Post by Modelman on May 5, 2005 19:50:53 GMT
WHAT MAKES A GLOW PLUG HOTTER OR COLDER?
Many elements influence a glow plug's temperature range, but primary is the thickness, length and composition of the wire used to form the coil. It will be impossible to find out anything about the composition of the wire because most manufacturers keep it a secret, but the wire can certainly be measured. Other factors that affect a glow plug's temperature include the size of the hole in which the wire is installed, the type of plating used on the glow-plug housing and the material the glow plug's housing is made of.
The plug on the left, an O.S. F, is rated "hot" for use in 4-stroke applications. The thin element wire and the large number of coils create more resistance, and this results in higher operating temperatures. The Enya no. 5 plug on the right is one step up from the coldest plug. The thicker element wire and lower coil count reduce the plug's temperature.
The best way to keep track of your glow plugs is to store them in their original packaging; the plug type is printed right on it. A visual inspection won't help you much, since some plugs don't have any temperature information printed on them; that's why the original packaging comes in handy.
IS ONE TYPE OF PLUG MORE DURABLE THAN ANOTHER?
If the fuel mixture is properly adjusted, most plugs should last equally long. When the fuel mixture is on the lean side, the hotter plugs tend to be more susceptible to damage as a result of their typically thinner elements. The quality and consistency of the material within the glow plug's element can also affect durability, and this varies among manufacturers but can be sorted out with experience. So yes; within the various brands, there are slight advantages to colder plugs, but these advantages are not enough to justify choosing them if the result is diminished performance.
These glow plugs have very different electrode designs, but despite the visible differences, electrode design has no bearing on plug performance.
BEST-KEPT TUNING SECRETS OF THE PRO'S
One of the best-kept secrets of the most experienced nitro racers and engine tuners is that you can net some serious horsepower gains by experimenting with various glow plugs. As mentioned earlier, a glow plug is the ignition system for a nitro engine. Anyone who has ever worked with spark-ignition systems knows that ignition timing can have a profound effect on engine performance. "Ignition timing" is when the fuel mixture is ignited in relation to the position of the piston and crankshaft during the compression stroke. When the piston is at top dead center (TDC) of the cylinder, the crankshaft's journal, to which the connecting rod is attached, is pointing straight up. This puts the piston at the highest point of its travel in the cylinder; therefore, the crankshaft is at "zero" degrees. The crankshaft must rotate a full 360 degrees to make a full cycle, so the amount of crankshaft rotation in degrees is used to measure the events that take place inside the engine; for example, ports opening and closing and ignition. Although you can't measure or definitively set when ignition takes place inside a nitro engine, it helps to be able to visualize what's happening when you experiment with different plugs. Let's say, for example, that the fuel mixture is ignited precisely at the moment the piston reaches the very top of the cylinder. This would effectively mean the ignition timing is taking place at zero degrees of crankshaft rotation. Installing a hotter plug in the same engine makes the fuel ignite sooner because less compression is needed to heat the plug's element to the point that the fuel will ignite. Let's say that now, ignition occurs 10 degrees before the piston reaches TDC. In ignition-engine-speak, that would mean that the timing is set to 10 degrees advanced, or 10 degrees BTDC (before top dead center). What does all this mean? Simply knowing that plug temperature will affect when combustion takes place will, hopefully, help you understand why choosing the proper plug will improve performance. Generally, it's best to try to advance the timing or flash point of the fuel—in the case of nitro engines, as much as possible without going too far. If the mixture is ignited too early, then performance is lost and pre-ignition and detonation may occur. Picco's engineers don't use plugs to tune the engine; they simply find the proper plug for the application and stick with it. They haven't seen much difference in performance from changing to a slightly hotter or colder plug. They do, however, admit that getting too far away from the ideal plug temperature will have a negative effect on power production.
THE FINAL ANALYSIS
We hope you now know more about glow plugs and what to do with them. Most people don't think about glow plugs until they don't work. It's precisely then that this information should be most useful. Just keep in mind that there isn't a magic glow plug that will suddenly make your engine scream as it never has before; glow plugs are one of many elements that factor into overall performance.
Many elements influence a glow plug's temperature range, but primary is the thickness, length and composition of the wire used to form the coil. It will be impossible to find out anything about the composition of the wire because most manufacturers keep it a secret, but the wire can certainly be measured. Other factors that affect a glow plug's temperature include the size of the hole in which the wire is installed, the type of plating used on the glow-plug housing and the material the glow plug's housing is made of.
The plug on the left, an O.S. F, is rated "hot" for use in 4-stroke applications. The thin element wire and the large number of coils create more resistance, and this results in higher operating temperatures. The Enya no. 5 plug on the right is one step up from the coldest plug. The thicker element wire and lower coil count reduce the plug's temperature.
The best way to keep track of your glow plugs is to store them in their original packaging; the plug type is printed right on it. A visual inspection won't help you much, since some plugs don't have any temperature information printed on them; that's why the original packaging comes in handy.
IS ONE TYPE OF PLUG MORE DURABLE THAN ANOTHER?
If the fuel mixture is properly adjusted, most plugs should last equally long. When the fuel mixture is on the lean side, the hotter plugs tend to be more susceptible to damage as a result of their typically thinner elements. The quality and consistency of the material within the glow plug's element can also affect durability, and this varies among manufacturers but can be sorted out with experience. So yes; within the various brands, there are slight advantages to colder plugs, but these advantages are not enough to justify choosing them if the result is diminished performance.
These glow plugs have very different electrode designs, but despite the visible differences, electrode design has no bearing on plug performance.
BEST-KEPT TUNING SECRETS OF THE PRO'S
One of the best-kept secrets of the most experienced nitro racers and engine tuners is that you can net some serious horsepower gains by experimenting with various glow plugs. As mentioned earlier, a glow plug is the ignition system for a nitro engine. Anyone who has ever worked with spark-ignition systems knows that ignition timing can have a profound effect on engine performance. "Ignition timing" is when the fuel mixture is ignited in relation to the position of the piston and crankshaft during the compression stroke. When the piston is at top dead center (TDC) of the cylinder, the crankshaft's journal, to which the connecting rod is attached, is pointing straight up. This puts the piston at the highest point of its travel in the cylinder; therefore, the crankshaft is at "zero" degrees. The crankshaft must rotate a full 360 degrees to make a full cycle, so the amount of crankshaft rotation in degrees is used to measure the events that take place inside the engine; for example, ports opening and closing and ignition. Although you can't measure or definitively set when ignition takes place inside a nitro engine, it helps to be able to visualize what's happening when you experiment with different plugs. Let's say, for example, that the fuel mixture is ignited precisely at the moment the piston reaches the very top of the cylinder. This would effectively mean the ignition timing is taking place at zero degrees of crankshaft rotation. Installing a hotter plug in the same engine makes the fuel ignite sooner because less compression is needed to heat the plug's element to the point that the fuel will ignite. Let's say that now, ignition occurs 10 degrees before the piston reaches TDC. In ignition-engine-speak, that would mean that the timing is set to 10 degrees advanced, or 10 degrees BTDC (before top dead center). What does all this mean? Simply knowing that plug temperature will affect when combustion takes place will, hopefully, help you understand why choosing the proper plug will improve performance. Generally, it's best to try to advance the timing or flash point of the fuel—in the case of nitro engines, as much as possible without going too far. If the mixture is ignited too early, then performance is lost and pre-ignition and detonation may occur. Picco's engineers don't use plugs to tune the engine; they simply find the proper plug for the application and stick with it. They haven't seen much difference in performance from changing to a slightly hotter or colder plug. They do, however, admit that getting too far away from the ideal plug temperature will have a negative effect on power production.
THE FINAL ANALYSIS
We hope you now know more about glow plugs and what to do with them. Most people don't think about glow plugs until they don't work. It's precisely then that this information should be most useful. Just keep in mind that there isn't a magic glow plug that will suddenly make your engine scream as it never has before; glow plugs are one of many elements that factor into overall performance.
