flyrotary@lancaironline.net Mailing List Archive

Chris,

Regarding the oil pressure, I just wanted to remind you of one thing. The reason that the oil pressure goes up with thicker oil, is because less of it is flowing through the engine and more is going out the regulator.

I submit that it works like this: the oil gets thicker, it does not flow as easily anywhere although the pump still puts out the same amount of oil, that causes the pressure to go up, which opens the regulator a little more than it was when the pressure was lower, this causes a HIGHER PERCENTAGE of the total flow to go through the regulator instead of into the e-shaft. Since the total flow remains the same as when the pressure was lower (for a given RPM, the result is a net reduction in flow to the e-shaft. while it is probably true that the thicker oil will lube the bearing better, so not as much might be needed, don't forget that most of the oil going into the e-shaft is going to cool the rotors. And a reduced amount of thicker oil is not going to cool nearly as well as a higher amount of thinner oil.

There is obviously a balance/optimum oil thickness, and the manufacturer probably knows best by suggesting a particular thickness of oil. As we say in medicine, don't go chasing after lab numbers (which is what oil pressure really is). If you felt your oil pressure was too low you want to find the underlying cause rather than make it look better by thickening up the oil. If I had a patient who was severely anemic I could make the blood count look better by giving transfusions, but I might be missing the life threatening GI bleed.

Oil pressure too low? think of all those things on the list that Lynn sent out. Think that your application warrants a higher oil pressure? Then install stronger springs in the regulator and keep that oil flowing through the engine rather than rob the engine so you have a nice pretty number on a gauge.

And it appears that keeping with the regular weight oil will save some $$$ as well.

--
David Leonard

Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net

On Tue, Oct 26, 2010 at 6:50 AM, Chris Barber <cbarber@texasattorney.net> wrote:

Since my oil pressure was down a bit following my pressure repair I decided to take heed or some of the comments regarding one of the possible causes as presented here. It seemed to be the easiest that I could try.

So, I shelled out the bucks for some Royal Purple 50 (actually, 20/50 IIRC ). Geezh , I thought the 30 weight and 40 weight was pricey at $8 and $10 a quart, this stuff was $16.00 a quart. I drained about 2 to 3 quarts out of the pan and out of the filter and replaced it with the 50 wieght . So, now it was a blend of the 30 and the 50. I cranked up the engine and my oil pressure was up by about 10-15 psi. WOW! I did not expect such a dramatic increase. I had just run the engine earlier (before I went and purched the oil). Before the change, my idle pressure was around 28-30. After the change it was in the low 40's . The most psi I was getting before the change was about 50-55 psi at 6300 rpm. After the change it was at about 72 psi at 6300.

I let her idle for about ten minutes and all seemed good. So, since my temps seemed good and steady now that Outside air Temps were have now dipped down into the low 90 I decided to taxi around a bit. Yep, I sometimes enjoy taxiing around in my very expensive go-cart.

The engine was running sooooo smooth and strong. I was feeling pretty damn good about it all. Since I was moving around on the ramp where there was quite a bit of traffic following this weekends big 'ol Wings Over Houston air show, I reached down and switched on my nav /strobe lights. At the exact instant of turning on the light (which, btw, are on my secondary alternator circuit) the engine started faltering and wanting to stall out. WTF !!! I switched to the B computer and things smoothed out. Back to A and had to add throttle and mixture to keep it running and it was still rough. Back to B to make it back to the hangar.

Once back at the hangar, I checked the MAP table (RWS EM2 , btw) and nothing seemed changed from earlier. Kinda sounded like fuel was having trouble getting to the injectors. I would think to look at the injectors first, but am not inclined to focus here too much since the engien smoothed out when changed to the B computer. Since both computers use the same systems, it seems to be isolated to the primary computer. Please, correct what I am missing here. Since my judgment was clouded with anger, I put everything back in th hangar for the night. This good good bad good bad stuff is taxing and discouraging. I feel I am so close, then this nonsense. (on top of my RPM's cutting out around 6000 rpm - can slowly inch it up to 6300, with power to spare- if I go slowly, but cuts out at rpm over 6300 and change on the EM2 and an EGT reading issue). To quote Mork ....."Heavy sigh".

Trying to wrap my head around where to start on this latest PITA gremlin. It had been running as close to perfect as I could have imagined.

All the best,

Chris Barber

Houston