Ignition system

 So that with an engine the gasoline air mixture can be brought to the inflammation, a Zündfunke must jump over with the spark plugs. This succeeds, if between the electrodes a tension in the order of magnitude lies close to the spark plug of approx. 15 kV. This high tension is " by the so-called; Zündspule" , a Trafo with small number of turns on the primary winding and a high number of turns on the secondary winding, causes. The following sketch shows the structure of an older ignition system. As supply terminal an accumulator serves, to which the primary coil of the Trafos is attached. The primary circle contains two switches: • Ignition key • Circuit breaker The circuit breaker propelled by the engine sits in the distributor (an arrangement, which passes the high voltage on to the different spark plugs) and interrupts the primary-carrier flow whenever at the spark plug the spark is to jump over. With drawn in condenser does not have for the emergence of the high voltage a meaning, it serves only the noise suppression. The ignition system There are different ignitions with petrol engines, the usually most spread is those Battery ignition (coil ignition), also with the Harley. Structure of the battery ignition The battery ignition consists of an ignition coil, a contact or a transistor, the ignition cables, spark plugs and a mechanism, those for correct ignition ensures. Ignition coil The ignition coil is the heart of the ignition. 

  

One can do itself still so a mad if those purchase microprocessor-controlled ignition with twenty ignition curves etc. Ignition coil not the necessary energy to store can, is assigned trouble. Thus only times little theory. The energy of the ignition coil computes itself after the following equation. Two sizes are crucially for the magnetic field and thus for the stored energy. From the equation it is evident that the river is received squarely into the balance. Thus the increase of the river brings also a square increase to the energy. In that Practice is called that, one selects a coil with as slight a resistance as possible. Vehicles with starter and appropriate control are there already times coils also  or also less in the employment. We cannot make that however. W0,5  One limits the river for reasons of the life span of the contact for contact ignition  coils are common during contact ignition. With Won 3A. Therefore 5  electronic Ignitions permits one higher rivers, because the transistor these rivers scolded can. Crack point is then however the ignition coil and/or the energy dissipation in the coil. Became  a coil at 12V operates, gives that a river of 17A and Wone e.g. 0.7  one Energy dissipation of 206W. After a few seconds became it abrauchen. Thus limits . Wone the river, by selecting a coil with 2,5 to 3  By enlargement of inductance one receives also more Zündenergie. But that Relationship of inductance and Spulenwiderstand has influence on the switching on process the river. The river follows an exponential function, like with all saturation procedures. In the following example on-board tension is 14V, Spulenwiderstand of the primary winding  and inductance 10.4 mH. The time constant is thus 2.3 ms (L/R, W4,52  thus .)W10,4mH/4.52  After approximately 8 ms the Zündenergie 50 amounts to mWs. E.g. became one inductance. double (20,8mH), the Zündenergie would be 100 mWs. However only after 16 ms. higher number of revolutions does not have one the 16 ms available however necessarily. There thus are Borders set. At the Harleymotor one can work with good reason large inductances ), because the engine does not turn fast and onlyW(e.g. 14 mH with 3  two cylinders has. It come thus „slow “ignition coils to the employment.  coil of Dyna, W of a coil with a 3  WOne compares the energy balance 5  Crane or like it are called, results in that loosely the factor 2 in favor of  coil. Wthe 3  The burn introduction with the engine at operating temperature needs however only a small electricity. Therefore one notices no large differences there. To starting of the cold engine needs one however much energy. There one notices it already rather.

With the diagram one sees above that with the example after approximately 8 ms the river the final value reached. Thus maximum energy reached. It does not become more largely, also if the river flows longer. The energy dissipation of the coil rises however. Therefore is that Dwell angle so importantly. One „preserves “the coil, by one her not permanently under River sets. During the contact ignition the dwell angle is constant. Thus with small Numbers of revolutions rather too largely. Electronic ones work occasionally with a dwell angle Regulation. It keeps the time constant and not the angle. Then it gives (half) electronic ignitions, shear themselves not at all around the dwell angle, so that one  coil to drive must, because otherwise the energy Wit with 5  dissipation becomes too large. Strange to say is this ignition much likes (Dyna S). Ignition Differences becomes between contact and Transistorzündung (in Harleykreisen better admits as half and fully electronic device). The contact ignition has a quantity of disadvantages, in addition, some see advantages with it. We begin with the advantages. Is mechanical, one can repair. The voltage drop at the contact amounts to only 0,2V. The disadvantages are: - not maintenance-free - occasionally unreliable starting - bad operating attitude with the cold or engine not at operating temperature - Losses of energy at small numbers of revolutions (to slow opening of the contact) - Bad engine run at high numbers of revolutions (insufficient Zündenergie, see Coil) - Sensitive to contamination of Hochspannungsteilen, because Internal resistance of the ignition coil is larger During the electronic ignition one does not have all aforementioned disadvantages. Correctly dimensioned electronic ignitions outlast the life expectancy of an engine by far.

Well, an exception gives it. There is the so-called halfelectronic. With a transistor, the gate trigger time regulation is ignited effected however mechanically by means of disengaging mechanism with the well-known Fliegewichten. There is still Maintenance necessarily. Apart from the Dyna s are also here ignition  too Wcoils of 3  recommend. Spark plugs/ignition cables One takes the standard candles in the case of doubt. During the contact ignition are ignition cables with copper core still best. When electronic ignitions one should itself on the recommendation of the manufacturer hold. Usually are cables with carbon fiber core too use. Alternatively to it there are ferrous spiral so called cables. Have a smaller Resistance, absorb however sufficiently, because they have a high inductive portion. That is reached by the fact that the actual leader spiral around a core is wound. Ignition attitude „Correct “ignition depends of many influences: - Engine speed - Load of the engine (position butterfly valve) - Temperature of the engine - Temperature of sucked in air - Barometric pressure of announced air - Mixing proportion fuel/air - Kind of the used fuel That is valid for a given engine. Besides still further factors play a role, like e.g. compression ratio or the combustion chamber form. But that is not everything practically relevantly, because most ignitions with Harley only the number of revolutions to Determine the Zündpunktes consult. An example curve shows the following diagram of a Crane HI-4.