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Subject: Re: [LML] Re: Engine surging
From: Colyn Case <colyncase@earthlink.net>
In-Reply-To: <list-6499063@logan.com>
Date: Thu, 12 Dec 2013 22:16:07 -0500
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References: <list-6499063@logan.com>
To: "Lancair Mailing List" <lml@lancaironline.net>

Art,

on my IV-P the fuel flow actually decreases slightly with the electric =
fuel pump on.
did you watch fuel flow (and fuel pressure if you have it) while you =
were doing this?

Colyn

On Oct 2, 2013, at 7:48 AM, Bill Bradburry wrote:

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=20


-----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.=20

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.=20

Any and all advice appreciated.=20

Art

Sent from my iPhone; Art Jensen

> On Oct 1, 2013, at 1:30 AM, Charles Brown <browncc1@verizon.net> =
wrote:
>=20
> 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.
>=20
> 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
>=20
> On Sep 30, 2013, at 7:58 AM, Art Jensen wrote:
>=20
> 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.=20
> Art
>=20
> Sent from my iPhone; Art Jensen
> --
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>=20
>=20
> --
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