow as possible, but only as much pressure as you need. Once your pressure goes high enough to trigger the relief you recirculate the bypassed oil immediately back into the pump and that creates excessive heat in the oil. In a perfect world the pump creates the proper pressure/flow required by the build, but not enough to trigger the bypass. This is impossible considering the variables, but the closer you can get the better.
I see too often people putting a "modified" 08+ oil pump into thier cars as a common upgrade. A professional engine builder will properly match a pump to the builds tolerances and bearing clearnaces, but a larger pump should never be put on with a bigger is better mentality, because it's simply not true. IMO pumps in most setups should ONLY have porting to reduce flow restriction/cavitation and should never be shimmed or have the springs changed unless there is bench test data to prove the pump still properly regulates the oil pressure.