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About DHeal

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  • Location
    Santa Rosa, CA
  • Interests
    Flying my RV-12 E-LSA
  • Gender
  1. I do not know how your ignition modules control switches ("mags") are specifically wired in your aircraft. The ROTAX 912 Major Maint Manual has the generic wiring diagram for the ignition system. Knowing which of your switches controls which module/set of spark plugs will aid you in your troubleshooting. You could just replace all of the newly-installed spark plugs with the old used set of proven spark plugs (or a different set of new spark plugs) and see if the problem goes away. If the problem persists, perhaps trimming of the ignition leads is in order. The connectors "unscrew" from the wires.
  2. If you have an EGT probe on each of the four cylinders, you should see a rise* in the EGT temp on the cylinder with the misfiring spark plug/lead. Check that cylinder's spark plug's resistance (http://www.ngk-sparkplugs.jp/english/techinfo/qa/q08/index.html) or just replace the suspect spark plug. In addition, you could trim off the end of the plug's lead and reset the plug's connector. * The inefficient and prolonged burning of the single-plug combustion gases causes the EGT to increase.
  3. You should be able to detect a noticeable slight RPM increase (a hundred or two RPMs?) a few seconds after start-up as the Soft-Start system transitions from start-up timing to normal operational timing.
  4. The EGT can also be used to troubleshoot a defective spark plug (or associated wire) -- if the engine is running rougher than usual and the EGT is higher than usual in the specific EGT cylinder then one of the two spark plugs may not be firing correctly. This results from partially combusted burning gases flowing past the EGT probe.
  5. DHeal

    RPM Rollback

    OK, here's another "out-of-the-box" thing to check and hopefully dismiss: Are all of your fuel tank vents open and clear? Back-pressure due to a clogged or partially clogged fuel vent(s) might temporarily reduce fuel flow to the carbs.
  6. DHeal

    RPM Rollback

    "Out-of-the-box" thought here, but could the Soft-Start function be cutting in and out intermittently thus changing the timing???
  7. Application of carb heat causes intake air flow to be hotter (i.e., thinner) and typically results in a richer % mixture. If your engine is running roughly due to its being a bit on the lean side during reduced-power descent, application of carb heat may enrichen the mixture % sufficiently to smooth out the engine. Perhaps your engine is running a bit lean due to debris in the carbs or a mis-set venturi needle?? Just a thought.
  8. Also consider insulating wires and hoses from heat sources such as exhaust pipes and mufflers.
  9. It is my understanding that the new-style spark plugs ($22 each) require a new-style boot connector ($40 each) be installed on each spark plug wire. The new-style plugs are not compatible with the old-style boot connectors. Does anyone know if the old-style spark plugs will still be manufactured by NGK to be used on non-aircraft products (e.g., snowmobiles, motorcycles, etc.)?
  10. Beware of cheap, non-metallic oil filter wrenches that slip over the end of the filter. Many of these wrenches are made of plastic and typically either the fluted surfaces or the 3/8th inch drive socket cannot handle the removal torque. They are great for installing filters, but too weak for removal. Anyways, that's been my experience.
  11. Harbor Freight aviation supply sells a "Vice Grip-style" version of these oil filter pliers -- very useful in removing recalcitrant filters.
  12. Wow! Very enlightening pictures, particularly Roger's cutaway shot. One can easily see why "smacking" the boots onto the plugs is a bad idea. Great info.
  13. Is it possible to lean the 912 ULS somewhat to account for this configuration? I have an RV-12 ELSA and burn Autgas 91 (with @ 8% ethanol) @ 90% of the time.
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