The complete radio control model airplane FAQ.  


Ignition system FAQ's

What is the CH Ignition?

What is the Jump Start?

What is the SyncroSpark?

What is advanced and retarded spark timing?

What is the ProSpark?

Can I put an ignition system on my Glow engine?

Also read about Ignitions systems on our Engine Conversion Page.


What is the CH ignition that CH Electronics (now CH Ignitions) sells?

    The CH ignition is a CDI system. (CDI = Capacitive Discharge Ignition.) This company is the standard ignition system that is used by more engine mfr's than probably all other brands combined. It is reliable, not prone to excessive radio interference, and user friendly. There are several methods to charge a capacitor, but this one uses a step up transformer. Using a CDI, you don't need a flywheel or points. The flywheel is replaced with a simple disc that has a small magnet on it. That magnet is used in conjunction with a hall effect sensor to trigger the ignition to fire. 

    The standard CH ignition is a simple system that has fixed timing. You set the sensor to trigger at about 27-30 DBTDC, depending on your engine, and that's where it fires all the time. CH also sells ignition systems with the SyncroSpark timing module built in, or you can add one in-line later. (Read about it below.) Using this ignition system instead of a flywheel and magneto, you can expect to save anywhere from 3-10 ounces. One Husqvarna engine that I converted had an extremely light flywheel ignition, which would offer minimal weight savings if replaced. The Ryobi's and Homelite's, on the other hand, have quite large flywheels and you will save about 10oz by replacing them.

    For what it's worth, I highly recommend the SyncroSpark version, for any engine. The cost is $40 extra, but it's money well spent. Your engine will start much easier, with a lower likelihood of kicking back and biting your fingers. Not only that, you'll have a much smoother running engine. rcfaq


What is the Jump Start system that CH Electronics (now CH Ignitions) sells?

    This is from Terry Grant of CH Ignitions, the mfr. of the Jump Start:

    It is a battery powered system to boost the magneto output. It will make a hot spark at any RPM, most mags require 600+rpm to fire. It also retards the timing to around 5 deg BTDC so that the engine won't kick back. Once the engine starts it becomes a stock engine on the mag with no timing control. Terry

    At $60 for the Jump Start, you'd be better off buying a full ignition system with SyncroSpark. The Jump Start will make the plane easier to start, but it won't make the engine run better. A full CDI with timing control, on the other hand, will give you the benefits of the retarded starting timing, and also the benefits of retarded timing in the lower power band in addition to saving a little weight. rcfaq


What is the Syncro Spark that CH Electronics (now CH Ignitions) sells?

    The SyncroSpark is an electronic timing module, which is available as an add-on, or built into the CH Ignition system. Without it, you set the ignition to fire somewhere between 27 and 30 degrees before top dead center. (DBTDC) Your ignition will fire at that point regardless of the rpm the engine is running. When you plug a Syncro Spark in between the sensor and the ignition module, you will have an engine with variable timing on the ignition. It will retard the timing for starting by about 24 degrees, so you can hand start the engine with it firing at about 4 DBTDC. That makes hand starting MUCH easier. 

    The Syncro Spark also calculates the spark timing (advance/retard) based on the current RPM. When the engine is idling, the spark is retarded significantly, to smooth out the engine. As you increase the throttle, the module senses this and decreases the amount of retard. (Which is like advancing the timing.) This allows the engine to develop more power, since you can time it to run optimally.

    For what it's worth, I highly recommend the SyncroSpark version, for any engine. The cost is $40 extra, but it's money well spent. Your engine will start much easier, with a lower likelihood of kicking back and biting your fingers. Not only that, you'll have a much smoother running engine. rcfaq

    The use of the terms advance and retard are often misused. This is ok, as long as people are communicating, but it's usually easier to use the appropriate terms to make sure everybody is understanding. I'll define the terms just to make it simple. 

    When an ignition system has the sensor set significantly before TDC, the system will retard the timing to smooth out the idle. Retarding the timing is the act of pausing for a moment before firing the plug. The pause occurs at lower rpm's, and happens after the sensor detects the timing magnet. This is the method that the CH ignition uses. It was conveniently chosen, I assume, so that the SyncroSpark module could be plugged inline between the sensor and the ignition without any other modifications.

    Conversely, advancing the timing provides the same end results, but with the opposite method. Ignition systems such as the ProSpark system actually advance the timing. The ProSpark system has the sensor set at 4 DBTDC. As the engine picks up speed, the ProSpark will anticipate when the spark should occur, and it fires the plug before the sensor actually detects the timing magnet. rcfaq


What is the ProSpark system that Nelson Hobby Specialties sells?No Disk File

    The ProSpark is an electronic ignition system. It uses a CDI method for creating the spark. (CDI = Capacitive Discharge Ignition.) One neat feature that the Pro Spark has is that the variable timing is adjustable. You set the sensor to 4DBTDC, and start the engine. Then you tune the ignition system--there is a small trimmer pot on the circuit board that you turn to set the amount of advance (defined above) that the ignition will have at peak rpm. (You don't actually peak the engine out, but you back it off a bit from peak. That way you don't overheat your engine.) While having the variable timing adjustable can be helpful, it's also one more adjustment that can mess up your engine, in addition to being one more thing to break. Make sure to isolate your ProSpark from vibration, since tiny trimmer pots don't take well to shaking. rcfaq


Can I put an ignition system on my glow engine?

    Yes...but! You can put an ignition system on your glow engine and run it with glow fuel--Dick Hanson found that it added a couple hundred RPM to his ST 2300. (See the RPM chart for specific numbers.) You can also run the engine on gasoline, but you must run it with lots of oil--which defeats the purpose of running gasoline. You'll also lose power when you switch over to gas.  Most glow engines use bushings instead of roller bearings on the rod ends. Those bushings require a lot more oil than a bearing does, so you still have to run it at a MINIMUM of 10%, and NEVER let it see a lean run. Remember, too, that gasoline runs hotter than glow fuel. Unless you replace your bushings with roller bearings, don't waste your time trying to run gasoline in your glow engine. rcfaq





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