Best spark plug gap for stage IV?

blackie · 10-29-2004, 05:04 PM

This might be a silly question but is there a recommended gap for a stage 4 wrx, or should i just set the plugs to factory specs?? also what is the factory recommended spark plus gap?? thanks, BTW im using the BKR7E's if that makes a difference.

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moremaga · 10-29-2004, 05:25 PM

I have a stage 4 setup and use the BKR7EIX-11 NGK Iridium plugs. I gap mine at .026. That set-up has worked well for me so far.

fatray · 10-30-2004, 02:12 PM

NKG Iridium BKR7EIX Stock# 2667. Good to go no gapping required.

moremaga · 10-30-2004, 02:17 PM

What is the stock gap on those plugs?

Quote:

Originally Posted by fatray

NKG Iridium BKR7EIX Stock# 2667. Good to go no gapping required.

fatray · 10-30-2004, 02:42 PM

I have no idea I didn't check. From what I have read (do a search) on these fourms the BKR7EIX-11 are the same as the BKR7EIX except the plug gap. The -11 are for non turbo cars, NA.

blackie · 10-30-2004, 03:03 PM

ok well i just bought some bkr7e's should i just gap them to .026?

Unabomber · 10-30-2004, 03:20 PM

"Any larger gap suggested is wrong for a turbo app. A slightly smaller gap(.026" - .028" ) is commonly used in 'colder' plugs because of increased boost and the slightly smaller gap helps reduce spark blow-out."

-Uncle Scotty

blackie · 10-30-2004, 04:01 PM

Quote:

Originally Posted by Unabomber

"Any larger gap suggested is wrong for a turbo app. A slightly smaller gap(.026" - .028" ) is commonly used in 'colder' plugs because of increased boost and the slightly smaller gap helps reduce spark blow-out."

-Uncle Scotty

thats the answer i was waiting for

Sports Wagon · 10-30-2004, 04:40 PM

Teh spark plug FAQ http://forums.nasioc.com/forums/show...ht=spark+plugs

I have bkr7e's gaped to .032

hotrod · 10-31-2004, 01:33 AM

Although I generally agree with Uncle Scotty, on these sort of things, I have to make a qualified correction to that statement.

IF your ignition system is running at its limits, and having spark blow out problems, that is a correct statement. But you can actually increase the chance of detonation by running too small of a spark gap.

The small flame kernal created by a small spark gap, increases the length of time the combustion spends in the "slow burn" phase. When a spark plug fires it creates a small spherical kernel of flame about the diameter of the spark gap. This small flame grows relatively slowly until it gets to about .100 inches in dia, (2.5 mm) Then combustion accelerates rapidly. If the spark gap is smaller than necessary to give reliable ignition at high cylinder pressures, you cause two effects. First the spark jumps before the ignition coil reaches peak voltage ( this causes a relatively weak spark) and the slow burn increases the chances of detonation.

If you run a wider gap, you get better ignition due to higher spark energies required to jump the gap, and the hotter spark does a better job or lighting off hard to ignite mixtures. There is a trade off here, as the longer spark is also prone to being blown out at high rpm when mixture turbulence is very high. The higher spark energies also stress the ignition system more so you reduce the life time of things like ignition coils and spark plug wires (on cars that use them).

In my oppinion you should run the widest spark gap that does not cause breakdown and failure of the ignition coils over time, and does not cause high speed miss at high rpm and boost. Closing down the spark gap is a low tech cure for an inadequate ignition system. The older turbocharged NA subaru's often had to close down the gap to around .029 inches or so to avoid problems.

FYI I am running more than .030 gaps on my plugs. The factory recommended turbo engine spark gap is .028 - .031 inches. The maximum gap recommended from the factory assumes the spark plug will be left in place for the recommended service interval of 30,000 miles, over which time the spark gap will grow due to spark errosion and STILL meet emissions standards.

I am running more spark gap than the factory max with no problems, but I will change the plugs every 15,000 miles or so. This is with both pump 91 premium, 100+ octane race gas, and E-85 fuel ( 85% alcohol ) and even in cold weather I have seen no starting problems.

The rule of thumb I've heard is keep opening up the gap about .002 at a time until you get a high speed miss, or see indications of spark blow out (ie the engine falls on its face at high load and loses power under high boost high load conditions)

Then back off to the previous gap.

Larry

Uncle Scotty · 10-31-2004, 09:55 AM

Thanks for your input, Larry. I always like to read what you post.

I had problems at .030" and 22psi...and .028" cured it....so...all else considered the largest gap that dosen't cause issues, as you said, is better.

blackie · 10-31-2004, 05:51 PM

uhhh..... i gapped mine to .026 is that ok or what? will it cause a problem?

drees · 10-31-2004, 07:45 PM

Wow, informative post, Larry.

Blackie, go read it again, your answer is in there.

slprsube04 · 06-10-2007, 09:18 PM

very informative. thanks. altough i dont think i have enough patience to keep pullin the plugs out and regapping. not that fun especially when you have fat hands.

Sharky NRK · 06-10-2007, 09:36 PM

copper bkr7e

Sharky NRK · 06-10-2007, 09:38 PM

gapped at .28 they have NEVER given me issues, but I try and make sure I swap them at 10-15K intervals, its cheap insurance

Carnage02 · 11-28-2007, 02:30 PM

I just changed mine from the stock plugs (NGK platnum) to the NGK copper. I wasn't having any problems with the stock plugs and they were gapped to .035. I put the new ones in at .030 and I THINK they are causing issues... I had a hard time starting (just once) and I got misfires on 1 and 3, and I have been smelling a little fuel... any ideas?

Uncle Scotty · 11-28-2007, 04:00 PM

Quote:

Originally Posted by Carnage02

I just changed mine from the stock plugs (NGK platnum) to the NGK copper. I wasn't having any problems with the stock plugs and they were gapped to .035. I put the new ones in at .030 and I THINK they are causing issues... I had a hard time starting (just once) and I got misfires on 1 and 3, and I have been smelling a little fuel... any ideas?

...didn't put it back together right

DrumNWReX · 07-07-2009, 11:29 PM

Just curious, I changed my plugs today as is consistent with the 60k mile service. Used OEM NGK plugs, did not gap them. From what I understand, I think I did the right thing. Am I incorrect? Should I have tried to gap them? My car is completely stock. Please pm with responses, thanks

Uncle Scotty · 07-08-2009, 12:10 AM

Quote:

Originally Posted by DrumNWReX

Just curious, I changed my plugs today as is consistent with the 60k mile service. Used OEM NGK plugs, did not gap them. From what I understand, I think I did the right thing. Am I incorrect? Should I have tried to gap them? My car is completely stock. Please pm with responses, thanks

you did

XanRules · 07-08-2009, 12:39 AM

I don't think that you'd have to gap them yourself unless you're running a pretty insane motor setup.
Pre-gapped ones are working just fine for me.

kaisersouse · 07-08-2009, 08:26 AM

XanRules: It still doesn't hurt to check the gap IMHO. The tool is 99 cents at the automotive counter and it takes 2 seconds per plug.

Uncle Scotty · 07-08-2009, 10:29 AM

Quote:

Originally Posted by kaisersouse

XanRules: It still doesn't hurt to check the gap IMHO. The tool is 99 cents at the automotive counter and it takes 2 seconds per plug.

....until you destroy your iridium plugs by doing it

some plugs are VERY fragile and it is a virtual CERTANTY that you WILL destroy them if you put ANYTHING between the electrodes

been there
done that

and even knowing EXACTLY what you are doing and being careful WILL yeild destroyed plugs once in a while

BEWARE EVEN 'CHECKING' the gap on ANY iridium(or 'fine wire'type) plugs!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

kaisersouse · 07-08-2009, 11:30 AM

Quote:

Originally Posted by Uncle Scotty

....until you destroy your iridium plugs by doing it

some plugs are VERY fragile and it is a virtual CERTANTY that you WILL destroy them if you put ANYTHING between the electrodes

been there
done that

and even knowing EXACTLY what you are doing and being careful WILL yeild destroyed plugs once in a while

BEWARE EVEN 'CHECKING' the gap on ANY iridium(or 'fine wire'type) plugs!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Ahh I didn't realize this. My car is to slow for fancy plugs haha.

Sorry about that folks.

10-29-2004, 05:04 PM	#1
blackie Scooby Specialist Member#: 42979 Join Date: Sep 2003 Location: houston tx Vehicle: 03 wrx blizzzack stage IV	Best spark plug gap for stage IV? This might be a silly question but is there a recommended gap for a stage 4 wrx, or should i just set the plugs to factory specs?? also what is the factory recommended spark plus gap?? thanks, BTW im using the BKR7E's if that makes a difference. * Registered users of the site do not see these ads.

10-29-2004, 05:25 PM	#2
moremaga Scooby Newbie Member#: 12179 Join Date: Nov 2001 Chapter/Region: NWIC Location: Oregon Vehicle: 2002 WRX RA gears Blk	Gapping I have a stage 4 setup and use the BKR7EIX-11 NGK Iridium plugs. I gap mine at .026. That set-up has worked well for me so far.

10-30-2004, 04:40 PM	#9
Sports Wagon Scooby Specialist Member#: 43081 Join Date: Sep 2003 Chapter/Region: TXIC Location: FTW	Teh spark plug FAQ http://forums.nasioc.com/forums/show...ht=spark+plugs I have bkr7e's gaped to .032 Last edited by Sports Wagon; 10-30-2004 at 04:49 PM.

10-31-2004, 01:33 AM	#10
hotrod Scooby Specialist Member#: 14141 Join Date: Jan 2002 Location: [email protected] @ 5800 ft on 13T Vehicle: 2002 Impreza WRX	plug gap Although I generally agree with Uncle Scotty, on these sort of things, I have to make a qualified correction to that statement. IF your ignition system is running at its limits, and having spark blow out problems, that is a correct statement. But you can actually increase the chance of detonation by running too small of a spark gap. The small flame kernal created by a small spark gap, increases the length of time the combustion spends in the "slow burn" phase. When a spark plug fires it creates a small spherical kernel of flame about the diameter of the spark gap. This small flame grows relatively slowly until it gets to about .100 inches in dia, (2.5 mm) Then combustion accelerates rapidly. If the spark gap is smaller than necessary to give reliable ignition at high cylinder pressures, you cause two effects. First the spark jumps before the ignition coil reaches peak voltage ( this causes a relatively weak spark) and the slow burn increases the chances of detonation. If you run a wider gap, you get better ignition due to higher spark energies required to jump the gap, and the hotter spark does a better job or lighting off hard to ignite mixtures. There is a trade off here, as the longer spark is also prone to being blown out at high rpm when mixture turbulence is very high. The higher spark energies also stress the ignition system more so you reduce the life time of things like ignition coils and spark plug wires (on cars that use them). In my oppinion you should run the widest spark gap that does not cause breakdown and failure of the ignition coils over time, and does not cause high speed miss at high rpm and boost. Closing down the spark gap is a low tech cure for an inadequate ignition system. The older turbocharged NA subaru's often had to close down the gap to around .029 inches or so to avoid problems. FYI I am running more than .030 gaps on my plugs. The factory recommended turbo engine spark gap is .028 - .031 inches. The maximum gap recommended from the factory assumes the spark plug will be left in place for the recommended service interval of 30,000 miles, over which time the spark gap will grow due to spark errosion and STILL meet emissions standards. I am running more spark gap than the factory max with no problems, but I will change the plugs every 15,000 miles or so. This is with both pump 91 premium, 100+ octane race gas, and E-85 fuel ( 85% alcohol ) and even in cold weather I have seen no starting problems. The rule of thumb I've heard is keep opening up the gap about .002 at a time until you get a high speed miss, or see indications of spark blow out (ie the engine falls on its face at high load and loses power under high boost high load conditions) Then back off to the previous gap. Larry

10-31-2004, 09:55 AM	#11
Uncle Scotty * Banned * Member#: 16200 Join Date: Mar 2002 Vehicle: OK buy Nates beans westcoastroasting.com	Thanks for your input, Larry. I always like to read what you post. I had problems at .030" and 22psi...and .028" cured it....so...all else considered the largest gap that dosen't cause issues, as you said, is better. Last edited by Uncle Scotty; 10-31-2004 at 10:18 AM.

10-30-2004, 02:12 PM	#3
fatray Scooby Specialist Member#: 18150 Join Date: Apr 2002 Chapter/Region: MAIC Location: Baltimore MD Vehicle: 2002 WRX Wagon EJ207 Velocity Red, Liberal kit	NKG Iridium BKR7EIX Stock# 2667. Good to go no gapping required.

10-30-2004, 02:42 PM	#5
fatray Scooby Specialist Member#: 18150 Join Date: Apr 2002 Chapter/Region: MAIC Location: Baltimore MD Vehicle: 2002 WRX Wagon EJ207 Velocity Red, Liberal kit	I have no idea I didn't check. From what I have read (do a search) on these fourms the BKR7EIX-11 are the same as the BKR7EIX except the plug gap. The -11 are for non turbo cars, NA.

10-30-2004, 03:03 PM	#6
blackie Scooby Specialist Member#: 42979 Join Date: Sep 2003 Location: houston tx Vehicle: 03 wrx blizzzack stage IV	ok well i just bought some bkr7e's should i just gap them to .026?

10-30-2004, 03:20 PM	#7
Unabomber Big Ron Super Moderator Member#: 18062 Join Date: Apr 2002 Chapter/Region: MAIC Location: I can save you a ton of cash Vehicle: on car parts so PM me b4 j00 buy	"Any larger gap suggested is wrong for a turbo app. A slightly smaller gap(.026" - .028" ) is commonly used in 'colder' plugs because of increased boost and the slightly smaller gap helps reduce spark blow-out." -Uncle Scotty

10-31-2004, 05:51 PM	#12
blackie Scooby Specialist Member#: 42979 Join Date: Sep 2003 Location: houston tx Vehicle: 03 wrx blizzzack stage IV	uhhh..... i gapped mine to .026 is that ok or what? will it cause a problem?

10-31-2004, 07:45 PM	#13
drees Scooby Specialist Member#: 25905 Join Date: Oct 2002 Chapter/Region: SCIC Location: San Diego, CA Vehicle: 2003 Silver Wagon Tuned with Enginuity	Wow, informative post, Larry. Blackie, go read it again, your answer is in there.

06-10-2007, 09:18 PM	#14
slprsube04 Scooby Newbie Member#: 147486 Join Date: Apr 2007 Chapter/Region: NWIC Location: Seattle Vehicle: 2004 WRX PSM	very informative. thanks. altough i dont think i have enough patience to keep pullin the plugs out and regapping. not that fun especially when you have fat hands.

06-10-2007, 09:36 PM	#15
Sharky NRK Scooby Specialist Member#: 29549 Join Date: Nov 2002 Chapter/Region: TXIC Location: Hutto, TX Vehicle: 2003 WRX WRB	copper bkr7e

06-10-2007, 09:38 PM	#16
Sharky NRK Scooby Specialist Member#: 29549 Join Date: Nov 2002 Chapter/Region: TXIC Location: Hutto, TX Vehicle: 2003 WRX WRB	gapped at .28 they have NEVER given me issues, but I try and make sure I swap them at 10-15K intervals, its cheap insurance

11-28-2007, 02:30 PM	#17
Carnage02 Scooby Newbie Member#: 123060 Join Date: Aug 2006 Chapter/Region: NESIC Location: North Providence, RI Vehicle: 02 WRX and GC gravel	I just changed mine from the stock plugs (NGK platnum) to the NGK copper. I wasn't having any problems with the stock plugs and they were gapped to .035. I put the new ones in at .030 and I THINK they are causing issues... I had a hard time starting (just once) and I got misfires on 1 and 3, and I have been smelling a little fuel... any ideas?

07-07-2009, 11:29 PM	#19
DrumNWReX Scooby Newbie Member#: 99119 Join Date: Oct 2005 Chapter/Region: SCIC Location: San Diego Vehicle: 2006 WRX Cobb Stg. 2 OBP Clark Turner tuned!	Just curious, I changed my plugs today as is consistent with the 60k mile service. Used OEM NGK plugs, did not gap them. From what I understand, I think I did the right thing. Am I incorrect? Should I have tried to gap them? My car is completely stock. Please pm with responses, thanks

07-08-2009, 12:39 AM	#21
XanRules Scooby Guru Member#: 157348 Join Date: Aug 2007 Location: OOoOuuUUUGGGHH!!!!! Vehicle: I Thlammed My Penith in the Car Door	I don't think that you'd have to gap them yourself unless you're running a pretty insane motor setup. Pre-gapped ones are working just fine for me.

07-08-2009, 08:26 AM	#22
kaisersouse Scooby Specialist Member#: 85900 Join Date: Apr 2005 Chapter/Region: NESIC Location: Maine Vehicle: 2001 Forester S White	XanRules: It still doesn't hurt to check the gap IMHO. The tool is 99 cents at the automotive counter and it takes 2 seconds per plug.

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