Plugs (95770 v. 97506), gaps, and the N54

fmorelli

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I'm going to try to be as brief as possible but there are several related things I wish to bring up relative to plugs. I've done reading on Spoolstreet as well as other forum threads, with some success, but nonetheless ...

Background: my car is 30k miles, usual FBO, stock turbos, flexfuel. It's a non-abused car in my ownership since 23k miles. I've had timing correction issues with frequency pre flex fuel and post. I've been running NGK 95770s. I had this issue with stock Eldor coils running 0.5mm (0.0196") gap (feeler gauge set). They've always been torqued in at 17 ft lbs. Now with R8 coils and 0.6mm gap (0.0236"). I pulled the plugs today to drop them to 0.022" and want to share what I see and ask what others have observed.

  • The bottom of all the spark plugs all have some oil residue and carbon by the crush washer ring. Varying amounts up the threads. It took a wire brush to clean them up, including the crush washer face.
  • The bottom of the spark plug tunnels in the head, at the seating surface for the crush washer, have some oil and carbon (gritty) material. I went down in there with a long carburetor screwdriver and a rag with carb cleaner to knock it all loose and clean the mating surface.
  • I have a set of fresh NGK 97506 (aka BMW N20 -SILZKBR8D8S) plugs. They are very different. Aside from the 97506 being one step colder than the NGK 95770 (5992 if you think in old numbers), there are several differences, shown in the photos below:
    • The 97506 uses a sold copper crush washer versus the 95770 double hollow aluminum crush washer.
    • The ceramic insulation for the ground electrode on the 97506 is 5mm wide inside the steel shaft, versus 3.8mm for the 95770.
    • Finally the 97506 has a higher steel shoulder (past the threads) and as the last photo shows, protrudes 0.8mm deeper into the combustion chamber than the 95770.
IMG_20180719_114501.jpg


IMG_20180719_122605.jpg
IMG_20180719_122639.jpg


So here are some questions I have, and would like to hear any other observations people have as well:
  • I don't believe I should see any oil or carbon on the spark plug crush washer or head spark plug mating surface. This would seem to indicate that the plug washers are not sealed, correct?
  • 17 ft lbs is factory specified. Any opinions on this relative to higher combustion non-stock, and with different kinds of crush washers? How about in multiple use of a crush washer compromised in its first use?
  • Are the aluminum crush washers "use one" on the NKG 95770s?
  • Could this insufficient seal (I surmise) be contributing to my timing correction issues?
  • Finally I know people are running 2 step colder plugs on 500+ whp cars. Can I run them on my 425-50whp-ish motor? (I read somewhere that Pure runs the 95706 on all their cars). I know @[email protected] stocks these plugs from one of his posts.
Thanks for any input one provides.

Filippo

p.s. For @The Convert - sorry for the non-Mitutoyo measurements. At least underneath is a Starrett 4" double square with +/- .00001" tolerance. :tonguewink:
 

NoGuru

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I think I have just about the same setup Filippo, FBO running Flex Fuel (Between E40 and E50), and DCT.
So if you run two steps colder I will be curious to see how this works out. I very rearally get corrections so my I should stay one step NGK's at .022.
 

NoQuarter

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How fast would plugs get too hot that a colder plug helps? If the engine is cold and just cruising around long enough to get oil up to temp, Seems the first hard pull the plugs should be relatively cold enough to rule that out?
 

Rob09msport

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Plug temp is pretty instant the temp rating is based off how fast can shed heat into the heads.
 

matreyia

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@[email protected] just sent me this:



Filippo
Let me know when you get things figured out. We BL coil users are getting lots of different advice from both vendors and users. Totally confused... eventually, the NGK plugs give problems like oscillations or hesitations...etc. I just bought new set and am waiting for people to try different gaps. I read some folks just install the NGK without gapping at all and it worked...I think v8bait wrote this somewhere...

The problem is those plugs have crush washers that get loose and once you take them out, and reinstall, they get worked out and don't seal as well as initially. So maybe this is the issue contributing to the mess.
 

NoQuarter

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The problem is those plugs have crush washers that get loose and once you take them out, and reinstall, they get worked out and don't seal as well as initially. So maybe this is the issue contributing to the mess.

yeah. Maybe that is what is what was happening when we talked about plugs coming loose. Not so much a torque problem but more about the washer losing it's locking/spring effect.
 

BOosted 335i

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Are you guys positioning the plugs for better performance?for best combustion/burn you want the open part of plug at 12 o Clock?Away from piston?
 

matreyia

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Are you guys positioning the plugs for better performance?for best combustion/burn you want the open part of plug at 12 o Clock?Away from piston?

How would anyone be able to choose the orientation of the opening since you must prioritize proper torque values over orientation? I don't see how anyone could possibly do this even if it were a thing. Any insight would be helpful.
 

pdxbimmertech

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I believe indexing plugs is usually more of a domestic/V8 thing. I'm only speculating but I think you probably have to have a bunch of spark plugs on hand, the open end gets marked somehow and then installed and torqued. If the open end lines up in the correct place, you leave it. If it doesn't line up, you try more plugs until you get one that does line up. Not every plug will have the threads cut exactly the same meaning it may end up having the open end wherever it ends up. Only place I've ever heard of this being done was on domestic V8's honestly but if someone is trying to eek every last bit of power and uniformity out of their setup they might try it. I would bet that on the plugs that are produced for the N5X have a much more uniform thread starting point than others but that is purely speculation. This is at least my understanding of how this is done.
 

NoQuarter

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How would anyone be able to choose the orientation of the opening since you must prioritize proper torque values over orientation? I don't see how anyone could possibly do this even if it were a thing. Any insight would be helpful.

I wondered the same thing. But I saw something at Summit that seems to be washers of different thickness that is added to the plug to get it to stop at the correct orientation? But then I can't fighting with those to stay in place (if they even work like that) then you have the problem that the plug is now sitting further out?

Have not looked at this yet:
 

matreyia

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....if they even work like that) then you have the problem that the plug is now sitting further out?"


EXACTLY. Then you give rise to an even worse problem than if you didn't index the plug in the first place. It may be just useless voodoo in this case.
 

fmorelli

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The problem is those plugs have crush washers that get loose and once you take them out, and reinstall, they get worked out and don't seal as well as initially. So maybe this is the issue contributing to the mess.
  • I don't know if anyone is paying attention to their plugs - but the 95770 have use once double wall aluminum crush washers. I would love someone to debate this. Mine have been in and out several times in 7k miles and I think that's an issue.
  • There should be NO carbon or oil on the crush washer or the head seating area, yet I have it on multi-install 95770s all torque to spec. I would love someone to debate this as well.

  • I prefer the 97506 because I believe
    • unlike the 95770 washer that deforms, the solid copper crush washer doesn't function by geometrically deforming once.
    • 0.8mm deeper into the chamber is a country mile inside of a combustion chamber, and short of getting in the way of the spray pattern, would seem to be a good thing.
    • I'll take the 30% greater ceramic shielding (can't hurt)
Please debate, disagree, call me stupid ... :) ... I'd like the possibility of getting a bit smarter on all of this. And I'd like my timing corrections to drop - I'm pretty sure my setup is at fault.

Filippo
 
Last edited:

135iTX

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Is there really an advantage to running colder plugs if you are only FBO? I ask this because I have had no issues and great logs for 2+ years running OEM plugs with no gap changes FBO and E40 tune.