Problems with Tempest Fine Wire Plugs

[dwurfel]

I bought a set of Tempest UREM38S XL from Spruce. I installed them and engine seemed to run a bit rough. I did not do a run-up or take-off. I taxied back to the hangar and removed the plugs to find that there was a black carbon build up on the plugs. I put the old massive plugs back in and everything was fine and same as before. Also the threaded end that goes to the engine seems to be a bit longer than the massives. I have a 2012 XLS IO-360-M1A. From my research on the form seems I bought the right plugs. I had to go out of town for the summer so back into the issue. Has anyone experienced the same? Any help would be appreciated.

[Rick]

I believe the part number you want for the IO360-M1A is REM38S (or UREM38S) - without the XL. I believe the XL makes them "extra long", as you noted, which is not what you want. If you search this forum for 'REM38S' there are several threads with additional information on the fine wire plugs. I replaced mine several years ago and had no issues at all. I know others here have done the same...

[Antoine]

David:
Edit: oops XL? or not? Rick's input may make the rest of my post obsolete!

So you only did a minimal ground run? The carbon build up could simply be the consequence of bad combustion (running too rich). Was it on ALL plugs? If yes this will most probably burn off.

Why don't you try leaning a bit to see if the engine now runs smoother. If you only run an engine at low RPM with low EGT's it will quickly build up carbon deposits and will run rough.
I used to ALWAYS lean on the ground - it actually takes a lot of leaning for the engine to run well (half of the full excursion). The word "leaning" is actually misleading. It should be "tuning". At low RPM, our engines get far too much fuel and they really need to be leaned.
I have once cancelled a flight due to a fouled plug due to not leaning... lesson learned.

[1911Tex]

I don't know why folks still cannot understand that leaning your engine at or below factory recommended rpm (ex.: Continental is 65% power) and lean of peak, is a GOOD thing! On the ground, always lean to maximum rpm and a little beyond, just above sputter....watch your CHT/EGT and plugs benefit!

[Rick]

I don't know why folks still cannot understand that leaning your engine at or below factory recommended rpm (ex.: Continental is 65% power) and lean of peak, is a GOOD thing! On the ground, always lean to maximum rpm and a little beyond, just above sputter....watch your CHT/EGT and plugs benefit!

Totally agree! The ONLY argument I've ever seen for NOT leaning on the ground was that you could forget to enrichen before takeoff, with possibly dire consequences. But, if you lean excessively on the ground, as you suggest, you can't mess up - going full power will just kill the engine, instead of the occupants!

[Rich]

I think those making an automatic assumption that David is not basically familiar with mixture manipulation may be jumping the gun. Perhaps even a bit condescending, given that his home airport has a much higher elevation than most of ours. Taking off at full rich at TAD's typical Density Altitude, for example, can be a truly tense experience.

I changed to fine wires so long ago I've been trying to recall the nature of the change. At the time I was based at a 600-ft. elevation airport (Paine Field). I had had a couple of incidents with the massive electrodes (one fouling, another outright failure) of the massive-electrode Champions. I seem to recall having a bit of concern because the ME plugs were a higher nominal heat rating (40's) than the available FW (Unison at the time). I was assured that the 38s was the correct one. Of course I'd long had the habit of leaning for all operations save cold starts takeoff and climb. Given the low elevation of KPAE one could be a bit cavalier about leaning on the ground (pull it back a bit) and still not develop a noticeable problem. Actually just pulling the mixture roughly halfway back has worked for me for years, even at my current base (3250 ft. elevation)

I couldn't tell you whether the 38s non-XL plugs had longer threads than the ME's they replaced.

FWIW I have noted that at full rich mixture, unless Density Altitude is like 0 ft. or lower, my pre-takeoff mag checks always fail with excessive drop on either mag (this was true with the old ME plugs also). How much excess seems to be directly related to DA. The manual allows for recheck with a leaner mixture, and they pass when I do this.

David, as some have suggested it is possible you just need to use a more aggressive on-ground leaning technique than you have been. Note whether the massive-electrodes than seem to have no noticeable problem are the higher heat-range number. Your higher elevation airport may make this more critical than most of us experience.

[Colin]

"Pull it back to T to taxi." – my Long Beach CFII on what to do with the mixture after starting the engine.

[Lance Murray]

Sounds like the XL plugs are the problem.

On leaning I pull it back till it won't run anymore then push it forward just enough for it to run well enough to taxi. There is absolutely no threat in taking off with it leaned. It will not run above 1400 rpm or so.

[Rich]

Running rough could be caused by a single defective plug. Doing a ground run-up with the usual mag check, including leaning during same could tell you if you've got a bad plug and if so, which one it is.

[dwurfel]

Ok talked with the folks at Tempest. Went through my issues and they asked me to send them my plugs. First of all they confirmed that the UREM38S plugs were indeed my needed plug. Apparently the XL that Spruce uses on their site means nothing. In any case, they put the plugs under a microscope and measured resistance. Resistance was fine. The plugs were fouled for one simple reason: I put too much thread release coating on the plugs and it help foul them. In fact, at least one plug was shorted from the metallic based thread release. They also recommended using Tempest thread release from Spruce. It is not metallic and you only use it on the #2 and 3 thread from the bottom not the lower thread.
It is not metallic based. I will reinstall them this week and let you guys know how it turns out. By the way the folks at Tempest were teriffic to work with. Thanks for everyone's feedback.