Bob fixed me up with an advanced rotor. It's great! I was wondering about the shortening of the dwell on the strength of the spark. Does shortening the dwell weaken the spark?
Bob already shortens the dwell. That is how your advance curve gets steeper. The bikie thinks its turning 1500 rpm when you have 12, and the static advance is 17 degrees. So you'' stay at 17 no matter what, but at say 1700 rpm when its supposed to hit 17 degrees ... you'll prolly hit it at 1500, and as you rev your bike alwars things its running a higher rev and advances it accordingly.
On a 04+ I believe you'd have a tach also go wrong cos its picking up that same thing. heck, might be an idea to see exatly what is going on.
Cool.
Srinath.
Advancing the timing by turning the rotor doesn't effect dwell. Dwell is simply the amount of time a current needs to be applied to a coil to build up an given magnetic field known as flux. The ICM on the GS probably uses a fixed dwell time for the sake of simplicity. Some more complicated ignition systems calculate dwell based on the amount of current being sourced by the coils as that is the only changing variable that really matters in this application. In any case, RPM or crank position do not matter when calculating dwell.
On the pre-'04s, the metal tab would go past one of 2 VR sensors (one for each cylinder) on the crank causing a spike which signaled to the ICM 'the crank is X degrees BTDC', where X is greater than the maximum advance. The ICM then calculates the amount of time at the current RPM before the next ignition event needs to take place given an advance of Y degrees. The ICM will apply a current to the coils Z ms (the hard set dwell time) before the next ignition event, and then remove the current to cause the ignition event to occur.
'04+ are a little more modern in that the ICM knows where the crank is in its rotation at any given time, thus allowing for more flexibility and precision in its ignition control. On these models, there is a wheel with multiple teeth, all the teeth being alike except for one which is larger than the rest. There is also only a single VR sensor. The ICM is able to distinguish between the large tooth and the other teeth. The large tooth acts as a referance point to a certain point in the cranks position, while the other teeth act as 'pace marks'.
Lima is UBER.
Wow, even I learned something there.
So at a certain point you cannot increase the advance on the pre 04 bikes because the only trigger is the metal tab going across the VR sensor at X degrees BTDC
So:
Total Advance < X . (Can't be exactly equal either because the ICM has to has a little sliver of time to figure this out too.)