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Date: Fri, 04 Oct 2013 22:22:40 -0400
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Subject: Re: [LML] Re: Engine surging
From: bob mackey <n103md@yahoo.com>
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I know there are a bunch of Continental fans that don't want to hear this,
but...

The fact that the fuel pump can cause the engine to surge is indication of
a fundamental flaw in the TCM Continental fuel injection system. The fuel
flow to the cylinders is controlled by the fuel pressure and the throttle
position as well as the mixture knob. Why should the externally-applied
fuel pressure affect the performance of the engine? It should not. The
Lycoming injection system is controlled by the mass airflow into the engine
and the mixture knob. Switching fuel pumps on and off does not affect the
fuel/air ratio. This is the way it should be. the only responsibility of
the fuel pumps should be to provide *enough* fuel. Not to regulate the
pressure of the fuel and thereby control the fuel/air mixture.

If I were going to install a Continental IO-550, I would have to scrap the
crummy fuel injection system that comes with it. Options would be to
install a Lycoming system or perhaps an automotive system. Somewhat less
difficult would be to install a fuel pressure regulator to isolate the
engine from the effects of fuel pumps.

That might be an option for Art's situation.

Also look for a leak at the inlet of the "faulty" pump. If it can suck air
into the system, that could cause surging.

-bob


Art Jensen wrote:
> 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).

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<div dir=3D"ltr"><div><div><div><div><div>I know there are a bunch of Conti=
nental fans that don&#39;t want to hear this, but...<br><br></div>The fact =
that the fuel pump can cause the engine to surge is indication of a fundame=
ntal flaw in the TCM Continental fuel injection system. The fuel flow to th=
e cylinders is controlled by the fuel pressure and the throttle position as=
 well as the mixture knob. Why should the externally-applied fuel pressure =
affect the performance of the engine? It should not. The Lycoming injection=
 system is controlled by the mass airflow into the engine and the mixture k=
nob. Switching fuel pumps on and off does not affect the fuel/air ratio. Th=
is is the way it should be. the only responsibility of the fuel pumps shoul=
d be to provide *enough* fuel. Not to regulate the pressure of the fuel and=
 thereby control the fuel/air mixture. <br>
<br></div>If I were going to install a Continental IO-550, I would have to =
scrap the crummy fuel injection system that comes with it. Options would be=
 to install a Lycoming system or perhaps an automotive system. Somewhat les=
s difficult would be to install a fuel pressure regulator to isolate the en=
gine from the effects of fuel pumps.<br>
<br></div>That might be an option for Art&#39;s situation. <br><br></div>Al=
so look for a leak at the inlet of the &quot;faulty&quot; pump. If it can s=
uck air into the system, that could cause surging. <br><br></div>-bob<br>
<br><div><div><div><div><div><div><br><br>Art Jensen wrote:<br>&gt; <tt cla=
ss=3D"">The surging was first noticed after take-off with
 low boost ON at about 800 feet AGL leaned for altitude 2500 RPM WOT.=20
Being under the KFTG TCA climbs were in steps to 9500 MSL where I=20
leveled off to try to understand what&#39;s going on and see how changes in=
=20
operation affected what I was seeing and feeling. I reduced power and=20
went LOP same results. Then turned off the low boost and the surging=20
stopped. The engine ran very smooth. Turned the low boost back on and=20
the surging came back. Again I turned it off and it went away. I=20
determined I had found the cause (fuel pump) but still don&#39;t understand=
=20
why (what is beginning to fail) or the connection (how it plays a roll=20
to create the results I experienced).</tt></div></div></div></div></div></d=
iv></div>

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