I agree, Bill.  I have heard the same thing and when I stuck the different plugs in and had apex seal failure the next flight, I was certain that had occurred – that the plug had extended down into the combustion chamber and took out my apex seals.

 

However, when I took the engine apart I found that the plugs had nothing to do with it.  In fact the closest the bottom of the plug got to the chamber was 5mm.  I don’t think that  plug could extend into the chamber due to the fact both plugs sit in a chamber themselves which is narrower than the plug at the bottom.  That said it does look like it might be possible for a sufficiently long plug in the leading spark hole (has a large hole into the combustion chamber) to have the ground electrode extend into the chamber and clip a seal –I say might, it would have to be (in my opinion) forced.

 

In any case, I continue to fly with the stock plugs and replace them periodically.  One day I’ll clean up the bunch I’ve accumulate and fly the second half of my 1000 hours on them {:>)

 

Ed

 

 

 

Bill B

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Kelly Troyer
Sent: Wednesday, July 08, 2009 7:45 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] SAG- Spark plugs 2592 or 2692?

-------------- Original message from "Bill Bradburry" <bbradburry@bellsouth.net>: --------------

Kelly,

I don’t see a call out for the rotary engine in the Autolite info…???

 

Bill B 

 

---

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Kelly Troyer
Sent: Wednesday, July 08, 2009 3:27 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] SAG- Spark plugs 2592 or 2692?

Jeff and All,

 

       I believe the mystery is solved...............Apparently "AR2692" is a typo error

and "AR2592" is correct..............Check out the link below............Full of info..... 

 

   http://www.autolite.com/pdf/Autolite_HP_Apps.pdf

 

Kelly Troyer
"Dyke Delta"_13B ROTARY Engine
"RWS"_RD1C/EC2/EM2
"Mistral"_Backplate/Oil Manifold

 

-------------- Original message from "Kelly Troyer" <keltro@att.net>: --------------

Jeff,

  I have never found a trace of a "AR2692"............Lynn which is correct ??...................

--
Kelly Troyer
"Dyke Delta"_13B ROTARY Engine
"RWS"_RD1C/EC2/EM2
"Mistral"_Backplate/Oil Manifold

 

-------------- Original message from Jeff Whaley <jwhaley@datacast.com>: --------------

Lynn’s email referenced 2 part numbers … Poor folks race with Autolight AR2692 and … In the picture, left to right is the Autolight AR2592.

So which number is it correct? 2592 or 2692?

Jeff

 

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Kelly Troyer
Sent: Wednesday, July 08, 2009 2:35 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] SAG- Spark plugs

 

Lynn and Group,

 

         I checked my local "Auto Zone" and they claimed to be unable to get the "AutoLite"

AR2592 sparkplug...............Checked "Rock Auto" (Link below) and they have them in

packs of 4 for $2.69 (each plug)...........Ordered 8 of them for $21.52 + $5.47 shipping

but "AutoLite" has a rebate offer of $0.50 per plug for up to 16 plugs until Nov. 30,2009

for copper core plugs (rebate link below).............To find the sparkplug do a part number

search (AR2592) , Add the manufacturer (AutoLite) , Then use "all" for the part group

because if you use "Ignition" and "Sparkplug" for part type it will say "No part found"....

 

FWIW 

 

 

http://www.rockauto.com/catalog/raframecatalog.php?a=G-Store

 

http://www.autolite.com/rebate/pdf/spark-plug-09.pdf

--
Kelly Troyer
"Dyke Delta"_13B ROTARY Engine
"RWS"_RD1C/EC2/EM2
"Mistral"_Backplate/Oil Manifold

 

-------------- Original message from Lynn Hanover <lehanover@gmail.com>: --------------

In a message dated 7/7/2009 3:22:56 P.M. Pacific Daylight Time, bbradburry@bellsouth.net writes:

Steve,
I hope Lynn chimes in here.  He has seen a lot of plugs under a lot of
conditions.  They look pitted to me.  There seems nothing wrong with your
conditions.  The only thing on the list would be too lean.??
Someone is out there writing up a great response right now!  :>)
Bill B

That plug has been too hot.

 

Stock Mazda plugs are rather cold in heat range by way of the guards around the shell. The electrode runs a bit hotter than normal. Plug heat ranges are determined by how far down the shell the porcelain touches. The longer the heat path, the hotter the plug.

 

Using car plugs in the aircraft application seems to be asking for trouble. In the car on the freeway you use 2,600 RPM and 1/2 throttle, maybe 24 to 28 HP. Not much of a challenge for a spark plug. But there is the

driver who will jump into his 95 twin turbo in LA and run out to LasVegas at full tilt and expect to still have an engine when he gets there. And usually he does.  So, if I was to use a street plug in an aircraft, I would use the 93-95 twin turbo plug, whatever that is.

 

The aircraft application, less the 100LL fuel problem, is clearly a cold racing plug with a conventional gap or close to it.

 

Years ago when we started racing rotaries, Champion said to use the N-57G Fine wire center with gold paladium plating and a conventional ground strap. About 20% of the center wire is exposed in an end view.

 

The N-57G and similar are discontinued and the N-82 series replaced it. The shell is thinner and the porcelain is wider. Same fine wire center, no gold anything. 20% of the wire exposed in an end view.

Both worked fine even with points and a Kettering coil.

 

Poor folks race with Autolight AR2692 end style and small porcelain just like the N-57G. Full size center wire, conventional strap, but 100% of the center wire is exposed in an end view. Actually used by NASCAR and the local circle track people, and stocked by Autozone and others. About $5.00 a box of 4. They work fine. I raced them one weekend, no problems, but we were getting the NGK plugs for free so I stuck with them.

 

The NGKR6725-115 stamped on the body actually means that the heat range is 11.5 not 115. $25.00 each.

50% of the center wire exposed in an end view. Free for some Rotary engined competitors. Retracted gap (the whole thing is inside the shell. Fine wire center and fine wire ground strap. Ice cold. Long body so it is easy to install and remove in the rotary.

 

I grind off those eyebrow things above the plug holes so I can use any plug I like. And any 5/8" plug just goes in so easy. Most heat ranges are available in the 5/8" shells.

 

Rotaries do not like high heat range plugs. The housings crack across the leading plug hole. Over time a complete set of radial cracks form.

 

In the picture, left to right is the Autolight AR2592, Champion N-82, NGK R6725-115, and Champion

N-57G. 

 

Lynn E. Hanover

 

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