Originally Posted by Jeff Lee on Audiworld.com
A: Many people running higher boost and timing have often complained notice the following problems:
1) Slight missfiring/blowouts, sometimes known as "surging"
2) Slight Pinging (which leads to pre-ignition/detonation) at high boost, thus ignition timing pull (retard)
3) Loss of power past 5000RPM
Here are your solutions:
1) Most late model Audi's now use NGK as OE equipment...model number BKR6QP (On 1.8T most models, but same principles apply on all other cars)
The BKR6QP is Defined as: B = 14mm thread diameter, K = 5/8" projected tip, R = Resistor plug, 6 = Heat Range 6, Q = 4-ground electrode, P = Platinum
2) Our sparkplug is actually UNDERGAPPED, where NGK states all their plugs that dont have a (-xx) gap number to it, they should all be factory gapped at 0.0315". Most OEM plugs were gapped at 0.027"!!! (Probably lost a good 5hp from that alone). Because OEM plugs were made for longevity (~50k+), they were set to a lower gap--for the gap does get bigger through time and wear.
With my many years of sparkplug tuning and fiddling, I went to a local Kragen, and purchased COPPER plugs with the same specs mentioned above: BKR6E which is the same equivalent plug, just in a copper form.
I gapped the plugs from it's specs (0.028"?) to 0.032" (do not go over). The minute I fired up the car, the exhaust tone became a LOT deeper. So I took the car around the block, then on the fwy doing some 0-100MPH runs. The car became a LOT smoother. The powerband of the turbo will now make boost past 5000RPM, and the spoolup got a LOT quicker. The "Hesitation" at 5000RPM disappeared, and the idle became a lot smoother. Simply switching the plugs, I would say that my "Ass-Dyno" pretty much felt another 5-10hp difference in power. (will do a VAG-dyno soon.)
Now many would ask "Why use Copper when they don't last over 5k???" Well first of all, before my explanation, simply switching from platinums to standard coppers will lower your EGT temps anywhere from 30-40C Degrees!...read on:
Well, here is my explanation:
Personally, I think Platinums and (some) Iridium plugs should be BANNED from all forced-induced cars (turbo/supercharged) that is not running stock boost.
I have done spark plug tuning for many years now (indexing/j-gapping), and I've found Platinums/Iridiums to be inferior to copper plugs in a turbocharged environment. Now there are exceptions to this, which I will cover in the future, with the introduction of newer plugs on the market.
Platinum plugs (and Iridiums) were introduced to provide longevity (60k-100k+) to vehicles compared to copper plugs which foul after 3000-5000 miles, but they do NOT dissapate heat fast enough (which leads to pre-ignition/detonation) and do NOT provide a "better spark" like they have claimed...with their "fine-wire electrode" (which only causes problems).
Copper is one of the best conductors, but they just plain dont last. Using Platinum and Iridium plugs, the center electrode (fine-wire) thin, that under high boost, they get so hot, they will begin to "heat glow" and cause premature ignition in the combustion cycle (pre-ignition => detonation). This is a problem for all of us turbo guys. Copper on the other hand, has a much thicker center electrode, on top of that, the copper material is able to dissapate heat from the combustion chamber fast enough to keep the combustion temperatures lower.
Remember the TWO primary functions of a sparkplug:
1) To efficiently ignite the A/F mixture without missfires (gap..etc)
2) To pull heat from the combustion chamber into the head, where the cooling system should dissapate that heat. (Heat Range)
With those 2 in mind, coppers will work much better in these environments. For those thinking: "What If I just simple use a colder Platinum plug?" Well, for the kind of boost our A4's make w/ the Krispy-Kreme K03's, we will reach EGT's of over 900C Degrees (keeping in mind that Pre-ignition can start to occur at around 870C). Once those colder platinums reach preignition temperature, it will take them FOREVER to dissapate that amount of heat (with the details about the material/design I mentioned above). A platinum/Iridium plug in a colder heat range usually runs just as hot as a copper in the standard heat range when under high stress. So many people will use a Platinum/Iridum plug TWO steps colder to counter that. But using a plug that is 2 steps colder, will lead to two things:
1) More prone to carbon-fouling on "normal driving" where EGT's are kept low. (Plugs must stay above 550C Deg to burn off excess carbon deposits to "self-clean")
2) As a result, loss of horsepower from a less efficient/inhibited spark.
You need a plug that is actually "hot enough" to ignite the A/F mixture as hot as possible to get the most efficient combustion, as well as burn off carbon-deposits (~550C deg), and yet cold enough to prevent pre-ignition when compression is high (< 870C Deg).
With all that said, for those interested in going copper the "feel the difference themselves", I recommend the following plugs:
NGK: BKR6E, BKR6E-11 (-11 indicates a 0.044" pregap, which should be regapped anyways)
Denso: K20R, K20R-U11 (bigger pregap)
If you are running more aggressive boost as well as timing, it is recommended that you lower your heat range ONE STEP colder:
NGK: BKR7E (Part Number #6097), they are one heat range colder than stock (~80C degrees colder than our OEM platium plugs)