I also timed how long it took to build oil pressure from a cold start. Mine took less than 4 seconds to bring the gauge up to normal and the "no oil sound" was gone.
The OEM gauge is fake and means nothing for oil pressure for the first 30 seconds after engine start, then it only means you have a min of 6 psi. There is no psi transducer on the block, just a 6 psi switch.
Typically if there is a no oil psi at startup condition the gauge will read "normal" for 30 seconds, and then drop to 0 with a check gauges.
The OEM gauge will register pressure at the same time every time.
This is true, the OEM gauge does read normal at startup even when there is a no pressure condition, until the 30 sec (give or take) time has lapsed and the check gauges light comes on. Even during that time period when the gauge would read normal before it dropped off, the engine would chatter indicating the absence of pressure. There was a very significant audible difference when the pressure did build, it was like the cummins saying "Ahhhhhh" This is the reason I installed the aftermarket gauge, to see what the true reading was. Then of course it didnt want to show its face again!
I am not concerned about the bypass, only the PRV. For $80, its worth the piece of mind knowing there are 2 newly machined surfaces that are better matched rather than replacing a part of it... kinda like replacing piston/rings w/o honing or boring a cylinder.