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80 HP 912UL will not start

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1 year 10 months ago #12271 by RotaxOwner Admin
RotaxOwner Admin replied the topic: 80 HP 912UL will not start
That's an ambitious project! And while we'd all love to have a better mousetrap, do you really think that a small run of home-brew modules could be more reliable (or even as reliable) than the modules designed, tested and produced by the OEM supplier?

What are the odds? Pilots are certainly no strangers to risk assessment... It's your call!

I'd be remiss if I didn't remind everyone about this Service Letter: legacy.rotaxowner.com/si_tb_info/serviceletter/sl-912i-005.pdf

"The use of any third-party replacement kits, modifications, and non-genuine ROTAX components or accessories for ROTAX engines is NOT approved by ROTAX and very strongly discouraged..." (&etc.)

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1 year 10 months ago - 1 year 10 months ago #12272 by Shawn Mack
Shawn Mack replied the topic: 80 HP 912UL will not start
Thanks for the response but I actually don't see it as ambitious at all but a rather simple project judging by the simplicity of the module itself. Could it be made more reliable, absolutely! That's already been determined. It's just sad that for a few pennies the module could be made far better and more reliable given the responses from the other electrical engineers that have inspected the unit and its components.

I understand that this is not a Rotax built part but built "for" Rotax by Ducati. This module worked for your purposes and this is what you chose. And yes we are all aware of the service letter.

What's really frustrating is that Rotax wants nearly $2000 from me to replace both of these modules. Given what we now know is inside and how easy they can be reverse engineered and duplicated for a mere fraction of that, do you think this is a fair price to us owners? Look at it this way, Rotax is asking for us to pay 11% of the costs of a brand new engine to replace the little ignition modules. Does that seem logical?

If it's a known issue that these 2006-2007 model year modules go bad why does Rotax no offer up a program to swap these out? Is Rotax working on a "better mouse trap"? Seems like there are more and more people recently with this same issue.

I'm not pointing blame at anyone specific but rather just venting at the cost of these modules when there is no way they should cost this much. I love my plane and the Rotax engine in it. It's the best engine out there for the LSA market in my opinion.

Why did Rotax stop the program where they offered the advanced start module "kit" with the 2 modules and easy start built in? I've searched high and low and can't find this anywhere. I'd gladly pay $931.12 for this "kit" with 2 modules if I could find one.

Can you offer me this same deal for the "kit" so I can repair my plane and enjoy flying again? These modules seem to be on backorder everywhere.

Thank you
Last Edit: 1 year 10 months ago by Shawn Mack.

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1 year 10 months ago #12273 by Christos Deligiorgis
Christos Deligiorgis replied the topic: 80 HP 912UL will not start
You have done what i will do if i have the same problem , i will not pay $2000 for these modules that cost $400 the most.

Thank you for the information.
Chris

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1 year 10 months ago #12274 by Kevin Stewart
Kevin Stewart replied the topic: 80 HP 912UL will not start
Hi Shawn,

I am more than happy to share all of the data that I have given that I am unlikely to do anything with it myself. I have a circuit diagram, parts list and even a PCB layout in Proteus (can supply Gerber files). I have sourced the connectors for the 4 pin and 6 pin variants.

The following need to be considered if making one of these ignition modules:
  1. Can you construct it to a suitable IPC class?
  2. How are you going to test it?
  3. Are you going to improve it?
  4. How are you going to mitigate common mode failure?
  5. How are you going to indemnify yourself against any losses resulting form a unit failure?

It sounds like some of us have the capability to fulfil the construction requirement so that is no problem.

You cannot just put the module in the plane, start the engine and conclude that it works correctly. Without the original test specification you would have to determine suitable limits for the pick-up amplitude, supply voltage, load, etc. You may also want to do some temperature testing and some form of temperature cycling soak test.

Some form of test fixture capable of driving the modules with different amplitude and frequency trigger signals whilst evaluating the performance of the output switch will be needed.

Given that the current design has problems, are you going to try to identify where the weak points are and change them?

If you build yourself 2 new modules then in some ways you have a potential common mode failure - you and your assumptions about how to build the modules ;-)

The most difficult issue I see is how to defend yourself against potential claims following an accident where it is discovered that you have built the ignition modules yourself. I am guessing that in some countries you may be allowed to make your own components and your insurance will cover you. In other countries you would need approval from your governing body for the 'modification'. This could be more problematic.

All of the above is possible, I do it for a living in a safety related industry but it is all non-trivial to do properly. I dare say that with appropriate evidence you could convince the various approval bodies to accept your module as a suitable replacement. The rub is that all this 'development' would have cost you a fair premium and if you included your time then it would likely cost you more than buying the Rotax units :-(

Don't get me wrong, I love building and repairing things but you have to look at the whole problem. I think that the approach that the Dutch guys have taken at Carmo Electronics is interesting. They seem to have a test fixture where they can run the units and then determine what has failed, they then repair just that part of the circuit. That is probably more defendable than building an entirely new circuit.

To proceed any further I think that you need to build a test fixture and that is not a 5 minute job. You need to be able to generate the trigger signals with the correct phasing and adjustable amplitude. This would allow you to investigate how a working unit operates as well as investigate a faulty unit. The circuit is simple, so once you can see what is not happening you can probably de-pot just the relevant section of the circuit and repair it.

I am open to other suggestions and ideas...

Kevin
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1 year 10 months ago #12275 by Mark Kyle
Mark Kyle replied the topic: 80 HP 912UL will not start
Hi Shawn

The original modules made by Ducati do fail regularly and I was looking at upgrading the components that fail. BUT the new modules like I have on my 912 are made by Motorini and they do not fail. I have searched the world looking for a dud Motorini unit and as yet have not found one single unit. The later version like mine has the softstart built in BUT you dont have to use it. The softstart option is only for the later 912 engines that have the updated timing on the flywheel sensors. If you do not enable the softstart option and this is just a matter of 2 wiring pins then the Motorini module is fine for use on the older 912 that do not have the modified timing. This is why I didnt go any further. I have all the circuits for the older one and was going to make one but why do that when it would be much better to make the later version that does both older and later motors and also is super reliable. So be on the lookout for the later Motorini modules and that is the one I want to pull apart

Mark

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1 year 10 months ago #12279 by Shawn Mack
Shawn Mack replied the topic: 80 HP 912UL will not start
Thanks Kevin and Mark.....

I am excited to pick up this project where you all left it. I have access to a perfectly good 2009 912ULS on a test stand. I can pull any and all measurements from this running engine with known good Ducati dual 6 pin modules. This is a good start, no pun intended.

Mark, do the Motorini modules look different? Can you post a pic?

Kevin, I have the files you posted but they are only PDF's of the board files. I use Eagle but a friend of mine uses Proteus and Altium. Are you willing to share files? My email is srmack68 at gmail dot com if so.

I'm going to be taking several readings in the next week or so. This will be a great start as to what the little engine is doing.

I am also going to send my defective units to Carmo for repair and then determine what they repaired or replaced.

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1 year 10 months ago #12280 by Mark Kyle
Mark Kyle replied the topic: 80 HP 912UL will not start
In all the modules I have worked on after pulling tem apart the only things that have failed were the 2uF cap lost its capacitance down to as low as .5uf and the small BC547 style smd failed and also the fet had failed..this was across more than 3 modules so that seems to be the failures. The biggest amount of failures was the large Cap losing its capacity once it gets below about 1.5uf then they dont have enough grunt to fire

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1 year 10 months ago - 1 year 5 months ago #12281 by Kevin Stewart
Kevin Stewart replied the topic: 80 HP 912UL will not start
I suspect that the 2uF cap is over-stressed. Being potted it probably runs very hot and there will be quite a high dV/dt. It would be nice to up-rate this component. I too have seen a faulty SMT transistor (although I think that it is a BC849) so I guess this it too could be replaced with a more rugged component.

I've put the Proteus project and a copy of my wiki on my read only Google drive here:
https://drive.google.com/open?id=0B6ytVYfsfAiNflZzQnhkMG5SMllWWDlDdm5zX3RiZ3doU0E3T2lWRk5jNjdJaldqUW1MbUk

Help yourselves and if there is anything else that you need let me know.

If you have an engine on a test stand then you could potentially characterise the trigger inputs by attenuating the sensor outputs until the ignition stops firing. This would give you the minimum threshold on a working unit. This would be a very useful value to know when testing a newly constructed circuit.

Kevin
Last Edit: 1 year 5 months ago by Kevin Stewart.

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1 year 10 months ago - 1 year 10 months ago #12310 by Shawn Mack
Shawn Mack replied the topic: 80 HP 912UL will not start
Thanks Kevin, I got the files. I'm headed down to the LSA show here in Florida this week but will have a quick peek before I go. I'll drop in on the Rotax booth and have a look at the new modules if they have them on any display engines.

I'm also picking up some defective dual 6 pin modules from a local mechanic while at the show.

Shawn
Last Edit: 1 year 10 months ago by Shawn Mack.

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1 year 9 months ago - 1 year 5 months ago #12349 by Shawn Mack
Shawn Mack replied the topic: 80 HP 912UL will not start
Well I received my new modules that I had to order from a European Rotax distributor because no one in the US had this "kit" with the two modules and soft start feature. Plane is back up and running so I can start my testing and take some readings. The new modules I bought with the soft start feature built in have no names or markings on them other than the part number, 965444 and the 2015 serial numbers. They no longer say Ducati on them. They cost me around $1300 delivered to my door from Europe.

I'm still thinking of sending my old ones to the Netherlands for repair to see what they are doing. I have access to a few other dead units and I'll open them soon and take some readings.

I contacted a Rotax certified mechanic recently and told him of my issues. He later sent me this info he said he found on a LSRM chat room.

"There is a known problem with certain ignition modules with part number ending 726. They begin to require higher and higher RPM to fire until it reaches a point above that which the starter can reach. If you do get them to fire they work okay for that day, then revert to not firing the next time you try to start the engine. Went through this last winter with a customer's 912 ULS. The good news is that Rotax was cutting a great deal on new modules (with part number ending 927) that don't have the problem and also include a soft start circuit built in. We sent the modules to Lockwood for testing and they confirmed the problem. The test was free since it established that the old modules were indeed failed and qualified for a special price on the new modules that was less than half price of the old modules. There is some wiring adaptations that must be done, but it takes less than 10 minutes (all parts are included in the kit) and you're good to go."

I'll update everyone after some further testing.

Shawn
Last Edit: 1 year 5 months ago by Shawn Mack.

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1 year 5 months ago #13398 by Mark Kyle
Mark Kyle replied the topic: 80 HP 912UL will not start
Hi Shawn

Have you found a broken set of the new style ignition modules at all?. I still have not managed to find even one faulty set with the soft start feature. I keep searching and asking but nothing yet. I gather yours is all up and going now with no issue?

Mark

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1 year 4 months ago #13459 by Shawn Mack
Shawn Mack replied the topic: 80 HP 912UL will not start
Hi Mark,

I have not found a defective "soft start" module as of yet. I have came across a few of the standard ones from some local Rotax repairmen I have contacted.

My new ign modules with the soft start did arrive and they work beautifully. They better for what they cost.

Still working on the circuit and hoping to get a prototype board made for testing. I sent you a private email.

Shawn

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1 year 3 weeks ago #14592 by Mark Kyle
Mark Kyle replied the topic: 80 HP 912UL will not start
Well after a bit of pressure from some flying mates I decided to get my backside into gear and get this project going. This prototype has been tested on a test cell driving Rotax coils and 4 plugs. The unit was then placed on a motor in a aircraft and then started on this module and run for a while on it a few times. This was to guage temperatures of components. I have upgraded the critical components and the ones we know that usually fail with higher current and voltage specs. The unit is now being potted into a 3D printed case I have made and it will go on a flying aircraft for some further testing.

The next version will have another part changed out to a better spec as it was showing some heating...not a lot mind you but to be on the safer side I have selected the best one that is available. Over the next couple of weeks I will have a couple of these updated versions running on 3 aircraft flying to see how we go. One unit will also be run at max rpm on the test cell for 24/7 for several weeks.

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1 year 2 weeks ago #14636 by Shawn Mack
Shawn Mack replied the topic: 80 HP 912UL will not start
Looks great Mark, keep us up to date on your progress and findings.

Any thought of test flying a unit BEFORE you pot it? This way you could get temp readings after landing.

I understand the potting helps with vibration but a vented case with a tiny fan might be a better option along with mounting it to the firewall rather than the top of a hot engine.

Either way, great work!

Shawn

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1 year 2 weeks ago #14637 by Mark Kyle
Mark Kyle replied the topic: 80 HP 912UL will not start
Hi Shawn

The test jig made up actually drives a set of Rotax coils and driving 4 plugs. We tested the module with this as this is how we found the heat on the FET. This is the reason for the upgraded FET again. The rest of the board is fine with heated components after running. We are pretty confident with the state of things at the moment. The current unit about to be actually flown has my first upgraded FET but the next one which will be in the test jig running 24/7 will have the latest upgrade. Then we will test that in flight as well. Every single unit will be tested for an hour or so at max RPM on the jig before being potted. This jig will also be able to test old units to see what the failures are as well

Mark

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1 year 2 weeks ago #14651 by Conrad Beale
Conrad Beale replied the topic: 80 HP 912UL will not start
Mark,
Is there any chance you could email me. Conrad at conairsports dot co dot uk.
Thanks

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1 year 2 weeks ago #14652 by David Wallis
David Wallis replied the topic: 80 HP 912UL will not start
I had one of my modules delivered to Carmo in Belgium. Meanwhile I was lucky enough to get a set of the new soft start modules from Leading Edge Airfoils www.leadingedgeairfoils.com and they work beautifully. That was in 2015 and they had some of soft start modules then. I just called and checked and they are no longer available at the old price, Part number 81-280.

I have not tested the one module repaired by Carmo but I am sure it will work just fine. My cost was around $275 with delivery transportation by my friend, included.

I was surprised to learn that Carmo actually has a branch is the USA that repairs ign. modules but they will not do the Rotax Aircraft modules here. I am guessing it is due to liability concerns. That was a year ago and i'm surprised no one in the US has made a replacement module yet.

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1 year 1 week ago #14668 by Mark Kyle
Mark Kyle replied the topic: 80 HP 912UL will not start
The ignition module was tested on a flying aircraft yesterday. All went extremely well. I will put a couple of videos up on Youtube. The box it is potted into is only a test unit it wont be the final design or material yet. The engine was started on the new module only and during flight the engine was operated only on the one module. I have a new board revision coming next week which looks like will be the production version for this one at the moment unless I fit a softstart into it as well. I want to prove the existing design first then add the softstart feature to it.
When the new board revision arrives I will be making a few up and they will be tested on another 2 aircraft for a while but at this stage everything looks great

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1 year 1 week ago #14672 by Mark Kyle
Mark Kyle replied the topic: 80 HP 912UL will not start
A couple of videos starting and flying the new module

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1 year 1 week ago - 1 year 1 week ago #14673 by Shawn Mack
Shawn Mack replied the topic: 80 HP 912UL will not start
Great job Mark! Keep us posted. Mine is very close and I'll send you an email later this week.

It really wasn't that "ambitious" of a project after all and it's undoubtedly a better mousetrap with better components.

I think Thomas Edison once said:
“To invent, you need a good imagination and a pile of junk.”

Well, we started with a pile of junk and out of the old module came these. Time will tell but this is a great start, no pun intended. :)
Last Edit: 1 year 1 week ago by Shawn Mack.

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