Mark Wegmet wrote: > If you are running a Corvair or VW based auto engine from the mid to late > '60's (sorry, didn't read the whole thread), 25 psi at full operating > temperature is normal unless you have a high pressure / high volume oil > pump. Typical bypass pressures are cold and will run about 60 psi... > remember, when that thing activates the oil you are getting is unfiltered!
25 psi on a Corvair running at cruise would worry me. The rule of thumb is 10 psi per thousand rpm is a minimum. I've been known to run as low as 30 psi at 3000 rpm and it does work, but much lower than that would make me wonder where my oil pressure was going. According to the GM Corvair manual, the Corvair oil pressure regulator activates at 35 psi, although that is warmed up, not cold. At colder temps that number is a little higher. On the Type 1 VW engine, one of the bypasses dodges the oil cooler when the oil is cold and therefore thick (high pressure), and is called the "oil pressure relief valve". By avoiding the cooler, the oil warms up faster. The other is the "oil pressure control valve", and is vents excess pressure directly into the crankcase. It might be noted the Type 1 VW engines don't even have an oil filter in the automotive application. The Corvair has three bypasses, and the one that relieves excess pressure also simply bypasses oil to the sump, not bypasses the filter. There's another bypass that does that job, but it is quite often removed in aircraft use, as mine is. I use oil filters that have a bypass built in that activates when the filter is clogged (due to high pressure on the inlet side of the filter). At that point, any oil is better than no oil, and you'll be landing shortly anyway. I have a thermostatic bypass that only routes oil to the cooler when the oil is warm and needs to be cooled. Mark Langford N56ML "at" hiwaay.net website at http://www.N56ML.com --------------------------------------------------------
