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Engine basics => Engine set up tips => Topic started by: frank mccune on September 10, 2017, 08:01:56 AM

Title: Using a short plug in lieu of long plug?
Post by: frank mccune on September 10, 2017, 08:01:56 AM
     Hello:

     I found a stash of short glow plugs.  What are the negatives if any, to use these for sport flying in engines designed to use long plugs?

                                                                                                              Tia,

                                                                                                               Frank McCune
Title: Re: Using a short plug in lieu of long plug?
Post by: Perry Rose on September 10, 2017, 09:31:52 AM
The .46LAS comes with a short plug and runs fine with it.
Title: Re: Using a short plug in lieu of long plug?
Post by: dennis lipsett on September 10, 2017, 12:33:58 PM
Quote from: Perry Rose on September 10, 2017, 09:31:52 AM
The .46LAS comes with a short plug and runs fine with it.

The la46 uses a medium plug it is shorter than a long plug and longer than a short
Title: Re: Using a short plug in lieu of long plug?
Post by: RandySmith on September 10, 2017, 01:18:54 PM
typical thing is  they run cooler  and  not as clean

Randy
Title: Re: Using a short plug in lieu of long plug?
Post by: Steve Helmick on September 10, 2017, 04:21:14 PM
A "kid" in our club some years ago had a U-Key 35 with a Fox .35 Stunt and bought a short Fox glowplug for it (as recommended by the knuckleheads at his LHS). It would start, but was very touchy on the NV and barely ran. We screwed in a Thunderbolt R/C Long and it was entirely different and relatively civilized, so flying could commence.

Short glowplugs belong in engines .15 CID and smaller. But I guess if you wanted to (and could do the machining), you could lower the glowplug seat enough to get the business end of the short glowplugs flush or slightly protruding into the combustion chamber. That would make them run properly, unless they happen to be Fox or Fireball glowplugs, of course.  D>K Steve
Title: Re: Using a short plug in lieu of long plug?
Post by: dennis lipsett on September 10, 2017, 05:40:28 PM
Quote from: Steve Helmick on September 10, 2017, 04:21:14 PM
A "kid" in our club some years ago had a U-Key 35 with a Fox .35 Stunt and bought a short Fox glowplug for it (as recommended by the knuckleheads at his LHS). It would start, but was very touchy on the NV and barely ran. We screwed in a Thunderbolt R/C Long and it was entirely different and relatively civilized, so flying could commence.

Short glowplugs belong in engines .15 CID and smaller. But I guess if you wanted to (and could do the machining), you could lower the glowplug seat enough to get the business end of the short glowplugs flush or slightly protruding into the combustion chamber. That would make them run properly, unless they happen to be Fox or Fireball glowplugs, of course.  D>K Steve

I kept Fox and Fireball plugs for all of the cheapskates who were always borrowing something and then having to chase them to get it back. They would put up with crap runs because it was free.
Title: Re: Using a short plug in lieu of long plug?
Post by: Ron Cribbs on September 10, 2017, 08:56:27 PM
Compression.

It may not seem like much, but read Mr. Helmicks comments above.