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Explanation of the Working of Ignition Coils Please!!!

Morizzi said:
I'm personally not paranoid about this at all. I use 3 ohm coils because that is what they came with. Funnily the small blocks came with 5 ohm despite it being written they need more spark. :lol: If you have ever tested an OEM coil you will have found them at about 3.4 ohms and a 5k ohm plug cap at around the 4.85 mark! So much for precision.

The thing that amuses me about this thread and the same one on Wild Guzzi is the contradictory statements that are made that no one seems to pick up. Either the posters that do understand don't read it or don't care. Either way I just find it amusing.

If you look above there is a statement Points ignition 5 ohms, electronic ignition 3 ohms. This is contrary to the fact that the points dwell can control the time of current flow. It should, if logic flows, be the reverse.

I really see this as a storm in a tea cup. Semantics at its best that if you take it into context of all the threads that have been written over ensuring a full 12V at the coils to ensure a good spark then it is again contradictory. They even go on to advocate the use of a relay and a direct feed on the ignition circuit to ensure the full amount of zap. :lol: Instead of a ballast resistor just use the OEM ignition circuit to feed the coils. :lol:

If you are so concerned about heat in the coils with electronic ignition why don't you just wire them in series and drop the resistance in the HT lead? That would give you 6 ohms instead of 5 and you can drop the 5k ohms in the HT circuit to a 1K plug cap or simply use silicone leads that have a listed ohms/m?

Ballast resistors don't last forever. They are another item that can fail. Luckily as long as you can diagnose the problem they can be bypassed to get you home. If you dare! :lol:

When I was in the army I had to be a parachutist. The motto of The Parachute School is "Knowledge Dispels Fear." In this case it should be "Holistic understanding dispels paranoia." :lol:

The GT40T is designed to run cooler. It is cheap at around $60 or $120 for the pair and far less than the $400 quoted above. I can buy 3 pairs and still have change! My last set of 3 ohm coils lasted 31 years! How old are you and how long do you expect to live? Just do the maths. :p

I do enjoy a good techie discussion. It stimulates my brain to think thing through and drag out old memories that I haven't used in a long time. Thank you. Look at the big picture though.

Rod
Click to expand...


I stand correct , points 5 ohms electr. iggy 3 .
if you run 3 ohms coil on points the coil will get really hot and can burn out.
with elec. iggy does not really matter, they will work fine with both !
this is what i learned in years of wrenching on harleys ( pre 84 ) i don't thing guzzis are different besides that HDs use one coil for two spark plugs.

btw been in the " paracaditisti " 3 years , and done something like 80 jumps as a "civil " but that's another story...here...we are not trying to show who's got more brain or balls... just talking about MOTORCYCLES . ;)
 
Seeing as we are talking about contradictions. The guy talking about others suffering from paranoia appears to be suffering from it himself in bucket loads :cheer:
 
Well Don,

It is clear you don't appreciate the effort I have gone to explain the issues that you raised. :roll:

Good luck with your bike. You are clearly no longer in need of any of my advice. :lol:

Rod
 
Arveno , 3-3.5 ohm standard coils are fine on a Guzzi points ignition , they are not fine on a dyna111 system which requires a 4.5- 5 ohm primary coil circut .. We are fitting the ballast simply to add resistance to the primary circut to limit voltage .
A GT40 coil is designed to run on 13.8 volts ie full battery voltage / alternater output , A GT40r coil is designed to run on about 9 volts and seeing as how the battery / alt voltage is 13.8 we meed to put a resistor in circut to knock the voltage down for normal running . The resistor can be bypassed for starting.
Coils are not as simple as you think. The amount of turns ( of wire ) in a coil primary and secondary windings is more important than the resistance ( resistance to current flow in a coil should be refered to as impedance, which is a complicated combination of resistance , capasitive reactance and other magic ) . a 3ohm coil may have a primary winding with a long thick wire , or a short thin wire , still the same resistance but the two would behave totally differently in use , same with the secondary winding.................... bla bla bla. If you really want to know coils get on the net or find some text books but I tell ya your probly better off just believing that some things are so and accepting the simple explanation , religious people do it all the time :D
 
Since were on the topic of coils and ignitions I thought I'd show a short clip of the Chrysler pointless ignition adapted to the Guzzi.

Pickup coils are exactly 135 distributor degrees apart. In this example a Y connector is used sending the pickup coil signal from each of the pickup coils to the single control module to fire one coil. This set up would be for using the wasted spark system with a spark coil having two wires.

I currently run the bike with two independent systems. Each pickup coil triggers a separate control module and spark coil. But wasted spark seemed OK although I thought I could detect a slight backfire at the higher rpms as the RH (I think) would be on intake stroke. Independent systems guarantee no such possibility and provide a safety should there be a component failure.

Also without a ballast resistor there is too much spark and it will eventually leak. This ends up as a misfire or backfire. So the ballast resistor not only makes the spark manageable and keeps the coil operating temperature down but it also allows the alternator to keep up with battery output at idle. It took some experimenting to get the optimal ohm value.

http://home.comcast.net/~gustofur/Guzzi/Spark.wmv
 
Just wanted to say thanks to Mc Tool for the explanation I requested and it made sense.

Lot of good info here IMHO from everybody. I like Mc Tool and Morizzi question Arveno's blanket statement of 3 Ohm coil on the Dyna. On other electronic ignitions it may be Ok but it's well documented on WG and probably here to, of owners either burning out the Dyna or the coils when using 3 Ohm coils. Remember the Dyna has to carry the current too.

I agree with Morizzi that you can use points gap to alter dwell time. I think Cliff Jefferies also does an ignition module that has a selectable dwell. Its the only electronic unit I know that does this.

Morizzi may well have a point that its a storm in a teacup. Guess it comes down to if you're happy with it and it runs Ok or not.

If it was me I'd give the ballasts a try and if they didn't work go to the higher Ohmage coils.

John
 
Ok, I got it , i was wrong but i don't see why on HDs is the other way around , i know this is a Guzzi forum not a HD forum but because the are lot of gearhead around here....i am sure someone can have an explanation on why on HDs points ignition want 5 ohms coil ?

well, learning something new everyday...

I am new to this forum, i've been in others forum and well, let me say that's not nice when between forum members there is some " friction" .... this is just an internet forum, we should not take anything personally , of course lack of respect is not acceptable.
 
ARVENO said:
Ok, I got it , i was wrong but i don't see why on HDs is the other way around , i know this is a Guzzi forum not a HD forum but because the are lot of gearhead around here....i am sure someone can have an explanation on why on HDs points ignition want 5 ohms coil ?

well, learning something new everyday...

I am new to this forum, i've been in others forum and well, let me say that's not nice when between forum members there is some " friction" .... this is just an internet forum, we should not take anything personally , of course lack of respect is not acceptable.
Click to expand...


I would guess that on a points system, a five ohm coil would reduce the current through the points as compared to a 3 ohm coil and consequently extend the life of the points (as well as the coil). On an electronic pointless system the power handling capacity of the switching transistor would probably be more substantial and less prone to failure. Concern then with an electronic system would then be for longevity of the coils and as has been stated with all things being equal the 5 ohm coils would draw less current, therefore less heat and then logically longer duration before failure. However the 3 ohm coil would provide greater secondary voltage especially at the higher RPMs. But I don't imagine Harleys as high revers?
 
Arveno

I hope I did not cause any offence, certainly none was intended. You have posted about as often as me so I guess we are equal as far as board stats go.

I try to be tactful and not use provocative language or statements. You will find some tend to be more "Ahem" forthright than others.

All in all its a pretty well behaved place and there is a load of knowledge on here on things Guzzi you'll be pushed to find anywhere else.

Anyway welcome to Guzzidome and please hang around

John
 
"ahem forthright" ( quiet snigger ) yeah thats probly me :lol: , but friction , offence ...... nah , I didnt see none of that :D , oh yeah ! someone mentioned a Harley :p :p but thats all :lol: :lol:
 
Old Jock said:
Arveno

I hope I did not cause any offence, certainly none was intended. You have posted about as often as me so I guess we are equal as far as board stats go.

I try to be tactful and not use provocative language or statements. You will find some tend to be more "Ahem" forthright than others.

All in all its a pretty well behaved place and there is a load of knowledge on here on things Guzzi you'll be pushed to find anywhere else.

Anyway welcome to Guzzidome and please hang around

John
Click to expand...

John , Nope ! NO ONE caused any offence..... I was just saying.... i felt there was a bit of "friction" .... but being english my second language...sometimes i don't get when someone is just playing....

I agree with you there is a bunch of knowledge on this board , that's why i joined and well ... because i only rides HD Guzzi and BMW... ( all pre 84 )sometimes i mention them.... :)

sure...i keep on hanging around... :lol:

respectfully
Marco
 
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