I have some follow-up on the surging problem. Turning off the TCU does not help
anything. In fact, the engine seems to surge and be a little rougher. I have
checked the plugs which were new two hours ago. The air filter has no effect
on the problem. I have checked the tubing, it is six years old, but looks
to be in good condition and no cracks...course you can't see the underside of
a lot of the tubing. The surging varies. I ran it yesterday and it did not
surge
at all...manifold pressure up to 38 and it seemed to be cured. Then today
I ran it again and the surging was back. The surging is over a range from 5000
down to 2000. Someone was of the opinion that it was almost like the engine
was being turned off and as the RPM dropped, being turned back on. Since the
problem occurs only at the higher throttle settings, I had assumed it could
not be the electrical system. The engine does diesel some when turned off.
It has done that for a year or so. I usually turn of
f the
fuel pumps first and when the pressure drops, then turn off the ignition. The
dieseling is worse if the enginie is hot...like up at 200 degrees or so. The
surging is less severe when the engine is hot...up in the 200 range, and worse
with the engine temp at 130.
I am leary of the carbs but it sounds like I will have to tackle them if no one
comes up with an alternate idea. No one around Knoxville has experience with
a Rotax. I asked our AI if he knew anything about Rotax engines and he said,
"Heck, I can't even spell it!" The intermittant nature of the surging has
added
to the frustration. I can't see anything being done to the engine that makes
it behave different. I have the same gas(half auto high test and half 100LL)
in the plane that was in there when I did two flights before the surging
started. The mag check is normal. Running both fuel pumps increases the
pressure
reading but does not change the surging. It did not surge for 500 hours
running on one pump. Thanks for the ideas thus far.
Ken Carpenter
-------------- Original message --------------
From: "ALAN YERLY" <budyerly@msn.com>
Guys, Here is my one and a half cents.
When working with Jerry Hope's 914 we found that the reset switch was all that
was necessary to cure the surging... That is always my first in-flight
correction.
For my older engine, the wiper on the pot in the turbo servo wore out with
time and the servo began to hunt. By hitting the reset switch, it momentarily
cuts the power and stabilizes the manifold/boost and the servo related
surge/boost
fluctuations stop.
As for the carb related problems, With the engine at idle, servo locked out
(reset
switch held to eliminate the servo from operating), run the engine up until
you see about 35-39 inches of MP. If the engine does not surge, it is not
the carbs. If you have the dual manometers, and can watch the MP on each carb,
that will tell you volumes about your carb health. If one of the altitude
compensators
is hanging up, the engine will sag, calling for more boost, then the
engine boost clears the carb balance problem, but that causes a momentary over
boost which then causes the servo to cut boost, which then causes the carbs
to be out of balance again. In this case you will see it in the twin manometers
and a carb rebuild kit for $45 will fix you up. The carbs on a 914 take
about 2 hours to get on and off, and 1 hour to replace the seals in the carbs.
Then you get to retune the throttles. Pay attention to the position of the
needle valve slide clip during the rebuild. If you g
et one
position off, you will be running richer or leaner than normal. Bing has
troubleshooting
manual on the web and Rotax has the carb balancing video you can order,
so check it out.
If your throttle position sensor is worn, that too can cause the computer to
force
the engine into a surge on the older slower computer processor. The program
sold by Rotax can check the position sensor.
For low boost, or leaks, wow, that's a new one on me. I don't get to fly that
high so I have no experience. My low boost problems is because I don't set the
cable right on the servo or the cable slips.
Rich Schultz found with running on AV Gas, his carbs stayed in tune if he added
just a bit of Marvel Mystery Oil to his gas to lube his carb. His problems
cleared
up.
Bud
Custom Flight Creations
(813) 653-4989
----- Original Message -----
From: Paul McAllister
Sent: Thursday, October 09, 2008 9:20 PM
Subject: Re: Europa-List: engine surging
Hi Folks,
Could I offer a contrary view? I got to 600 hours on my 914 with no
sign off issues wih the carbs, but on the adivce of many I sent my
carbs into Lockwood to have them overhauled. What a mistake, the
airplane now uses .3 to .4 more gallons per hour than before and it
took me 4 tries to get the inlet system sealed up again so I could get
maximum boost.
Actually it still is not right, I can only get 27 inches and 16k feet
and I should be able to get 34" so the darn thong is still leaking.
With that said, it may well be your carbs, but the first place I would
go is fuel filters, then look at the fuel pressure (needs to be
measured differentially), then onto the turbo waste gate. What you
will need to do is disconnect the cable and move it by hand to check
for "stickyness".
After all of the above, yep, I'd mess with the carbs.
Just my 2 cents worth.
Regards, nbsp; Features Chat, --> http://www.matron======================
bsp; via the Web title=http://forums.matronics.com/
href="http://forums.matronics.com";>http://forums.matronics.com
<html><body>
<DIV>I have some follow-up on the surging problem. Turning off the TCU
does
not help anything. In fact, the engine seems to surge and be a little
rougher. I have checked the plugs which were new two hours ago. The
air filter has no effect on the problem. I have checked the tubing, it
is six years old, but looks to be in good condition and no cracks...course you
can't see the underside of a lot of the tubing. The surging varies.
I ran it yesterday and it did not surge at all...manifold pressure up to
38 and it seemed to be cured. Then today I ran it again and the surging
was back. The surging is over a range from 5000 down to 2000.
Someone
was of the opinion that it was almost like the engine was being turned off
and as the RPM dropped, being turned back on. Since the problem occurs
only at the higher throttle settings, I had assumed it could not be the
electrical
system. The engine does diesel some when t
urned
off. It has done that for a year or so. I usually turn off the fuel
pumps first and when the pressure drops, then turn off the ignition.
The dieseling is worse if the enginie is hot...like up at 200 degrees or
so.
The surging is less severe when the engine is hot...up in the 200 range,
and worse with the engine temp at 130. </DIV>
<DIV>I am leary of the carbs but it sounds like I will have to tackle them if
no one
comes up with an alternate idea. No one around Knoxville has
experience with a Rotax. I asked our AI if he knew anything about Rotax
engines and he said, "Heck, I can't even spell it!" The
intermittant
nature of the surging has added to the frustration. I can't
see anything being done to the engine that makes it behave
different. I
have the same gas(half auto high test and half 100LL) in the
plane that was in there when I did two flights before the surging started.
The mag check is normal. Running both fuel pumps increases the pressure
reading but does not change the surging. It did not surge for 500 hours
running on one pump. Thanks for the ideas thus far.</DIV>
<DIV>Ken Carpenter</DIV>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #1010ff 2px
solid">-------------- Original message -------------- <BR>From: "ALAN YERLY"
<budyerly@msn.com> <BR>
<STYLE></STYLE>
<META content="MSHTML 6.00.2900.5626" name=GENERATOR><!--[gte IE
5]><?xml:namespace
prefix="v" /><?xml:namespace prefix="o" /><![endif]-->
<DIV>
<DIV>Guys, Here is my one and a half cents.</DIV>
<DIV> </DIV>
<DIV>When working with Jerry Hope's 914 we found that the reset switch was all
that was necessary to cure the surging... That is always my first
in-flight
correction. For my older engine, the wiper on the pot in the turbo servo
wore out with time and the servo began to hunt. By hitting the reset
switch, it momentarily cuts the power and stabilizes the manifold/boost and
the servo related surge/boost fluctuations stop.</DIV>
<DIV> </DIV>
<DIV>As for the carb related problems, With the engine at idle,
servo locked
out (reset switch held to eliminate the servo from operating), run the
engine up until you see about 35-39 inches of MP. If the engine does not
surge, it is not the carbs. If you have the dual manometers, and can
watch the MP on each carb, that will tell you volumes about your carb
health.
If one of the altitude compensators is hanging up, the engine will
sag, calling for more boost, then the engine boost clears the carb balance
problem,
but that causes a momentary over boost which then causes the servo
to cut boost, which then causes the carbs to be out of balance again.
In this case you will see it in the twin manometers and a carb rebuild kit
for $45 will fix you up. The carbs on a 914 take about 2 hours to get on
and off, and 1 hour to replace the seals in the carbs. Then you get
to retune the throttles. Pay attention to the
posit
ion of the needle valve slide clip during the rebuild. If you get one
position
off, you will be running richer or leaner than normal. Bing has
troubleshooting
manual on the web and Rotax has the carb balancing video you can
order, so check it out. </DIV>
<DIV> </DIV>
<DIV>If your throttle position sensor is worn, that too can cause the computer
to force the engine into a surge on the older slower computer processor.
The program sold by Rotax can check the position sensor.</DIV>
<DIV> </DIV>
<DIV>For low boost, or leaks, wow, that's a new one on me. I don't get to
fly that high so I have no experience. My low boost problems is because
I don't set the cable right on the servo or the cable slips.</DIV>
<DIV> </DIV>
<DIV>Rich Schultz found with running on AV Gas, his carbs stayed in tune if he
added just a bit of Marvel Mystery Oil to his gas to lube his carb. His
problems cleared up. </DIV>
<DIV> </DIV>
<DIV>Bud</DIV>
<DIV>Custom Flight Creations<BR>(813) 653-4989</DIV>
<BLOCKQUOTE style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px;
BORDER-LEFT:
#000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV style="FONT: 10pt arial"><B>From:</B> <A
title=mailto:paul.the.aviator@gmail.com
href="mailto:paul.the.aviator@gmail.com";>Paul McAllister</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=mailto:europa-list@matronics.com
href="mailto:europa-list@matronics.com";>europa-list@matronics.com</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, October 09, 2008 9:20
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Europa-List: engine
surging</DIV>
<DIV><BR></DIV>--> Europa-List message posted by: "Paul McAllister" <<A
title=mailto:paul.the.aviator@gmail.com
href="mailto:paul.the.aviator@gmail.com";>paul.the.aviator@gmail.com</A>><BR><BR>Hi
Folks,<BR><BR>Could I offer a contrary view? I got to 600 hours on my
914 with no<BR>sign off issues wih the carbs, but on the adivce of many I sent
my<BR>carbs into Lockwood to have them overhauled. What a mistake,
the<BR>airplane now uses .3 to .4 more gallons per hour than before and
it<BR>took me 4 tries to get the inlet system sealed up again so I could
get<BR>maximum boost.<BR><BR>Actually it still is not right, I can only get 27
inches and 16k feet<BR>and I should be able to get 34" so the darn thong is
still leaking.<BR><BR>With that said, it may well be your carbs, but the first
place I would<BR>go is fuel filters, then look at the fuel pressure (needs to
be<BR>measured differentially), then onto the turbo waste gate. What
you<BR>will need to
do is
</B></FONT></PRE></BLOCKQUOTE>
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