Spark Plugs

[JoeyBananas]

I thought re-gapping Iridium was a no no

[EALm4]

Originally Posted by JoeyBananas

I thought re-gapping Iridium was a no no

It's fine. Gap to .018 for high boost, e85, meth on the NGK two step colder plugs.

I have a set I'm throwing in very soon. However I took a look at the install process and man a TON of stuff has to come off. Total PITA lol

[schnell1982]

OEM plugs only
Re-gap like everyone else noted but also need to TORQUE to spec.
It plug needs to be facing a specific direction once torqued.
This is something that is overlooked for some reason.

[mark5092]

Originally Posted by sky03

what is stock gap ?

Mine were all at .028

When I purchased new set of factory plugs from dealer to regap, they were all at .028 also. Mine are set at .022 per email from Terry.

[F80Paul]

Originally Posted by EALm4

It's fine. Gap to .018 for high boost, e85, meth on the NGK two step colder plugs.

I have a set I'm throwing in very soon. However I took a look at the install process and man a TON of stuff has to come off. Total PITA lol

It's not that bad. With the right socket extensions and a little patience I was able to replace the back plug without removing the cross bracing. Another trick is to use a piece of rubber hose to start the plugs so there is no chance of cross threading.

I went .18 with a new set of factory plugs and it cured my misfiring issues.

[CaryTheLabelGuy]

Originally Posted by mark5092

Mine were all at .028

When I purchased new set of factory plugs from dealer to regap, they were all at .028 also.

Yes, .028 is the stock gap, which is mostly fine for stock boost levels as long as all the plugs are consistently .028.

However, the stock gap can be inconsistent and vary from plug-to-plug and should be verified. If you're going to go through the trouble of verifying the stock gap, you might as well run a set of new plugs if you've increased boost over stock and gap down a bit to at least .022. Most setups run best at .018-.022, depending on how much boost is being run and what the heat range of the plug you've chosen is.

Most of the time, the OEM Bosch plug can be re-used but will need to be gapped-down like stated above. The OEM Bosch plugs have multiple ground straps and special care must be taken to ensure an even gap amongst all of the ground straps. Plug Indexing is not an issue with these plugs due to having multiple ground straps, but proper torque is very important because the plugs two main jobs is to create spark to ignite the Air/Fuel mixture and to remove heat from the combustion chamber (the plugs heat range) the latter requiring a proper heat-sink between the plug's base and the cylinder head as this is how the plug removes heat from the combustion chamber and transfers the heat to the head and into the coolant system (through heat-sinking). If the plug is improperly torqued, the heat-sink process is hindered and will create issues in that cylinder.

If you're running more than say 24# of boost, I'd say move to the NGK 95770 (old PN 5992) gapped to .022. This plug is the same heat-range as stock (N55/S55).

If you're running more than 26-27#+, E85 w/higher than stock boost pressures or aftermarket turbos, Meth Injection, I suggest a one-step cooler plug like the NGK 97506 plug gapped down to .018-.020.

If you aren't experiencing misfires on the stock plugs and are running moderate boost levels, stay on the stock plugs until it's time to change them or something else changes.

[F80Paul]

Does anyone know the heat range of the factory Bosch plugs? I think it's 5 but it's hard to find specs on them. According to this chart the Bosch 5 would be the same as the NGK 7. It gets confusing. I'm getting ready to install upgraded turbos and want to get it right.

[CaryTheLabelGuy]

Originally Posted by F80Paul

Does anyone know the heat range of the factory Bosch plugs? I think it's 5 but it's hard to find specs on them. According to this chart the Bosch 5 would be the same as the NGK 7. It gets confusing. I'm getting ready to install upgraded turbos and want to get it right.

Just go with the 2-step colder plugs I just listed above your post. Lol. I did the hard work for you.

[F80Paul]

Originally Posted by CaryTheLabelGuy

Just go with the 2-step colder plugs I just listed above your post. Lol. I did the hard work for you.

I think those are 2 steps colder than the stock N54 plugs. I've read that the s55 OEM plugs are one step colder than the N54. Can you confirm this? The s55 plugs don't have multiple ground straps, makes me think you are thinking of the N54 possibly?

[CaryTheLabelGuy]

Originally Posted by F80Paul

I think those are 2 steps colder than the stock N54 plugs. I've read that the s55 OEM plugs are one step colder than the N54. Can you confirm this? The s55 plugs don't have multiple ground straps, makes me think you are thinking of the N54 possibly?

You're correct, the 97506 plug is 1-step colder than stock(N55/S55). When I wrote the post, I was thinking N54 - that's my bad. To my knowledge, there isn't a "9" heat range NGK plug that we know of for this application. That would be 2 steps cooler than stock N55/S55.

I fixed the post.

Edit: there is this plug, but it's supposedly pretty hard to get ahold of and it's 2-steps colder than stock. NGK SILZKBR9F8S

[F80Paul]

[QUOTE=CaryTheLabelGuy;21536417
If you're running more than 26-27#+, E85 w/higher than stock boost pressures or aftermarket turbos, Meth Injection, I suggest a one-step cooler plug like the NGK 97506 plug gapped down to .018-.020.
[/QUOTE]

Got a set of 97506. For high boost 32psi or so w/meth do I want to gap closer to .18 or .20? Pro's/cons? thx!

[schnell325]

Originally Posted by F80Paul

Got a set of 97506. For high boost 32psi or so w/meth do I want to gap closer to .18 or .20? Pro's/cons? thx!

Did you find an answer on your gap question?

[F80Paul]

Originally Posted by schnell325

Did you find an answer on your gap question?

Yes, .018" was suggested for high boost.

[CaryTheLabelGuy]

Originally Posted by F80Paul

Yes, .018" was suggested for high boost.

Yes, for high boost, you'd need to gap-down to .018.

[CaryTheLabelGuy]

So I gapped my stock Bosch plugs down to .019 today and I noticed the stock ZCP plugs were gapped between .025 and .026, which is smaller than the .028 of the stock non-ZCP plugs. It seems BMW has smartly decided to go with a slightly tighter gap for the ZCP.

[Bmw doubles]

Same but different inquiry. Is the best solution to avoid spark blow out to use an old technic called side gapping? Expose the electrode and then tap the shroud down to the same .18-.22?

[CaryTheLabelGuy]

Originally Posted by Bmw doubles

Same but different inquiry. Is the best solution to avoid spark blow out to use an old technic called side gapping? Expose the electrode and then tap the shroud down to the same .18-.22?

Good question, but not relevant to Iridium plugs and especially not relevant to Iridium tipped electrode with platinum tipped ground strap plugs such as the NGK equivalent replacements (NGK 97506) for the stock Bosch plugs.

Side-gapping is a good technique to expose more spark to the AFR mixture thereby causing a larger flame-front and thus more efficient combustion. However, this is mainly for copper-tipped electrode plugs which are very cheap and don't last long (require very frequent changes). The reason copper plugs don't last long is because, while copper is an excellent conductor, it's very soft and will wear (round) very fast, especially on the sharp edges. When side-gapping a copper plug, you get an even sharper edge on one side of the electrode due to the side-gapped ground-strap, however the plug will wear and round that side of the electrode even faster and will require being changed even sooner and also the gap will open up even further as the electrode wears on that one side. Copper-tipped electrode plugs also have much wider tips than Iridium plugs (see below) and this becomes its downfall as the plug wears. The electrode literally becomes a large round dome that has no hard edges for the spark to jump from and also creates a larger and larger gap as it wears. Side-gapping these plugs helps initially (when plug is brand new) but will wear that edge so badly that the electrode will have no hard edge for the spark to jump in very little time and again will effectively create a much larger gap in an even shorter amount of time (especially in high effective compression engines).

An Iridium-tipped electrode plug such as the OEM Bosch and NGK replacement plugs, have a very fine tip (.006-.008) and is very hard and takes much longer to wear and keeps a sharper edge as the plug wears. This fine-tip keeps a constant sharp edge for the spark to jump from, to the grounding strap. However, as the iridium plug ages, most of the wear is transferred to the ground-strap which slowly erodes and rounds. The NGK Laser Iridium OEM plugs feature platinum at the underside of the ground-strap to help slow ground-strap wear which helps keep gap constant and keeps a good surface for the spark to jump to. I'm not sure if the Bosch OEM plug features platinum in the ground-strap, but I believe it probably does as well.

So to answer your question more directly, side-gapping an Iridium-tipped electrode plug is a waste of a good plug, especially if the ground-strap is platinum-tipped. I wouldn't do it and I wouldn't advise anybody to even attempt it unless you like wasting money.

[Bmw doubles]

Originally Posted by CaryTheLabelGuy

Good question, but not relevant to Iridium plugs and especially not relevant to Iridium tipped electrode with platinum tipped ground strap plugs such as the NGK equivalent replacements (NGK 97506) for the stock Bosch plugs.

Side-gapping is a good technique to expose more spark to the AFR mixture thereby causing a larger flame-front and thus more efficient combustion. However, this is mainly for copper-tipped electrode plugs which are very cheap and don't last long (require very frequent changes). The reason copper plugs don't last long is because, while copper is an excellent conductor, it's very soft and will wear (round) very fast, especially on the sharp edges. When side-gapping a copper plug, you get an even sharper edge on one side of the electrode due to the side-gapped ground-strap, however the plug will wear and round that side of the electrode even faster and will require being changed even sooner and also the gap will open up even further as the electrode wears on that one side. Copper-tipped electrode plugs also have much wider tips than Iridium plugs (see below) and this becomes its downfall as the plug wears. The electrode literally becomes a large round dome that has no hard edges for the spark to jump from and also creates a larger and larger gap as it wears. Side-gapping these plugs helps initially (when plug is brand new) but will wear that edge so badly that the electrode will have no hard edge for the spark to jump in very little time and again will effectively create a much larger gap in an even shorter amount of time (especially in high effective compression engines).

An Iridium-tipped electrode plug such as the OEM Bosch and NGK replacement plugs, have a very fine tip (.006-.008) and is very hard and takes much longer to wear and keeps a sharper edge as the plug wears. This fine-tip keeps a constant sharp edge for the spark to jump from, to the grounding strap. However, as the iridium plug ages, most of the wear is transferred to the ground-strap which slowly erodes and rounds. The NGK Laser Iridium OEM plugs feature platinum at the underside of the ground-strap to help slow ground-strap wear which helps keep gap constant and keeps a good surface for the spark to jump to. I'm not sure if the Bosch OEM plug features platinum in the ground-strap, but I believe it probably does as well.

So to answer your question more directly, side-gapping an Iridium-tipped electrode plug is a waste of a good plug, especially if the ground-strap is platinum-tipped. I wouldn't do it and I wouldn't advise anybody to even attempt it unless you like wasting money.

Copy that. Yeah, there are so many mixed reviews about side gapping. Most reviews are 4-6 years old and everything boosted but a BMW application. I'm pushing 19psi and the stock gap .27 and is experiencing spark blowout. Going to tap down my stock plugs to
.22

Any advice on how to properly index my plugs when I reinstall?

[Bmw doubles]

For instance this is an image of the s55 engine, but still the same idea for the n55 in terms of injector and plug design. In this image, isnt that a bad position for the open part of the electrode to be facing the injector? If that is not the best position then wouldn't indexing the plug with the ground strap shrouding the injector from spraying it directly would be best?

[CaryTheLabelGuy]

Originally Posted by Bmw doubles

Copy that. Yeah, there are so many mixed reviews about side gapping. Most reviews are 4-6 years old and everything boosted but a BMW application. I'm pushing 19psi and the stock gap .27 and is experiencing spark blowout. Going to tap down my stock plugs to
.22

Any advice on how to properly index my plugs when I reinstall?

Do you have any plans on running ethanol or methanol? I suggest going to the NGK 97506 1-step colder plugs if so and gap them .018-.020. You could probably get away with .022" @ 19#, but a plug job is such a PITA you might as well just gap down a little further for the sake of time and effort of having to pull them and re-gapping again.

I'm personally running .019" currently on the stock Bosch plugs at stock boost with a super special E85 mixture and will be swapping these out for a set of NGK 97506 N20 plugs gapped @ .019" (again, 1-step colder than stock) because I'm about to start turning the boost back up. I've got the plugs gapped and ready to go.

[CaryTheLabelGuy]

Originally Posted by Bmw doubles

For instance this is an image of the s55 engine, but still the same idea for the n55 in terms of injector and plug design. In this image, isnt that a bad position for the open part of the electrode to be facing the injector? If that is not the best position then wouldn't indexing the plug with the ground strap shrouding the injector from spraying it directly would be best?

There is a lot of conflicting advice on DI engines in regards to indexing. Every DI engine is different in how it utilizes/implements Direct Injection. In the case of BMW's implementation I'm not totally sure if indexing really makes a difference. I wouldn't worry about it as DI engine's don't typically benefit enough from indexing to offset the hassle of indexing.

[Bmw doubles]

Thanks for the input CaryTheLabelGuy I'm running about e30 in total all stock hardware minus a DP and a tune. I thought .19 since I've read that the gap increases slightly over time. Thanks again.