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.