[mark christopher]

PART2

The simplest accessory to check is the glow plug but it is also the one that gives you the exact image of the engine health. The thread is silver color but is made with an alloy composed by Platinum and Rhodium! To keep a constant look at glow plug will help you to understand How To make the carburetion. In the following way:

Take the glowplug away and look at the thread:



· If the thread has a dark colour and the plug seems humid, the carburetion is too rich and

the engine does not work at its best. You have to lean the carburetion closing the full speed

needle.



· If the plug body (the part surrounding the element) is wet and the element is shiny, and in its original location, then change to a “colder plug” (assuming that your engine temperature is on the cool side).



· If the plug body is dry, and the element is shiny, the plug is correct for the conditions.



· If the spiral of the plug is a little bit pressed and bent it means that the engine has too

much compression. If you are racing on a sea level track, with 25% or more nitro could be the main reason. Than you need to check under head shims and in such a case insert a tenth.

· If the plug body is dry, and the element is a dull grey, the engine is running too lean -

change to a “ hotter plug” to correct the condition.



· If the thread has a dull, as sanded, it means that the carburetion is too lean (poor of fuel)

and you can damage the engine. You run the risk to break the thread and to make it fall

down on the top end of the piston, damaging also the sleeve. In both these cases, we

suggest you to replace the old with a new plug.

Apart from when actually burned out, a plug may need to be replaced because it no longer delivers its best performance, such as when:

· Filament coil has become distorted.

· Filament surface has roughened while.

· Foreign matter had adhered to filament or plug body has corroded. Engine tends to cut out

when idling.

· Starting qualities deteriorate.



Rules of thumb.

You can only “ Read” your plug in a nearly new state [Wire like new and shiny] a grey plug can still operate well. But after it has totally gone grey performance can start to fall off. To test just put in a new plug and if there is no difference in performance save the gray one or put it back in. If your engine does not feel or run right away a new plug before making major tune changes.

· Wire and surrounding bottom of plug wet, with like new shiny wire = rich side of optimum power 85%

· Wire and surrounding bottom of plug starting to dry and wire starting to gray = Very close

to optimum power 95%

· Wire and surrounding bottom of plug dry, wire totally gray but not distorted optimum

power 100%

· Wire and surrounding bottom of plug dry, wire distorted = slightly lean DANGER

· Wire and surrounding bottom of plug dry, wire broken and distorted or burnt up =

extremely lean possible engine damage!

For ultimate power a competition modeler will juggle combinations of plug, compressions and type of fuel (mainly nitro methane content) but this is way beyond the needs of the normal driver.









The pro’s best kept tuning secrets

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 deal centre (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.