25 Dec 2014

Merry Christmas and happy holidays everyone.

Getting the alternator working was easy thanks to an extensive and very helpful article on Pirate4X4. It’s a 4-wire GM alternator, so connecting the “L” wire to ignition through a resistor and the “I/F” wire directly to +12V ignition resulted in 14.5V even without using the remote sense.

The dry sump system is now full, 9 quarts between the tank and two filters. Took the car out and warmed the oil up to 70 degrees C in light driving; the oil-to-coolant heat exchanger worked well to help warm it up, so there shouldn’t be any issue with overly-cool oil. After the drive, oil pressure was 60-65 psi above 2000 rpm and 25 psi at idle, but until the car’s run hard it’s unclear where it’ll end up. Since it’s 60 psi at 2000 rpm, that seems promising for when it’s hotter. At this point nothing will be done until the car is run hard to better establish a baseline – it may well be correct where it is. That said, I’m going to ask the pump manufacturer what “normal” is. That is, since the oil pressure regulator is kicking in at 2000 rpm it means that at any speed above that, excess oil is flowing through the regulator instead of the engine. I’m wondering if the pump could be slowed down so that oil pressure rises more proportionally with engine speed, something more on the order of 10 psi per 1000 rpm perhaps.

Since I’m still using the OEM valve cover, the vent is still present. Out of curiosity, with the car idling I put my finger over the vent to see how well the pump was sucking air out of the crankcase. It was doing its job and it gradually started pulling a vacuum, which was good, but what was surprising was that at the same time, a noise became audible. It’s hard to describe what it sounded like, sort of a warbling. As soon as I removed my finger it disappeared, so it’s definitely vacuum related – the question is, what’s making the noise? Google-foo shows that when a dry sump system is added to an engine, some people report hearing interesting new noises. I can probably find the source by using a stick held to my ear, but then what, what would I do about it? I suspect it’s just the way it is.

Somewhat related is deciding how much vacuum is correct and there are two very different views on this. One says that there’s no such thing as too much crankcase vacuum, while the other says that the vacuum will cause all kinds of problems because it’ll unseat engine gaskets and piston rings. From an engineering point of view I have a hard time believing this since a perfect vacuum is only 15 psi. Applied over the cross section of say, the valve cover gasket, (between mounting points for example) and it’s only going to see about a pound of force. Plus, such gaskets tend to be well contained so I have difficulty seeing how they’re going to get unseated.