Mailing List flyrotary@lancaironline.net Message #52655
From: Tracy <tracy@rotaryaviation.com>
Sender: <rwstracy@gmail.com>
Subject: Re: [FlyRotary] Oil pressure change...wow (and other stuff)
Date: Tue, 26 Oct 2010 10:19:02 -0400
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Hi Chris,
You didn't say but my guess is that the next time you fire it up everything will be fine on both computers.

The problem is likely to be the same cause as some other anomalies that have been discussed here.  The nav/strobe lights probably presented a big enough momentary load to spike the voltage below the minimum for the EC2/3 and caused a corruption in some vital bit of data. 
I can't emphasize this enough -  Remember that you are installing a digital computer into a very noisy environment and power distribution is not a matter of just hooking up everything to +12V.  Some time ago I added a suggested electrical system layout in the installation guide but it is rarely followed.  For example, most builders don't understand why they should need 3 separate wires coming from the battery.

The next question is usually "why did it only happen on A and not B if that is the problem?  That's just the nature of digital electronics.  It either crosses some critical threshold of voltage or it doesn't.  Just one of the trade-offs with digital electronics.  A  set of points & a coil could care less about voltage transients but computers are much less tolerant. 

Tracy


On Tue, Oct 26, 2010 at 9:50 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

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