I have been looking at getting new spark plugs for a while but there is a lot to think about when deciding on a set. Then I found this article Audigeeks.com written by Jeff at Audigeeks.com
Its a well written piece that filled in a lot of the blanks. I thought other members might benefit from this article so I have posted it here and referenced the article to the original author and thread.
Originally Written By: Jeff
Contact: [email protected]
Q: What about Spark Plugs? What should I get?
A: Many people running higher boost and timing have often complained about 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 as a final result of 1 & 2.
Here are some causes/solutions that I've found:
1) Most late model Audi's now use NGK (older ones used Beru) as OE equipment...model number PFR6Q (On most 1.8T models or something equivalent on the 2.7T's, but same principles apply on all other cars), a Premium Platinum plug built for nothing else but longevity.
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" 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 on the electrodes.
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.
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:
Auto makers built their cars to be maintenence-free, and no prudent consumer in their right mind would buy a car with plugs that you have to change every 3000-5000 miles these days (unless it was a hand-me-down used car). Most modern day vehicles will use iridium, while most are using platinums.
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 of electricity and heat, 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) unless they were properly designed to pull the heat. This is a problem for all of us turbo guys running high boost. 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. Coppers use thicker electrodes simply based on the fact that they can easily jump the spark, whereas platinum and iridiums will require a fine wire to better direct the spark to prevent missfires.
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).
*Note* These are merely just "recommendations" by AudiGeeks.com from their experiences with other members and their own cars. There is no such thing as a "magic" plug, and all cars (depending on tune, fuel, condition, climate, etc) will respond differently to different plugs. You may have better luck with a #7 plug, whereas someone who lives in sub-zero degree climates can get away with it with a #6. Below is a quick reference and application guide that will assist you in choosing the right plug.
HOT - NGK #6 (OEM Range for 1.8/2.7 Engines) - Stock car with stock boost/timing, or mildly-tuned car in cold climates.
Recommended Plugs in this Heat Range:
- NGK BKR6E (Copper)
- NGK BKR6EIX (Iridium Version of the same plug above)
- Denso K20R (Copper)
- Denso IK20 (Iridium Version of the same plug above)
- NGK PFR6Q (OEM Platinum) - If you're planning to stick with stock boost
COLD - NGK #7 (One Step Colder) - Cars with basic "chip/intake/exhaust" bolt-on upgrades (K03, K04, etc): Drop one range.
Recommended Plugs in this Heat Range:
NGK BKR7E (Copper)
NGK BKR7EIX (Iridium Version of the same plug above)
Denso K22R (Copper)
Denso IK22 (Iridium Version of the same plug above)
COLDER - NGK #8 (Two Steps Colder) - Cars with bigger turbos will benefit from these, whereas a regularly chipped car may foul these.
Recommended Plugs in this Heat Range:
Champion C63YC (Copper)
NGK R5672A-8 (Copper, Non-Resistor plug)
NGK BKR8EIX (Iridium)
Denso IK24 (Iridium)
Bosch FR5DTC (Copper)
Bosch F5DPOR (Platinum/Side Fire)*
* - Many members have found real good luck with the Bosch F5DPOR's, this is why: Despite all the "con's" about platinums (poor conductivity, poor heat dissapation qualities), the engineers at Bosch has managed to engineer the F5DPOR's so that they are still able to fire the A/F as well as pull away enough heat. The F5DPOR's unlike conventional plugs, use a "Side-Fire" technology, where instead of a standard "projected" electrode into the combustion chamber, the ground electrode was placed on the edge of the plug so that it fires closer to the flame kernel. By doing so, the F5DPOR's are able to still keep a thick center electrode (to pull heat away faster) without having to go with a smaller electrode in order to fire. The F5DPOR's heat range is also equavalent to that of a NGK #8 (TWO steps colder than stock), in order to give the same effect as a #7. But because it is a platinum plug and not copper, they will not foul "as" easily where a copper would have. Because of these two important attributes, Bosch was able to use these plugs to both last like other platinums (up to 60k), while still function under more extreme environments. Platinums however, still do not compare to iridiums in longevity, as well as heat/electro conductivity.
Below is a quick cross-reference list for all the plugs listed above in Heat Range:
NGK 5 6** 7 8 9
Denso 18 20** 22 24 27
Bosch 8 7** 6 5 4
Champion 11,12 9,10** 7,8 61,63 59
** - Audi/VW Factory 1.8T/2.7T Heat Range
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Originally Posted by pohsib
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