RI A6

I happened onto RS246 and read a thread on "Stalling on startup", and a bit of a discussion about spark plugs. Someone posted the Audi part number for our plugs, so I did a bit of searching.

The Audi part number is 101-905-621,which is an NGK PFR7W-T.

So then I read a few other interesting webpages at the NGK site. It seems that the spark plug is designed to:

"to solve the carbon fouling problems associated with direct injection engines."

As a disclaimer, I've had only one misfire event in 21K miles, and that was on a cold humid morning for just a moment at startup. But, I find it interesting that Audi had a new plug specifically designed to fight fouling in FSI engines.

http://www.rs246.com/index.php?name=PNphpBB2&file=viewtopic&t=6 1840&postdays=0&postorder=asc&start=0& amp;sid=d4e79ec596c6f965bc437c5b062e6bdb

http://www.ngk.de/HYBRID_SPARK_PLUG_OE_SUCCESS_F.3863.0.html<ul><li> <a href="http://www.ngk.de/Spark_plugs_with_supplementary.655.0.html">NGK Hybrid spark plug</a></li></ul>

SteveRS4

The plot thickens

daveak05

i think it's simply a diff temp range, as is denoted in the part no. are you sure Audi had a new plug designed, rather than just going with a higher temp range to fight carbon fouling?

RI A6

"In this design a conventional ground electrode is supplemented by two smaller ground electrodes close to the nose of the ceramic insulator. If carbon deposits prevent the spark from firing at the primary ground electrode then the spark will travel across the insulator to one of the secondary electrodes and burn off the carbon deposit until sparking takes place again at the primary electrode, so guaranteeing reliable ignition."

Doesn't sound like just a heat range difference to me.

daveak05

yes, but you've seen 2 electrode and even multi electrode plugs in use before, right? remember the old Splitfire spark plugs of many years ago?

i have a sneaking suspicion we've had this discussion before. in any event, the tech description(from Bentley?) about efficiency of one electrode fouled so the other burns the carbon of the first is a bit of a stretch...whether described that way by Audi or not...IMO.

RI A6

The tech description is from NGK. They are literally sparking across the fouled insulator. The design is such that under normal operation the spark occurs under the normal place. But when carbon fouls the plug tip, and covers the insulator, this design develops a spark from the body across the insulator, before it leaks down the insulator. This is covered by several NGK patents.

DrCondor

conscious of plugs/small differences.

daveak05

all i'm saying is this is not new, NGK recently has moved into multi-electrode designs. so have others. look at Bosch plug lineup some time. what they're doing in the particular case of burning off carbon, which is still higly questionable IMO, is not magic. a fouled plug will fire and burn off carbon if the cause of the fouling is removed. however, most just replace the fouled plugs upon discovery.

daveak05

do you really think NGK designed a special plug for the few thousand RS4's at the request of Audi? or do you think Audi, in search for an improved plug for the RS4 engine, found that NGK(among others i'm sure) had one that would fit the need? which scenario is more plausible to you? i mean, really.

RI A6

My guess is that Audi started running into fouling problems with FSI engines and found that the NGK design would help. However, I think that NGK also saw that plug fouling was going to be a problem with direct injection engines and had the plug design in it's back pocket. The patent was applied for in 2004 and just released yesterday, interestingly enough. If you look at the drawings in this patent, it is the same plug. You'll also find that VW/Audi FSI engines are the only application for this plug.


United States Patent 7,230,370
Kato June 12, 2007
Spark plug

Abstract

A spark plug including an insulator having an axial hole in an axial direction of the spark plug; a center electrode disposed in a tip end side of the axial hole of the insulator; a metal shell surrounding the insulator; a first ground electrode including a first ground electrode body having one end joined to the metal shell, and a noble metal tip joined to an inner side face of another end portion of the first ground electrode body and disposed opposite a tip end face of the center electrode across a first discharge gap. One end of the second ground electrode is bonded to the metal shell, and the another end is disposed opposite a side peripheral face of said center electrode or a side peripheral face of said insulator across a second discharge gap. Furthermore, the spark plug is characterized as having a distance t and an included angle .theta. as defined herein.
Inventors: Kato; Tomoaki (Nagoya, JP)
Assignee: NGK Spark Plug Co, Ltd. (Aichi, JP)
Appl. No.: 11/013,355
Filed: December 17, 2004