REFLECTOR: Engine/Prop woes

[Chuck Jensen]

Hi, Scott,

Step number 1.  Find out what your oil pressure is.

That may sound stupid, but you only think you know what it is, based on the Dynon readout.  I had the same low oil problem in  my IO-540 Lycosaurous, so a mechanical direct read gauge was plumbed in to take physical readings, rather than sensor readings.  Turns out through the different temp ranges, the actual readings were 7-10 psig higher than what was displayed on the GRT EFIS, which put me within normal ranges.  Likewise I was concerned about the very low oil pressure at idle with hot oil, but it turns out that's within normal ranges as well.

As they say, or at least I do, 'before you solve a problem, make sure you have one'.

Chuck Jensen


-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
Behalf Of Scott Derrick
Sent: Sunday, July 19, 2009 8:41 PM
To: Velocity Aircraft Owners and Builders list
Subject: REFLECTOR: Engine/Prop woes


I received my prop back from Catto a week and a half ago.  This was the
2nd go around in an attempt to re-pitch it for the reduced horse power
of my 520, since I decided leave the turbo on the bench.

I waited to remount it as I was deep into building new engine cowls and
didn't want to switch gears. 

Finally finished the cowlings enough that I can work on them with the
prop on the engine so remounted the prop yesterday and fired her up.  I
had left the tuning project dangling a month ago because my static was
so low I was afraid it may be effecting the setup procedure. 
Continental and Cessna only provide a setup procedure that assumes your
running a constant speed prop...

Well the bad news is the static is still too low in my opinion.  I did
see 2060, which is better than the 1930 I was seeing before, but 2060 is
pretty low.  It was very hot, close to 100 and density altitude was
approaching 11,000 ft. That does seem to reduce static RPMs somewhat.  
I emailed Catto to see what he thinks. He didn't charge me for the 2nd
repitch but it still costs me $$250 for every round trip of the prop.

I was thinking maybe the RPM would pick up with just a bit of forward
speed?  Maybe at 50 knots?  I might take her out on the runway and see
how she does on a fast taxi test..  Probably just wishful thinking.

The real bummer though was not the prop. I was running the engine a lot.
probably 10 starts and stops with a full throttle engine run every
time.  I have never really gotten the engine hot and that was one of my
goals for this test run. Finally got the oil temp up to 210 degrees
which allowed me to see that all the joints in the oil lines from the
engine up to the nose and back though the two heat exchangers were all
tight with hot oil.  The bummer was I noticed the oil pressure at 210
degrees F was down to 35 at 2000 rpm and dropped to 11 at idle.   I got
a  low pressure  alert from the Dynon!  WTF?  The oil pressures are well
within spec at the 140 degree mark, which is all the engine book lists..
I've changed the oil filter twice on this engine and cut both open.  The
first had a minuscule amount of metal, not nearly as much as I would
expect from a fresh rebuild. The second change had almost none so I
don't think its an internal wear problem.  Well I was bummed and pushed
her back in the hanger to think things through(and cry in my soup!). 
Talked to the AP/IA on the field who supervised the rebuild.  NO clues..

Got home and started search the Internet.  Found a reference on
SacSkyRanch one of my favorite mechanics sites.  They had a  list of
about 25 items that could cause low oil pressure.  Most were of the low
all the time, which I don't have.  They had the classic dirty seat on
the pressure regulator which I already knew about and was planning on
checking. Then near the bottom they listed a bunch of Continental turbo
charged engines.  Said if you are running "Full Flow Lifters" on the
exhaust valves to improve cooling of the valves  they can reduce
pressure  5-7  psi.   Well I'm running  "Full Flow  Lifters" on all  12
valves, per  ECI's  recommendation!  A possible 10-14 PSI reduction! 
Which if added to what I was seeing puts me way into the high end of the
green.   I hope this is it. I'm calling Continental next week to verify
this...

At least the cowls are ready for their first  shot of primer and the 
induction scoop/filter  box/ alternate  air box combo is close to done
also.

Scott