mauricejota7604
Hero member
- Location
- Victoria Australia
Hi all can anyone tell me can you run 5000 ohm resister plug caps with Nology coils with no issue or should you use just non resistor clip on plug caps.
resistor plug caps and Nology coils
- Thread starter mauricejota7604
- Start date
Rob
Hero member
- Location
- Midlands, UK
Resistor plug caps are used to cut radio frequency interference - suppression, in other words. It's usual practice to use with copper cored HT leads. Other types of HT lead (graphite or similar core) typically remove the need for them. Any HT coil should be suppressed, so the answer to your question is 'yes'! (It's good not to use both types of suppression in a single system)
Dellortoman
Hero member
- Location
- Tasmania, Australia
I'm using NGK resistor plug caps with Nology coils and copper core HT leads on my RGS mongrel. Bike starts and runs well enough in the workshop, but I haven't had it on the road yet.
Guys
You are correct the purpose of resistor caps ( or carbon silicone impregnated High Tension leads) is to eliminate radio interference. However the positive affect of resistor caps or leads is that the coil must produce a higher discharge voltage to bridge the resistance consequently that has the affect of making a stronger voltage charge at the Spark plug tip.
The Ignition coil will only produce what it has to, so if there is copper impregnated leads and only the spark plug gap to jump that's only what the coil is going to produce. If you have the 5,000 ohm resistor cap, plus the spark plug gap, the ignition coil has to produce more voltage to bridge the 5,000 ohm resistor and the spark plug gap prior to firing the spark plug which at the end will be a lot stronger charge at the plug. If you measure the voltage at the spark plug with an oscilloscope; the voltage produced in an ignition system with no resistor caps will be in the vicinity of 7.000 Volts and if resistor caps are fitted you will get anything up to 10 to 12,000 volts. If on one power stroke one cylinder finds itself with a lean mixture due to poor turbulence at the spark plug tip, you will need the extra voltage to ignite properly what fuel you have between the tip of the plug. Of course there are other variables such as engine compression/load/air fuel ratio etc that affect how much voltage the ignition coil has to produce to jump the spark plug gap.
By the ignition coil having to produce more voltage it will leave less reserve voltage left as the spark plug gaps widen with use and resistor caps increasing resistance with age. So the trick is to have all three resistors of the same value, and the spark plug gaps the same size.
I also have a Benelli 254 4 cylinder bike on which I have fitted an electronic ignition system plus 5,000 ohm resistor caps. It has improved starting, idling and performance quite considerably.
What I strongly suggest is
1) all resistor caps to have the same resistance value if possible. you can have a tolerance between each of no more that 1 to 2,000 ohms.
2) spark plug gaps all the same.
3) If a cap has more than 10,000 ohms resistance throw it away and get a new one.
Resister caps that are faulty affect Ignition timing, spark plug efficiency which all can lead to poor engine starting/performance and abnormal fuel ignition which can cause, in extreme cases ignition detonation leading to piston failures.
spags
You are correct the purpose of resistor caps ( or carbon silicone impregnated High Tension leads) is to eliminate radio interference. However the positive affect of resistor caps or leads is that the coil must produce a higher discharge voltage to bridge the resistance consequently that has the affect of making a stronger voltage charge at the Spark plug tip.
The Ignition coil will only produce what it has to, so if there is copper impregnated leads and only the spark plug gap to jump that's only what the coil is going to produce. If you have the 5,000 ohm resistor cap, plus the spark plug gap, the ignition coil has to produce more voltage to bridge the 5,000 ohm resistor and the spark plug gap prior to firing the spark plug which at the end will be a lot stronger charge at the plug. If you measure the voltage at the spark plug with an oscilloscope; the voltage produced in an ignition system with no resistor caps will be in the vicinity of 7.000 Volts and if resistor caps are fitted you will get anything up to 10 to 12,000 volts. If on one power stroke one cylinder finds itself with a lean mixture due to poor turbulence at the spark plug tip, you will need the extra voltage to ignite properly what fuel you have between the tip of the plug. Of course there are other variables such as engine compression/load/air fuel ratio etc that affect how much voltage the ignition coil has to produce to jump the spark plug gap.
By the ignition coil having to produce more voltage it will leave less reserve voltage left as the spark plug gaps widen with use and resistor caps increasing resistance with age. So the trick is to have all three resistors of the same value, and the spark plug gaps the same size.
I also have a Benelli 254 4 cylinder bike on which I have fitted an electronic ignition system plus 5,000 ohm resistor caps. It has improved starting, idling and performance quite considerably.
What I strongly suggest is
1) all resistor caps to have the same resistance value if possible. you can have a tolerance between each of no more that 1 to 2,000 ohms.
2) spark plug gaps all the same.
3) If a cap has more than 10,000 ohms resistance throw it away and get a new one.
Resister caps that are faulty affect Ignition timing, spark plug efficiency which all can lead to poor engine starting/performance and abnormal fuel ignition which can cause, in extreme cases ignition detonation leading to piston failures.
spags
