I was hoping one of the experts could answer a question for me about the ignition on a late model (2009) Dyna "96" inch stock engine.

Since this engine has "Single Fire" ignition and also does Not have a Cam sensor, how does the ignition know the difference between TDC of the compression stroke and TDC of valve overlap.

Each 360 degrees of revolution of the crank looks exactly the same electrically to the ECM. Therefore how does the ignition system know NOT to fire on valve overlap and at the same time to know to fire on the compression stroke.?
Thanks!

 

Does not have to be from an expert. Answers from non-experts also welcomed

 

Crank position sensor.

 

basically the crank sensor sends a signal to the ecm, triggered by the teeth you see on the crank, number one is determined by the distance between a couple of the teeth being different from the rest. about as simple as i can put it....

 

Yes, I understand that part about the crank sensor and the tooth count w/ a missing tooth for reference but since there are Two complete revolutions (720 degrees of crank rotation) for 1 complete cycle, two #1 position marks (missing tooth) pass the crank sensor for each complete cycle. How does the ECM know the difference between TDC of valve overlap and TDC of the compression stroke?

In years past, a cam position sensor told the the ecm which TDC was compression and which TDC was valve overlap. And when we had dual fire coils it did not matter because each plug was fired twice for each complete cycle. The plug fired on TDC of exhaust (overlap) and it also fired on compression.

Now with late model bike, they are single fire and they have no cam sensor... That's why I asked because this really has me puzzled.

 

The crank actually slows on the compression stroke.

 

Tks Lonewolf, The Crane ignition systems work that way and I was wondering if the stock Delphi did the same thing. That is a pretty trick way to phase the ignition system system to the crankshaft. It almost sounds like it would work only in theory but I guess it does work in practice because I see no other way to do it without a cam sensor or dual fire ignition.

According to Crane, their system only phases during cranking and not while the engine is running so it appears to me if the system looses sync for some reason, you have to restart the bike to sync/phase once again. Of course if you happen to loose 2 (or any even #) of sync pulses you are really back in sync or phase once again. Any odd order of sync misfires will be the kiss of death.

It amazes me that within all the Harley service manuals I have read, there is NO mention of it anywhere. It must be one of their "secrets"..

Tks again!