Spark plug gap vs. Performance

[jimrobbington]

I know there are other spark plug threads out there, but none like my intentions for this one.

I have been reading about and playing with spark plug gap for some time now, and it honestly does affect performance. I wanted to try to compile honest experience from members who have done the same, to see the results for better understanding and suggestions of settings and why people choose their specific setup for plugs.

For a quick overview of how spark plug gap relates to real world performance:
http://www.custom-car.us/ignition/spark-plug/gap.aspx

For example, I believe stock suggestion is .028 gap. Most people run a .032 gap, and use a step colder range, ie BKR7E. I have loved the copper plugs and that's what I use, plus they are like $8 a set, but need to be replaced around 5k miles if not sooner.

I bought two brand new sets of plugs. One I gapped to .037, the other at .04. I ran the .037 gapped plugs for about 2k miles. Then, I swapped in the .04 gaps for another 3k or so miles. Then, I swapped the .037 back in, and the difference is pretty amazing.

In my results, both .04 and .037 felt more powerful than .032. During this time, I never did any other modifications. But, the difference was that with the .037's I have quicker power in lower RPMs, and 2nd gear is amazingly strong. With the .04's, there is less immediate punch, but there is more power stretched through the RPM range.

The link above states that timing has a direct relationship with spark plug gap as well, but it doesn't explain it. In my opinion, I believe that timing can be tweaked to produce better and better results unto a point where you run out of potential. Question is, how?

I have REVO tuning, where you can adjust timing on a scale of 0 - 9. Setting 3 being the suggested notch for 91 octane fuel. I run with it on 4, yet still only run 91 oct. 93 is very scarce in the mountain regions. If I had true 93, I could run on 5 or maybe 6 for timing.

Regardless, if you have had good experiences with spark plug gap in your life, post your results. I'll go first.


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[jimrobbington]

Octane fuel: 91
Sparkplug and gap: BKR7E .037
Stage: Stage 2 REVO
Pumps: stock HPFP, Dw301 lpfp
Elevation: 5600 ft
Pros: Makes 2nd gear feel like a rocket ship. Crazy linear low end torque.
Cons: Not as much higher end power than a larger gap.

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[Mister W]

Interesting thread. Subscribed.
I'm running .04 on bkr7e. At first the engine sound to run smoother, seems having less torque too. Will post reviews in more km. Maybe it's just me, but it seems to give me more mpg.

Sent from somewhere using smoke signals.

91 oct
unitronic 1+
bkr7e 0.04 gap for now
stock pumps
no elevation

[g_man]

Subscribed. I don't get to see my A4 for a few more months but when I get home I'm going to play around with this. I'm halfway through that 9 page article as well. Good site, thanks.

[jrtrainor]

Subscribed will be running .4 on next set that show up tomorrow.


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[jimrobbington]

Subscribed will be running .4 on next set that show up tomorrow.


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Think Deuce Bigelow: Thats a huge gap!

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[yungcotter]

I've experimented with sparkplugs a bit as well. The fist thing i did was regap the stock bosh plugs to .032 didn't do much. The fist time I changed them I went with NGK BKR7EIX iridiums one step colder gaped to .032. Car felt better and got a bit better mpg. Next I went to the copper version of that plug BKR7E and went to .04 car idles rougher but felt better when standing on it. Also had a bit of cold starting issues took a few extra cranks. I have been running Bosch platinum F5DP0r side fires (no gaping required) for the last 15k and they have been the best sofar. Better idling and it feels more powerful no cold start issues.

apr stage1
93 octane
stock pumps
0-1500ft altitude

Edited for exact sparkplugs part numbers.


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[jrtrainor]

Think Deuce Bigelow: Thats a huge gap!

Sent from my porcelain throne.

I figure with water meth stage 2+ apr on 100oct Tune it would be appropriate.

Think .37 would be better? Open to suggestions.


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[seal66]

Octane fuel: 91
Sparkplug and gap: BKR7E .037
Stage: Maestro stage 1+
Pumps: stock HPFP
Elevation: 5600 ft
Pros: Makes 2nd gear feel like a rocket ship.----yes my 2nd seems fast as heck now
Cons: 3rd feels very weak

[Krusty]

I had stock spark plugs and the car was running a bit rough, switched to the NGK iridium and everything became very smooth.

Octane fuel 91
APR stage one
NGK BKR8EIX 0.032"
AEN CAI

[Jay-Bee]

I kicked it up to a 0.042" gap (Charles.Waite's thread was talking about 0.044") and felt a nice increase in power... however I had old coilpacks and this new larger gap and voltage demand pretty much killed my coilpacks (i had the old ones any way) so I got new coilpacks and it was good for 6 months. I don't know why but I had a problem a month ago with a no start issue, and turned out my plugs were fouled to shit, even though I wasn't near my oil change yet when i usually do them.

So I threw some new BKR6E plugs in at 0.036 and it seems to be the "sweet spot" for my car.

I'm bone stock w/AEM intake, always run Shell 91. 300-350m altitude

[konarider94]

I figure with water meth stage 2+ apr on 100oct Tune it would be appropriate.

Think .37 would be better? Open to suggestions.


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He is making light of the fact you left out a zero. .4 >> .04 , whats funny is you did it again with the .37 (almost 3/8")

[CorneliusRox]

Octane fuel: 91
Sparkplug and gap: BKR7E .045
Stage: Vast Stg 1
Pumps: stock
Elevation: 5600 ft
Pros: I rev through 1st a lot faster, and slightly more power everywhere else.
Cons: None

[jimrobbington]

I figure with water meth stage 2+ apr on 100oct Tune it would be appropriate.

Think .37 would be better? Open to suggestions.


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Lol, just giving you shit because you missed a zero. I think Corey has been running .044. I don't think any gap is too big yet.

Edit, didn't see the whole second page that explained this. Lol.

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[jimrobbington]

This would be even more interest with the okada coils to see how big you could go

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[Schweini]

great thread. I have the Bosch platinum F5DP0r side fires, and have had them since changing the stock plugs at .028. So I have nothing to compare them with really. I do know with the side fires, they were a huge night and day difference than the stock .028 plugs.

I have some BKR7E's sitting right in front of me which I've already gaped to .032 and waiting to toss them in. This is an interesting thread, might make me try some re-gaping.

[Goldfinger978]

Hmm interested in trying this. I'm running a TP and Revo Stage II software as well. Where did you guys order your plugs from? Is BKR7E the part number from NGK? So I should just be able to search for that and be able to order the right ones? Thanks in advance.

[jrtrainor]

Hmm interested in trying this. I'm running a TP and Revo Stage II software as well. Where did you guys order your plugs from? Is BKR7E the part number from NGK? So I should just be able to search for that and be able to order the right ones? Thanks in advance.

Local auto parts store. Europaparts. God forbid but ecs if hell freezes over.


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[jimrobbington]

Hmm interested in trying this. I'm running a TP and Revo Stage II software as well. Where did you guys order your plugs from? Is BKR7E the part number from NGK? So I should just be able to search for that and be able to order the right ones? Thanks in advance.

Yep, local stores have it for like $2 each. No point in paying shipping

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[vwnobby]

THEN:
Octane fuel: 93
Sparkplug and gap: NGK Iridium BKR7EIX-11 .028
Stage: Revo Stage II
Pumps: stock HPFP
Elevation: 175 ft
Pros: Resolved my surging issue I was getting when I went StageII.
Cons: Nothing I noticed, except maybe slight decrease in mpg

NOW:
Octane fuel: 93
Sparkplug and gap: NGK (4644) BKR7E gapped at whatever they come from factory
Stage: Revo Stage II+
Pumps: APR HPFP
Elevation: 175 ft
Pros: Less expensive than the Iridiums, running latest coil packs car pulls nice. Will attempt to gap wider at next change.
Cons: Nothing I noticed, except maybe slight decrease in mpg

[vwnobby]

Hmm interested in trying this. I'm running a TP and Revo Stage II software as well. Where did you guys order your plugs from? Is BKR7E the part number from NGK? So I should just be able to search for that and be able to order the right ones? Thanks in advance.

I just bought 8 of the BKR7E from Rockauto.com. Found a 5% off coupon code online - total shipped was $17.39! Can't beat that.

[yungcotter]

Hmm interested in trying this. I'm running a TP and Revo Stage II software as well. Where did you guys order your plugs from? Is BKR7E the part number from NGK? So I should just be able to search for that and be able to order the right ones? Thanks in advance.

I get mine off amazon with prime shipping.

[Charles.waite]

I'd like to suggest people list what coils they have too, though I know not everyone is as anal as I am about that, haha.

B7:
Octane: 92 (boo washington)
Tune: Stage 0 (stock)
Stock Fuelling
Elev.: ~Sea Level
Plugs: BKR6EIX-11
Gap: .044"
Coils: 07K-905-715F
Pros: Smoother idle
Cons: None

B6 (1.8t):
Octane: 92 (boo washington)
Tune: APR Stage 1
Stock Fuelling
Elev.: ~Sea Level
Plugs: BKR7EIX-11
Gap: .044"
Coils: 07K-905-715F
Pros: Smoother idle, Gutsier low end, Stronger boost onset, Smoother power delivery
Cons: None

I found my B6 especially REALLY benefited from the larger gap. Having the tune, it REALLY helped with the larger gap providing the stronger spark when the boost pressure crept up towards 19. I peak at 19 and hold around 15 on my 1.8t with these coils and haven't had a SINGLE issue in over a year with this setup.

With my B7 the results were less exciting. I actually ran a .044" gap on the regular coils (not sure what part number but they were a few years old) and the car ran great, no breakup or misfires, even though the coils were older. With the new coils there doesn't seem to be much of a difference. To be honest, on a stock engine, I'm not sure the larger gap does a whole lot. My B7 feels really slow compared to my b6 even though power levels are roughly on par. I think the power onset is so much difference, the greater amount of boost makes the car FEEL faster even though it might not be.

[vividracing]

Very interesting thread!Good info!

[turbowop]

I don't think I've ever heard of so many people talking about how spark plug gap or different plugs relate to power so much. I am of the belief that unless your car is having ignition breakup, you won't really make any more substantial power with one plug over another, or even a larger gap. Maybe a couple of horsepower. From the way you guys talk this up, it's as though you think you are gaining 50hp or more. Regapping turns 2nd gear into a rocket ship? Really?

I can see changing to a different heat range (colder) on a modded car to keep from getting detonation, which could increase power if the car was seeing knock, but gap size and plug brand shouldn't be that noticeable. Are you guys testing all this on dynos? Or just with your butt dynos?

FWIW, I have to use plugs that are two heat ranges colder on my Mitsu, non-projected type plugs, gapped at .020, to keep the spark from blowing out when boost and methanol comes on. Larger gaps or projected tips and I would get nasty ignition breakup. Standard cheapie NGK coppers. I've never heard of any Mitsu guys making more power by changing gaps or plug brand/type. Maybe it's different in the Audi world, but the basic engine dynamics are still the same, right?

[CorneliusRox]

This of it like TIG welding because that's basically what spark plugs do. You have an electrode that creates an arc. The finer the top, the more precise the arc. The bound tip makes it arc in a circle almost which simply creates more arc. The bigger the arc, the more amperage drawn, and the hotter the spark.

So the bigger the gap, the better the fuel will burn.

The limits are these:
1) The bigger the arc, the more current drawn, the more stress on the coil pack.
2) Too big of a gap can actually make the plug arc to the head, which isnt a good thing.

[Goldfinger978]

Just swapped my old ones. First time since ownership (owned A4 for about 6 months) Looked like the original set too...
Feels a little peppier, but nothing crazy. I can't really get on 'er b/c my stock clutch is slipping due to the increase in power from the TP/Revo Stage 2 software.

Octane fuel: 91
Sparkplug and gap: BKR7E .037
Stage: Stage 2 REVO
Pumps: stock HPFP
Elevation: Not sure, but live in San Diego, CA

[turbowop]

This of it like TIG welding because that's basically what spark plugs do. You have an electrode that creates an arc. The finer the top, the more precise the arc. The bound tip makes it arc in a circle almost which simply creates more arc. The bigger the arc, the more amperage drawn, and the hotter the spark.

So the bigger the gap, the better the fuel will burn.

The limits are these:
1) The bigger the arc, the more current drawn, the more stress on the coil pack.
2) Too big of a gap can actually make the plug arc to the head, which isnt a good thing.

But a small change to the gap size doesn't make for a substantially better burn does it? Not enough to feel in the seat of the pants, eh? I mean, the spark just ignites the mixture, it doesn't actually do the burning. Once the mixture is ignited and the burn propagates across the combustion chamber, the spark no longer plays a role.

[Older_not_Wiser]

Subscribed. Interesting stuff. Going to have to play around a little with some different plugs/gaps.

[jimrobbington]

Maybe it has something to do with direct injection differences? Its definitely noticeable in the butt dyno.

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[CorneliusRox]

But a small change to the gap size doesn't make for a substantially better burn does it? Not enough to feel in the seat of the pants, eh? I mean, the spark just ignites the mixture, it doesn't actually do the burning. Once the mixture is ignited and the burn propagates across the combustion chamber, the spark no longer plays a role.

It's definitely noticeable. try it

[Charles.waite]

It's not even direct injection it's just a more complete, faster burn. Better flame front propagation. Etc.

It's not ground breaking power gains, and that's not the goal. But the engine runs smoother that's a fact. And my 1.8t at least pulls a tad harder.

[turbowop]

I'd like to see some dyno results.

[jimrobbington]

I'd like to see some dyno results.

As would I, but I don't have the $90 bucks to waste on a dyno run of different sparkplug gaps. I'm interested in the results, yes. But I'm not trying to prove an advancement in tuning capabilities either. I did all my own "testing", and came up with interesting results and opinions. I just wanted to see if others are having similar results, and what works better for others. I also hoped to instigate others venturing this territory for a more diverse spectrum to find a clear answer to these questions.

IMO, the spark is one of the most important things there is to run an engine. Its right up there with air and fuel. There wouldn't be thousands of different sparkplug options out there if they weren't on to something. Nor would there be $800 coil pack options.

The way I see it is, yes, you are right. There's a very finite amount of fuel that can be burned in the chamber. But, if you can change the characteristics of that spark, you can in a way, also change the nature of the combustion, thus slightly altering not the amount of power, but the curve. I'm not going to begin to act like I know any of the engineering and physics related facts on how this works. But if say, adding a larger gap, causes more of the fuel to be burned faster, then you could advance/retard your timing to take advantage of the new combustion characteristics, and thus have a dyno noticable gain.

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[Charles.waite]

I'd like to see some dyno results.

What would that prove?

I wasn't claiming it added x horsepower. All I ever said was the engine ran smoother and felt like it pulled harder through the revs. Definitely a difference felt on the butt dyno.

[turbowop]

Or it's just placebo because you want to feel something better after testing eleventeen different spark plug gaps. Remember back in the day when Splitfire spark plugs came out? People thought they felt results with those too...

[jrtrainor]

Red packs
Bkr7eix gapped to .04
Elevation 150-100ft
Stage two apr watermeth 100oct file
Low end is the same high end is pulling ever so slightly better. Could just be the new plugs and new coils.


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[jrtrainor]

Or it's just placebo because you want to feel something better after testing eleventeen different spark plug gaps. Remember back in the day when Splitfire spark plugs came out? People thought they felt results with those too...

Maybe unicorns fart rainbows... Can't argue with what Someone feels.


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[turbowop]

I'm not trying to troll or bust balls here. I just don't trust butt dynos, and that's all anybody seems to be using as their test equipment regarding all of this. How many people say they feel their cars are smoother and pull harder with an APR carbon intake? Same deal. Everybody got shut down pretty hard once the actual dyno results came out, yanno?

[jrtrainor]

Double post


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