What problems from wrong spark plug gap?

shemoves · Post by **shemoves** » Sun Dec 30, 2007 1:49 am

I may have made the gap on a set of spark plugs too close...what problems would that usually cause?

internetautomart · Post by **internetautomart** » Sun Dec 30, 2007 2:12 am

less power.

shemoves · Post by **shemoves** » Sun Dec 30, 2007 2:19 am

LOL. Would it run rich/lean? Higher/lower EGTs? More/less resistance to detonation?

dzx · Post by **dzx** » Sun Dec 30, 2007 2:24 am

it won't change how rich or lean your car is. However the larger the gap, the greater the chance of misfire.

internetautomart · Post by **internetautomart** » Sun Dec 30, 2007 2:24 am

you will probably run richer because you have a smaller spark so incomplete combustion will happen as well.

"A small kernel will make the engine run as though the ignition timing was retarded, and a large one as though the timing was advanced."
the quote is from WIKI so take it for what it is.

evolutionmovement · Post by **evolutionmovement** » Sun Dec 30, 2007 2:49 am

It depends on the cylinder pressure. A higher pressure will benefit from a reduced gap.

206er · Post by **206er** » Sun Dec 30, 2007 4:10 am

benefit might be a strong word, a narrow gap will be harder to blow out.
a narrower gap will be easier on the coils.

evolutionmovement · Post by **evolutionmovement** » Sun Dec 30, 2007 4:16 am

OK. The higher the cylinder pressure, the harder it is to ionize the air for the spark to jump the gap. A longer distance can cause a delay in firing or a miss altogether.

ericem · Post by **ericem** » Sun Dec 30, 2007 5:29 am

What are you guys talking about? How do I gap the plug correctly? I just set my torque wrench to 15ft-lb's and tighten away!

evolutionmovement · Post by **evolutionmovement** » Sun Dec 30, 2007 6:14 am

With a $1 plug gapping tool. Some plugs come pre-gapped, but you should probably check them even so.

ericem · Post by **ericem** » Sun Dec 30, 2007 7:45 am

Oh god!! No wonder my car feels so angry!!

vrg3 · Post by **vrg3** » Tue Jan 08, 2008 4:34 am

Most spark plugs are pregapped from the factory these days... Most of us like to use NGK BKR6E-11 plugs, right? The "11" means "1.1 millimeter gap."

So you generally don't need to adjust the gap at all.

entirelyturbo · Post by **entirelyturbo** » Tue Jan 08, 2008 5:30 am

Every BKR6E11 I've ever installed is gapped right around .043 from the factory.

I usually run a .040 gap, but I honestly would probably do better to run a bigger gap. I'm nonturbo and stock, so running a smaller gap doesn't do me much good. Maybe that has something to do with why my engine pings on 89 octane.

SemperGuard · Post by **SemperGuard** » Tue Jan 08, 2008 6:14 am

Gap? Just slam those bitches home with an impact right out of the box. Gapping is for suckers.

sammydafish · Post by **sammydafish** » Tue Jan 08, 2008 4:53 pm

206er wrote:benefit might be a strong word, a narrow gap will be harder to blow out.
a narrower gap will be easier on the coils.

The concept that high boost can blow out a spark is a farce, lets set that record straight. Plugs don't blow out, the ignition may lack the power to jump a spark across the dense air (an insulator) that is in the cylinder during scenarios with extremely high cylinder pressures. similar to what evolutionmovement's post says. Nothing in this situation is getting "blown out"

entirelyturbo · Post by **entirelyturbo** » Tue Jan 08, 2008 11:57 pm

SemperGuard wrote:Gap? Just slam those bitches home with an impact right out of the box. Gapping is for suckers.

Don't expect me to retap the spark plug threads in your heads after you strip them out. Not without some money involved anyway.

AWD_addict · Post by **AWD_addict** » Wed Jan 09, 2008 3:12 am

SemperGuard wrote:Gap? Just slam those bitches home with an impact right out of the box. Gapping is for suckers.

Don't read the labels on each plug either, they should all be what you want. No time for anti-seize either, just get those things in there!

SemperGuard · Post by **SemperGuard** » Wed Jan 09, 2008 4:11 am

subyluvr2212 wrote:
SemperGuard wrote:Gap? Just slam those bitches home with an impact right out of the box. Gapping is for suckers.
Don't expect me to retap the spark plug threads in your heads after you strip them out. Not without some money involved anyway.

I wont expect you to because it wont happen. If anything the insulator will crack.

Anti-seize is for wimps.

Suckers and wimps I say!

entirelyturbo · Post by **entirelyturbo** » Wed Jan 09, 2008 4:36 am

Your spark plugs shouldn't be in the engine long enough for you to need anti-seize.

Mr. SemperGuard, you do understand our heads are aluminum right?

I'd be more than happy to demonstrate on your engine how easy it is to ruin aluminum threads

I like how you're calling people wimps, and then using an impact wrench to tighten spark plugs

evolutionmovement · Post by **evolutionmovement** » Wed Jan 09, 2008 5:00 am

I never use antiseize, just a little oil on the threads and I've never had them stick.

SemperGuard · Post by **SemperGuard** » Wed Jan 09, 2008 11:39 am

subyluvr2212 wrote:Your spark plugs shouldn't be in the engine long enough for you to need anti-seize.

Mr. SemperGuard, you do understand our heads are aluminum right?

I'd be more than happy to demonstrate on your engine how easy it is to ruin aluminum threads

I like how you're calling people wimps, and then using an impact wrench to tighten spark plugs

Baby you should know me by now. If one of us ever ends up on each others coasts, I will gladly slam multiple spark plugs home with an impact for you

. Repeating as much as you like. Heads, block, tranny, whatever. It's all aluminum. Slam it all home with the impact. Of course if you want to use a 1" impact with the side grip and really go to town of course you'll kill something.

We should end this before the thread gets closed.

entirelyturbo · Post by **entirelyturbo** » Wed Jan 09, 2008 7:50 pm

I'll just open it back up...

tmarcel · Post by **tmarcel** » Thu Jan 10, 2008 2:42 am

vrg3 wrote:Most spark plugs are pregapped from the factory these days... Most of us like to use NGK BKR6E-11 plugs, right? The "11" means "1.1 millimeter gap."

So you generally don't need to adjust the gap at all.

If you guys are looking to push things a bit further (larger than stock turbos and more boost), I would definitely not run the NGK -11 plugs on turbo motors. That's far too much gap for boosted applications running decent sized turbos and a bit of boost. Sure, you can do it, but it'll put a lot of strain on your ignition system and compromise misfires as well.

On decently modded Subarus, I typically run NGK BKR7EIX and even the 8's for cars making a bit more power. These plugs are gapped at .030" out of the box. If the Subaru layout wasn't so dificult to work on (well at least on Imprezas) I would try pushing the gaps out a little. But it works great like this and no worries. Plus, Iridium performs as well as copper and has the maintenance life span of platinum.

sammydafish · Post by **sammydafish** » Fri Jan 11, 2008 6:48 pm

tmarcel wrote:
vrg3 wrote:Most spark plugs are pregapped from the factory these days... Most of us like to use NGK BKR6E-11 plugs, right? The "11" means "1.1 millimeter gap."

So you generally don't need to adjust the gap at all.
If you guys are looking to push things a bit further (larger than stock turbos and more boost), I would definitely not run the NGK -11 plugs on turbo motors. That's far too much gap for boosted applications running decent sized turbos and a bit of boost. Sure, you can do it, but it'll put a lot of strain on your ignition system and compromise misfires as well.

On decently modded Subarus, I typically run NGK BKR7EIX and even the 8's for cars making a bit more power. These plugs are gapped at .030" out of the box. If the Subaru layout wasn't so dificult to work on (well at least on Imprezas) I would try pushing the gaps out a little. But it works great like this and no worries. Plus, Iridium performs as well as copper and has the maintenance life span of platinum.

the 6 -7 -8 you refer to is plug temperature, not gap. It refers to the rate in which the plug can dissipate heat to the head. Unless you have a preignition problem and believe the plug is the hot spot, or you have a fouling problem, there is no reason to change the plug temperature from stock.

Hotter plugs resist fouling, but can become to hot and cause preignition.

tmarcel · Post by **tmarcel** » Sat Jan 12, 2008 4:38 am

sammydafish wrote:
the 6 -7 -8 you refer to is plug temperature, not gap. It refers to the rate in which the plug can dissipate heat to the head. Unless you have a preignition problem and believe the plug is the hot spot, or you have a fouling problem, there is no reason to change the plug temperature from stock.

Hotter plugs resist fouling, but can become to hot and cause preignition.

Thanks for letting me know this FACT about heat range and plugs

What part above didn't I make clear. I said that a -11 plug was the wrong way to go for boosted motors. I said nothing about NGK's "6-7-8" heat range being a problem. You make more power, you need a cooler plug - period

The plugs I recommend are .030" gap out of the box. Choose the heat range according to predicted power output - pretty much common knowledge.

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What problems from wrong spark plug gap?

What problems from wrong spark plug gap?