What do Spark Plug Markings Mean?

Adam Mechanic

Explaining what the letter and number on your spark plugs actually mean. Please like and follow for more content.

Transcript

00:00hi everyone just doing a quick video on spark plugs and what these letters and

00:05numbers mean when you buy a spark plug so I've got myself a brand new NGKR spark plug here

00:10I'm just going to go through the letters and numbers and let you know what they mean so on

00:15this particular one what I do have is B C P R 6 E Y okay so I'm going to take them in turn as to what

00:32these all mean so B the first letter on there is the thread diameter

00:38obviously you get different size of that in this particular instance

00:4640 millimeters thread diameter the C is to do with the construction

00:51and in this case the construction is to do with the size of the hex bolt here so

01:01this hex bolt here is designed to be removed with a hex size

01:07of 5 eighths of an inch the next one P and R are to do with the the way that the spark plug operates

01:17so PR the PR the P section stands for projected

01:21insulator type

01:26and the R stands for resistor so that's how it works so the ceramics here is obviously the resistor

01:34that should never be cracked otherwise you may get a miss but yeah the R stands for resistor

01:39okay six is the next one so that's to do with the heat range of the of the spark plug itself

01:49so different spark plugs are designed to work in different operating temperatures and different

01:54operating ranges so this can be anything from two to ten so this is midway through the range

02:01so this is a six so it's designed to deal with average engine temperatures

02:06obviously the hotter the cylinder is going to get the higher that number would be on the spark plug

02:10that's designed to go in that particular engine

02:13E is your thread reach

02:16and that's 19 millimeters so that's the depth here so how long that thread goes for some will be shorter

02:28and obviously some will be longer than that so the thread reach is important to make sure you get the

02:32right one for the engine to make sure it seals up the cylinder properly and this particular case he does

02:37he does represent 19 millimeters when dealing with NGK and then Y is the firing of that spark plug

02:47so the firing is how it's how it lets the spark fire so this particular one if we can get the camera close

02:54enough it's got a grooved electrode so in the middle of that bottom bit there you hopefully can see a groove

03:00there and that is all that is indicating is that it's a grooved electrode so Y for NGK is to signify that it is a grooved

03:09single electrode

03:14obviously there'll be different types there's multi ones this is just a single electrode on this particular spark plug

03:23the one other piece of information you get on there in this particular one is 11

03:28so 11 in this case is to do with the gap size so if i cross-reference this with the NGK website

03:35it shows me at 0.044 of an inch

03:43which to me is 1.1 millimeters so that's actually telling me the gap that i need between the electrode and the spark plug tip

03:51just to make sure it fires across for the right amount of time if that's too narrow then it will

03:55fire across fine but it won't be firing for long enough and it may not burn all the fuel air mixture

04:01so you may get rough running you could even get a misfire if it's not firing for long enough because

04:05it doesn't have time to burn all the fuel air mixture if that gap's too wide then the spark even

04:10those 18 000 ish volts or 15 to 20 000 coming down here potentially if the gap's too wide it can't arc across

04:18if it can't arc across then you're going to get a misfire obviously because it is not burning the

04:21fuel air mixture in the cylinder so it is very important to make sure you gap these properly

04:25with a feeler gauge i'll do that on a different video but yeah so hopefully that makes sense in

04:29terms of information that you get a spark plug it's always important to make sure that you get the

04:33same four spark plugs for four cylinders if you've got a four cylinder engine otherwise the resistance in

04:39spark plugs can be different the way that they fire may be different and therefore you may get again

04:43rough idle so try and make sure you've got matching spark plugs so if you did have three of this type

04:49then you'd know where to go and what to get and what code to put in to make sure you have a engine

04:54that runs smoothly on all four cylinders hope that makes sense see you next time

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