So I'm thinking about the oiling system on a conventional vehicle, and was wondering how much pressure headroom the manufacture's design into the system to drive flow through the oil filter before putting the oil pump into relief mode.
Remember from out past discussions that as long as the oil pump is not in relief mode, all if it's output flow must flow through the oil filter and engine, which can be though of as a series resistance circuit.
Here's an example:
Let's say the oil pump on an engine puts out 60 psi before its relief valve starts to open, which will then keep the max pump pressure at a maximum of 60 psi while in relief mode.
Let's say that with oil at normal operating temp, and at high engine RPM that the max volume of oil out of the pump creates a 50 psi pressure drop across the engine's oil system. This means that there is 10 psi of pressure "headroom" to overcome any flow resistance of the oil filter before the pump would start going intt relief mode, at which point you would start to loss oil volume through the engine.
One interesting thing I see on many automotive chat boards is that someone will say they installed an ACDelco Ultraguard or a PureOne filter and claim the "oil pressure decrease" because of the proclaimed restrictive filter. But if you think about what's really going on in the oiling system, as long as the oil pump is not in relief mode, or the filter in not in bypass mode, the same volume of oil is coming out the filter and going into the engine (at the same engine RPM of course). Since the oil pressure gauge is normally located at the inlet to the engine's circuit (i.e., between the oil filer and engine), the pressure reading at that point will be the same when the flow is the same. Note that throughout this discussions I'm assuming the oil viscosity and engine RPM is the same, so those parameters are constant and out of the picture.
So what this tells me is that if the oil filter is a little more restrictive, but not enough to cause the oil pump to go into relief mode (hence the importance of proper filter pressure headroom), then you will never see any difference in engine oil pressure from just a slightly more restrictive oil filter.
But if you did see a drastic decrease in oil pressure, then that could be an indication that the filter is so restrictive that it took up the pressure headroom and cause the pump to hit relief, which will cut the flow volume, which will then decrease pressure. For guys who actually see a major drop in oil pressure, I'm thinking they have used up their pressure headroom and have gone into pump relief.
If the filter went into bypass before the pump went into relief mode, then I would expect to see a slightly higher engine oil pressure due to the fact that the filter's restriction is being bypassed, which will increase flow and hence the oil pressure going into the engine.
Just some late night thoughts ... what's your take?
Remember from out past discussions that as long as the oil pump is not in relief mode, all if it's output flow must flow through the oil filter and engine, which can be though of as a series resistance circuit.
Here's an example:
Let's say the oil pump on an engine puts out 60 psi before its relief valve starts to open, which will then keep the max pump pressure at a maximum of 60 psi while in relief mode.
Let's say that with oil at normal operating temp, and at high engine RPM that the max volume of oil out of the pump creates a 50 psi pressure drop across the engine's oil system. This means that there is 10 psi of pressure "headroom" to overcome any flow resistance of the oil filter before the pump would start going intt relief mode, at which point you would start to loss oil volume through the engine.
One interesting thing I see on many automotive chat boards is that someone will say they installed an ACDelco Ultraguard or a PureOne filter and claim the "oil pressure decrease" because of the proclaimed restrictive filter. But if you think about what's really going on in the oiling system, as long as the oil pump is not in relief mode, or the filter in not in bypass mode, the same volume of oil is coming out the filter and going into the engine (at the same engine RPM of course). Since the oil pressure gauge is normally located at the inlet to the engine's circuit (i.e., between the oil filer and engine), the pressure reading at that point will be the same when the flow is the same. Note that throughout this discussions I'm assuming the oil viscosity and engine RPM is the same, so those parameters are constant and out of the picture.
So what this tells me is that if the oil filter is a little more restrictive, but not enough to cause the oil pump to go into relief mode (hence the importance of proper filter pressure headroom), then you will never see any difference in engine oil pressure from just a slightly more restrictive oil filter.
But if you did see a drastic decrease in oil pressure, then that could be an indication that the filter is so restrictive that it took up the pressure headroom and cause the pump to hit relief, which will cut the flow volume, which will then decrease pressure. For guys who actually see a major drop in oil pressure, I'm thinking they have used up their pressure headroom and have gone into pump relief.
If the filter went into bypass before the pump went into relief mode, then I would expect to see a slightly higher engine oil pressure due to the fact that the filter's restriction is being bypassed, which will increase flow and hence the oil pressure going into the engine.
Just some late night thoughts ... what's your take?
