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  • Re: NGK Spark Plug for 915is?

    by » one year ago


    Before the Rotax “one fits all” plug was released, I believe the 914 used a slightly cooler plug, such as the NGK DPR9EA-9.  When you add turbo charging or any other feature to an engine to get more HP, this typically means using a cooler plug to help optimize the combustion temperature. Previous to the new Rotax plug, the plug temperature progression from the 80, 100, and 114 HP engines demonstrates that (NGK temperature range 7, 8, 9, respectively). 

    What’s unclear to me is in which direction Rotax compromised. In other words, is the new plug optimized for the higher HP engines or the standard engines?  Without knowing the Bosch part number or heat range for the Rotax plug, it’s hard to know.  If I was taking a guess at it, I would tend towards the cooler plug (from the 914) for use in the 915 engine since they are both turbocharged.  But I hate guessing.  


  • Re: NGK Spark Plug for 915is?

    by » one year ago


    Don't the NGK plugs require a different connector than the Rotax plugs? So, on a 915iS, wouldn't you have to change the connectors if you wanted to switch to NGK?


  • Re: NGK Spark Plug for 915is?

    by » one year ago


    "Don't the NGK plugs require a different connector than the Rotax plugs?"

    No


    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


  • Re: NGK Spark Plug for 915is?

    by » 12 months ago


    Dear Glenn

    Have we been screwed all this time about the thermal values of the spark plugs for different Rotax engines? No, but Now. For some Rotax engines the Rotax spark plugs are to cold. It never could be that a spark plug can substitute other plugs with differerent thermal values.

    I had the same problems - contact with Rotax is nonsens - your worse your time and you be fustrated too, they never are interested in your problems, they never accept your experiance.  The guilty party is always the user.

    So i did my own testrow (I made a tiny documentation about this), Rotax, NGK and NGK iridium was into test. Short result: Rotax spark plugs get to fast a black carbon, the spark ist not steady. Below 4000 rev. the spark find his way only at one side of the electrode. Rough running, Nearby the resistance of 5 kohm is very variable. This ist not really a problem but it shows the quality standard of the russion Bosch spark plugs, labeled with Rotax.

    I cannot understand that experts are not louder in this case. In my opinion the livetime of your enginge reduses dramatically with Rotax spark plugs. I can understand if somewhere say "make our own decisions" but in my oppinion to put it this way is irresponsible


  • Re: NGK Spark Plug for 915is?

    by » 9 months ago


    Has anyone tried a normal spark plug in their 915 that can share their results? Im looking at spark plugs now and really don’t want to spend $250 on replacements. 

    On a related note, how often is everyone actually replacing their spark plugs? Rotax specified every 100 hours if using avgas which seems really excessive, but I haven’t examined my plugs yet to see how they actually look. We are running avgas 30-50% of the time. 


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