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Which Spark Plug number?

rvanstory

Well Known Member
I have never been a fan of Champion plugs as they have given me some "issues" on other planes in the past. Champion is what came in my IO-540D4A5 So, planning to change my plugs out to Tempest soon.

When I look at Tempest fitment guide, they recommend UREM38E or UREM40E. The plugs that came in the engine (Built by AeroSport Power) are REM37BY.

I have a SureFly mag on left side (set-up with timing advance at altitude) and a Slick Mag on the right. Here's my questions:
1) Between the UREM38E & UREM40E, which would be better for my setup?
2) The UREM37BY (long reach) plug is not recommended by Tempest, but the plane has been flying well with the REM37BY put in by engine builder. Should I replace with those, or stick with what Tempest (and Champion) recommend?
 
I have an IO-360 built by Licon. I called them up and they recommended the REM37BY. I think I would go with the builders choice. I was by the Tempest booth at Sun n Fun and they demonstrated how their REM37BY plug was superior to the Champion version.
 
I spoke with Les Staples who designed the SureFly SIM at Lakeland. He said the BEY’s are great. I like them because I can gap them wide on the SIM and narrow on my Slick and they almost never foul.
 
I prefer the fine wire's REM38S however the new prices are getting a bit out of hand, maybe on sale at Osh.
 
I like them because I can gap them wide on the SIM and narrow on my Slick and they almost never foul.

Mark,
Can you tell me more details about this? Why different gaps? What do you set them at?

Thank you all for the input and advice.

Does anyone know why Tempest or Champion does not list the 37BY's as a plug for the IO-540D4A5 on their fitment charts?
 
Mark,
Can you tell me more details about this? Why different gaps? What do you set them at?

Thank you all for the input and advice.

Does anyone know why Tempest or Champion does not list the 37BY's as a plug for the IO-540D4A5 on their fitment charts?

I would guess that most of the 540's were equipped with the mag harness with the larger nut on the end of the wire; Mine did. The 37BY is the version with the smaller threads on top. I know they have a version with the larger threads, but likely a different number. Sorry, but don't know the number.

Mags use low energy coils and the energy drawn is set by the plug gap. Therefore plugs for mags must use a smaller gap to keep from over driving the coil and shortening their life. EI's typically have stronger coils and the larger gap will produce a larger a more powerful spark with a lager gap. They are designed to handle it and they are fed power from the bus and not limited by internal generator output like the mag.

Larry
 
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Sorry to resurrect an older thread. Im replacing my plugs and am currently running UREM38S plugs. I’ve read in several locations that guys really like the 37BY as they seem to foul less and are a bit shorter than the 38E or 40E plugs. These advantages sound good to me. Im running an IO-540 with 10:1 pistons in an F1 Rocket.

This plug is not recommended on the Tempest application chart for my IO-540C4B5 engine but it seems many guys are running them on this engine or one very similar. All I can gather is the 37BY is a longer reach plug then the 38 or 40s. Is this the only difference aside from plug temp? Are the threads for the intuition wires the same?
 
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