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Curious on where this guidance came from and if the ground electrode only blocks say 20deg why is it important?
 

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How exactly would one make sure that the spark plug was oriented that way? If MB wants it that way then each plug must be manufactured such that the threads and alignment of the plug end up in the position they want it once its installed and torqued to 23nm. Which I am guessing would be the case if thats true. Would not really be any other way to make sure of that.
 

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It sounds like repeated poor advice. If you look up this practice in general it's for getting that extra 1% out of a race engine but you really need to have a dyno and a lot of time at your disposal.
 

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Discussion Starter #9
It sounds like repeated poor advice. If you look up this practice in general it's for getting that extra 1% out of a race engine but you really need to have a dyno and a lot of time at your disposal.
It not poor advice...so go ahead and install your champions. Too much to type..but fuel delivery is very complex...multiple fuel injections per stroke. Reduced fuel economy to potentially burned valves.
 

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Discussion Starter #10 (Edited)
And as far as the reason behind indexing for race engines is the large amount of fuel entering the combustion chamber...could wash the electrode...so the thinking is aim it at the exh. valve. Our engines are totally different and you aim it at the injection port. To back up a little, I worked on race cars many years ago...we were using basically a NASCAR (late model dirt) engine and it was not a major concern..and then on to jet engines after that...so I do have a pretty good understanding of how things work....but I don't have all the answers and I don't pretend to. From what I've read there could be damage done to these engines. Again...I'm going to make the marks on the plugs and see where they end up at 23 nm and if they are all over the place I think we will have our answer.
 

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So this is from "Spark Plug Indexing for Direct Injection Engines QEC / ES" John Dahlquist June 19, 2014 Version 3? (Which is a different plug than the m274 as shown on the following page) And the NGK press release is from Oct 2015. I would think NGK has the issue sorted if you use NGK Stock No. 90654.
 

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I would think NGK has the issue sorted if you use NGK Stock No. 90654.
Confirmed the MB Branded NGK plug and the NGK aftermarket 90654 are both SILZKFR8E7S. Plugs are not that bad to change, everything comes out pretty easy although the foam engine cover is basically designed to tear in one spot and was the most difficult part of the job (off and on). In addition to what the WIS says I also disconnected the 2nd lamda sensor and took the bolts out for the top of engine wiring loom in order to get the #4 coil out. Could be done under 2 hrs no problem if you don't have to run out for the required 14mm spark plug socket or spend the time cleaning out the rain tray. I did have to touch of the paint on my rain tray where it didn't bond on the airbox mount.
 

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Confirmed the MB Branded NGK plug and the NGK aftermarket 90654 are both SILZKFR8E7S. Plugs are not that bad to change, everything comes out pretty easy although the foam engine cover is basically designed to tear in one spot and was the most difficult part of the job (off and on). In addition to what the WIS says I also disconnected the 2nd lamda sensor and took the bolts out for the top of engine wiring loom in order to get the #4 coil out. Could be done under 2 hrs no problem if you don't have to run out for the required 14mm spark plug socket or spend the time cleaning out the rain tray. I did have to touch of the paint on my rain tray where it didn't bond on the airbox mount.
How many miles on your unit?
 

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I would like to know also about leaving the foam soundproofing off the engine permanently. My only concern would be the heat shield attached on the passenger side of the foam needing to stay in place for some reason.
 
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