[Prev][Next][Index][Thread]
Hi Tech Ignition Stuff
<<<< I'll let this post go since it has so much info on igintion coils and
this is a "hot" topic these days. However, please direct replies that are
not Tesla coil related to the people who are interested and not to the
Tesla list. - Terry >>>>
Hi Gary, All
Newer ignition systems (well the HEI has been around since the end of ī74)
donīt use points at all. They all use pure solid state stuff because of
maintainence free operation. (Meaning more bucks for less work at service
intervalls)
Iīll only try to "touch" each system out there, without going into the details
too much (otherwise Terry will kill my post, because he doesnīt want car stuff
on his list)
1.) HEI systems. The spark is controlled via a reluctor wheel running inside a
pointed cage around which a pickup coil is wound. This low voltage triggers an
SCR switch, which in turn fires the coil. Pretty effecient self contained
system (everthing is inside the distrib cap). Spark voltage starts to drop off
above 4500 rpm.
2.) Magnetic crank trigger systems: A pointed wheel is connected directly to
the crank (eliminates cam chain stretch error, etc). A blunt point magnetic
sensor picks up the individual pulses and transfers them to the ignition box
(low voltage/high current amplifier). Very high tech, low jitter system. Good
for rpms up in the 12 grand range. Timing accuracy in the +/- 1/4° crank
revolution range. A lot of really high tech systems (like mine) go a step
further to a distributerless system. 4 igniton coils fire those nice american
V-8īs. No distrib cap and finger to wear out, no timing accuracy losses, due
to a misaligned rotor and cap electrode (yeah, about 95% of the distrib
systems WILL have lots of losses to to misaligned cap and rotor) And no
voltage losses(due to ionization, etc), either. Last but not least no problems
with coil saturation.
3.) Mallory type systems (which I donīt like for various reasons): These use
an infrared LED and a shutter wheel to pick up the individual pulses. Okay for
use to about 6000 rpm. Much above this and the timing accuracy rapidly goes
down the drain. Very sensitive to dirt and moisture.
4.) Old points type: This was a simple (very maintainance intensive system)
mechanical switch, where a lobe on the distrib shaft opens the switch at the
right time. Horrible dwell values, as the points wear down the ignition pulses
get worse and worse. No good for high speed operation.
5.) Unloaded points type (transistor ignition) : This system still used the
points type switch, but in this case the points do not switch the high
ignition coil current any more, but only the base current of a power
transistor. Same as above, except the losses at the points are less and they
donīt wear out as fast.
6.) Hall Sensor trigger systems: These systems work similar to the magnetic
crank trigger systems, except they donīt use a simple coil as a pickup and a
toothed steel plate as a trigger. Instead they use a Hall sensor. The biggest
advantage they have is that the pulse is nice and clean (the Hall switch acts
similar to a Schmidt trigger and shapes the pulses "internally") and the
output of the sensor is much higher than the magnetic pickup. Which means less
misfire and the wires to and from the sensor are easier to route in the engine
bay (lots of EMI floating around). However they arenīt any good for super high
rpm operation and the Hall switch itself is is very suspectible to magnetic
interference. Last but not least you need "flying" magnets on the trigger
wheel. (i.e. harder to balance and magnets donīt really like being flung
around at high speeds).
I donīt think any of these systems would be really suited for DW Tesla Coil
trigger usage. Solid state Tesla coils might be able to use the one or other
system.
However I donīt think they are worth the trouble to setup, because you can go
for an SCR/MOSFET pulse controlled circuit and adjust the timing (in/out of
sync to the mains) via a simple triggered NE-555.
Coiler greets from germany,
Reinhard