Indexing Spark Plugs - Why And How - With EngineLabs
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- Опубліковано 3 гру 2023
- Spark plug indexing can be a confusing subject. In this video, EngineLabs Editor Greg Acosta offers a quick walkthrough of the whys and hows of spark plug indexing.
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I've seen countless tests where indexing the plug nets ZERO gains on track or dyno. 99.99999% unnecessary unless you're having clearance issues with the top of the piston. That is the only good reason to spend the time to do it...
You are absolutely correct on all accounts !
It might or might not help depending on the engine,but if something is possible why leave it untouched
Agreed, but if that 0.0001% means the difference between loosing or winning, every bit helps.
That's the thing, it won't make the difference between winning and losing. Not a bit.@@TS-qd2uj
I'm an old school drag racer and back in the day we would side Gap the plugs clip off the top of the ground exposing the electrode Bend the side to the proper gap
Due to the fact that the plug doesn't fire till the next stroke when the valve is closed , indexing is irrelevant in a 4 stroke.
A 2 stroke mota is another matter.
This is what l have learned racing both mota types over my 70 yrs.
How do you determine the correct ground strap position for the plug in a two stroke?
Nice and easy to follow video! Plug indexing is old school; but why some engineers design to place spark plug closer to the exhaust valve on many 2-valve per cylinder engines?
Just an old jeep guy here ( we're usually just happy when all four are firing) Wouldn't changing the depth with the spacers be more detrimental to the firing of said cylinder ?
You're generally talking less than .030 of depth change, which should be negligible to both spark location and compression ratio. Or, even advantageous, if you are trying to clear a piston dome.
fantastic video - I knew it existed but had no idea how it worked - but now I do - thank you very much
Glad it helped!
Honda insight gen 1s uses indexed plugs. Though sadly not available anymore. People feel it does make an mpg difference but keep in mind the engine runs near mis-fire lean with little throttle. ( 25:1 ) So it's possible that a misaligned spark might not ignite the complete fuel air charge causing te ecu to see misfires and add more fuel.
thats why i stored up on them :)
So it's more important to index than purting shims and changing the depth of the plug in the cylinder? If one believes indexing affects flame propagation, then I'm sure the depth of the plug does as well.
"In theory" being the key words. This will have zero affect on a 4 stroke engine since they fire at or near TDC right as the compression stroke is finishing, meaning that the entire chamber is filled with the compressed mixture and will fire no matter what way the strap is facing. The gap is the one thing you really need to worry about to make sure you have and adequate amount of spark interacting with the compressed gases.
GREAT VIDEO AND SUBJECT ,BUT I HAVE ONE SOMETHING TO ASK FROM GREG WHERE CAN I GET A INDEX TOOL WITH THE NUMBERS,PLUS WILL HELP V-6 .CHRYSLER 3.8 ,KEEP UP THE GREAT WORK AND PERFORMANCE INFORMATION,
Everything I've found that is pre-marked is VERY expensive. Luckily, the easy way to make them (easier than how I did it) is to get a Proform or Moroso blank one, and just use a scratch awl and straightedge between corners, which will give you six sections, then split the flats which will give you 12 total sections, instead of the 8 I scribed with the rotary table.
By the time the plug fires the air/fuel charge will likely be coming toward the plug from a different direction, the combustion chamber shape will determine that. When you pull used plugs you're likely to see that one side is darker than the other, and in theory, that's where the fuel is hitting the plug and where you'd want your gap opening to face.
Does the ground strap face the number you want to index or face away.
The "performance theory" is that you want the ground strap away from the center of the intake valve. So you're indexing the unshrouded part of the plug towards the intake valve. In the case of dome clearance, you are angling the plug however you have to, in order to clear the piston's dome.
Like Markgoulette just said about unless you are addressing clearance issues you are wasting your time. Try a set of Diamond Fire e3 Spark Plugs and see, feel, smell, and hear the difference instead. When your car only has about 145 hp on a good day, a 5-10 hp boost is VERY noticeable
1st Volkswagen is doing it.
2nd The intake air moves down in a spiral. GDIs have the injector in a specific location. How do you know where the open side of the spark plug has to be? 🤷♂️
Glad you had your gloves on
Gotta keep those parts nice and shiny for the camera.
How much does the final torquing vs finger tight change the position of the ground strap of the spark plug?
Say your example spark plug when finger tight was an 8, what would that same plug be when tightened to the correct torque specs with the extra partial turn to crush the crush washer?
Taper seat torque specs call for 5-10 lb-ft, or finger tight plus 1/16 turn.
Awesome, thank you.@@EngineLabs
Hmm. What about the change in depth?
I don't think .010 to .032-inch of plug depth is going to make a measurable difference on anything.
It seems to me if indexing where to be used. Wouldn't you want the side 180 degrees from the strap need to be aimed at the fuel concentration area. Not the lean area.
nice video and idea, makes us think 🤙... so now there would be different depths of the spark on each of the cylinders? doesn't that retard/advance the ignition? would be interesting to have numbers on ignition timings per cylinder due to this change. One would thing is more efficient to have the spark at the same depth. Even with the obstruction the spark strap represents. Isn't like a fraction of volume of the mix that has to go around the strap compared to the extra travel of the whole area (volume) the mix has to do before reaching spark? id think dome's design and location of the spark hole would also matter. With that logic, the bigger the engine, the depth would matter more?. the smaller the engine the obstruction would matter more?...for the common engines, even for some racing due to clearances this is unnecessary... i'd imagine.
This is a nascar thing. Doesnt make sense on low hp, but at 900hp 8k rpm it does make sense.
So what about 4 valves per cylinder heads
And may I add plugs that aren't taper fit but use a crush washer.. asking for a friend
Indexing plugs makes no difference in power output. There's no point in placing the ground strap pointing towards the intake valve because it is closed at the time it fires. Produce a video that shows a dyno run with a power increase. Not happening.
Blinker fluid. Do they not realize how a 4 stroke works?
Bear in mind that @6000rpm there are 50 firing events per second. By indexing the plugs you're keeping the plug's electrode as dry as possible for the next spark. This was important back when your coil barely made 20,000 volts. Today, not so much.
You probably lose/gain more horsepower from the weather and barometric pressure changes in the 25 minutes between runs down the dragstrip.
You indexed finger tight. Where's that ground strap going to be when you tighten?
The plugs he was indexing were 'washer less'; tightening to-torque is usually less than 1/16th turn, so moot in this case. It could be less exact when using spark plugs with a crush washer. Guessing, indexing plugs, unless you're a racer; isn't enough a difference to make a difference.
@@chuckgrenci6404 - exactly.
With a crush washer, you either account for the amount of crush past finger tight, or you can chuck the tool in a vise (that is why the tool is hexagonal) and get the plug fully seated.
surface discharge plugs eliminate this concern.