Art,

Explain this phenomenon to the guys at GAMI.  I bet they can explain what is
happening to your engine.
http://www.gami.com/contact/contact.php

B2


-----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Art
Jensen
Sent: Tuesday, October 01, 2013 2:57 PM
To: lml@lancaironline.net
Subject: [LML] Re: Engine surging

Charley,
The surging was first noticed after take-off with low boost ON at about 800
feet AGL leaned for altitude 2500 RPM WOT. Being under the KFTG TCA climbs
were in steps to 9500 MSL where I leveled off to try to understand what's
going on and see how changes in operation affected what I was seeing and
feeling. I reduced power and went LOP same results. Then turned off the low
boost and the surging stopped. The engine ran very smooth. Turned the low
boost back on and the surging came back. Again I turned it off and it went
away. I determined I had found the cause (fuel pump) but still don't
understand why (what is beginning to fail) or the connection (how it plays a
roll to create the results I experienced).

Still looking for the expert who can put it all together so that I can come
up with a plan of action for repair.

Called Lancair to price a new Dukes Fuel Pump, $3350, might be a bargain
tomorrow but at that price I'm not going to R&R as a test. Haven't checked a
price for overhaul assuming my problem is in fact the pump.

Any and all advice appreciated.

Art

Sent from my iPhone; Art Jensen

On Oct 1, 2013, at 1:30 AM, Charles Brown <browncc1@verizon.net> wrote:

Just a thought ... if there wasn't any rpm change, and you heard or felt

surging, it could be a torque increase that causes a pitch increase, and
increased thrust.  And if MP was constant, then the only thing *that* leaves
is mixture.  If you're running lean of peak, power depends significantly on
mixture.

The thing is, this sounds backwards.  If it's worse when you turn the

boost pump ON, then it sorta seems that you were running so far rich of peak
that additional fuel pressure degraded power?  I'm not aware that the engine
can even produce a mixture that overrich, except at very low power settings.

Charley

On Sep 30, 2013, at 7:58 AM, Art Jensen wrote:

Looking for thoughts from the collective minds of the LML.  Last flight in

my IO-550 normally aspirated legacy, I noticed surging in the engine with
the low boost pump on. I did not notice any surging when I turned the boost
pump off. Also did not notice any fluctuation in RPM. Nor did I see any
fluctuation in RPM when I downloaded the engine data. The obvious question
would be what are the possible causes and does it make the airplane unsafe
for flight as there is no surge when the boost pump is off. I don't
understand how I could feel and hear surging in the engine yet see no
fluctuation in RPM, so I'm stumped. Any ideas would be appreciated, thank
you.

Art

Sent from my iPhone; Art Jensen
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