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Interesting, Ed!
What I observed was, at least on one rotor, only one of the 3 readings
appeared 5-10 psi lower. That would point to the side seal(s)! Would
never have occurred to me. Didn't even check those tolerances this time
around, even though I used side seals from my existing engine in the
rotor from the spare engine. Need to repeat those compression tests,
looking a bit closer at the differences and also with oil, as you
recommened.
But, I'm not taking that engine apart again unless I get blow-by again
or some other serious problem!
Much easier to install a primer system, and I'd much rather be flying!
I might experiment with oil mixture - try to go down to 4 oz per 5 gal ?
It flies, and I'm not going to beat Tracy at Sun 100 anyway, so who
cares - will be saving fuel running at lower power :)
Now in the future those primer injectors could be used for NOX
injection, hmmm...
Finn
Ed Anderson wrote:
Hi Finn,
That compression sounds a bit low for a rebuilt engine even at 100 rpm.
I have found that if ends of the side seals are not trimed to be very, very
close (but not touching) the round corner seal, compression at low rpm may
suck. This condition does not seem to hurt medium to high rpm operations
but it makes it hard to start at low rpms. Try squirting some light weight
oil (say 10 weight) into the spark plug hole turn it over a couple of times
before hooking up the compression checker. Your low rpm compression should
show considerable improvement.
Another thing. Can you tell anything by observing the compression gauge
needle movement. For instance if you have two faces with low compression
and one with adequate compression on a rotor, it is probably an apex seal
between two chambers. If the compression is the same for all faces of a
rotor but low, it could indicate inadequate sealing by the side seals.
I tried to be overly cautious and put too much oil in my gas on break-in and
ended up losing compression. I know it sounds crazy, but my compression
dropped from an initial 110 psi (before I put additional oil in the
gasoline) to around 70 psi during cranking. I couldn't figure out what the
problem was, then Leon described "poisoned gasoline". The theory is too
much oil in the gasoline, causes the apex seal to ride on a thick film of
oil around the rotor chamber. As the chamber starts to compress the air,
the pressure "blows" through this oil film past the apex seal losing
compression. I initially thought it was a crazy idea, but following Leon's
advice, I drained all of the "poisoned gasoline" and filled the tank with
new gasoline with the proper oil mixture and within a couple of minutes of
running my compression was back. So I would mix my oil with the gasoline
the same as for operation and not over do it.
My engine continue to show slow improvements in compression up to the
current 120 hours of run time.
Now if I could just wade through the 14" of snow we received over the past
24 hours and get to my workshop, I could finish wiring up my DIE intake
manifold.
Ed
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message -----
From: "Finn Lassen" <finnlassen@netzero.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Friday, February 27, 2004 9:31 AM
Subject: [FlyRotary] Compression sucks!
Finally brought a compression tester to the airport yesterday. 30 - 45
psi at low (maybe 100 RPM).
So, I'm definitely going to install some kind of primer.
How many hours is it going to take for apex seals to seat better?
Any recommended RPM for running in the engine? 4,500, 5,000, 5,500?
Mix extra or less oil in the gas during this?
Hoping to have right radiator installed this weekend, so I can start
running at full power.
Finn
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