Experiences - Comparison "new" Rotax spark plugs vs NGK

1. My original plugs were Rotax.  I replaced them with NGKs at 200 hours, and just replaced those with same at 400.  I noticed absolutely no operational difference.

2. Legal... are you asking about certified engines, warranty, what?  NGK says not to use their plugs for aviation, so I guess you wouldn't have much of a chance suing them for any problems, haha.

3. What's the "different principle", exactly?  I would just refer you back to 1, above.

Thank You,

Hello,

Thank You for your response.  Which kind of engine do you have 912 UL or ULS or others?

Why do you changed to the 7 times expensive Rotax spark plugs,  because there was no obvious advantages like your experiences? Maybe you have good reasons - let us know.

The old NGK have one electrode and the spark runs directly to the center (vertical). The new one have two electrodes and the spark runs horizontal.  There is no control which electrode arm sparks. Maybe in a awkward position one electrode arm can hinder (not optimal) the ignition due the flow into the combustion chamber. On short flights or longer landing setting there is a possibility for more soot compared with NGK.

Independencly of the approval from NGK, Rotax delivered the engines with NGK spark PLUGS in the past. There was no discussion about guaranty and warranty about the spark plugs. Now there is a discussion. Many problems and failures can argue with a lack of no certified spark plugs (unless the real cause). 

Guarantee and Warrantee is not a question of certified or not. This is a trade question, depends of the country this can be several years after buying a new engine

By the way - do you have experience with Rotax service/warrantee/obligingness?

Thank You and greetings.

I changed FROM the Rotax plugs, not TO them.  Mine is a ULS.  As you note, NGKs were provided with the engine for years.  My understanding is they only changed that practice because NGK requested that their products not be used for aviation.  However, NGK's performance on these engines has been well proven.

I asked for clarification about your question on "legality",  but I still do not understand what you are asking about there.

I do understand the obvious physical differences between these plugs, and that the gap on the Rotax plugs cannot be modified.  But is that what you mean by a difference in principles??  I do not perceive the advange of that design in this application.

Hi all

Good discussion about spark plugs.  Perhaps some real science is needed to see what is happening.  I suggest this: 

https://www.sciencedirect.com/science/article/pii/S2090447912000883

the conventional spark plug design, single electrode, is a staple and has worked well for a long time.  the new Rotax plug with the dual grounds seems to confuse people and nobody likes the cost.  This is a problem that nobody can solve, cost, given that it is a private label plug due to legal reasons.  So the question remains is the new dual ground really better?  in a word yes.  Read the report, consider that they show 2 options that are not possible and just look at the advantages of the dual ground vs the single.  the new Rotax plug fits all the 9 series engines and for good reason, it is more stable and in the combustion chamber the development of the flame kernel is better.  

In the end Rotax cant allow NGK for legal reasons, the new plug however does have advantages.  it may not be  something we can perceive while flying but it indeed performs better.  

Cheers

I think the important question is, do the expensive plugs perform better in any meaningful manner?