Always understood that most of the journal wear occurs at start up rather than at normal operating conditions.
Ok, so why does the flatheat N have the 0-50 psig oil pressure gauge and the OHV NAA have the 0-80 psig oil pressure gauge?
Both engines have equal rated 2000 rpm and nearly equal 6.6/6.7 CR after 85000 serial #.
The oil pump capacity was increased at some point on the N series?
Larger capacity oil pump would increase the back pressure at the journal at equal RPM?
Maybe the larger capcity pump was incorporated to increase the longevity of the engine and not to increase the oil pressure on a new or new rebuilt engine?
So what is the concern about oil back pressure, since the oil pressure is not in the equation for oil film thickness?
In my opinion the N series engine needs to have minimum of 15 psig oil pressure @ 1500 rpm.
Maybe the NAA needs more oil back pressure than the N, since the gauge has a greater range or with a larger capacity pump than the N, the oil pressure is higher.
The tire mfg's are always researching & testing to come up with the ultimate thread pattern to reduce the chance of hydroplaning, which creates a thin film of water between the tire and road in heavy rain conditions. The water film supports the "gravity" weight of the vehicle, which is basically the same physics as the engine journal. Michelin Tire has a great video on U-Tube.
Oil pressure issue seems to be one of the most frequent FAQs on the N forums.
AKA "raven" on the NTC forum