Spark plug gap argument thread

[V8weight]

I spoke with Kyle last night at length on the subject of spark plug gaps. It's critical on a tuned forced induction car to close up the gap to prevent the spark from "blowing out" under increased cylinder pressures. Being up north where ambient temps are down to about 0-10F, we both seem to be experiencing problems with spark blow out, in varying degrees of severity. With lower ambient temps come higher air densities, and in theory, higher cylinder pressures. I can hear my car stutter and fart out of the exhaust at the onset of full boost, where timing advance is at it's highest. This is a rare event for me, usually when the car is not fully warmed up (pre-heatsoak, when air density is at it's highest). My plugs are currently gapped to .028-.029. Kyles car seems to suffer worse, same symptoms only far more often and all across the boost curve. He believes his plugs may be opened as far as .040. I think this may be less of, or even a non issue for our southern friends in warmer climates, as this was never an issue for me in the summer months.

I'm heading out to the garage today to take my gap down to .024, maybe .025 to see if this helps. For reference, the stage 1-3 S4 owners are running .022-.024 on their cars, and theirs call for a stock .032 gap just like ours. I think Kyle is doing the same, so hopefully this works out for his car. If anybody has any thing to add to the subject, feel free.......

[MaxRS6]

Would it be worth a call to the APR techs to determine if they have a recommended gap setting?

My experience with APR suggests they would be happy to discuss possible issues/resolutions and review some logs. I ocassionally get a misfire code through Vag-Com but it is rather rare.

Less than .03 worth but u get watch u get...;0

[V8weight]

Would it be worth a call to the APR techs to determine if they have a recommended gap setting?

My experience with APR suggests they would be happy to discuss possible issues/resolutions and review some logs. I ocassionally get a misfire code through Vag-Com but it is rather rare.

Less than .03 worth but u get watch u get...;0
They may have a suggestion, if only I knew someone that probably has their number memorized by now, that could give them a call and pick their brains. I know that they participate on some of the larger national forums, it's too bad they don't swing through here every once and a while.

[MaxRS6]

I'll certainly give them a call on Monday and see if I can pick up any pearls. If you have anything specific other than the spark gaps, let me know and I'll be glad to ask the questions.

[speedtrapped]

Hmmm, very interested, turns out on cold start again I sputtered and misfired, misfire code, lean, rich code....and I fixed MAF connections, it's been prevelent ever since temps have been 20-25 degrees. Tech pulled only one plug randomly and gap was .28, all coils and plugs new, looking forward to your results Pat

[4everRS]

for anyone who read the 2nd page of my "early xmas" thread, this was one of the first things I could think of after putting the ecu on program 2. Of course like many of us, I though worse thoughts like TC failure. Haha

Max, its not really an issue of a misfire as no codes are thrown when it happens. The coil is still sending the signal and its not predetonating, just not detonating at all due to blow out. At least this is my theory.

I'll be closing the gaps a little later today. Scraping grout right now, yeah!

[V8weight]

for anyone who read the 2nd page of my "early xmas" thread, this was one of the first things I could think of after putting the ecu on program 2. Of course like many of us, I though worse thoughts like TC failure. Haha

Max, its not really an issue of a misfire as no codes are thrown when it happens. The coil is still sending the signal and its not predetonating, just not detonating at all due to blow out. At least this is my theory.

I'll be closing the gaps a little later today. Scraping grout right now, yeah!
I think you're correct Kyle, as far as the ecu is concerned, detonation is complete, and no fault will be registered in this event. Almost done here, I'll check back in after a test drive.

[JSRS6]

I am in the middle of this process(literally). I will be gapping mine but forgot the torque requirement on the plugs. Anyone got the specs?

[speedtrapped]

So pat if gap is to wide and ambient temp very low, hence air denser and psi stronger?, the ECU won't throw codes? I am get misfire codes ......I am curious and my question should be a diff thread, But could aces be effecting my start up? I have only run 1.5 tanks of the aces, and I know brian said it may run funky in beginning? I am only curious and not suggesting BND fluids is to blame.

[V8weight]

I am in the middle of this process(literally). I will be gapping mine but forgot the torque requirement on the plugs. Anyone got the specs?
Torque spec for the plugs is 30Nm, or 22ft/lbs, or 264in/lbs.

[V8weight]

So pat if gap is to wide and ambient temp very low, hence air denser and psi stronger?, the ECU won't throw codes? I am get misfire codes ......I am curious and my question should be a diff thread, But could aces be effecting my start up? I have only run 1.5 tanks of the aces, and I know brian said it may run funky in beginning? I am only curious and not suggesting BND fluids is to blame.
I think that you are experiencing a large un-metered air leak myself. Re-gapping the plugs surely won't hurt, but you either have an air leak around your MAF sensors, or some kind of vacuum leak. Find a local shop with a smoke tester. Don't bother with the driveway mechanic pressure testing method, a proper smoke test should isolate a leak pretty quickly. Or, you still have a problem with the MAF sensors themselves, or the wiring. Good luck.

[speedtrapped]

Ty, I will have it smoke tested

[V8weight]

Done, and test driven. This was a relevant experiment. No more silly business on acceleration (though it didn't happen very often anyhow), just smooth gut wrenching acceleration. Have fun, going driving!

[JSRS6]

Ha! I just finished too! About to go driving as well. I regapped at .025.

[V8weight]

I set mine at .024", seems to have smoothed out not only the power band, but the idle as well. I'm thinking that anybody with a tune on their car should think about running a .024 gap, and maybe .028 for stock.

[V8weight]

There is a such thing as having your plugs gapped too tight. This is easily checked by connecting a vacuum gauge and monitoring it at idle. If the gap was too narrow, the gauge will fluctuate about 2 inches of vacuum. I checked mine and it's a steady 20 inches, no fluctuation. This is the only way I could think to check and make sure I hadn't gone too far.

[JSRS6]

It feels fine at idle now.

[JSRS6]

And the power does feel smoother.

[V8weight]

And the power does feel smoother.
Well, if nothing else, we've created a new placebo effect ;)

[JSRS6]

Well, if nothing else, we've created a new placebo effect ;)

Hah! This is entirely possible in this case. But my idle is definitively smoother now.

[V8weight]

Hah! This is entirely possible in this case. But my idle is definitively smoother now.
Ya, same here. I should have thought to hook up the vacuum gauge prior to re-gapping to see if there was an improvement in vacuum. At any rate, it sure feels smoother at all rpms.

[yokust]

Normally the only time you need to reduce the gap on plugs is when the spark output of coils is too weak

Alot of big horse power cars, run a larger gap with a stronger coils

This is why on my car I swapped for the new push down coils, because they have a stronger spark then the bolt down coils. All the issues you have been describing is why I swapped coils and all went away with the coils

[V8weight]

Normally the only time you need to reduce the gap on plugs is when the spark output of coils is too weak

Alot of big horse power cars, run a larger gap with a stronger coils

This is why on my car I swapped for the new push down coils, because they have a stronger spark then the bolt down coils. All the issues you have been describing is why I swapped coils and all went away with the coils
I know you've probably said it before, but what coils are you running? Same part number as say, a B6 S4? I think I may have some spares if that's the case.

[ttboost]

My 996 Turbo plugs are gapped at .025 and I run 1.3bar or so...and no misfires there...

[V8weight]

My 996 Turbo plugs are gapped at .025 and I run 1.3bar or so...and no misfires there...
Not exactly apples to apples. Your 996 has a compression ratio of 9.4:1, the RS6 is 9.8:1. I run about 1.25bar max, cylinder pressures may actually be higher in the RS6.

[ttboost]

My 996 compression ratio under 1.4bar of boost is: 21.55:1, The RS6 at 1 bar is: 19.6:1. Pretty close. I guess my point was an .025 gap is good for almost 20lbs of boost on that particular car. When I finally do my plugs in the RS6, They will be gapped at .025.

[V8weight]

My 996 compression ratio under 1.4bar of boost is: 21.55:1, The RS6 at 1 bar is: 19.6:1. Pretty close. I guess my point was an .025 gap is good for almost 20lbs of boost on that particular car. When I finally do my plugs in the RS6, They will be gapped at .025.
If using the 1.3 bar like you stated earlier, and no correction for altitude, your compression under boost comes to 21.7:1, and my car at 1.25 bar comes to 22.13:1. It's probably not necessary to reduce the gap as far as .024, but like I said earlier, I had a steady vacuum reading, so it's not doing any harm. I figured if I was going to bother pulling the plugs and adjusting gaps, I would go to one extreme. I'm due for new plugs in 5k, so I'll try .025 then and retest.

[ttboost]

If using the 1.3 bar like you stated earlier, and no correction for altitude, your compression under boost comes to 21.7:1, and my car at 1.25 bar comes to 22.13:1. It's probably not necessary to reduce the gap as far as .024, but like I said earlier, I had a steady vacuum reading, so it's not doing any harm. I figured if I was going to bother pulling the plugs and adjusting gaps, I would go to one extreme. I'm due for new plugs in 5k, so I'll try .025 then and retest.

Yeah, I used a 1000ft altitude in my calc...no biggie...and I plan on turning my boost up :)..., as soon as I fix some issues. DV's done, and N75 next... wasn't holding full boost after the flash...

[V8weight]

Yeah, I used a 1000ft altitude in my calc...no biggie...and I plan on turning my boost up :)..., as soon as I fix some issues. DV's done, and N75 next... wasn't holding full boost after the flash...
What diverter valves did you go with?

[ttboost]

What diverter valves did you go with?

Stock OEM upgraded ones. Had them in the 996 for the last 2 years at 1.3bar and been fine. Don't remember the part number? Maybe 750N?

[4everRS]

just got done test driving myself. Gapped them to .025. Problem solved. No more sputtering. Tried both 91 and 93 modes from APR. I think I'll be keeping it in 93 mode.:revs:

[V8weight]

Stock OEM upgraded ones. Had them in the 996 for the last 2 years at 1.3bar and been fine. Don't remember the part number? Maybe 750N?
Ya, that's the one. We're running the Bosch 710N's in our cars at the shop as well. I went with the Forge 007's, it allows you to fine tune the spring tension using the Vag to graph out specified and actual boost drop when they divert pressure for the load reduction during shift points. It was nice to be able to tune how fast it recovers from dumping boost. I should get my hands on a pair of diaphragm valves someday just to see how they compare, I installed the Forge's shortly after buying the car.

[MaxRS6]

just got done test driving myself. Gapped them to .025. Problem solved. No more sputtering. Tried both 91 and 93 modes from APR. I think I'll be keeping it in 93 mode.:revs:

Congrats!

[V8weight]

just got done test driving myself. Gapped them to .025. Problem solved. No more sputtering. Tried both 91 and 93 modes from APR. I think I'll be keeping it in 93 mode.:revs:
Congrats Kyle! Feel better? I'm glad you brought this whole thing up, I never really thought this far into it, I was just assuming you needed a new set of plugs in general. It's funny, there seemed to be an RS6 community plug change today. Shouldn't we be out Christmas shopping?

[ttboost]

Shouldn't we be out Christmas shopping?

I'd rather put a tunnel in my forehead...

[V8weight]

I'd rather put a tunnel in my forehead...
LOL, my phrase was, "Go shopping? I'd rather slam my d&%$ in a door"! Haha

[MaxRS6]

Owoooo- Stay away from that gap

[V8weight]

Lucky for me, Rachel is able to see the subtle humor in that. :)

[JRS-RS6]

OK I'm in when I finally get home and get the snow tires on the car I want to go to 0.025 also! Pat we can do the vacuum test pre and post on my car for reference.

Reference Post for Spark Plug Change - http://rs6.com/showthread.php/20226-Spark-plug-change-guide?p=180936#post180936

Does anyone have the PN for the two grommets under the Airbox?? I need to replace both and my Etka is on my home PC.

[marklar182]

N10551301

I was just about to order one!

[V8weight]

I think .024 is in fact a bit too tight. While the car does feel smoother, the butt dyno says it's a tad down on power, especially considering the 15F ambient temp. I'm going to open them up to .026 and check the vacuum reading again.

[V8weight]

I think .024 is in fact a bit too tight. While the car does feel smoother, the butt dyno says it's a tad down on power, especially considering the 15F ambient temp. I'm going to open them up to .026 and check the vacuum reading again.
Increased the gap to .026" and gained 2in/hg of vacuum.


N10551301

I was just about to order one!
One of my grommets finally disappeared (must have crumbled and pushed through the bottom). I decided I was going to be clever and run to the parts store and pick up two "Help" universal PCV grommets. I found two that seemed close, and fit them to the air cleaner, and they seemed to be a perfect, although tighter than stock fit. When I fit the air box, it didn't seat down properly. The new grommets fit so tightly, that I could not get the air box back off! Eventually got it, but moral of the story: There's not anything that you can get for the beast from O'Rielly's Auto Parts. Doh!

[4everRS]

moral of the story: There's not anything that you can get for the beast from O'Rielly's Auto Parts. Doh!
Except my autolite spark plugs! Hehe.

[V8weight]

Except my autolite spark plugs! Hehe.
Alright, edit: There's not anything that you can buy for the beast at O'Rielly's that's good for the beast.......;)

[JSRS6]

Well apparently i need two grommets...ive never seen them before...

[speedtrapped]

Pat what vac do pull now? 20?

[V8weight]

Pat what vac do pull now? 20?
22in/hg.

[hahnmgh63]

I have seen 4 RS6's with the Aircleaner off and all 4 had only one grommet? I'm thinking that most cars left the factory with only 1 instead of 2? What have you guys found?

[V8weight]

I have seen 4 RS6's with the Aircleaner off and all 4 had only one grommet? I'm thinking that most cars left the factory with only 1 instead of 2? What have you guys found?
Out of the half dozen RS6's that I've had my mitts on, only mine and Dave's have still had the grommets, and like I said, one of mine is mysteriously absent now. They live a hard life, and it appears that they crumble and fall below the intake. It would be funny to pull the intake and find a pile of these things.

[ben916]

Out of the half dozen RS6's that I've had my mitts on, only mine and Dave's have still had the grommets, and like I said, one of mine is mysteriously absent now. They live a hard life, and it appears that they crumble and fall below the intake. It would be funny to pull the intake and find a pile of these things.

Ya lost me without a photo...

[V8weight]

Ya lost me without a photo...
I don't have a great pic, but they're circled here.
http://i722.photobucket.com/albums/ww228/Pellis833/002-21-1.jpg

[JRS-RS6]

Ya lost me without a photo...

http://i783.photobucket.com/albums/yy119/JRS-RS6/7_Grommet_holes_circled-in-red.jpg

Oops Pat beat me to it.

[snoopra]

I lost both to the intake death valley the last time I pulled the intake. Got a new set waiting.

[V8weight]

I lost both to the intake death valley the last time I pulled the intake. Got a new set waiting.

Where have you been? I was contemplating starting a "where's Snoopra" thread today.

[snoopra]

I'm working nites:( ...no days off.. :( .....till mid January. I still sneak on to read the latest:)
We've been in the news too many times in the past months (We, meaning the Refinery) so my expertise is needed for some repair guidance :)

[ramin]

Hi Guys, I have been reading the forum for years but this is my first post.

I noticed everybody talked about calling APR but I didn't see any updates. I called them today and they said the tune is based on the OEM plug gap, so their recommendation is to just stay with that same gap of 0.032.

[ttboost]

Hi Guys, I have been reading the forum for years but this is my first post.

I noticed everybody talked about calling APR but I didn't see any updates. I called them today and they said the tune is based on the OEM plug gap, so their recommendation is to just stay with that same gap of 0.032.

Then their tune doesn't raise the boost level at all, or VERY little.

[V8weight]

Hi Guys, I have been reading the forum for years but this is my first post.

I noticed everybody talked about calling APR but I didn't see any updates. I called them today and they said the tune is based on the OEM plug gap, so their recommendation is to just stay with that same gap of 0.032.

The stock plugs come pre gapped to .028- .029".....

[Brav]

Another request - anyone have info on which uprated "snap on" coils to use?

[ramin]

The stock plugs come pre gapped to .028- .029".....

Just to be clear, APR didn't tell me the size of the gap. I inserted that per my search online. The APR guy just said to stay with stock size.

See, for example, http://rss.rpmware.com/ngk/ngk_spark_plug_iridium_ix/bkr7eix/i-134850.aspx

[ramin]

Then their tune doesn't raise the boost level at all, or VERY little.

I am not sure how much APR stage 1 increases the boost level, but I suspect there are other ways to address boost level increase other than changing the spark plug gaps. Couldn't they just change the timing?

[ben916]

I am not sure how much APR stage 1 increases the boost level, but I suspect there are other ways to address boost level increase other than changing the spark plug gaps. Couldn't they just change the timing?

off topic:
Welcome!
Got a VIN?

On Topic:
The stock plugs come pre gapped to .028- .029"..... as Stephen says BUT there was prior posting about AFTER tuning, possibly EuroChg tune, the idle was rough, not smooth, etc - a change in the gap to .025 - .026 made all the difference and all the issues went away

[4everRS]

APR definitely changes boost levels. I have data logs to prove it. However, I am a bit disappointed in them right now as they told me over the phone to send some data logs addressing a question I had and I haven't heard back 3 weeks running. Anyhow, I run my plugs at .025. If your coilpacks are old, you may be losing voltage and thinking the plug gap is the problem.

Better coilpacks are the revised 1.8t packs. http://www.ecstuning.com/Volkswagen-Jetta_IV--1.8T/ES279618/
Get them at genuine for a better price. They are not bolt down and there is a rubber piece you have to trim to fit the 4.2 hole. you can always use hold downs if you want.

[hahnmgh63]

Many Turbo engines that have had boost levels increased, can use a slightly smaller plug gap as the increased cylinder pressures (denser charge) makes it more difficult for the electricity to jump the gap. Modifying the ignition system to higher voltages can alleviated this but is not easily done on our cars. A perfectly working RS6 ignition system with fairly new coils and new plugs will probably not notice a difference but the coils loose voltage over time before they throw misfire codes or fault (check the resistance of a new coil against your used coils sometime).
As for the new 1.8t coils that is a debate that has been going on for years and has been discussed here before. I also have a daily driver 225bhp 1.8t Audi tt (which specs the exact part # as our cars)(chipped of course w/ downpipe etc.. to over 265bhp) and most of the modified tt guys believe that sticking with the 'E' revision coils but only one that are Hitachi manufactured. Do a Google search and you will find mountains of forum activity on this, just pay more attention to the later dated forum activitiy as many have learned a lot from past coil revisions.

[kismetcapitan]

pulling timing on turbo engines generally kills power, as timing is usually advanced to the point of detonation then backed off a bit. Does make ignition mapping easier with turbo engines than with N/A engines, where the sweetspot for optimum ignition timing feels to me to be half voodoo - must sacrifice live chicken to find the right timing :P

Too big a gap in relation to the boost pressure can blow out the spark, and then you'll misfire on that cylinder. I know I went on about this on another thread, but what about surface gap plugs? After scores of headaches with plugs, heat range, and gapping on my Skyline, I just went with surface gap and never had to think about the ignition system again. It did benefit from new coilpacks as well as an ignition amp however - it takes a lot of juice to arc across that gap on a surface gap, and to cut through whatever crud has built up on the thing.

[DiscoPotato]

As far as I know if you apply an aftermarket tune to your car, you have to shorten the gap. Being a B5 S4 owner I know this all too well. Im running a gap of .026 on a custom stage 2+ setup.. Stock for me is .032. Even tuning companies call for the shorter gap once a new tune is applied. This is attributed to the raised boost, and thus cylinder pressure.

Ive read multiple threads on this exact subject on many different forums on many different types of Audis.. They all came to the same conclusion..

Safe & smooth = Smaller gap

If you are experiencing spark plugs backing out i'd check your tourques, etc as well. But with a slightly smaller gap you will see that your car will pull smoother.

[ramin]

Thanks Guys! I will shorten the gap per your emails once I do my 55k service. My car seems to be running fine now with whatever gap there is. All previous service was done by the dealer, so I am not sure if they even checked the plug gaps when they replaced them last.

[RSSIK]

I agree with Discopotato.. I couldnt have said it better myself.