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Cmead

EDM Sparkplug Gaskets - High Temps

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The Varieze just returned to flight this morning!  With the temperature around 70'F we took off, wide eyed and excited...for about 10 minutes per hop, got two total in.

We put an EDM-830 in ,and at the suggestion of another, we used the spark plug gaskets instead of the CHT Head Probes.  We are reading about 420 (ish) on number 4 cylinder, (O-235-C2C - Silver Bullte Prop, 3" extension).  We can only run about 2250 RPM, in slight climb or even level flight we get those temps.  I know we have some baffle work to do, but I was wondering with the inaccuracy of the gaskets, should we be overly concerned?  Anyone else running something simular? 

EDM states that the spark plug gaskets on Lycoming "could read 50 to 60 degrees higher"!  WOW...that's totally insane when you spend good money for good information.  Are the CHT Probes really that much better?

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1 hour ago, Cmead said:

EDM states that the spark plug gaskets on Lycoming "could read 50 to 60 degrees higher"!  WOW...that's totally insane when you spend good money for good information.  Are the CHT Probes really that much better?

While there is very little evidence that there is a large difference, especially on updraft cooled engines, between plug gasket probes on the top and head probes on the bottom, the answer is yes - probes in the head (if there ARE places for them - some heads are not drilled/tapped) are better and will be more accurate, because you're actually measuring what you care about and what the POH / engine operating manual determines the limits are. No one ever lists limits for spark plug gasket probes, so who knows what the right answer is? Maybe you're reading high - maybe you're reading low. No way to know.

I NEVER recommend plug gasket probes unless the heads aren't prepped for the internal probe. And I definitely recommend using probes with bayonet mounts - WAY easier to install and remove for service.

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Posted (edited)
3 hours ago, Cmead said:

We can only run about 2250 RPM, in slight climb or even level flight we get those temps.  I know we have some baffle work to do

Some pics of your baffles would tell a lot.  Easy to post pics in these threads if you can get them from your phone to a computer.  

It's easy to make the bayonet CHT probes.  If your thermocouple wires are long enough, you can cut off the ends and make the bayonets but the type J wire is common enough.  See some here:  https://www.canardzone.com/forums/topic/18661-kents-long-ez-project/?do=findComment&comment=63649    I see the wire on ebay https://www.ebay.com/itm/Glass-Insulated-Thermocouple-Wire-GG-J-20-25-N-High-Temp-20-AWG-Type-J/253706994421?

Or you can order it from Omega   https://www.omega.com/en-us/search/?text=GG-J-20

Edited by Kent Ashton

-Kent
Cozy IV N13AM-750 hrs, Long-EZ-85 hrs and sold

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I'll try and get some pics tonight.  

Thanks for your help.

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