REFLECTOR: Auto spark plugs

[aminetech at bluefrog.com]

Thanks.  What happened when it was time to replace?

If I understand correctly how to determine the relative heat range by measuring the depth of the ceramic insulator, then the X27GPR-U
has the same heat range as the REB32E aviation plug that I was using on both the mag and the EI.  I had similar fouling and electrode erosion problems with the aviation plug/EI, but not on the mag.  Also the problems with the aviation/EI plug were not as severe as with the Denso.  This may be because the massive aviation electrodes better tolerate the overheating that I believe is occurring.  I haven't found any information to indicate that the (5 times) higher EI voltage requires a cooler plug compared to the mag, but my experience seems to suggest that.  I think the plug overheating can also explain the high CHTs that I've had running LOP.
--- scott at tnstaafl.net wrote:

From: Scott Derrick <scott at tnstaafl.net>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Subject: Re: REFLECTOR: Auto spark plugs
Date: Sat, 13 Nov 2010 16:06:03 -0700

ON my IO360 running a Lightspeed, they would last about 400 hours. Never 
had one foul.

Scott

-------- Original Message --------
Subject: REFLECTOR: Auto spark plugs
From: <aminetech at bluefrog.com>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Date: 11/13/2010 01:42 PM

> I replaced the Denso X27GPR-U plugs with $2 autolite plugs (seems like that should be illegal at only $2).  What a difference.  The engine runs great, CHTs are all the same.  These plugs are supposed to be one heat range lower.  The Denso's worked great when new, so it will take time to tell if there is a difference.  What experience do others have using auto plugs with EIs?
>
> John
>
> --- sbjknox at earthlink.net wrote:
>
> From: "sbjknox"<sbjknox at earthlink.net>
> To: "Velocity Aircraft Owners and Builders list"<reflector at tvbf.org>
> Subject: Re: REFLECTOR: Running LOP -- Climbing or Cruising
> Date: Fri, 12 Nov 2010 16:17:49 -0600
>
> No, the thread depth does not change, only the structure of the ceramic
> insulator.
>
> Sid
>
> ----- Original Message -----
> From: "Brent Bourgeois"<bjb3013 at yahoo.com>
>
>
> The hot / cold of a plug is the measure of how much heat the plug conducts
> out of the cylinder. The thread depth (length) changes not the ceramic or
> the electrode. Search hot / cold racing plugs on the internet
>
> Brent
> N61VB
> New Orleans
>
>
> From: aminetech at bluefrog.com<aminetech at bluefrog.com>
>
> Are you saying the cooler plug has a shorter center electrode? Can I file
> mine off to make them shorter? I'm planning to get some cooler plugs, but
> they won't come until next month and I really need to keep flying now.
>
> John
>
> From: "sbjknox"<sbjknox at earthlink.net>
>
>>> That's interesting. I'm currently have spark plug issues and I'm
>>> planning to try a cooler plug. Could I simply add a washer to my
>>> existing plugs to get less reach and effectively make it cooler?
>>> John
>
> My opinion (not a fact) is just the opposite. The washer would create a
> longer path for heat to flow from the plug body to the cylinder. You want a
> lower heat-resistant (shorter) path from center electrode to the cyl...that
> is why a colder plug will have a shorter exposed (exposed to the hot
> combustion gas) center electrode insulator.
>
> Sid Knox
> Oklahoma
>
> Velocity 173 RG N199RS
> Starduster N666SK
> KR2 N24TC
> W7QJQ
>
>
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