rogerCT2K

Thanks for thinking along on the path of the ignition of a Rotax 912 with me for a while Carl! Best regards Roger

But all this has lead us far away from a quite simple problem, how to solve a bad mag drop. Best regards Roger

It is strange that Rotax sticks with a system that dates back to the seventies. The ignition timing should be a curve instead of a two level system. To take an example somebody said here mine turns perfectly at 1200 revs, but don't forget that at that moment the pre-ingition is 26°, that is probably the ideal value at max rpm.but certainly not at 1200 rpm.! In this digital era it is very simple to let the timing be at the ideal moment at any number of revs, one could even change it with the load and the atmospheric conditions. But all this has le

Hi Carl, I think you undertstood me wrong, the 10amps is for the ignition "and" the injection system, mainly to boost the fuel pressure (pump) I think. And for the strong vibrations at low revs: -6° is just way too much, it could even be that the best is + a little something! That can be tried out with some electronic or mechanical hocus-pocus. Best regards Roger

Hi all, I just checked the net for "Silent hektic rotax 912" and it seems the system still exists. So there is one of the answers to the question "how the hell do people tune their engines ????" There are probably others too. It seems the system takes 10 Amps, I am not sure if I have 10 Apms to spare ?? I also do not kow if one can purchase the ignition system seperately. Best regards Roger

No prop rpm's, engine rpm's!

Hi Carl and all, I didn't know sending an Email adress was illegal! About the 2000rpm idle of the Rotax 912: I saw a 912UL turning at 750 revs in Germany, equipped with an electronic injection and ignition system of a Check compagny (Silent Hectic or so if my memory serves me well, it has been a long time ago) and it turned smooth like butter. One of the reasons you have to let the Rotax run at 2000 revs is the ignition, 6° advance is way too much at low revs! So electronic weirdo's stop what youre doing and make us a ingintion box with a good curve! Best regards Roger

Hi Dexter, Those measurements were taken the first time the "professional" did my carbs (for only 700 Euro's) and told me the mag drop was too big. Since then it has gotten worse. The plane I had before my CT2K was a Rans Coyote ESII, one could land it on a dime while asleep, only good so because the fantastic German Hirth engine did quit on me 12 times. My CT2K flies like a dream but lands like a drunken Dinosaur, I had already twice a "vache" (that is how the French say that the engine is nice and quit all at once) with my 912, once in the middle of the French alps. That is more than enough! Cheers Roger

Hi Carl, We will probably lose our high "Cadet" grade now, because this has nothing to do with the subject but I had 3 Beetles. With the oldest one (1958) I drove back from Germany with a split cylinder head, the one that is hardly reached by the cooling fan, and it still brought me and my dad home (with a good puff of smoke behind). Brings back old memories. The system was beautiful in its simplicity and worked perfectly, probably the only good thing we can thank the greatest dictator ever for. Ferdinand Porsche must have had a very bad night when he thought of that wonderful idea. It is also possible he just stole it from somebody else. I have made an aircraft engine from an old Subaru EA71 and it goes like a bat out of hell every time one touches the starter button, on only one ignition system that the Japanese stole from the humble Beetle. It is still in my garage and every now and then I let it run a bit, just to enjoy the noise coming out of a good old flat four with a direct coupled two blade propeller. The sound of music, even the neighbors enjoy it! (When they are awake of course). To be honest my Rotax 912UL still runs good, although a bit rougher then before but it has cost me more just to have the carbs done (700 Euro’s) than I ever paid for one of my Beetles. Best regards Roger

Hi Carl and all, Mine were never shielded and my radio works perfect, so don't worry about that. They are probably leaking now and my radio is still ok. By the way, if you would open the ignition box and see what is inside and compare it with the price (900Euro's) you would realise that Rotax is very willing to sell you another one every year, the profit must be enormous! No wonder they put it on the engine and let it vibrate happely along with all the rest. I am an electromechanical engineer, but if I would be an electronic weirdo i would desing and produce my own box that performs much better then that one. It gives about 6° up to 1000rpm and 24 or so when "more". That is about as sophisticated as the mechanic system in the old VW's made in the second world war. Best regards Roger

Hi Carl, My carbs are comletely redone by a professional under my supervision, absolutely nothing wrong with them! How the position of the needles (with perfectly synchronised carbs and needles in the same position) could affect the mag drop is just a mystery to me! Rotax does not provide any explanation either! Roger

Hi, In my opinion the HT leads do not have to be shielded at all!

Hi all, While the wife lies here baking her but of in the Tenerife sun I found the readings (of my flydat) I wrote down the first time I did my ignition check at 4000 rpm: Both: 4000 rpm right front 673° back 734° and left front 711° back 781° A 3930 rpm 710 782 744 811 B 3800 rpm 720 844 692 843 The high temperatures (reading in degrees Celsius) on "B" jumps out, could it be that a faulty coil or damaged HT leads cause higher temperatures? Rotax says: the max speed drop on one ignition should be max 300rpm, so these readings are very good and the difference between the two should be max 115rpm, so too high in my case. Since then it got worse. They also say that a wrong needle position in the carbs can cause a high mag drop. Has anybody have an idea what the logic behind that statement is? Best regards Roger

Hi Carl and all, I must say I already suspected the HT leads, so my next job after the vacation (we are in south Tenerife now until 3 april) is changing them all by new silicone ones from a motorcycle shop nearby, I already did this by a few of my cars with excellent result. It seems a bit of a mess to do so, but i guess it is the next logical step. I must say that there is no visible change in take off revs, but then I don't know when the problem started since I always did the check at 3000 revs until lately. They have always been too low since the Germans fitted a neuform 2 blade propeller on my new plane with a lot of pitch. The take off revs are only 4600 in my case (80Hp engine). On the other hand it makes my CT go like hell (240 km/hour) at top speed with 5600 revs. Many thanks to all for the suggestions, we should all fly together and have a good Belgian beer on my account afterwards. Just let me know when you come over! Best regards Roger

Yep, that is correct! I had to upgrade my brakes to be able to do it without blocking the wheels every time. Best regards Roger