Umm...this topic has been discussed before. Not exactly the topic on bosch vs NGK, but the difference between platinum and copper plugs. I think Jeff has posted something about this on the forums...
I guess I will just copy it and paste it ( i actually found it on AW)
http://forums.audiworld.com/a4gen2/msgs/263262.phtml
After chipping my 03 1.8T the other day to a 1.5bar program, I noticed some problems.
1) Slight missfiring/blowouts at ~5000RPM on 4th gear
2) Slight Pinging (which leads to pre-ignition/detonation) at high boost
3) Loss of power past 5000RPM (due to the size of our K03's...as well as sparkplug gapping/etc)
So on Saturday morning, I pulled out my OEM plugs, and this is what I found:
1) Don't know about the 02's, but my 03 OEM plugs are actually "NGK"...model number BKR6QP (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) 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". My OEM plugs were gapped at 0.027"!!! (Probably lost a good 5hp from that alone)
With my many years of sparkplug tuning and fiddling, I went to a local Kragen, and purchased a COPPER plug with the same specs mentioned above: BKR6E-11. Same plug, just in a copper form, with a bigger 0.044" pregap.
I gapped the plugs from it's specs (0.027"?) to 0.032". 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 sell Iridiums???" 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 Iridium plugs should be BANNED from all forced-induced cars (turbo/supercharged).
I have done sparkplug tuning for many years now (indexing/j-gapping), and I've found Platinums/Iridiums to be inferior to copper plugs in a turbocharged environment.
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 (1.2 bar..and in my case... 1.5bar), we will reach EGT's of over 900C Degrees (keeping in mind that Pre-ignition occurs 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.
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)
I have personally used a colder plug, because my chip is making 1.5 of INSANE boost, and I am personally using the following:
NGK: BKR7E (Part Number #6097), they are one heat range colder than stock (~80C degrees colder than our OEM platium plugs)
Well, here's my $0.02 (maybe $0.03) about this issue, feel free to comment or correct me if you have any concerns.
Happy Boosting
-Jeff
Denim Blue 1.8TQ 5-speed
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Originally Posted by Entertainment72
. They should be less than $2 a plug.
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