[svxfiles]

Originally Posted by Huskymaniac

Just the man I need. Where in the oil path was your gauge located? Can you describe the oil path in a simplified way like:
Pump -> Filter -> Gauge -> Engine Passages

I was exchanging posts with a guy on the Acura forum that claimed the bypass pressure may not matter. His reasoning was that the oil pump is positive displacement and will push the desired flow regardless of the flow resistance in the path. It will just result in higher pump pressure. I can see that, to an extent. But every pump is limited in the pressure it can generate. I just don't know if we are anywhere near that limit.

It helps to assume flow rate and pressure are linearly related for both the filter and the engine passages. That isn't exactly true but it is close enough for now. I have no feel for the "resistance" or the engine which is to say the pressure divided by the flow rate. (psi/gpm) Any idea on that...assuming normal operating temperature? Also do you have an idea of the oil pump's typical flow rate as a function of RPMs...also at normal operating temperatures? We can get the filter resistance from the datasheets, I think. Together, we could estimate at what RPMs the filter will go into bypass.

But if our pump can generate the necessary pressure to push the desired flow through both the filter and the engine at redline, maybe we don't even need to worry about the bypass pressure. In fact, a high bypass pressure would even be desirable since the oil will remain filtered at all times. Then the question would be, do we need it filtered at all times? I mean, how fast does an engine get exposed to particles that need to be filtered anyways? Maybe the time it spends near idle is enough time to filter most of the particles out. Having to pump a high flow rate through a high pressure will consume energy. That means less HP and poorer MPGs.

Filters are one giant engineering tradeoff. High efficiency versus high flow. More time filtering versus less energy required to pump. And then you have overlap. High efficiency versus less energy required to pump.

Do modern engines use filters with lower bypass pressures because their pumps have limited pressure and they want to maintain high flow at high RPMs or do they use them to conserve energy by limiting flow resistance and, hence, pressure, at high RPMs and high flow?

And to make it even more complicated, the oil viscosity will have an effect. The thicker the oil, the more resistant to flow the filter and engine will be and the higher the pressures will get. I was SHOCKED to find that Acura suggests 0W20 oil for the TL. Many people assumed that was to improve gas mileage to meet CAFE standards and that they weren't overly concerned about the impact of super thin oil on engine wear since their engines will easily get past the warranty period. Also, most people use synthetics on those cars and synthetics do tend to be thicker at normal operating temperature and also tend to shear less under high stress (high RPMs). Still, my gut tells me to run 30 weight oil and take the 0.5 MPG hit.

T fitting at the stock oil pressure sensor location.