Wasted Spark on Singles?

[Kurt in S.A.]

I'm aware of the "wasted spark" ignition system on the twins.  Since the points are running off the camshaft which is turning at a different speed than the crankshaft and the single set of points must work with both cylinders, both plugs fire at the same time when one cylinder is on the compression stroke and the other is on the exhaust stroke.  Hence the "wasted spark".

I got to looking at the R25/2 and realized that the points are running off the crankshaft.  Since two complete revolutions equals a complete 4-stroke cycle, does that mean that on the rotation where the piston is coming to TDC on the exhaust stroke, the plug will also fire, thus still a "wasted spark"?

I think that's the only way this will work.  Just trying to learn...

Kurt in S.A.

[Kurt in S.A.]

[Taz]

Hello Kurt.

Yep. hole in one. You got it absolutely right. The ignition system is firing every 360° of the crankshaft although every 720° would be completely sufficient for the engine to work properly...

Best regards, Tas

[mekgyver]

Hi Kurt,

yes it's right, the second spark is firering into the open exaust channel and is usually called "wasted spark".
The Einzylinders (monos,one-pot-engines   what you want) have it's ignition contact at the crankshaft
and due to the 4-stroke-concept, there will be a wasted spark after the working+exaust-stroke.
Only the R27 has it's ignition contakt at the camshaft and so there will be no wasted spark.
A good concept due to have enough time to load the ignition coil at higher revs above 6000 U/min [1/60sec]

I hope my english was not sooo bad  
regards, mek        

[berndr253]

Hello Kurt,

the ignition "drive" of the single-cylinder-engine - except the R27 - are fitted on the crank shaft. Because of the specific cycle of our engines crank-shaft will rotate two times to work all the 4 steps of the four stroke cycle.
Indeed an ignition is only necessary once - but because of the fact the ignition control is arranged on the crank-shaft we have two ignitions per cycle - excepting the R27-engine.
Here you can find the ignition "arrangement" fitted to the camshaft. Because of that  there ist only one ignition per cycle as its needed.

But don't worry about that - at the speed out engines are working on it doesn't matter wether there is one or two ignition procedures per cycle. Things may change on higher speed level.

Regards

Bernd

PS Seems that it be useful to wait with answers for a while - Mek had the same "inspirations" like me at the same moment. May be the motto "everything is said, but not everyone has spoken" is true

[Rawost]

and hopefully I won't be the only one in future, who is answering your questions - Faules Lumpen-Pack!! Kommt raus aus euren Löchern! Misdkerle!  

Kann Knut wohl jetzt zurücknehmen!
Now Knut can retract his abuse

[Kurt in S.A.]

Great!  I'm not so worried about the wasted spark method...simple enough and seems to work just fine.  As I said, it just dawned on me that the ignition was crank-mounted, as the camshaft is buried inside the engine case.  Interesting that the R27 uses the camshaft again...I presume that an extension of the camshaft is visible when the front engine cover is removed?

I was just telling someone today, that I wish I could read-write German...I see a lot of posting going on and I'm sure I'm missing a lot of good info.    For now, I'll just keep "bothering" you guys in English!  You know what they say...a person who speaks more than one language is multilingual...a person who speaks only one language is American!!

Kurt in S.A.

[rolf.soler]

Only the R27 has it's ignition contakt at the camshaft and so there will be no wasted spark.
A good concept due to have enough time to load the ignition coil at higher revs above 6000 U/min [1/60sec]

Yesss !
long live the R27
spark plugs last double the time 

[rolf.soler]

I presume that an extension of the camshaft is visible when the front engine cover is removed?

Yes. There is a small cover over the camshaft end, on which the advance unit is mounted  - to access the advance unit and ignition points and adjust timing. This cover shows you that it is a r27, not R26, at first glance. Unfortunately it is right beside the exhaust pipe....burnt fingers are a sure sign somebody tried to adjust the ignition timing on a R27...No motorcycle is perfect
Rolf Dr.L(ivingstone)

[Taz]

Hello Kurt.

...I was just telling someone today, that I wish I could read-write German...I see a lot of posting going on and I'm sure I'm missing a lot of good info.    For now, I'll just keep "bothering" you guys in English!  You know what they say...a person who speaks more than one language is multilingual...a person who speaks only one language is American!!...

So why not learn German-sounds like a good reason to me Ok, ok, I have heard a lot of people say that speaking German sounds like the person doing so is being strangled and to be perfectly honest at least 50% of the postings here are just social interaction (i.e. teasing and gabbling) so it may be of reduced interest for you...but if it's ok for you to be answered in olde world English then you are mostly welcome to continue bothering us (btw. this is precisely what your questions are not doing, otherwise you wouldn't get such a lot of technical response)

Best regards, Tas

PS: The same thing (re. multilingual) goes for the majority of the Germans or the French as well, so you're not alone-don't worry about it

[† Knut]

Kann Knut wohl jetzt zurücknehmen!
Now Knut can retract his abuse

YESSS. I'm perfectly happy and satisfied  

Knud (Deatcher of the chatterboxes   )

[Stefan]

...a person who speaks only one language is American!!

...or French.

[† odeon8]

enough time to load the ignition coil at higher revs above 6000 U/min [1/60sec]

Well, 6000 U/min is 10 ms for one revolution; so the charging time for the
ignition coil is only 5 ms. This is not enough for 100 % charging energy,
but enough for operating the engine (about 80%).
BMW changed the breaker´s location at the R27 to the camshaft because 7500 RPM
will make the spark energy too weak.

See also here.

Greetz,
Thomas

[BenW]

I was just telling someone today, that I wish I could read-write German...I see a lot of posting going on and I'm sure I'm missing a lot of good info.    For now, I'll just keep "bothering" you guys in English!  You know what they say...a person who speaks more than one language is multilingual...a person who speaks only one language is American!!

Kurt,

Considering this quote of your fellow countryman, intrepid traveller, author, and renowned connoisseur of Germany, Mark Twain, I wouldn't bother trying to read or speak German:

"My philological studies have satisfied me that a gifted person ought to learn English (barring spelling and pronouncing) in thirty hours, French in thirty days, and German in thirty years. It seems manifest, then, that the latter tongue ought to be trimmed down and repaired. If it is to remain as it is, it ought to be gently and reverently set aside among the dead languages, for only the dead have time to learn it."

On the other hand, this forum actually may make it worth trying...

Cheers,
BenW

[Kurt in S.A.]

BenW -

Thanks for the encouragement...or is that discouragement!    I did take German in college, but that was a lifetime ago.  My family roots are German, and I keep uncovering documents written in German.  Not to mention, that I'm interested in following the history of my little Schätzchen that spent a lot of its life in Montabaur.  At some point, in the not too distant future, I hope to make it over there and meet some people and go through the police records for the bike.

So, maybe there is some "push" to move me more in that direction.  Time will tell...

Kurt in S.A.

[rolf]

Don't forget: Mark Twain was a Humorist ...mostly

[Heiko]

in the not too distant future, I hope to make it over there and meet some people

I hope you will visit the Ruhrgebiet chapter of einzylinders! 


Heiko B(andidos mechanic  )

[Kurt in S.A.]

I hope you will visit the Ruhrgebiet chapter of einzylinders! 

Is that up southwest of Hannover?  My father's family emigrated from near Braunschweig, so I had hoped to travel up there to do some research.  Might be worth a visit to the general region.

Kurt in S.A.

[BenW]

Kurt,

The 'Ruhrgebiet' (i.e. 'Ruhr district') is indeed located in the western part of Germany, appr. 150 miles southwest of Braunschweig. It is the largest urban agglomeration in Germany. Main cities include Dortmund, Bochum, Essen, Muehlheim, and Duisburg.

Montabaur is on the way between Frankfurt airport and the Ruhrgebiet, half way to Cologne.

Cheers and happy travelling,
BenW

[berndr253]

Hello Kurt,

if you are in the "Ruhrgebiet" and like to talk to another BMW-Single-Cylinder-driver you are invited to stay at my home. I'm living in Dortmund, the city in the eastern region.
In former times the "Ruhrgebiet" was an industrial region with coal and steel industry. Things and times changes and now the air become clean and the sky blue (if it doesn't rain). Indeed result of that was that unemployment rised and it was not easy to find other places for the workers who lost their jobs.

The name of that region is based on the fact that a river flows through all the cities - the "Ruhr".

Best regards

Bernd

[Kurt in S.A.]

Bernd -

I appreciate the offer...very nice of you.  I'll definitely keep that in mind.  Now if I can just find a gap in my work!!!

Kurt in S.A.