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Correct Spark Plugs for 2005

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Correct Spark Plugs for 2005

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Old 02-25-2011, 02:25 PM
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Default Correct Spark Plugs for 2005

This is a new car for me and I have searched around for what most people use when replacing plugs. I'm just wondering what most people replace the factory stuff with. I'm just looking for the best overall plug. Any help is appreciated.
 
  #2  
Old 02-26-2011, 06:00 PM
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I have never liked the results of any single prong plug in any multi intake valve engine. Tuners used to be forced to use spacers with single prongs to make sure the prong faced the same direction in relation to the intake valves, in order to get consistent firing from cylinder to cylinder.

I would stick with either Bosch or NGK 4-prong plugs. In my personal experience, 4 prong Platinums tend to be smoother (yet very powerful) at high rpms, but a hair soft on take off. Thick electrode 4 prongs tend to be a hair rougher running (slightly hotter burning), but faster off the line and, to me, feel powerful but a little "strained" at high rpm...but both very acceptable...some don't feel the difference...I do.

I like dealing with these guys and they have a big variety of compatible plugs:

http://www.partsgeek.com/catalog/200...park_plug.html
 
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Old 02-26-2011, 10:08 PM
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That's exactly what I was looking for. I appreciate the great response.

Do you have a specific plug you like over another? I have always been a Bosch guy for all my german cars, but never owning an Audi before so people say otherwise.

Thanks again.
 
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Old 02-26-2011, 10:30 PM
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One last question, does either the thicker or thinner give you any difference in gas mileage?

Thanks again.
 
  #5  
Old 02-26-2011, 10:42 PM
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I completely dissagree. 4 prong plugs suck *****, especially for tuners.
Let me explain:
You can't gap the plugs, you get what you get. This is huge for tuners, not so much for A8 engines though. Another reason (and this is a biggie) is electricity follows the path of least resistance, now the common confusion is if you have 4 prongs you have 4 different paths for the electricity to follow right? Wrong.
You actually have 4 ways for your plug to foul up now, generally one prong will have less resistance than the other 3, so it will most likely only fire on that prong (most of the time). Since there are 3 other prongs this will reduce cylinder scavenging and incomplete burning in the chamber. This in turn fouls up the plugs faster, when one of the prongs foul up it actually has less resistance than the other prongs. A fouled plug isn't just a plug with some carbon on an electrode, it's a plug with some crud which electrically connects the center and the outer electrode, thus conducting and preventing a spark.
So if the spark is being conducted thru the crud on the fouled prong it will reduce the chance of a good spark, creating a missfire.
I'll stick with my old fashioned single prong NGK's thank you!
 
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Old 02-26-2011, 10:44 PM
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Originally Posted by WNTITAL View Post
One last question, does either the thicker or thinner give you any difference in gas mileage?

Thanks again.
Absolutely not, the ECM will fire the same amount of fuel in the combustion chamber regarless of what plugs you put in there.
 
  #7  
Old 02-26-2011, 10:47 PM
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I ALWAYS use Bosch plugs.
Some Audi (and other German car) owners tell me they are just as happy with NGK (?).
Mpg seems about the same with both platinum and thick electrode...just slightly different behavior.
In Porsche's, I always used the thicker type...but in my A8, I prefer the platinums slightly better. Most would say they don't notice any difference in "off the line"...it is a very subtle difference even to me and can't say it would show in a 0-60 test...probably more of a "smoother feel", rather than speed(?).
 
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Old 02-26-2011, 10:54 PM
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auditech79 - If you prefer the NGK singles, do you like the Iridiums or the platinums? Or does it really make a difference?

My A8 has 53000 on it and I want to change them now while I have the time and since I don't believe they have been done. I haven't pulled them yet, but it's not going to hurt to replace them.
 
  #9  
Old 02-26-2011, 11:03 PM
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Originally Posted by auditech79 View Post
I completely dissagree. 4 prong plugs suck *****, especially for tuners.
Let me explain:
You can't gap the plugs, you get what you get. This is huge for tuners, not so much for A8 engines though. Another reason (and this is a biggie) is electricity follows the path of least resistance, now the common confusion is if you have 4 prongs you have 4 different paths for the electricity to follow right? Wrong.
You actually have 4 ways for your plug to foul up now, generally one prong will have less resistance than the other 3, so it will most likely only fire on that prong (most of the time). Since there are 3 other prongs this will reduce cylinder scavenging and incomplete burning in the chamber. This in turn fouls up the plugs faster, when one of the prongs foul up it actually has less resistance than the other prongs. A fouled plug isn't just a plug with some carbon on an electrode, it's a plug with some crud which electrically connects the center and the outer electrode, thus conducting and preventing a spark.
So if the spark is being conducted thru the crud on the fouled prong it will reduce the chance of a good spark, creating a missfire.
I'll stick with my old fashioned single prong NGK's thank you!
Well, we'll have to agree to disagree on this one.
I first noticed the multi valve motor/ plug type correlation with my 16V Scirocco...it ran horrible (rough and low powered) no matter what brand, heat range or gapping with any single prong.
I know you can radically change running characteristics with gap, but with every multi valve motor I've had (all of em since that car), my experiments yielded the same results...even on the Porsche's (huge difference). The Scirocco (while stock) actual lost almost 0.2 seconds on 0-60 with best single prong over thick electrode 4-prong.
I haven't dared tried it on the A8...learned my lesson and LOVE the 4-prongers. Never had a fouled one in any engine (NOT so of singles), always even wear on tip all around, all plugs look the same and long mileage.

Never read or researched deeply to figure why I get such great results from 4-prongers OR why they come from the factory in practically everything German (every last one I've bought since the mid 80's) for many years now.

..BUT, I'll go with my personal experience over "your" logic on this one ....no offense.
 
  #10  
Old 02-26-2011, 11:18 PM
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The dealer stocks single prong NGK platinum plugs. Thats the ONLY plug audi allows under warranty. Why? Ask audi.

Its not just my logic, i've actually seen the prongs break off 4 prong designs. LOTS of missfire cars that came in (usually turbo cars) had these plugs in them and this was the results on most of them.

They would either have one or more of the prongs fouled up, or just plain broken off. It goes without saying the little metal prongs bouncing around the top of the piston isn't good for the cylinder walls.

I guess anyone can run what they want, but i'll NEVER recommend a multi pronged plug.
 

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