keye

what is the difference between a cold plug and a medium plug..bought a .61 como motor off ebay and need to get plugs...was told that the Mcoy MC9 plug is the one that is needed but it comes in a cold plug...again what are the differences and advantages with cold and medium

JohnBuckner

My Feedback: (1)

All our two stroke glow engines are actually semi diesel engines and we have no way practical way to control the ignition timing other than by glow plug heat range. A hot plug will have the effect of advancing the ignition timing and a cold plug will have the effect of retarding the ignition timing similar to the same in any spark ignition engine.

Typically most sport engines will do well with a hot or medium plug but in a high performance environment where high nitro is used and the engine is heavily proped among other things then a cold plug will help in keeping temps down by retarding the ignition a skosh.

The MC9 is a very cold plug and I have used them a lot in certain kinds of racing but I think its too cold for your old
Supertiger (Como) and throttling will probably suffer. Instead I think an ordinary MC59 hot would do just fine if not then the MC8 medium.

John

keye

thank you

downunder

What John said but typically the best plug for your engine/prop/fuel combination is the one that gives the most revs (gives the best ignition timing) although usually there'll only be maybe a few hundred revs difference so a reasonably good tacho is helpful here. Don't overdo the nitro in your Como (Super Tigre).

Hossfly

As John B told you the Como, manufactured by the real Super Tigre, Italy, will do well on the hot plug such as the McCoy 59. That plug is my normal first choice for the normal sport/scale engine set-up.
If you can obtain them, the best all-around McCoy is the McCoy 50. The McCoy 50 has the idle bar and IMO for the older engines in the sport and scale area, the I-B still is more dependable and has a wider range of being OK than the non-I-B which is by far the normal plug of today's RC flier. BTW, I am familiar with all the theories, don't argue with them, but I use what works best for me within the specific situation.
You will like the Como. I have a number of them, however it seems to be the engine that ST used for experiments. There were a lot of changes along the road back then when Comos were in production. There is a real story about those engines: why they were produced and why production was stopped.
Good luck.

JohnBuckner

My Feedback: (1)

Keye In case you are not familiar with the idle bar glow plugs that Horace refered to above and they are not as common as they once were, the one on the left is an idle bar plug. They have a bar welded across the top above the element and the idea was to act as a sheild to keep fresh unburnt gasses and fuel from quenching the glow element in days when the old loop scavenged engines were commonplace.