01' Guzzi V11 Ignition Coils Melting (Earthing Issues?)

[Guzzi2Go]

Nothing flows continuously here, especially if no other resistors than coil's own (in the whereabouts of 0,5-2 ohm)  are used. Coil's primary circuit is armed (grounded) just a few milliseconds before the spark fires and its inductance controls max current till wanted "state of charge" is achieved. Timing is calculated so that in the worst case no excessive current flows.

 

BTW, the fuse for this circuit (Injectors/Coils/Pump) is 10A. The pump will consume good deal of that, so what remains must be enough for both (or all four). 

 

A permanent primary circuit short, provided the fuse does not blow, would possibly impede all other consumers in the circuit (injectors, pump, other coil). The coil would get hot, but there would definitely be no firing on its cylinder if it would get that far at all.

 

Must say that I also don't see how the engine would run on both cylinders for a while no matter which scenario is considered.

[bbolesaz]

The MyECU uses a MTP6N60E FET.  That FET has an Rds = 0.94 ohm (typ).  So, if the ECU fails and leaves it on continuously, the coil current will be 12.7 amps.  Of course, in that case, there's no way the engine sparks.

 

Dwell time is typically in the single digit milli-seconds.   At 5000 RPM, one revolution takes 12 msec.  So the dwell is around 40% or less, leaving the average coil current less than 5 amps.

 

So, it the OP is literally burning up coils, I think he is better off checking the secondary side than the primary.

[luhbo]

Yes, he should look on the secondary side.

As written above, a grinded HT cable for instance, making contact to the engine, can cause a continuos and destructive current through the coil. The positive side is continuously on and the two inductors are connected on one side. Perfect path.

 

I forgot to include the previously mentioned coil schematics, sorry for that.

 

http://mgaguru.com/mgtech/ignition/pics/circ_ic.gif

[swooshdave]

I belive coils have different resistance values. Something like 3 ohms, etc. If the wrong coils were used could they burn up?

[luhbo]

That's the Internet. You'll never know what he's done before. Wrong coils can get damaged, why not. Maybe the 'new' one just was more 'another' one, already damaged from other experiments or just an obscure shop find.

[emry]

Coils do come in two distinct varieties when it come to the primary resistance and I agree the problem is with too much current through the primary side. TCI (Points fall into this) or CDI. TCI coils have a few Ohms of resistance and induce voltage into the secondary through a collapsing field, this is why dwell is important. CDI coils have very little resistance, normally a few tenths of an ohm, and work off a rising field to induce voltage in the secondary. 

 

Using a CDI type coil on a TCI bike will allow it to run, until either the coil or the ECU cook due to the extra current. Using a TCI coil on a CDI unit will cause a very weak spark and normally cause the CDI to find an alternate path internally for current, which then fails.

 

The original coil could have just partially shorted out some of its winding til it smoked. If a CDI style coil was then used as a replacement, it could have quickly have gotten cooked. 

 

I originally learned this lesson in the 80's with GPz900, I just had to have those high-output Accel coils.... Went through 4 TCI units, and 3 coils before I figured it out.

[swooshdave]

Went through 4 TCI units, and 3 coils before I figured it out.

 

That was an expensive lesson...

[gstallons]

Yes , there is a gap @ the spark plug . You do not want an open in the primary or secondary windings of the coil . an open in the spark plug wire , cap or the internal connection of the spark plug .  

The ignition coil is a step-up transformer . In a conventional electrical system , an open in the secondary will increase amperage in the primary . 

[gstallons]

emry . CDI is capacitor discharge ignition ? What is TCI ?

[emry]

Transistor Controlled Ignition. Works just like points but is controlled electronically instead of mechanically. 

[emry]

Here is three relevant articles.

 

https://www.yamaha-motor-university.com/ymu/motorsports/advertising/YMU%20Service%20Limit/docs/Three%20Ignition%20System%20Types%20September%202012.pdf

 

https://www.yamaha-motor-university.com/ymu/motorsports/advertising/YMU%20Service%20Limit/docs/Troubleshooting%20TCI%20Ignition%20Systems%20October%202012.pdf

 

https://www.yamaha-motor-university.com/ymu/motorsports/advertising/YMU%20Service%20Limit/docs/Ignition%20Coils%20July%202013.pdf

[gstallons]

Hey , this is good stuff . how did you latch on to this ?

[emry]

I little side project I was involved in. It has been neglected unfortunately.

 

The main page has a few other articles if you are curious. https://www.yamaha-motor-university.com/ymu/motorsports/advertising/YMU%20Service%20Limit/index.html

[gstallons]

I am always curious .  You are really up on electronics & I like it .

[Chuck]

I've been following this thread.. just trying to learn something about an old 1000 SP I had that suddenly started eating RH coils on a trip out to California. It took 2 of them to get me there, and I arrived on one cylinder. Much head scratching and parts changing went on. I eventually cured it by running a wire directly from the points to that coil, but still don't understand what was going on.