Ignition checks

by David Stewart in 912 / 914 Technical Questions 10 years ago

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Re: Ignition checks

by David Stewart » 10 years ago

David Stewart

1 5 0

I pulled up the Video on the needle and found out about the notches. Both needles were on the 3rd notch, so don' t believe that is the problem. My A&P hasn't come up with anything yet. No one seems to know why there is such a difference in the rpm's between the two module switches. When would be a good time to call you at your business?

Thank you

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Re: Ignition checks

by Gordon Halsted » 10 years ago

Gordon Halsted

1 1 0

Have you tried. Reversing plugs between box and coil to see if there are any changes?

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Re: Ignition checks

by Roger Lee » 10 years ago

Roger Lee

126 5.13k 4.58k

Ignition rpm difference can be affected by plug gaps, bad connection with the plug wire and boot, loose ignition wire on your switch, thermal paste on the plug tips, switched plug wires bad wire or connection at the module 6 pin connectors,. All these should be ruled out no matter how sure you think they are good. Take a look at each one.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: Ignition checks

by Mike Goodrich » 10 years ago

Mike Goodrich

8 123 0

Can someone confirm if this
" if the A modul controls the top plugs of 1&2, and bottom plugs of 3&4, and the B modul controls the bottom plugs of 1&2, and top plugs of 3&4,"
is true.
I am looking at a friends 912 that has a similar problem and his wiring diagram shows the A module firing the top plugs and the B module the bottom plugs. It's the same for my 914, see attached "914 ignition diagram.jpeg".

His 912 (100HP) has an 800 rpm drop on one switch (can't remember if it's left or right) he has had the ignition modules checked by the French Rotax agent on another engine, he's changed plugs, plug leads and caps. The last thing he did was he swapped the plugs between the ignition coils and the modules (see attached "ignition check.jpg") and the problem changed to the other switch. This suggest to me that his problem is probably more something to do with the ignition coils and wiring up to the modules. Has anyone any experience with this or any comments to make..

David
Sorry to steal your thread, I thought it might be interesting to compare but if you prefer I'll start another thread.
Mike G

914ignitiondiagram.jpg (You do not have access to download this file.)

ignitioncheck.JPG (You do not have access to download this file.)

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Re: Ignition checks

by Rob Seaton » 10 years ago

Rob Seaton

3 1.32k 240

Hi Mike,
The 914 is wired to fire the top plugs on A module and the bottom plugs on B. This is because the ignition is staggered to avoid detonation: A fires at 26 degrees BTDC and B fires at 22 degrees BTDC. How do they do this? The flywheel lobes are different length.
Rob

Thank you said by: William Ward

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Ignition checks

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