NGK Spark Plugs - how to decode the letter & numbering system #1453 (2023)

Introduction

Ever wondered what the number & letter code means on the side of an NGK spark plug? Well, finally, they caught my attention after all these years so I did a little research to find out more...

In this video I run through how to decipher the Spark Plug code - for example, a BPR8ES? What does it mean? Well, you may be surprised to know that each of the characters has a specific meaning & here's how to decode it...

I have really only brushed the surface on the NGK coding but I'm hoping this video helps give you the basics so you'll know how to decode your own spark plugs.

Here's the link to NGK's 2015 Motorcycle Spark Plug catalogue - lots of really useful info & it includes the decoding table I used in the video:

www.ngkntk.co.uk/wp-content/uploads/2011/03/2015-Motorcycle-catalogue.pdf

Andy Mechanic

Content

Now then, crew and welcome back to the Andy mechanic YouTube channel now I've been working with spark plugs for many many years and I've still never got around to learning what all the numbers and letters mean on the.

Why I use ng case map looks so how to decipher the code.

You know BP our 60s or whatever.

It is.

What does that really mean, because each letter and each number does have a very significant meaning, and sometimes you know you need a spark plug for your car.

That's gone, there's a non resistor type or you might have to have all of the soot, that's a resistor type, and you want to make sure that the guys selling them over the counter is giving you the right ones.

So, a bit of research and I found online on the NGK spark plug website a really cool little table to help you to you know decipher that code and I thought I'd.

Do a few of a few of the spark plugs I've got kicking around the workshop with you to give you an idea of how to use this chart.

Hopefully, it's going to be helpful to a few and I'm sure there'll be a lots of comments on this down the bottom.

So if you read those as well, you know he'll, give you more information, I'm sure about these different types of spark plugs and why they all vary a little bit for each application and there's a lot more spark plugs out there now than there ever used to be because there's so many specialist applications, so I thought the first one that I'd pick up is and they're all that my spark plugs draw.

Is this one here? Look it's a CR 6h s, a I, hope to then go.

Oh I care.

I know the six is a heat range, but that's pretty much all I know.

Oh, it's got an hour in it as well, which means it's a resistor, but let's do this properly.

So we know what it all means right: let's head down to the bench actually I'm, just thinking it before I started to film using the sheet.

You know on the bench which you can probably hardly read.

So hey I've got some screen capture software, so I'll use that on the laptop and we'll go through a few different plugs got quite a selection here, so we've got a there's, no unlock another one, so I'll read them out as I'm going through the screen capture.

You know on the laptop and I'll talk you through how to work at each one, and there aren't there's, there's a few exceptions to the rule as well.

I've noticed, but this is, you know, a journey that our learning curve that I'm really keen to get my head round, because you know I deal with spam, plugs on a regular basis and it's it'd be good to be able to interpret and have a good idea of what those numbers and letters mean all right.

It's going to get my laptop right, so the first plug is: was it a CR? 6H s a so? What does that mean? Okay? Well, the first letter can be a B or a C or a D and so on, and we look down this table here and C tells us that it's a 10 millimeter thread.

It's got a one.

Millimeter pitch and the socket size to fit that span plug should be 16 millimeters.

Well, that was easy enough.

Okay! Well, the next letter is an R.

Well, I know that is aa stands for a resistor type spark plug, and it could be any of these here.

Look so put em for compact L for short type P for protected center, electrode insulator.

Obviously after resistor you for surface or semi surface discharge and as ed inductive suppressor I've, never seen one with the Z.

Hmm, okay, what's next? Well, it's a number and it's a number six, and now it's got to do with the heat range.

Most people know the heat range.

One thing to bear in mind is the lower the number, the hotter, the plug temperature and the higher the number.

The cooler is very important not to get that mixed up as Benjamin found out what this DT hold the piston poor life.

Okay.

Now the next letter is a H, so we need to look down here for H and that tells us the length of the plug the threads that go into the cylinder.

How long those threads are.

Now the next letter, as it is on here is an S.

The S stands for nickel non v, grooved center electrode, so it's nickel plated and the last number we've got all the last letter is an A and that a stands for a special designing, see down here.

Look a B, D, etc special designs.

So that's very specific to the application.

Well, that's that one isn't it wasn't too difficult, but this table is really helpful to try and work these out.

Okay.

So let's just choose another one right: it's how about CPR 7 EI, - 9 that sounds complicated right, so log, so starting off again see what we've already done C before so that's 10 your thread, 1 mil pitch 16 mil socket size.

Now the P stands for a protected center, electrode insulator.

Really so a little look, that's the spark plug okay! Well, I! Don't know, I can't see any kind of additional protection.

It looks like a normal spark up to me, but it is quite long.

Isn't it on the threads so I'll come to that in a minute.

Okay, so P covers the protected center, electrode insulator and then we've got the old R.

So it's also got the R, which means it's a resistor type of spark plug.

So this one is a slightly cooler spark plug than the previous one.

This is a number seven and then we've got an e, so the e stands for the thread reach of 19 millimeters and to confirm the thread.

Reach is this length here from from there right down to here, so that, in this case, is about 19 millimeters yeah there to there right what else for God's okay.

So it's got an a on the end, so that means it's a special design again and then it's got a dash and a number nine well.

This example appears got an 11 on the end, so we'll follow that little line down, and that tells us that's.

If it's got a nine, it's already got a preset plug gap of 0.9 millimeters.

Now that might not necessarily be correct for your application, but it means it's quite at the factory with a preset little gap.

So this plug gap here between the two electrodes is 0.9.

Millimeters, just there look yeah easy and you can check it with a feeler gauge.

That's not hot! That's not putting my videos.

Ok, let's do one more for a third spark plug then, just for an example: let's go for the CR 9 ii model.

I suppose right.

So that's what it looks like again.

Quite a small thread size so thread size.

C again, we've got the 10 millimeter diameter one will pet the pitch and a 16 mil socket size.

Now.

The next one is the our circle resistor again and the 9 is the heat range.

This plug is quite a bit cooler than the previous ones have been looking at and it's got an e on the end, which means it's thread.

Reach is 19 mil, so that was actually quite an easy spark plug to do.

Excellent and you'll need to set the plug gap yourself, because it's not preset at the factory, okay, spat bugs all over the place.

Now, let's do one more before our voyage to death.

Every guard says this is a dr 8 e a and it's a used one, excellent okay, the 8 EA, sir D, will give us a 12 millimeter thread diameter.

So it's a bit bigger than that than the last one.

So 12 mil thread diameter and it's got a pitch of 1.25 millimeters and the socket size to go on here is an 18 millimeter socket and you should always use a proper spark plug socket because it's got the rubber sheath to hold it in place.

Okay, what else we got? So it's a our is the next letter.

So it's again it's a resistor type.

Look like most plugs are these days and it's number 8 on the heat range.

So it's somewhere by in the middle, really isn't it and E, which means again.

It's got a 19 mil thread reach across here down into the head and last one is a for Apple, and that means it's of a special design.

Yeah, pretty easy! Isn't it so there you go, got spark plugs all of our workshop.

Now they were tied it required, but that little chart there was really really helpful and what I'll do is I'll put a link to to where I got that from off the internet bit further down.

So you can actually download that chart yourself and give you somewhere safe because it's actually very informative.

There was a couple of things that I couldn't work out.

How to decipher that's gonna, be working, progress, I think I had one plug, which was a what was it was.

It was a D DCP, so somebody can tell us what that means: yeah that one there I think it was DCP r8e now, obviously, the r8 is easy and the DS easy, but the CP so needs to do with ISO standard says here.

If it was a if it was a BCP, not a DCP, the height from the gasket.

The top terminal is fifty point.

Five millimeters on a BK type spark plug mmm, which is 2.5 millimeters shorter than a BCP type.

That's a note.

Alright, so BCP will be 53 millimeters but looks of it anyway.

Yeah well, good I'm sure you know still learning okay.

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Alright, crew! Well, until next time, I'll see you around Cheers Oh.

What else.