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  #131  
Old 05-08-2016, 12:51 PM
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Toobuilder Toobuilder is offline
 
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Running the RPM up to 2700 should increase the required advance, but how much depends largely on mixture. I picked 2300 RPM because that is my normal cruise RPM. Each airplane/engine/prop and mixture condition will dictate a specific "best" timing set.
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  #132  
Old 05-08-2016, 02:25 PM
rv7charlie rv7charlie is offline
 
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Thanks; that's what I would think, but wasn't sure.

Back to the Megajolt & trigger wheels; how flexible is the software on the required number of teeth? Could it be told to run on 6-1? 4-1? In other words, does it just count teeth to set advance, or is it smart enough to measure rpm (with the missing tooth interval) and calculate an advance *time* at a given rpm? Reason for asking is that it would make a triggering system a lot simpler. I've never actually a Lightspeed system, but from what I've seen in pics, it appears to use a simpler trigger system than a full fledged many-tooth wheel.

Thanks for any info,

Charlie
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  #133  
Old 05-09-2016, 02:37 PM
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Default Function of the EDIS module

I think that is a function of the ignition module not the Megajolt software.
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  #134  
Old 05-09-2016, 03:43 PM
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Quote:
Originally Posted by rv7charlie View Post
Back to the Megajolt & trigger wheels; how flexible is the software on the required number of teeth?
You want a Megasquirt, not a Megajolt. Megasquirt will accept all kinds of inputs. Megajolt is a simplified system for control of a Ford EDIS ignition only...and that means 36 minus 1 trigger wheels.
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  #135  
Old 05-09-2016, 07:11 PM
rv7charlie rv7charlie is offline
 
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Ah, that explains it. A friend installed a Microsquirt on a Jeep, & he told me that it could use multiple trigger methods. I was hoping the jolt would get the same flexibility.
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  #136  
Old 01-13-2017, 01:40 PM
rwtalbot rwtalbot is offline
 
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If I understand this system correctly the EDIS is capable of running without the ECU/Megajolt and will fire at 10 degrees BTC. If one were to position the pickup so that corresponds with 25 degrees BTDC on our engines failure of the Megajolt in cruise is almost a non event.

One Megajolt is also capable of firing multiple EDIS units. So it is reasonable to build a dual ignition system with one Megajolt and two EDIS units? It may actually be preferable to reduce programming requirements etc.

Presumably the EDIS is a CD ignition, and would compare to the PMAG in terms of spark energy and duration?

Has anyone measured the current requirements of the system to size an appropriate backup battery?
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  #137  
Old 01-21-2017, 11:11 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by rwtalbot View Post
If I understand this system correctly the EDIS is capable of running without the ECU/Megajolt and will fire at 10 degrees BTC. If one were to position the pickup so that corresponds with 25 degrees BTDC on our engines failure of the Megajolt in cruise is almost a non event.

One Megajolt is also capable of firing multiple EDIS units. So it is reasonable to build a dual ignition system with one Megajolt and two EDIS units? It may actually be preferable to reduce programming requirements etc.

Presumably the EDIS is a CD ignition, and would compare to the PMAG in terms of spark energy and duration?

Has anyone measured the current requirements of the system to size an appropriate backup battery?
EDIS uses standard inductive coils. However, that is not a downside for our application in my opinion. There's lot's of hype about capacitive discharge coils, but most of it doesn't directly translate to benefits for our engines. CD fires a hot spark, but it's duration is very short compared to a standard coil. CD ignition systems tend to be less reliable than inductive. These have been common in the hot rod scene for some time and lots of guys have reliability issues. Do the research on pro's and con's of each before assuming CD is better.

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Last edited by lr172 : 01-21-2017 at 11:15 PM.
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  #138  
Old 01-22-2017, 07:14 AM
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Quote:
Originally Posted by rwtalbot View Post
If I understand this system correctly the EDIS is capable of running without the ECU/Megajolt and will fire at 10 degrees BTC. If one were to position the pickup so that corresponds with 25 degrees BTDC on our engines failure of the Megajolt in cruise is almost a non event.
Kirk (see earlier, this thread) is planning to install his #2 ignition without a Megajolt box, EDIS module only, thus fixed timing at 25 degrees via offsetting the pickup 15 degrees.

Quote:
One Megajolt is also capable of firing multiple EDIS units. So it is reasonable to build a dual ignition system with one Megajolt and two EDIS units? It may actually be preferable to reduce programming requirements etc.
The programming requirements are nil. The ignition maps are created offline. With two maps stored on your laptop, plug in, open one at a time in the Megajolt software, and flash each with two keystrokes. For the second ignition, just move the RJ11 plug from #1 to #2 and repeat.

Quote:
Presumably the EDIS is a CD ignition, and would compare to the PMAG in terms of spark energy and duration?
As Larry noted, the EDIS system is inductive, not CDI. Spark characteristics will be very similar to a P-mag, because a P-mag uses the same Ford coil. To clarify; there are two Ford coils, early and late model. The early model incorporates positive plug wire retention. The late model has a flat bottom, so mounting is simplified (like on a P-mag body), and it has taller towers. Choose your preference; there doesn't seem to be any practical difference in output or reliability. Other coils seem to work fine too. Select one without internal switching.

Energy, duration, and claims of increased HP are mostly BS.

Quote:
Has anyone measured the current requirements of the system to size an appropriate backup battery?
An English builder did so as part of his LAA approval, and reported 1.05 amps at 14.4 supply voltage at 2750 rpm. You can read about his work in the August 2011 LAA magazine. Kirk and I made local measurements on the lathe, but I seem to have misplaced the notes.

I've flown one EDIS paired with a Slick for a year. It has been trouble-free, so now I'm installing a second EDIS. The battery for #2 is a Motobatt MB3U AGM rated at 3.8Ah, charged via a Schottky. Both the PC925 main and the little MB3U are located in the cool space behind the baggage compartment. Power feeds are battery direct via fusible links for circuit protection, independent of the aircraft system. KIS is good.

Diagram (updated 2018):



So far, the only potential issue I've seen has to do with timing at cranking speeds. The system fires before TDC, so users with low inertia propellers could conceivably get kickback. It doesn't seem to be a problem with a metal Hartzell. Exactly how far before TDC may depend on EDIS module part number. We've measured as little at 2 degrees at very low RPM, and nobody has ever reported more than 10. It ramps up as RPM rises, transitioning to the mapped values at about 500 RPM.

Early P-mags had the same problem, since corrected with software. The EDIS doesn't seem to offer a software-based approach to retarding the spark at cranking speeds (no Megajolt control below 500 RPM), so the only way to do it is with a mechanical offset, which I flew most of last year. To fire ATDC during cranking with the EDIS, I retarded the trigger wheel 10 degrees, and uploaded a map with all values advanced 10 degrees. The result is a very soft start, almost like a turbine spooling up, in particular hot starts using the "slowly advance the mixture knob" method.
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Last edited by DanH : 12-05-2018 at 08:36 AM.
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  #139  
Old 01-22-2017, 08:39 AM
rv7charlie rv7charlie is offline
 
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Dan,

This thread seems to be mixing MegaJolt>EDIS and EDIS-only setups. In your last post, I assume that you're speaking of programming your MegaJolt, right?

Thanks,

Charlie
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  #140  
Old 01-22-2017, 08:54 AM
Tom Martin Tom Martin is offline
 
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Kevin
Nice, easy to follow, wiring diagram, and simple is the operative word. For the backup battery the diagram shows it connected directly to the main battery negative post.
If the shared positive connection at the master solenoid fails, you have that 3.8ah left to get you on the ground, but it something should happened to the main ground connection, or the main battery itself, you could potentially lose both systems. I think it would be possible to ground that second battery to separate ground, eliminating a single point ground failure? This might cause a ground loop problem for your radios but at that point you are just trying to get on the ground.
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Last edited by Tom Martin : 01-22-2017 at 08:58 AM.
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