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Grumpy old man

Wasted spark ignition?

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Grumpy old man

Hi Boffins 

I presume the above is when the spark fires both on compression stroke and exhaust,  hence wasted spark. So does that mean the engine has to have a 180 degree crank which would not be the NC because that's 270. Does anybody know whether my cbf500 is 180 degrees crank and will it be a wasted spark system? 

Thanks

Lloyd 

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embee

Basically you're right. The term usually just means one spark each revolution, hence one of them being "wasted". The reason for it is usually either a shared double ended coil used for two cylinders which are one revolution apart (so timing is the same), however the more common underlying technical reason is that many bikes simply use a crank mounted timing trigger wheel with no "cycle reference" (e.g. a camshaft mounted sensor) to tell the ECU which revolution it is on, so it just sparks each rev anyway. The NC uses the spacings on the trigger wheel to identify the crank angles for the 2 cylinders and will spark each coil at the appropriate angle for that cylinder, but as far as I'm aware it's still wasted spark. NC coils are individual for each cylinder.

Generally cars don't use it as they have more sophisticated systems which do identify cycle, and this means that they can minimise the energy in the ECU drivers. Of course there are double ended coil car systems which essentially will have a waste spark in one cyl, but individual on-plug coils are more common in current engineering.

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Spindizzy
38 minutes ago, embee said:

Basically you're right. The term usually just means one spark each revolution, hence one of them being "wasted". The reason for it is usually either a shared double ended coil used for two cylinders which are one revolution apart (so timing is the same), however the more common underlying technical reason is that many bikes simply use a crank mounted timing trigger wheel with no "cycle reference" (e.g. a camshaft mounted sensor) to tell the ECU which revolution it is on, so it just sparks each rev anyway. The NC uses the spacings on the trigger wheel to identify the crank angles for the 2 cylinders and will spark each coil at the appropriate angle for that cylinder, but as far as I'm aware it's still wasted spark. NC coils are individual for each cylinder.

Generally cars don't use it as they have more sophisticated systems which do identify cycle, and this means that they can minimise the energy in the ECU drivers. Of course there are double ended coil car systems which essentially will have a waste spark in one cyl, but individual on-plug coils are more common in current engineering.

Wasted spark used in aeroplane engines as its simple. Mechanical system with magnetos and breaker points. Technology hasn't changed in years as it works and is reliable. 

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