Dear Mr Austin, I am an ardent admirer of your flawless project, which provides great motivation for all the tinkerers among us. Unfortunately, the thread collapsed some time in January, so we never found out what happened to the twin plug ignition system. I own a set of Land&Sea twin plug heads for my Merc 2.5 ROS, which I would like to fit with a reliable ignition system. Your advice/reason for not proceeding with the twin plug system would be greatly appreciated, and I trust not only by me. I see that the OMC Ficht motors also utilize dual wound coils, but doubt whether any of these would work with the Merc electronics.
Kind regards, Wolfgang (South Africa)
According to the pictures in this thread as of July 2017 it is still a duel plug motor. I`ve seen nothing that changed that. I guess I just figured it must have worked.
DB
Finally got a chance to run the fuel injected beast on the improved dyno. Not the best video, but at the time it was our best spur of the moment option. Start up good, even being on alcohol.
https://www.youtube.com/watch?v=wuCKmzWzHY4
Ran very rich and was sluggish to about 6000 then started clearing out. Once to 6500-7000 it started its surging. This is the kind of problem that I experienced with the carbs except the carb could not handle and engine would die if you did not back off throttle quickly.
It is really hard to keep track of all that is going on while bring the engine up. Only after the runs and listening the the videos do get a true ear on what it sounds like. It sounded good but yet strange. The numbers reflected pulling something between 190 and 220 HP. Why? Those are the differences between what is seen from the foot pound numbers and the formulas for the hydraulic computations.
After the runs, I pulled the plugs from number 1 and 2 cylinders. Had started to make the nice brown colors that you look for.
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Is it just me, but it looks like the center electrodes are burnt all to hell.
Jeff
PS: Great HP numbers! Congrats. Have you considered using a data logger?
"We live at the bottom of an ocean of air." - General Marvage Slatington
If the surge happens with both type fuel systems I think you can rule them out as the problem. It would be a strange coincidence for two completely different types to have the same issue. Whatever it is it sounds like it`s common to both systems. Maybe there is something going on with the firing/advance. Lastly could it be the dyno? Just guessing here. Nothing beats hands on.
DB
The following day, wanting to do a compression check, I pulled the balance of the plugs and was shocked at what I found. I continued to run the compression checks to determine if the problem found was deeper. Good news was that all compression's were between 155 and 165 PSI.
Found that number 6 had not even fired during that complete session. Hard to understand how you would miss that while running, but with your adrenaline running high and not knowing what is about to self destruct, making dyno runs still make me very nervous. Having broken the one rod I GET VERY SKIDDISH each time I START IT UP. I Just have to syke myself up to do the job.
After discovering the problem I removed the cylinder heads to confirm that the cylinders were ok. As you look at the pictures of the heads, which were still the dual plug heads, the surface gap plugs were not used by choice. They were acting only as plugs for filling the plug holes because I removed the dual coils in an attempt to eliminate one more potential problem. Final testing of the dual wound coils will have to wait until the existing issues are resolved. Looking at the head photos, top center then bottom, read the color of the steel jacket of the plug thread body and you see that they are black from the heat and have a tinge of brown color on the insulator. Except number 6. No color at all. The head was full of burnt oil residue. The vacuum of the dead cylinder was pulling the exhaust back into it from number 5.
Attachment 62974
Attachment 62975
Attachment 62976
Will be interesting what it will run like when it fires on all 6 cylinders. I have replaced the heads with the spare set of single plug heads. They included different coils and better water sealing plug wires and boots. The heads have tighter combustion chambers. Compression check with the single plugs heads checked at 210 PSI.
Ready for the next run.
Attachment 62977
Attachment 62978
The following day, wanting to do a compression check, I pulled the balance of the plugs and was shocked at what I found. I continued to run the compression checks to determine if the problem found was deeper. Good news was that all compression's were between 155 and 165 PSI.
Found that number 6 had not even fired during that complete session. Hard to understand how you would miss that while running, but with your adrenaline running high and not knowing what is about to self destruct, making dyno runs still make me very nervous. Having broken the one rod I GET VERY SKIDDISH each time I START IT UP. i Just have to psyched myself up to do the job.
After discovering the problem I removed the cylinder heads to confirm that the cylinders were ok. As you look at the pictures of the heads, which were still the dual plug heads, the surface gap plugs were not used by choice. They were acting only as plugs for filling the plug holes because I removed the dual coils in an attempt to eliminate one more potential problem. Testing of the dual wound coils will have to wait until the current issues are taken care of. When looking at the head photos, top center then bottom, read the color of the steel jacket of the plug thread body and you see that they are black from the heat and have a tinge of brown color on the insulator. Except number 6. No color at all. The head was full of burnt oil residue. The vacuum of the dead cylinder was pulling the exhaust back into it from number 5.
It will be interesting to see how it runs on all 6 cylinders. I have installed the extra set of heads that I had made with a single plug. The heads also have tighter combustion chambers and checked out at 210 PSI after installation. They also include a different set of coils and better set of water sealing plug boots and wires. Like the original Quincy looper, the pistons are just lightly touching the heads. So light that you can just see the machining tool marks on the piston tops in the light brown burn color on the heads. You can barely see in the head photos.
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Powerabout thanked for this post
Hi, thank you for responding to my mail.
I was referring to post #504 "Next came the removal of the dual coils replaced by the standard Merc coils. Then with a new set of plugs, leaving the one plug in each cylinder as a non functional plug, the engine sounded much stronger."
So the jury is still out on the dual plug ignition system. Will be interesting to see how it works out with the Merc switch boxes.
Rgds, Wolfgang
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