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Thread: Spark plug temperature comparisons (6's/7's/8's) - S3 2.0T (8P2)

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    warren_S5's Avatar
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    Post Spark plug temperature comparisons (6's/7's/8's) - S3 2.0T (8P2)

    As I went out to have a check of the car this morning I decided to have a look at the various plugs that have been in the car since it was new.

    I was hoping by performing direct comparisons on all 4 grades I might be able to learn something about the way they are coping with TFSi fuelling characteristics.

    I have used 4 plug types since having the car:

    1) Bosch platinum single electrode - OEM plug supplied from factory (In for 11k on Revo Stg1 - removed due to stutter at 5,000rpm)
    2) NGK Iridium 6 (BKR6EIX) - Recommended OEM temperature grade (in car for 15k on Revo Stg 1 - no issues, removed for stage 2)
    3) NGK Iridium 7 (BKR7EIX) - One steps colder (In car for 6k on Revo Stage 2, changed for 2+, no issues other than electrode discolouration causing concern)
    4) NGK Iridium 8 (BKR8EIX) - Two steps colder (Run for 7k on Revo Stg 2+ under duress, removed due to stuttering idle and strong smell of unburned fuel and carbonation on rear of car)

    Here is a photo of the plugs taken out of the car (anti-clockwise):

    1) OEM Bosch (Left hand side)
    2) NGK Iridium BKR6EIX (Bottom)
    3) NGK Iridium BKR8EIX (Right)
    4) NGK Iridium BKR7EIX (Top)



    If you look more closely at the electrodes / tips you can see from the colour of the ceramic cuffs that the plugs are obviously running at significantly different temperatures inside the chamber, and interestingly the cooler plugs are showing a much redder colour around the ceramic cuff. Whether this is stained from additives in the Shell V-Power or just running hotter I have no idea, but the NGK 6's electrode tips are much whiter (none of these plugs have been cleaned up).



    So whilst I have read there are benefits to running the cooler 7's, of all the plugs these looked the most 'scorched' plugs here (granted I've been running the 8's for less miles).

    The OEM plugs are absolutely blackened, and are the only plugs I have had outright performance issues with. The car would stutter at 5,000 rpm and there was marked pitting on the electrode tip. Supposedly according to Audi they should be good for 60k miles, not 11-12k!!! Make of that what you will.

    I hasten to add, I'm not a plug guru. This thread isn't to scare or concern anyone, it's just a purely observational thread that provides people with some photographic comparisons of plugs with comparitive mileages running in a tuned 2.0TFSi S3 engine. If we can learn anything along the way, then its all good.



    I've dropped in a set of new 6's today (I had some spare), and will monitor how things run, and I have a set of 7's winging their way to me from the interweb. I'll try and do some back to back comparisons in due course.

    Any thoughts or analysis greatly appreciated as always.

    Cheers
    Warren
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    paddy's Avatar
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    Those 6's look spot on. the 7's and 8's are both showing signs of Insulator Glazing

    Glazing appears as a yellowish, varnish-like color. And indicates that spark plug temperatures have risen suddenly during a hard, fast acceleration period. As a result, normal combustion deposits do not have an opportunity to burn off" as they normally do. Instead, they melt to form a conductive coating which will eventually cause a misfire.
    In fairness your plugs are having a hard life in your tuned engine and it dosnt surprise me the OEM plugs cant cope for long.

    Interesting pictures and they really show the difference quite well between the heat ranges. this could become a very good thread .
    Last edited by paddy; 15th May 2010 at 10:38.
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    I am going to run the 6's for the foreseeable future.

    I've had really mixed feedback on spark plugs. Some say that the increase boost will require a plug with a thicker ceramic collar to reduce the heat on the electrode. I have been warned if the plugs get too hot the electrode tips could drop off into the chamber.

    However, whilst I believe this may be the case for the 'old skool' turbo charging systems the TFSi system is a very different animal, and the way they system obviously mixes its fuel into the chamber means that maybe the heat issues may not be so prevolent.

    I spoke to a guy a couple of months ago at RGS Motorsport. He currently races Lotus F1 classic cars as he was a test driver for them back in the day. Really has his head screwed on, and he believes resolutely that if your engine is mapped well, even with modifications you should NOT need to deviate from the OEM plug temperature.

    I think switching from platinum electrode to iridium is not likely to cause any pain as it is just harder, and the thinner tip allows you to generate a similar spark with less strain on the already known to be weak coil packs.

    I do hope the thread generates some useful debate as I think it could be an area which is causing premature issues / knock on effects in these engines. My fear is if people take the wrong plugs for too long, are there more permanent issues being created inside the chamber (as no error codes come up until you feel there is an issue).

    I haven't driven the car since putting the 6's back in, but the idle is straight away far more consistent.
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    paddy's Avatar
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    I agree that your OEM plugs should be fine but i would expect service life to be shortened. Iridium has a melting point of about 2500/c, thats about 5 times the melting point of platinum. Being that much more durable the electrode in a plug can be made a lot thinner than an OEM plug. the advantages of this include a lower voltage needed in the electrode before the spark will jump. It also tends to stop flair when a plug reaches a point where individual sparks join and become almost a flame at high revs. As you say less voltage before a jump means less strain on the coils. ( strictly speaking Audi individual coils are not coil packs).
    this issue is important and your plugs are a window on the inside of your engine and how efficient you combustion is and ultimately how efficient your engine is. Get this wrong and it can mean disaster. I had a VR6 golf in the 90's and that developed a rough idle. I pulled the plugs and found the ceramic insulator missing on one. A quick compression test showed a drop of 30% on that pot. whether it had damaged a valve seat or scored the bore i dont know but it soon started to burn oil and i sold it quick.
    In my bike racing days we used to use gunsons colour tune which was essentially a glass spark plug which meant you could see the colour of the spark with the engine running and adjust mixture to fine tune a nice blue flame, it didnt take much to turn a yellow flame blue. these days you could not adjust mixture so you just have to rely on the manufacturers or tuners map to get it right.

    sorry to Rabbit on but people often dont realise that plugs, even with all the diagnostic equip available, still should be your first port of call if you think you have a problem.
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    paddy's Avatar
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    One other point worth mentioning is that the higher the compression ratio, the higher the resistance across the plug so the higher the voltage needed to make the spark jump. this once again will make Iridium plugs much better in high boost engines as they need less voltage at a given atmosphere to work.
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    Paddy, do you know the torque settings for a plug that has been reinserted (eg not on a fresh new washer), as I am concerned mine may not be done up tight enough.

    NGK recmmended on box hand tight plus 0.5 to 0.66 of a full turn, at 0.25 of a turn mine felt very tight. Don't want to thread the head.
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    paddy's Avatar
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    I just checked elsaWin and it says about 30NM which is about 22lb/ft. The tight plus .5 turn doesn't work twice because the first time your collapsing the seal washer.
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    Cheers Paddy, now all done up to that torque setting.

    Popped one out (!) to have a look, and for a new plug there is SHEDLOADS (and I mean shedloads) of carbon deposit on the plug body (if you look at the plug pictures above, they are all black around the solid metal body of the thread which butts into the chamber). Didn't expect it to be so pronounced in one journey.

    Too much fuelling on Revo maybe (Boost 9, Timing 5, Fuelling 8)??
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    Yea i see what you are saying. I suspect its just that part of the plug is a lot colder because of the heat sink into the head. I expect it will initially coke up where it protrude into the combustion chamber but only till it seals the gap between plug and the carbon coat in the chamber. The colour of the centre ceramic is the best indicator and that looks fine on 6's.
    My knowledge doesn't really extend past motorcycles into Turbo's but the basic principles apply on plugs i think. Its quite possibly;e that a lumpy idle is an air leek somewhere. If that is the case then you need to find that before paying to much attention to the plugs as that might well effect their colour.
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    i was having an air leak to after a service which I mentioned recently, and i've just installed a Neusped induction kit and now the idle seems fine.
    I think i had an air leak in my OEM airbox as it had been removed so many times recently and cracked somewhere.
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    An interesting thread warren,
    I've bought some Denso IK24s (2 grades cooler than standard) on the strength of recommendation from other stage2+ ed30 owners. Car is currently running standard plugs so will be interesting to see if there is a perceived difference.

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    After 8k my car was smelling like it had a fuel leak. People would comment that the car stank of fuel at tick over.

    Keep an eye on the insulator to see if it glazes. Happy to accept that the fact my car seems to be chewing plugs may be down to me doing quite a few short around town journeys which means it's just throwing fuel into the system, but 8k out of a set, stinks to me that the TFSi engine may not be happy with them unless I have a major issue (which isnt immediately apparent)
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    Quote Originally Posted by robern2 View Post
    An interesting thread warren,
    I've bought some Denso IK24s (2 grades cooler than standard) on the strength of recommendation from other stage2+ ed30 owners. Car is currently running standard plugs so will be interesting to see if there is a perceived difference.
    I just got these fitted, but I can't comment on them just yet since I have a vacuum air leak which is making the car idle rough. Once that leak is sorted will give you an update. However in the rev range the car does feel extremely silky and smooth going.
    Last edited by Haz1; 17th May 2010 at 21:02.
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    That is what is particularly bizarre, at speed the 7's / 8's feel better, more consistent even faster. I think Spin did a thread somewhere which proved this, but in my engine they have a significantly shorter life span which seems to indicate they might work better in specific conditions, but not necessarily for longer.

    Would love a bird eye view to see how the three different plugs perform in chamber under load, but no appetite to fund the research!!
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    Interesting you mention the smoothness, that's exactly the same comment other stage2+ users have mentioned.



    Quote Originally Posted by Haz1 View Post
    I just got these fitted, but I can't comment on them just yet since I have a vacuum air leak which is making the car idle rough. Once that leak is sorted will give you an update. However in the rev range the car does feel extremely silky and smooth going.

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    Im going for stage 2+ in v soon, I plan to change the plugs before going in to my local tuner, should i go 6 or 7's?

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    Quote Originally Posted by gynads View Post
    Im going for stage 2+ in v soon, I plan to change the plugs before going in to my local tuner, should i go 6 or 7's?
    I've got Denso IK24 and I can't rate them enough, the car is idling really smooth and also the acceleration doesn't have any dips in it as far as i've experienced. For some reason the car feels faster through midrange and top end with these yet silky smooth, ie feels like there is a bigger engine under the bonnet lol
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    Quote Originally Posted by Haz1 View Post
    I've got Denso IK24 and I can't rate them enough, the car is idling really smooth and also the acceleration doesn't have any dips in it as far as i've experienced. For some reason the car feels faster through midrange and top end with these yet silky smooth, ie feels like there is a bigger engine under the bonnet lol
    im on stage 1 with evoms... was planning on changing plugs... should i go for these? im planning on TBE and remap v.soon too? will they compatible??
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    i was runing stage 2 with oem NGK spark plugs and had a lot of missfires and problems with acceleration which almost made me to go for the new clutch as it was like the clutch is slipping. after 15000km's oem plugs were done (6000 with remap). changed to the IK24's 500km's ago and i didn't have a single problem since then. as Haz1 said idling is smooth, acceleration too, there are no signs of missfires, and i don't even have problem caused with bad fuel (i don't use it, but in case you get stuck somwhere where there isn't better quality fuel). don't know does it feels faster throught midrange and top because i did te FMIC too so i'm puting that fo intercooler.
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    I used the denso's a few times in the Type R, Im sure it was IK24's i used when it was supercharged? ok thanks lads ill go for those then, are they all one fitment?

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    gynads's Avatar
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    Just looking at DENSO's sparlk plug cross referencing chart, here http://www.globaldenso.com/en/produc...ce/1037_3.html
    and it shows the IK22's as being a replacement for the 7's. IK20 for the 6's and IK24 for the 8's? so am i right in thinking then i need to be two steps colder for stage 2+ ?

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    I thought the same thing too due to the 2 steps colder but was advised they were best for higher boost pressure the stage 2+ (and BT) have, no problems yet so can't complain.
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    Hi guys, very interestng thread.

    Is there a particular part number for the NGK Iridium 6 (BKR6EIX) (or the Denso equivelent Ik20) as I'm thinking of getting these for mine, I seem to be suffering with some flat spots around 4000 rpm's, this may help resolve it.

    Where would be the best place to buy them? I've done a search of the web but I am uncertain of the fitment.

    Cheers in advance

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    *edit*

    It's Ok now! I've found my answer, thanks anyway!
    Last edited by Audi-Rog; 16th July 2010 at 10:34.
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    hi guys ive got a 2010 audi s3 with an mtm map and also having an issue with spark plugs,
    mapped at 7k started suddering at 7300k took back under warranty had new audi plugs,at 11300
    same issue again so fitted ngk BKR7EIX lasted 2k same issue again so fitted factory ones back and took back to audi,
    was put on lap top no fault codes then sent off to audi for more extensive diag into cause,was told audi are aware of this and currently working on a solution short term fix is to fit another set!!!so on to my next set and all is ok for now!any more info call me on 07977334041 col

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    Quote Originally Posted by colb1977 View Post
    hi guys ive got a 2010 audi s3 with an mtm map and also having an issue with spark plugs,
    mapped at 7k started suddering at 7300k took back under warranty had new audi plugs,at 11300
    same issue again so fitted ngk BKR7EIX lasted 2k same issue again so fitted factory ones back and took back to audi,
    was put on lap top no fault codes then sent off to audi for more extensive diag into cause,was told audi are aware of this and currently working on a solution short term fix is to fit another set!!!so on to my next set and all is ok for now!any more info call me on 07977334041 col
    I am SO pleased you have posted this, not because I want you to have an issue, but because TOO MANY people have been laying the misfire blame at Revo's door, and I've never believed that to be the case, I've ALWAYS thought it was an Audi issue.

    Halle-****1ng-lujah!!!

    This seems to be an epidemic issue which is as prevalent as the fuel pump cam follower issue / coil pack issue .......

    This is an award winning engine, and I think the combustion process is flawed. I'm tempted to have my plugs re-gapped down to 0.7 or 0.6mm from the normal 0.8mm once my car inevitably starts doing it.
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    When mine went to the independant when i was having problems, after sorting the inlet manifold flap, he put the new ngk's in and gapped them at 0.5. Still running fantastic. I definatley think the 0.8 is to big of a gap

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    So for all those who've spent the last few weeks championing that this is a Revo specific issue...... now maybe the time to reflect and realise your trusty Audi and it's lean burn lump ain't quite as complete a product as you once thought as if it can happen with an MTM map...... Nothing is as clear cut as you may think when it comes to engines and tuning.

    Ill cue the tumbleweed for when this thread goes unresponded to, but to me it's a clear message that we're ALL treading in very unfamiliar territory where there are SO many veriables that we only partially understand. It's not our remit to point the finger at any one company until we have conducted the appropriate research and gathered clear evidence or facts before we start posting any derogatory or defamitory accusations. Yes we'll be precious because we pay out a lot of money for our cars and modifications, and yes they should just work, but we're asking a lot of what is basically a 2.0l lump pushing out in excess of 300 brake, and because these cars are subject to continual changes to meet as a minimum Euro and tax bracket thresholds the world can change and move on.

    For recommendations as to which plug to choose read this: Spark Plug recommendations for S3 8P 2.0T (OEM & modified)

    I will get mine out and change them once my new plugs turn up. Must head out and buy a feeler gauge as I've lost my old one.

    For those of you who have never gapped a plug before, here is a 'How to Guide' from NGK USA:

    Last edited by warren_S5; 15th November 2011 at 09:55.
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    Still however no one has a definitive answer on which is best.

    Ive ran the 7's and had a few dips, ran the 8s now for a bit and the dips have returned. But saying this our climate here is much much hotter than you guys over there too.

    May swap back to the 7s and see if there is any difference again.

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    Quote Originally Posted by fuzion View Post
    Still however no one has a definitive answer on which is best.

    Ive ran the 7's and had a few dips, ran the 8s now for a bit and the dips have returned. But saying this our climate here is much much hotter than you guys over there too.

    May swap back to the 7s and see if there is any difference again.
    Im convinced the answer is less in the temperature of the plug and more in the gapping of the plug but because that requires effort and tools itis largely ignored by the masses.

    My next plugs are set to 0.698mm
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    Seems to me warren you are settling on about the recommended plug gap used by everyone in the 1960's onwards ie. .025" ( actually .0265) ish. All plugs were gapped at 25thou from mowers to race bikes, it was a std Champion gap and most feeler gauge sets had a plug gaping 25 thou blade as their largest blade. Of course then you had another factor which was the dwell angle as well ie the points gap. the wider the gap the longer the points stayed open and the more time the coil had to recharge. Anyway...I am sure anyone under 40 is getting bored now :-)
    My point is that a coil in those days would charge to about 20,000v before discharge and one of the advantages of electronic ignition was the much higher ignition coil voltage which meant you could run much wider plug gaps. The reason for this was the low gap and the high voltage meant that the point at which the spark became a flame was lower ie: lower revs. at 10000rpm a plug needs to put out a individual defined spark about 42 times per second and the smaller the gap the more likely the spark becomes a flame. Things are better today because in days gone by and engine would have 2 sets of points for 4 cylinders so the plugs would fire twice a rev once at BDC and once at TDC near enough so the plugs were firing at 80 times per second.
    My point here ( i do have oner somewhere) is you are absolutely spot on in that gap is very important, more so as you tune an engine. As turbo or compression goes up so does resistance across the air gap of the plug. Too bigger gap and you will blow the spark out at high revs, to small and you will lose the spark definition. also to a lesser extent a spark takes twice as long to jump 40 thou as 20 thou so you also alter the timing by a small amount. also you have too add in , as you are, heat as well. Because you are out of the factory comfort zone with engine and plugs experimentation is your best option so it will be interesting to see what you come up with. I was doing this with M/C drag engines 25 years ago and i am bored with it now so good luck and i will just steal your findings rather than make my own this time :-)
    Ibis white Revo S3 and now matching Vivaro LWB HR 2900 :-)

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  34. #33
    warren_S5's Avatar
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    I don't disagree Paddy.

    I think the thing I've noticed since running the 8P2 for 60k (40k at S2 or above) is the condition the plugs were in, and it's not that the plug is damaged in any way, it's the heavy sooting that to me says I'm sure something in the set up is not right, and having tried temperature settings 6 / 7 / 8 it only got worse with colder plugs. Stage 2+ adds 38% more BHP with the additional fuelling, extra air in and out, and to be honest on reflection I feel like a bit of a dick that I didn't think to investigate changing the plug gapping earlier given the way the car was eating plugs (plugs that could be salvaged to run a bit further with a gentle clean up).

    When the plugs look as carbon fouled as they did on some of the ones I pulled out of 8P2 something is not 100% right. I've never had a car which leaves so much carbon build up on plugs and through to the tail pipes. They were all fitted to manufacturer torque settings, and run with V-Power / overserviced etc.

    It was NGK who suggested (whilst they obviously don't recommend it), that I drop the gap to 0.6mm, so I've settle on going half way towards that on my next set of plugs to see what difference it makes. Whilst the TFSi system is advanced, unpleasant side effects of the way it runs see valve coking / sludge etc. in very young engines (as low as 20k miles). Whether this is down to the lack of a 5th injector or just running at the extremes of whats possible????

    People seem to be happy chucking in another set of plugs, then another, and another. Bunging another 50bhp at a car and then expecting it to take care of itself is at best optimisitic. It's like repeatedly sticking your arm in a lion cage and wondering this time if it wont get bitten off! My other concern is what assocaited side effects could be building up in the wings alongside this issue for later on???
    Audi S5 3.0V6T Coupe Black Edition

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    Can I ask why are you using heat range 6 standard s3 8p plugs are 7's in ngk form Bosch and ngk use different numbers for the same heat range a Bosch 6 is a ngk 7

  36. #35
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    I still use the stock plugs and simply change at each service(which in my case is every 5 000-6 000 miles).

    The car runs 2.0bar+ as well as WMI,and a reliable 500+bhp with no problems.

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    Warren great thread, I have the same stutter at 5k and black carboned up plugs. Just wondering did you ever solve this? How did you get on with dropping the gap down to 0.6? I have nobbers old s3 I believe it has your old itg intake on it stage 2+
    Thanks in advance

  38. #37
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    Quote Originally Posted by Poma7 View Post
    Warren great thread, I have the same stutter at 5k and black carboned up plugs. Just wondering did you ever solve this? How did you get on with dropping the gap down to 0.6? I have nobbers old s3 I believe it has your old itg intake on it stage 2+
    Thanks in advance
    I'm not sure what the answer to this is in terms of a surefire cure.

    I still use stock plugs,changed every 10 000 miles on mine,or earlier if it begins to hesitate,and that's it.

    It also runs pretty rich under full throttle,so if anyone's plugs were going to silt up,it should be mine.

    How long ago were yours last changed?

  39. #38
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    I changed from Iridiums to these (see link) and didn't suffer again:

    Spark Plug recommendations for S3 8P 2.0T (OEM & modified)
    S3Alex likes this.
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    Which ones warren 7's 8's or the stock ones? I've seen that thread and bought a set of 8's and ran fine for couple of days then misfires like mad under boost (lots of popped) abit like when traction control kicks in

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    Alex when I bought the car it had denso racing plugs in 31 so 10 temp rating in ngk terms in. I started getting a stutter at 5k. I changed plugs for standard ngk platinum ones. And it almost wouldn't boost misfiring like mad. So I bought a set of iridium 8's ngk still and fitted those was still the same. I've since sorted that fault it was the pcv valve shot. I've replaced with a revision n one and now boosts again properly. But still have the stutter at 5k if I clean the denso plugs and put them in it runs perfect. But only lasts afew days and they are carboned up again. And the stutter comes back. I have checked the gap on the densos and it's 0.8 on all 4. On Monday night I cleaned the denso plugs and refitted started it up and it was running on 3 cylinders on idle so I changed all 4 coil packs and it ran perfect until today when the stutter is back! Do I try the ngk iridium 8's now I have new coils in? Or do I try the stock ngk platinums?

 

 
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