erf?
10char

 

Kinda surprised there isn't ignition noise on there as well...

 

erf? is that like.. error factor or something?

There very well could be ignition noise on there. The "flipped positive" sine wave from the rectifier is apparent but there were also large variations. (Can sort-of be seen in the picture, the large dip) Might be due to firing the coils. I had the scope set to trigger on the rectifier oscillations and not the larger dips.

So here's something for discussion, correct me if I'm wrong but I don't think you can effectively utilize wasted spark on a 90deg twin (you end up firing a plug on the intake stroke) so there is a coil that fires each engine revolution. At idle (1000 RPM) The frequency of noise from the coils should be 17Hz. Also the RC51 utilizes CDI type ignition so it has to charge up those capacitors which might result in the dips, though I would expect to see more of an RC type curve and not the flat spot.

 

wow, havent seen an o-scope like that in a while

 

Yup I think this scope is circa early 90's. The price was right and is more than adequate for my needs. Some of the old school engineers I work with refuse to use anything but analog scopes.

You can use a waste spark system on a v-twin, the reason it will work is that when you are firing one cylinder will be pressurised and the other will be at or near atmospheric (ie a big pressure difference between them)...

Yes, it would be like a current divider, the current follows the path of least resistance. In the specific case of the RC51 I don't believe it is wasted spark as it has two coils, but in a general case this makes sense.

 

You can use a waste spark system on a v-twin, the reason it will work is that when you are firing one cylinder will be pressurised and the other will be at or near atmospheric (ie a big pressure difference between them)

There are a couple of things that go into effect when spark occurs:

Compressed air is a lot more conductive, so if we look at this as a simple parallel resistive circuit you can appreciate that the energy going into the compressed cylinder will far outweigh what goes into the other one.

The second is that you are trying to conduct across a gap, the resistance of the air and the size of that gap determine the threshold voltage at which a spark can occur. Once a spark has occurred ozone is produced further lowering the resistance across that gap...

The end result is that the compressed cylinder will spark and due to the decreased resistance due to both pressure and ozone there won't be enough energy available to the other one for it to reach its threshold value so it doesn't spark, and all of the energy that was there for it to use goes into the compressed cylinder.

Make sense?

And yep, roughly 17hz would be correct.