can I connect 2 edis to one mega?

[knuckle_buster]

I am replacing a dual magneto on a revmaster VW engine, I have two seperate edis systems mounted and working. I use one for starting and the other for running, What I need to know is how to conect both edis' to one mjlt? Or do I need to get two?

[brentp]

There should be enough current on the MJLJ output to drive two EDIS modules, *but* we haven't tested this. So, in principal, it should work.

The bigger question is, are the EDIS modules being driven from the same VR sensor, or are they otherwise perfectly synchronized?

Tell us more about why you have two different EDIS modules- why do you need a separate one for starting?

Regards,

[fikus01]

if the rev master is the 4 cylinder surely you would only need 1 edis and 1 megajolt and it should all work fine weather you are starting or not!!

[knuckle_buster]

The edis modules are completely seperate, two sets of spark plugs, two edis modules, two VR triggers, the only common point is the 36-1 tooth wheel. I am using two edis, because there are two sets of spark plugs each cylinder has two plugs. I currently use one setup for starting, as it starts better with the timming set at tdc and the other setup, set for 29 btdc. What I want to be able to do is run the engine correctly with the mjlt controlling both edis at the same time. I don't think I mentioned the engine is in an airplane, that's why there are two ignitions, as a safety backup.

[fikus01]

aahh i see, explains a bit. the edis modules on there at the mo are literally setup with power and have the vr sensors positioned to give you the correct timing. have i got that right? very clever i must say.

well im a beginner to all this but 1 megajolt and 1 edis with split leads (2 sparks on each coilpack terminal) would do it if the spark had enuf strength but in my mind the better idea would be 1 megajolt, 1 edis and 2 coilpacks to give u your twin spark! i think brent is the person to confirl weather the mjlj/edis could handle both coilpacks!

i think you would come into complications trying to run 2 edis at the same time, there could be minute internal differences in the modules meaning your sparks could be arriving at diffrent times! not ideal i wouldnt have thought! having a nice big switch to swap them over in the event of a failure mite not hurt tho!

[brentp]

First of all, a single MJLJ will not be able to handle two EDIS modules at the same time. The MJLJ conforms to the Ford EDIS specification, where the SAW signal is sent to the EDIS module immediately after it receives the PIP signal waiting for the PIP signal. If they are out of phase, one of the EDIS modules will receive the SAW signal at the wrong time.

However, there is good news. Because you can tailor the ignition advance to your preference, you can set a "cranking" advance, of say, 0 degrees, and then when the engine is running, you can have the normal advance you prefer. All with one EDIS module and one MJLJ.

With 3.1 firmware or later, there is a special behavior for cranking RPM (i.e. when engine speed is below 457 RPM) -- it uses the ignition advance value specified in the lowest RPM bin / lowest load bin in the ignition table. (i.e. upper left hand corner of the table when using the configuration software).

Do you have a dual plug setup? If so, you might be able to drive two edis modules from the same VR sensor- they would then be synchronized and therefore will be able to accept the SAW signal emitted from one MJLJ.

Does this answer your question or meet your needs?

P.S. I hope you realize that the MJLJ is NOT (repeat NOT) certified for aircraft use!!! I'm sure you've heard this on other stuff, but it's worth repeating!

If you want full rendundancy, you may want two EDIS / MJLJ systems running in parallel.

Thanks,

[knuckle_buster]

I'm not worried about the mjlt not being certified for aircraft, That is not a problem when you are registered as expiramental. I have a mjlt on order with the map option, I will make sure it's operates correctly one one edis before I try anything else. Not to start another thread, but how about using the mjlt with a dual dis module from a Mustang? The dis from a 91 Mustang is setup to fire two banks of four plugs, using two coil packs. It also uses the pip and saw pulses the same way an edis uses them. The major difference is it uses 2 Hall sensors instead of the vr and 36 -1 tooth wheel. The big draw back is then I loose redundency.