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Date: Wed, 02 Oct 2013 13:29:41 -0400
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From: Roger Iverin <roger@iverin.com>
Subject: Re: [LML] Re: Engine surging
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Hi Art,

Does the pump run smooth?  May it be cavitation of some reason?

I actually have a Dukes low boost for sale.

Best regards
Roger Iverin


On 2013-10-02 13:48, 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
> 
> 
> -----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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