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From: George Braly <gwbraly@gami.com>
Subject: RE: [LML] Re: Tempest spark plugs
Thread-Topic: [LML] Re: Tempest spark plugs
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In a word - - yes. =20

The correct approach to selecting spark plugs is to always use the coldest =
plug that does not result in an unacceptable level of deposits or fouling.

If your 38 heat range plugs are clean  in normal use,  then moving to the n=
ext colder plug is good practice.  Watch them and check them for deposits.

If they remain clean  (likely if you normally run LOP) then consider moving=
 colder, again, at some point down the road.=20


-----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Lorn=
 H Olsen
Sent: Wednesday, February 15, 2012 7:24 AM
To: lml@lancaironline.net
Subject: [LML] Re: Tempest spark plugs

George,

I have been using REM38S plugs for about 1,000 hours. My engine is an O-320=
-D1F 8.5 compression, 160HP Lycoming. I run as lean as possible for a carbe=
d engine. As far as I know, the 38 has been the standard recommended plug f=
or this engine. Should I be considering cooler plugs?

Lorn

> From: George Braly <gwbraly@gami.com>
> Date: February 14, 2012 7:51:26 AM EST
>=20
> Colyn,  let me respond.
>=20
> a) So far,  only the Champion fine wire plugs are showing a significant p=
roblem with cracking of porcelain on the central electrode.
>=20
> However,  since the scrutiny started - - an unrelated collateral issue ha=
s arisen from observation of the frequently encountered high resistance of =
the internal RFI  resistor.  THAT issue is identical for both massive plugs=
 and fine wire plugs.   That problem is not nearly as significant as the cr=
acking insulator problem.
>=20
> b) TAT has no evidence that the Tempest plugs have any issues of any kind=
.  Fine wire or massive.
>=20
> c) We do prefer the 29 heat range plugs.   If they were available we woul=
d recommend 27 heat range plugs.  The reality is that the only people that =
need high heat range plugs are people who operate with rich mixtures - -  t=
o keep down plug deposits.  With routine lean mixture operation there is so=
 far no discernable plug deposits on colder heat range plugs.    I have per=
sonally operated a set of experimental  -27 heat range plugs for several hu=
ndred hours.  The plugs remained clean.   In general,  everyone should atte=
mpt to identify and operate with the coldest heat range plugs that do not c=
reate deposits or accumulate oil.=20
>=20
> d) I think this is covered above - - -=20
>=20
> Regards,  George

--
Lorn H. 'Feathers' Olsen, MAA, ASMEL, ASES, Comm, Inst
DynaComm, Corp., 248-345-0500, mailto:lorn@dynacomm.us
LNC2, FB90/92, O-320-D1F, 1,800 hrs, N31161, Y47, SE Michigan


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