Quote:
Originally Posted by _____That_-_GUY_____
Curious to see how it flows.
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From sump, to pump, filter, LH head, block, to RH head. This is the path and order across the main galleys.
Quote:
Originally Posted by DocWalt
Again, bypass flow still has to go through the pickup.
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No. Bypassed oil goes right back into the suction side of the pump. It's all contained within the pump.
Quote:
Originally Posted by DocWalt
also, positive displacement pumps always move the same amount of fluid given the same fluid conditions and RPM. They'll just generate more pressure (which gets relieved out the bypass when not needed)
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That would be true if it weren't dynamic, but the pump is constantly changing RPM. Not only that, but the system's flow rate also is changing due to temperature and AVCS demand.
Quote:
Originally Posted by Ultramaroon
I don't think the fa20 has a regulator, There's only the relief valve which I understand opens at 140-ish PSI. If it had a regulator, pressure would not fluctuate dramatically with RPM and temp. It would also not hit 120 PSI at high idle on cold start.
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Some call it a regulator, some call it a bypass. It's the same thing.
It does not open at 140psi.
Here's a plot showing oil pressure. Where the ramp rates change is where the bypass just cracks open and starts regulating. I would call it 75psi... which coincidentally, it right in line with 95% of the other oil pumps Subaru uses. The reason pressure keeps climbing after the bypass opens is because flow is increasing, further compressing the bypass spring, requiring more pressure to keep it open enough for the additional flow. Eventually what can happen is the bypass will aerate (if you have too big of a pump and an engine not made for it, for example), because flow out the bypass is horribly turbulent. Think of water coming out of a hose with your thumb covering the end. If you run too big of a pump AND shim it to increase pressure, then that inner gerotor usually lives a short and violent life.
Flow is linear with RPM through the rotors (assuming constant temp and no AVCS). The bypass valve regulates the pressure and flow actually going into the engine.
