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rlborger(at)mac.com
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 Posted: Mon May 21, 2012 4:27 am Post subject: Lack of power with water heated carb body mountings |
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Juergen,
OK, I'm assuming a constant speed prop on 912S as the 914 does not need carb heat and a 912 does not normally call for a constant speed prop.
Yes you can rate the power by the numbers. The charts on page 5-5 of the Operators Manual give power vs fuel flow, manifold pressure, etc. These should tell you what power is produced at what RPM for a given manifold pressure and what fuel flow to expect at that power setting.
At flat pitch, takeoff setting on the prop, and 100% throttle, what is the RPM and what is the manifold pressure?
The 912S operators manual says you should have 5800 RPM, the manifold pressure should be around 30 in or 1 bar (1015.8 hPa).
At the same time, the fuel pressure should be between 2.2 psi & 5.8 psi (0.15 bar & 0.4 bar) and fuel flow 7 gal/hr (27 l/h).
If you don't reach those numbers, then you are down on power and you must figure out why. It's either not receiving enough air flow, enough fuel or the ignition could be failing at some, lower, RPM. Which of those numbers are not within the operating specifications.
It is not bad phrasing, you are doing great. I have never seen one of the carb heaters so I did not understand that they change the length of the intake tubes. That should not be an issue as long as the cross-sectional area has not been reduced.
So, find out your takeoff numbers and see if there is an indication of why you are not making the necessary power.
Blue skies & tailwinds,
Bob Borger
Europa XS Tri, Rotax 914, Airmaster C/S Prop.
Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP
3705 Lynchburg Dr.
Corinth, TX 76208-5331
Cel: 817-992-1117
rlborger(at)mac.com
On May 21, 2012, at 2:18 AM, europapa wrote:
Bob,
I have got a two blade MT electrical constant speed propeller.
So I preset the rpm I want the prop to turn and the control unit keeps
for example the engine at 5200rpm even with the throttle at 40%.
So the power the engine delivers cant be calculated via manifold pressure and rpm. As there is no indicator for the pitch of the blades.
So I can not rate the lack of power by numbers.
The "longer suction tube" are the 15mm the carbs have been retracted from there original position due to the carbheaters. The length the carbheater body is adding.
Sorry for my bad phrasing.
Juergen
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rlborger(at)mac.com
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| Posted: Mon May 28, 2012 9:45 am Post subject: Lack of power with water heated carb body mountings |
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Thanks very much for letting us all know the source of the problem.
Enjoy our holiday with the family.
Blue skies & tailwinds,
Bob Borger
Europa XS Tri, Rotax 914, Airmaster C/S Prop.
Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP
3705 Lynchburg Dr.
Corinth, TX 76208-5331
Cel: 817-992-1117
rlborger(at)mac.com
On May 28, 2012, at 7:13 AM, europapa wrote:
As it seems, it has been all my fault.
I now removed the carbs and inspected them.
The plungers have not been aligned correctly,
I did not glue the carbs into the carb heaters
and the time I had the problem with the low power it was a hot day
with about 28°C.
Put that all together and I have to be glad that it flew anyway.
Now I fixed all that and am sure the heat from the carb heaters has nothing to do with the lack of power.
Due to professional and familiar commitments (family holidays and all the work that has to be done be for that I can leave my business alone) I may not test it the next two weeks but then I hope to bring good news to you.
Happy flying!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=374081#374081
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