[johnung]

I received a lot of conflicting information when I was researching spark plug options for the N55 engine. I read forum posts, phoned tuning houses, talked to BMW techs and talked to techs at spark plug manufacturers. Here's what I collected in hopes that it will lead to discussions that will clear things up.

BMW might recommend changing the stock plugs every 50,000 miles with normal driving. BMW/Bosch plugs on tuned higher horsepower cars should be changed every 20,000 to 30,000 miles. NGK Laser Iridium plugs on tuned engines should be changed every 15,000 to 20,000 miles. The front three spark plugs on the N55 are very accessible but the rear three plugs require removing more stuff to gain access to them. Labor-only to change all six plugs is roughly 1.5 hours. These plugs require a special 14mm bihex spark plug socket. Some tuners sell them for about $20. I actually found one that is identical from a China eBay supplier for $3-$4, including shipping. Had to wait 3-4 weeks though.

In general, tuners advise to go with a spark plug that is rated one-step colder if mods are added to a car that increase its horsepower. Some more specific rules of thumb that I heard are to go one-step colder for every +10 psi of extra boost, and go one-step colder for every 75-100 horsepower added.

Much of the confusion about N55 spark plugs seems to come from mixed conversations about N54 engine spark plugs. The stock N54 plugs are one-step hotter than the stock N55 spark plugs. So many N54 owners have gone to stock Bosch N55 plugs to go one-step colder on their N54 engine. When people start talking about this plug or that plug being one-step colder it often gets lost in translation whether they are referencing the N54 or N55 engine.

Bosch ZR5TPP33S (BMW# 12120037582) Double Platinum, about $12 each but $45 each at my insanely expensive dealer. Stock plug on N55 engine, gapped to about 0.030" to 0.032", not sure exactly.
The number 5 in the Bosch part number indicates a Bosch heat rating of 5. Heat ratings are relative to each other for a given manufacturer. But one manufacturers number is different than another's number. For instance I've been told that a Bosch 5 is equal to an NGK 7.

Bosch One-Step Colder Spark Plug- I haven't come across one yet. I also am not sure which way the Bosch numbers run so not sure if a colder plug would be a number 4 or a number 6.

NGK5992 ILZKBR7A-8G Laser Iridium Plug (discontinued by NGK, but many still being sold by tuners.)
NGK95770 ILZKBR7B8DG Laser Iridium Plug (replaced NGK 5992) both about $12-$14 each. Gapped to 0.031" or 0.032" out of the box.
Both of these plugs have a number 7 in the middle of their part numbers indicating that they have an NGK heat rating of 7. Remember that I was told that a Bosch #5 heat rating is equal to an NGK #7 heat rating. So it would appear that these are the stock N55 plugs made by NGK. But many people and some tuners claim that these are one-step colder plugs from NGK for the N55 engine. They are gapped down to about 0.020' to 0.022" because of the higher horsepower of the engine.

NGK97506 SILZKBR8D8S Laser Iridium Plug. Gapped to 0.031" out of the box. This plug is rated by NGK to be one-step colder than the NGK 95770. (Note the number 8 in the middle of the NGK part number.) In NGK lingo the higher numbers are colder plugs. So this #8 plug is colder than the #7 plugs. This plug is listed as standard for the BMW N20 and S55 engines. NGK tables also list this plug as the stock plug for the N55 engine. But that appears to be wrong. This #8 plug should be considered to be one-step colder than the stock BMW spark plug. (Burger actually lists this plug as 2-steps colder for the N54 engine, which would confirm that it is 1-step colder for the N55 engine.) For performance enhanced engines this plug should be gapped down to 0.020".

NGK6205 LKAR9BI9 Laser Iridium Plug. NGK Tech Support says that this is their plug that would be considered another step colder than the NGK97506, so it is 2-steps colder than stock. Gapped out of the box to 0.035"/0.036". NGK says that the minimum that this plug can be gapped down to for performance is 0.024". This is the only plug that uses a standard 14mm hex spark plug socket. However, it is also the only plug that has a threaded stud at the top, so you would have to find (6) screw-on solid tops for them.

My most obvious current questions are:
1) Which NGK plug really is 1-step colder and what should it be gapped to? Is it the NGK 95706?

2) Are the tuners saying that the NGK5992/NGK95770 are 1-step colder, but that doesn't appear to be correct. However, maybe their advice to use these plugs for higher performance N55 engines (gapped down to 0.020" to 0.022") is actually working, even if it is being labelled incorrectly as 1-step colder. I've been told that the stock Bosch plugs are fragile and difficult to gap down. Maybe that is why everyone seems to go to NGK Laser Iridium plugs for performance engines. They can be gapped down much easier.)

3) Is there such a thing as a Bosch 1-step colder plug for the N55 engine?

My car's solution appears to be either the
A) NGK5992/NGK95770, gapped down to 0.020-0.022, OR the
B) NGK 95706 gapped down to 0.020-0.022.

UPDATE: I INSTALLED THE NGK 97506 PLUGS GAPPED DOWN TO 0.022". I HAVE 2015 335i XDRIVE N55 EWG RUNNING BOOTMOD3 STAGE2 ON 93 OCTANE. RUNS GREAT!!! MY PLAN IS TO CHANGE THE NGK's OUT EVERY 15k-20k MILES BASED ON WHAT I HAVE READ.

I HAVE RECEIVED A LOT OF POSITIVE FEEDBACK ON THIS POST. I AM GLAD THAT IT WAS HELPFUL!

I don't like to do a lot of research and not pass it on in hopes that it will help someone else. Hope this generates some good discussion and clears up some grey areas.

[JaredG_F30]

Thanks johnung this is very comprehensive. I'm my experience the NGK 95706 works great on my tuned N55 engine. From the research I have done these are one step colder then the stock Bosche plugs. I have mine gapped at 0.022" as the slightly larger gap seems to help with a slight rough idle issue and hesitation at light load. Others have stated that the stock Bosch plugs at the stock gap is good for 500hp so going to a colder plug with smaller gap may not be necessary. I have a set of new Bosch stock plugs so when it's time to change plugs I'm going to put the stock ones in and log to see how the engine likes the stock plugs. If I see timing issues I'll go back to NGK 95706.

[mike@x-ph.com]

Thanks

[johnung]

Originally Posted by JaredG_F30

Thanks johnung this is very comprehensive. I'm my experience the NGK 95706 works great on my tuned N55 engine. From the research I have done these are one step colder then the stock Bosche plugs. I have mine gapped at 0.022" as the slightly larger gap seems to help with a slight rough idle issue and hesitation at light load. Others have stated that the stock Bosch plugs at the stock gap is good for 500hp so going to a colder plug with smaller gap may not be necessary. I have a set of new Bosch stock plugs so when it's time to change plugs I'm going to put the stock ones in and log to see how the engine likes the stock plugs. If I see timing issues I'll go back to NGK 95706.

Thanks for the reply. I'm happy to hear that you have run the NGK95706 successfully. I was hoping for replies from folks who have real world experience with various plugs in the N55 as all of my statements are second hand and not from experience. You mentioned that 0.022" is the gap to use with them and it sounds like you have had the ability to log any timing issues. Has your experience with the NGK's all been positive? Curious what's moving you back to try the stock Bosch plugs? In general the folks whom I have spoken with who use Bosch do so because they never really considered or checked out anything else. I'm very curious what you discover by evaluating both Bosch stock and NGK 1-step colder.

FYI- Saw in your profile that you intend to upgrade to M Performance Brakes. Not sure if you mean Brembo 4-piston front/2-piston rear, OR Brembo 6-piston front/4-piston rear? I just upgraded my rear to Brembo 2-piston to go with the stock Brembo 4-piston fronts. Painted front & rear calipers to match. Hawk 5.0 pads and stainless steel lines all around. Great result! Instead of nose diving, whole car squats flat when braking.
Hawk 5.0 much better than stock and less dust. Dust not as sticky on wheels. Stainless lines makes brakes much more responsive. No play in pedal before they engage. Have a lot of detailed information about that brake project that I should post.

Was just in NC with my son and my car last month looking at colleges. Would like to check out your car next time we are there.

[jh_f30]

Excellent write up!

I'm also running the NGK 95706 on my tuned N55, but I gapped them to 0.020". My research also indicated that these are 1-step colder than stock. I've got about 15k miles on them and haven't had any misfiring issues.

This does remind me though that I ought to replace them in a few months.

The first 5 plugs aren't too bad to access. The last one is the real PITA.

[johnung]

Originally Posted by jh_f30

Excellent write up!

I'm also running the NGK 95706 on my tuned N55, but I gapped them to 0.020". My research also indicated that these are 1-step colder than stock. I've got about 15k miles on them and haven't had any misfiring issues.

This does remind me though that I ought to replace them in a few months.

The first 5 plugs aren't too bad to access. The last one is the real PITA.

Thanks! Great to hear from someone else with a good experience with the 1-step colder NGK95706. I'm starting to feel more confident that NGK may be the way to go.

[TEST DRYVER]

I'm also curious as to what spark plugs to use for my car. I have an F30 N55 EWG with aftermarket fmic, catted downpipe, charge pipes, and I run a BM3 stage 2 tune 91 octane. The car of course drives much smoother on the stock tune. I'm not expecting an aftermarket tune to be as linear as aftermarket, but the throttle response is a bit choppy, especially at low speeds. Best way I can explain the way it drives with the tune is: from a rolling start, light on the throttle will give you light power, but then bump up the power unexpectedly. I'm not talking about anything major here, there are no safety concerns, and I've owned enough tuned cars to know that aftermarket tunes are great for boosting power, but not usually keeping the power delivery as smooth as factory. I have no problem with that or my BM3. I would however like to smooth it out a bit without having to mess with aftermarket fueling products (fuel rails, HPFP, etc...). I'm thinking the proper spark plugs can help smooth out the power response a bit. Please correct me if I'm wrong.
Also, thanks for the information, buddy...

[harkes]

I just removed the NGK 97506 from the car last night to put the old factory plugs back. Have I slight stumble at idle that I'll try to test doing this.

Ran 24psi + meth on factory at stock gap - never a single issue.....

[AGONXF30]

Just use S55 OEM plugs. They cost like five bucks.

[Tchao]

Originally Posted by johnung

In general, tuners advise to go with a spark plug that is rated one-step colder if mods are added to a car that increase its horsepower. Some more specific rules of thumb that I heard are to go one-step colder for every +10 psi of extra boost, and go one-step colder for every 75-100 horsepower added.

That rule of thumb doesn't really apply to Direct Injection N55 engines.

The stock plugs work very well, but you might need to gap the stock plugs tighter. Most tuners now only recommend different plugs for high power level (6/700+) cars.

Also the stock Bosch plug now has a different p/n with an update.
Bosch ZR5TPP33S

[f32ftw]

I've been running the NGK 5992 plugs gapped to 0.022" for just over a year now. I was having a rough idle and figured I'd try changing the plugs. This helped and the rough idle is now barely even noticeable to me.

[johnung]

Originally Posted by Tchao

That rule of thumb doesn't really apply to Direct Injection N55 engines.

The stock plugs work very well, but you might need to gap the stock plugs tighter. Most tuners now only recommend different plugs for high power level (6/700+) cars.

Also the stock Bosch plug now has a different p/n with an update.
Bosch ZR5TPP33S

Thanks! I'll update the Bosch part number in my original post.

FYI- the top tech at my local dealer cautioned against attempting to change the gap on the stock Bosch plugs that comes out of the box. He said that they are very fragile. The NGK Laser Iridium are a different design and material that can be re-gapped much more easily.

Based on your comment about not needing to go 1-step colder, and how difficult it is to re-gap the Bosch plugs, maybe that is why I hear so much about people running NGK 5992 (discontinued) or NGK 95770 (replacement) plugs gapped down to 0.022". According to NGK, this is really the same heat range as the stock Bosch plug, but can be gapped down. Some of the confusion lies in so many people, including the people that sell them, saying that they are 1-step colder when they are really not according to the manufacturer. The NGK 97506 are 1-step colder.

Just throwing this out there: maybe what is really needed in a tuned N55 isn't actually a 1-step colder plug, but a stock plug (in terms of heat rating) but with the plug gapped down to 0.022" to perform best with the engine mods that have been done. Curious what others think.?

[johnung]

Originally Posted by JaredG_F30

Thanks johnung this is very comprehensive. I'm my experience the NGK 95706 works great on my tuned N55 engine. From the research I have done these are one step colder then the stock Bosche plugs. I have mine gapped at 0.022" as the slightly larger gap seems to help with a slight rough idle issue and hesitation at light load. Others have stated that the stock Bosch plugs at the stock gap is good for 500hp so going to a colder plug with smaller gap may not be necessary. I have a set of new Bosch stock plugs so when it's time to change plugs I'm going to put the stock ones in and log to see how the engine likes the stock plugs. If I see timing issues I'll go back to NGK 95706.

Besides the stock Bosch spark plugs and the 1-step colder NGK 97506, you also have an option in the middle to go with NGK plugs with the stock heat value but with the ability to easily gap them down to 0.022" for performance mods. That would be the NGK 5992 (discontinued) or NGK 95770 (replacement) plugs gapped down to 0.022". Any way you go please post your results.

I find this rough idle, stumbling at low speed curious and am hoping to hear the experiences of people either having it or not having it with various plugs and engine mods. Thanks!

[JaredG_F30]

I'm still covered under the BMW Ultimate Care Plan (their maintenance plan) so spark plug changes are free. Last time the car called for a plug change I had just gone FBO + tune and just changed to the 97506 plugs. I told the BMW SA that I had just changed the plugs so he gave me 6 stock plugs for free. They are just sitting in my garage. I bought the 97506 plugs from FCP Euro so my plan on the next plug change is to go to stock (since I have them already) while my replacement 97506 plugs are on the way from FCPEuro (which will be free due to their lifetime warranty program). Once they come in I'll get some logs on the stock plugs, swap over to the NGKs and log again to see if there is a difference. I'll never have to buy plugs again.

Originally Posted by johnung

Besides the stock Bosch spark plugs and the 1-step colder NGK 97506, you also have an option in the middle to go with NGK plugs with the stock heat value but with the ability to easily gap them down to 0.022" for performance mods. That would be the NGK 5992 (discontinued) or NGK 95770 (replacement) plugs gapped down to 0.022". Any way you go please post your results.

I find this rough idle, stumbling at low speed curious and am hoping to hear the experiences of people either having it or not having it with various plugs and engine mods. Thanks!

[Pray for Mojo]

FBO BM3 M235i, NGK 97506 gapped to 0.020". Idle was always good, but after removing cold start it bogged on takeoffs until slightly warm. Cleaned MAF sensor with CRC SensorKleen MAF cleaner, runs perfectly now, no more hesitation even when cold. Not sure how this setup will work when it's -30 out in winter here, might have to put cat heating back on.

[Tchao]

Originally Posted by johnung

Based on your comment about not needing to go 1-step colder, and how difficult it is to re-gap the Bosch plugs, maybe that is why I hear so much about people running NGK

You gap them like you gap any plug. Get feeler gauge set and tap it down to your desired gap...? I do not know about NGK vs Bosch in terms of gapping, but millions of Bosch plugs on the market are gapped all the time. I havent read any official documentation to say otherwise.

Just throwing this out there: maybe what is really needed in a tuned N55 isn't actually a 1-step colder plug, but a stock plug (in terms of heat rating) but with the plug gapped down to 0.022" to perform best with the engine mods that have been done. Curious what others think.?

The confusion and problem with this certain community is that people mod and run 400+ft/lb of torque at 2,500 rpm on 50K+ old spark plugs at factory gap, and expect the plug to perform at such insane cylinder pressures. And when they dont they think the 50k old plug is under performing when compared to fresh NGK's gapped properly. You cant compare an old warn shoe to a new one.

Another problem is the psychosocial one where more aftermarket means better. A spark plug that was designed specifically for your engine by teams of highly educated engineer is so easily overriden by a single FB or forum post.

Just because you read CBD oil cured a lady from cancer on facebook shouldnt mean you should withdraw chemotherapy for your mother and get her a vape pen.

[johnung]

Originally Posted by Tchao

You gap them like you gap any plug. Get feeler gauge set and tap it down to your desired gap...? I do not know about NGK vs Bosch in terms of gapping, but millions of Bosch plugs on the market are gapped all the time. I havent read any official documentation to say otherwise.



The confusion and problem with this certain community is that people mod and run 400+ft/lb of torque at 2,500 rpm on 50K+ old spark plugs at factory gap, and expect the plug to perform at such insane cylinder pressures. And when they dont they think the 50k old plug is under performing when compared to fresh NGK's gapped properly. You cant compare an old warn shoe to a new one.

Another problem is the psychosocial one where more aftermarket means better. A spark plug that was designed specifically for your engine by teams of highly educated engineer is so easily overriden by a single FB or forum post.

Just because you read CBD oil cured a lady from cancer on facebook shouldnt mean you should withdraw chemotherapy for your mother and get her a vape pen.

Thanks for the input. I have gapped many Bosch plugs myself way back in the past on other cars. My comment about this BMW Bosch plug being difficult to gap down came directly from the most experienced tech at my local dealer. He also has his own heavily modified N54. He said that he would never try to gap down the stock N55 Bosch plug because that particular plug is very fragile and not meant to be gapped down. He was pretty firm about it.

[johnung]

Originally Posted by AGONXF30

Just use S55 OEM plugs. They cost like five bucks.

The stock S55 engine plugs by NGK are the NGK 97506 which is supposed to be 1-step colder than stock in the N55 engine. I've seen them for about $17 each. I haven't seen a Bosch part number for the plug used in the stock S55 engine.

[johnung]

Originally Posted by TEST DRYVER

I'm also curious as to what spark plugs to use for my car. I have an F30 N55 EWG with aftermarket fmic, catted downpipe, charge pipes, and I run a BM3 stage 2 tune 91 octane. The car of course drives much smoother on the stock tune. I'm not expecting an aftermarket tune to be as linear as aftermarket, but the throttle response is a bit choppy, especially at low speeds. Best way I can explain the way it drives with the tune is: from a rolling start, light on the throttle will give you light power, but then bump up the power unexpectedly. I'm not talking about anything major here, there are no safety concerns, and I've owned enough tuned cars to know that aftermarket tunes are great for boosting power, but not usually keeping the power delivery as smooth as factory. I have no problem with that or my BM3. I would however like to smooth it out a bit without having to mess with aftermarket fueling products (fuel rails, HPFP, etc...). I'm thinking the proper spark plugs can help smooth out the power response a bit. Please correct me if I'm wrong.
Also, thanks for the information, buddy...

After digesting all of the information and conversations on this subject of spark plugs for modified N55 engines, I'm leaning towards using a stock plug (in terms of heat rating) that is gapped down in order to function efficiently with the engine performance mods. (meaning running smoothly without idle issues)

So that would be either the NGK5992 (ILZKBR7A-8G, discontinued by NGK) or its replacement, the NGK95770 (ILZKBR7B8DG) gapped down to 0.022". I've seen them priced as low as $12 each.

We have the same car. I'm curious about a few things if you don't mind:

First, you mention 91-octane in your post. I couldn't tell if that's what you run or if that is what your tune is set for. I'm lucky to have 93-octane readily available so that is all that I use. In my research concerning tunes every tuning "expert" asked what octane I was running and said that is a critical part of how much boost can be added to a tune and how smoothly the car will run when tuned.

Second, you listed a catted downpipe. I'm curious what your experience has been with it? If I do that in the future I'm considering a Wagner catted downpipe because of quality and price. I've been told that there won't be a smell or a bunch of Check Engine Lights. I've been told to expect about a 20-25 horsepower increase. I'm assuming that the cat in the aftermarket pipe won't be as effective in emission control so I need to do more research on my state regulations. Wondering which downpipe you installed and what your experience has been?

Third, how has your experience been with BM3 tune and what were your decision factors for that instead of say, a JB4? Thanks!

[TreyR28]

I actually replaced the plugs on my 335 today. My car is at ~56,000 miles and to my knowledge the plugs had never been replaced. Lately I had been noticing a rough idle when stopped and the car studdering/“breaking up” when at full load.

I couldn’t believe how much of a difference it makes! Car idles smoothly and drives much better when accelerating.

I have never changed plugs before and it took me a little over an hour. I’d recommend anyone do this job themselves. It was very straightforward and even the back 2 plugs that have limited room to work on are pretty easy, just took a little more work.

I found a thin walled spark plug socket on Amazon for $6 that I ordered yesterday and was able to get same day delivery. My local BMW dealer in Charlotte price matched GetBMWParts price of $16 so overall it was under $110 to do since I had all the other tools that were required.

[TEST DRYVER]

Originally Posted by johnung

After digesting all of the information and conversations on this subject of spark plugs for modified N55 engines, I'm leaning towards using a stock plug (in terms of heat rating) that is gapped down in order to function efficiently with the engine performance mods. (meaning running smoothly without idle issues)

So that would be either the NGK5992 (ILZKBR7A-8G, discontinued by NGK) or its replacement, the NGK95770 (ILZKBR7B8DG) gapped down to 0.022". I've seen them priced as low as $12 each.

Thanks! I'm going to give that a try! Maybe it will also help the choppy throttle at WOT, when doing a high speed run. I pushed the car the other night, I was out on the freeway, in the open desert, without a car in sight. I put the car in Sport mode and floored the throttle. Between 120-140mph, the car starts to have what feels like fuel cutoff. Now this only happens for split seconds at a time, and the car is still rapidly accelerating, but there's what feels to be a misfire or fuel cutoff for very brief split seconds. It makes you feel uneasy, like you're about to damage something. I'm going to try the plugs you recommended and go from there...

We have the same car. I'm curious about a few things if you don't mind:

First, you mention 91-octane in your post. I couldn't tell if that's what you run or if that is what your tune is set for. I'm lucky to have 93-octane readily available so that is all that I use. In my research concerning tunes every tuning "expert" asked what octane I was running and said that is a critical part of how much boost can be added to a tune and how smoothly the car will run when tuned.

It sucks! I know... 91 octane is our Premium fuel in Arizona. You can find 95 or 100 octane, but you have to go out of your way as there are very few gas stations that carry that out here. Plus, I used to fill up with 95 octane on my previous Golf R APR Stage lll (which I sold a few months ago). It's between $6-8 a gallon!!!


Second, you listed a catted downpipe. I'm curious what your experience has been with it? If I do that in the future I'm considering a Wagner catted downpipe because of quality and price. I've been told that there won't be a smell or a bunch of Check Engine Lights. I've been told to expect about a 20-25 horsepower increase. I'm assuming that the cat in the aftermarket pipe won't be as effective in emission control so I need to do more research on my state regulations. Wondering which downpipe you installed and what your experience has been?

So I purchased this 2015 335i M-sport with adaptive suspension for my wife a few months ago, and since I drive it half the week, I decided to start modding it a bit =)
I did quite a bit of research and bought all my stuff through Mike at Extreme Power. He is beyond knowledgeable and helpful! I landed on an AR design catted downpipe (200 cell). It's been excellent! Even before the tune was properly applied, the car was noticeably quicker and had a much more pleasant sound (please remember, I had the CSF fmic and VRSF chargepipes installed, along with the downpipe, all in one shot). It's not loud and it doesn't smell! Actually, I don't notice any difference in smell from OEM. My CEL light didn't go on, but I only ran it for a couple of days before applying the BM3 tune, so there's no way for me to say whether a CEL light would of turned on had I ran it without a tune for longer. I can say, that it's been a great mod so far! To me, the stock car didn't produce enough sound (which is understandable, as it is a luxury sports sedan), and now with the AR design catted downpipe, the car produces a pleasant and slightly aggressive sound, although it's still fairly quiet and would still pass for a luxury car. I would like a bit more rumble, so maybe an MPE next.

Third, how has your experience been with BM3 tune and what were your decision factors for that instead of say, a JB4? Thanks!

To me it seems that most of the flash tunes are next level (you can control more parameters with a flash tune) compared to piggyback (JB4, DINAN, etc...) units. People generally run piggybacks because it sometimes takes longer for aftermarket tuners to crack the DME. Manufacturers are making it more and more difficult to reflash their ECU's, so aftermarket tuners create piggyback units to increase boost, add power, and keep the DME intact. There's also several people here that say that their JB4 can't be detected by the dealership, as long as it's completely removed before a dealership visit. I'm not sure I personally believe that, but that's just my uneducated opinion...

[TEST DRYVER]

I tried to respond to your comments or questions piece by piece, but it all came out in the blue quote above.