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Join Date: Aug 2004
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Found this on http://www.rcnitrotalk.com/forum/faq.php?faq=nitro_faq
Interestingly enough, most people do not pay close enough attention to their glow plugs. Whether it be running the wrong temp, the wrong size or just plain bad quality plugs, this is something that should not be overlooked. Below you will find some quick tips on glow plugs that should help keep you in the bash longer.
Always make sure your plug is tight at every fueling and always keep the plug area CLEAN!
1. Make certain you find out through your engines manual what kind of plug should be used. If that information is NOT in your manual, as I have found with some manufacturers, you may then want to contact the manufacturer directly. The most important thing to establish is a baseline as for temperature, size and style of the plug to be used. Make incremental changes from this baseline to affect performance.
2. Run the right size! If your engine calls for a short plug, then please, do not run a long! I've stood by listening to someone trying to start a mill only to hear the 'clanking' of the piston into the bottom of the plug. Needless to say, not a good choice. You can in SOME engines safely change the length of the plug, but I do not suggest it.
3. You can use ONLY the style that your button head calls for. This only pertains to Turbo and non Turbo type plugs. Turbo plugs are cut like an upside down road cone while non-turbo plugs are straight. Trying to make one fit into an engine that doesnt call for that type will result in stripped threading and a trip to your hobby shop. As for the bennefits of running either?!?! I prefer to run non-turbo plugs for all of my rides. They cost less and seem to work just fine. Some guys I know who run in on-road races will run nothing other than turbo plugs. They claim they get the extra edge they need to win. I cant vouch for real world performance gains.
4. Only change temps if you have to. You will find that a majority of eninges on the market will call for a medium temp plug. Depending on your altitude, you may need to change for that very reason. As well as ambient outdoor temps. If you live in the Arizona desert, I highly doubt a HOT plug is going to be helpful. Being as I live in a cool climate, I can run the varieties from cold all the way up to hot and in essence, change my timing. If you want to advance your timing so the engine fires before the piston reaches normal firing height, then change to a hot plug. If you want to let the engine load up with a bit more fuel before firing, a cold plug should do the trick. I only suggest that tuning veterans look to make these changes.
5. Installing the copper gasket! Sounds simple enough right?? Well, one of the more common mistakes I have seen made is improper installation of the copper gaskets. First and foremost, NEVER re-use a copper gasket from and old plug, on a new plug, unless you ABSOLUTELY have to. For instance, you lost it at the track but have to go into the A main in 1 minute. Go ahead, use it then! Once you install the plug with the gasket and tighten it up, that copper ring will form according to that plug and that engine head. After a typical plugs life span, the copper ring will be pitted, stretched and not as effective for holding a tight seal. If you switch plugs often, keep the copper rings in a bag or plug caddy with its corresponding plug. Lastly, there is a right way and wrong way to install that gasket. If you pay close attention, you will see the copper ring is shaped like a bowl. You always want to put the plug INTO the bowl itself and then install the plug. This will help keep the seal. Installing it the wrong way can result in nitro in the eyeballs.
6. Lastly, always check to make certain there is no damage to the plug coils and that the plug burns bright. Regular inspection of the glow plug will result in less frustration at the bash site or track. After all, it only takes 1 bad plug to cost you an A Main victory!
More about glow plugs
A Glow plug is a very crucial of your model glow engine. A glow plug is the ignition system for your nitro RC. Instead of a spark type ignition system like those found in car engines, the remarkably simply glow plug is what we use to ignite the fuel in our engines. It doesn't have a single moving part or adjustment; its only functioning component is a simple, stationary coil of wire. Using the proper plug type is key. You can also tune your engine very slightly with the use of different plugs. That is beyond the scope of this FAQ but we will touch on it briefly.
Types of plugs
Standard comes in two types, long plugs and short plugs. This changes the area between the glow plug element and the top of the piston stroke. This area can be referred to as the combustion area or chamber. Less area makes more makes for of a bang or hotter firing. This can actually increase compression. There are many different types of standard plugs for both long and short. They are heat rated. Hot, Medium and Cold are the three most common. Depending on the thickness of the element/coil determines a plugs heat range.
Turbo plugs are less common, more expensive, and are generally used in race bred engines. Turbo plugs feature a different type of housing; the end that goes into the combustion chamber is tapered. The tapered end mates with a head that is specially designed for use with turbo plugs. The head is also tapered to accept this type of plug. The supposed advantages are less compression leakage around the glow plug and less disruption of the combustion chamber. The hole in the cylinder head that exposes the glow plug to the air/fuel mixture in the cylinder is much smaller, and there are fewer rough edges to create unwanted hot spots. If you race be careful with Turbo plugs because they are only allowed in .21 buggy engines racing.
My take is to stick to Standard plugs. They are cheaper, easier to find, make the engines easier to tune for beginners. If you race you might look into the use of a turbo button for your engine to make it accept a turbo plug.
What type of Glow Plug do I use for XYZ brand/type engine?
First, check with your manufacturer. You will need to identify a few things before you can choose your brand/temp range. Does your engine take a Standard, or Turbo plug? Next if it is a Standard, is it a long plug, or a short plug? Once you have identified this information from the manufacturer now you can choose the brand/temp range of the plug.
Every manufacturer offers a temp range of plugs, from as few as three or four up to 10 or more. A glow plug is usually identified by a code that indicates its operating temperature; not the operating temperature of the engine or the outside air, but the relative temperature of the glow plug's coil. Every manufacturer has its own temperature-rating system, and general application recommendations are sometimes included to try to steer consumers toward the correct plugs for their needs. The process can be confusing, however, because a universal rating system does not exist for glow plugs. For example, an O.S. R5 plug is not the same as a McCoy MC-9, although both are considered "cold" plugs. A glow-plug manufacturer's guidelines will suffice for average hobbyist's who simply want their cars to run; racers and performance buffs, however, won't get the most out of their engines without a little experimentation. So what should you look for in a replacement plug?
A few factors come into play when choosing a replacement plug. What size is your engine? Smaller engine generally like hotter plugs, while larger .21 and above like a cooler plug. This is not always the case. Don't let this confuse you though, when making a plug choice you must factor all conditions and equipment, such as fuel. What percent of nitro are you using? Lower nitro % needs a hotter plug, and higher nitro content like 30% likes a cooler plug. So big engine, colder plug, low nitro% hotter plug. The compression ratio also comes into play when choosing your plug. This can be a little tricky. It is hard to find posted manufacturer compression data so you might need to experiment. Higher compression ratio likes colder plugs, where lower compression likes a hotter plug. If you are losing compression you might want to try a hotter plug for a little better performance. This brings me to my next point Shims or head shims. You can increase the area of combustion or lessen it with the addition or removal of head shims. More or thicker shims lower the compression; fewer or thinner shims raise it. Remember: when adjusting head clearances with shims, a plug change may be necessary (please do not do this unless you know exactly what you are doing, you can cause damage).
Notes, using too hot of a can cause detonation (very bad emm kay).Using too cold of a plug will cause a loss in acceleration and you will notice a lot of un burnt fuel coming out the stinger or tuned pipe.
Elevation matters. Elevation does not decide the plug, but understanding what happens at different elevations can help you better tune your engine and decide on the best plug (with all other factors included of course). It matters because at Sea level you have a lot more oxygen to combust the say @ 5,000ft. Because of the added oxygen you use a hotter plug and run richer at Sea Level. When you use a hotter plug you can actually run it richer and better protect your engine, at higher elevations you will want a colder plug. At high elevation a colder plug might work better because you need to lean your engine as to decrease the fuel to air ratio. You have to let in less fuel and more air due to the lack of oxygen. A colder plug will lower temps but this does not necessarily mean you are not running too lean.
I have seen time and time again a frustrated hobbyist try to tune a poor running engine when the actual cause is the plug. They tune, and retune and wonder why the engine will never run right. They look for leaks, clogged needles and all other sorts of goose chases. They tend to blame it on the engine rather than the real culprit (the glow plug). I suggest never trying to save money on a plug. It is a very, very important part of a well running nitro engine and can let you really enjoy your model, instead of constant frustration. I know there is a lot involved in this FAQ, but the fundamentals of glow plug 101 are very easy to follow. Stick with standard plug when you can. Find out if your engine calls for a short, or long type standard plug. How big is you nitro engine? What is the percent of nitro you are running in your fuel? What elevation are you at?
Glow plug guide:
Physical indications that you might need to change the glow plug are:
a. Twisted or mangled glow plug element. (This is usually caused by too high a compression ratio.)
b. Small "bumps" are attached to the glow plug element (This will generally be most noticeable during the break-in process. These are actually tiny pieces of aluminum that have attached to the element and these will severely hinder the operation of the glow plug.)
c. The glow plug element is no longer shiny but is dull, almost a white powder color. (This just comes with age and is a by product of the catalytic reaction. The shinier the wire, the better the catalytic reaction can be.)
Operating indications that you need to change your glow plug are:
a. The glow element will not light with a charged glow igniter. (This indicates that there is a physical short or breakage in the element wire itself)
b. Glow plug lights but the engine will not stay running once the battery is disconnected. (This is usually an indication if the microscopic particles we discussed earlier)
c. Glow plug lights, engine runs but there is a perceptible loss of rpm at full throttle when the battery is disconnected. (This is a typical indication that the white powder residue is building to the point that the catalytic reaction of the glow plug is no longer anywhere close to being optimum.)
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