 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
keithhickling(at)clear.ne
Guest
|
 Posted: Thu Feb 26, 2009 9:04 pm Post subject: large mag drop on both mags, 912uls |
 |
|
Hello all,
On first running my new 912 uls a couple of weeks ago, I got a mag drop pf just over 500 rpm on one mag and just under 600 rpm on the other mag, starting at 4000 rpm. All else was OK; oil temp and press, EGTs, CHTs etc, and the engine ran quite smoothely; even on 1 mag with the rpm drop it was not obviously rough or misfiring. Prop is Airmaster, operating correctly - testing done on fine pitch.
Our local Rotax man thought it was probably not a real mag drop but a tacho problem, though it sounded real. So yesterday we checked it with an optical tacho and it was real. The optical tacho showed a rpm drop on the prop from 1700 down to 1490, which is equivalent to a 500 rpm drop on the engine.
Another rotax owner here suggested it might be the mag ground leads shorting to the screen, as I had left the screen quite close to the end of the wire where it enters the ignition modules. So today I stripped the screen a bit further back, disconnected the screen ground and connected the mag shorting wires to 2 temporary switches, bypassing the ignition switch completely. This made no difference, still the same mag drop, eliminating partial shorting of the mag wires as a cause.
The plug gaps are correct, and the plug colour looks OK. The throttle cables are set correctly. The engine always starts first go, easily, and runs smoothly. Our local engineers have no ideas, although they are not very familiar with rotaxes. So I would really appreciate any advice on where to go from here - what should I look at next?
Thanks,
Keith Hickling,
New Zealand,
Mono XS, Kit 613.
[quote][b]
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
|
|
| Back to top |
|
 |
craigb(at)onthenet.com.au
Guest
|
| Posted: Fri Feb 27, 2009 4:53 am Post subject: large mag drop on both mags, 912uls |
|
|
just curious, but what happens if you pull the air intake line off the carbs and do the test. Other thing
is have you or the rotax man checked the timing. If the timing is late then you will get incomplete combustion of the fuel, and the extra plug firing will help overcome the late spark. If its late timing
it wont hurt the engine, but it wont be at its best either.
[quote] --
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
|
|
| Back to top |
|
|
budyerly(at)msn.com
Guest
|
| Posted: Fri Feb 27, 2009 7:20 am Post subject: large mag drop on both mags, 912uls |
|
|
<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]--> Keith,
I didn't notice what fuel you are running in on. 100LL aviation gas gives less mag drop than the 92 to 94 RMS Premium fuel here in the States. I must show my ignorance since most of my experience is with the 914. I have yet to see a mag drop below 300 on Premium and even less on Aviation Fuel. If the engine is running smooth as a sewing machine on one mag, I would suspect the octane rating.
Hope it all works out. I used to think that if it didn't say Lycoming or Continental, it didn't belong on an airplane. These Rotax's have changed my opinion. My experience is they start and run well when properly serviced right out of the box. Just wish they were fuel injected.
Bud Yerly
Custom Flight Creations.
[quote] ---
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
|
|
| Back to top |
|
|
hdwysong
Joined: 06 Jun 2008
Posts: 21
|
| Posted: Fri Feb 27, 2009 2:30 pm Post subject: large mag drop on both mags, 912uls |
|
|
| Quote: | On first running my new 912 uls a couple of weeks ago, I got a mag drop
pf just over 500 rpm on one mag and just under 600 rpm on the other mag,
starting at 4000 rpm. All else was OK; oil temp and press, EGTs, CHTs
etc, and the engine ran quite smoothely; even on 1 mag with the rpm
drop it was not obviously rough or misfiring. Prop is Airmaster,
operating correctly - testing done on fine pitch.
|
We chased a similar situation with our 914, Keith. Documented in the
archives here:
http://tinyurl.com/76oxud
Long story short, our issue was with the carb needle settings (... set
too lean as delivered from the factory).
Good luck!
D
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
