Transistor ignition? can someone identify?

[bassy]

I found this item at upi the other day and i am not completely sure what it does, or what benefits it has. it was hooked up to the coil and i assume it is a resistor.It has 4 cables coming out of it and is rather large just to be a resistor. its hooked up to a 4k with points. can anyone shine any light on any of the specs for this?

it says ULTRA, TRANSISTOR IGNITION

thanks, matt.

[Earlyrolla]

It would be a transistor assisted ignition module if that is what is cast into it

At a guess the module will use the switching signal from the points as an input and switch the coil via a power transistor.

The purpose... Well normal points will eventually wear on the contact surfaces due to the continual arcing resulting in degraded performance of the engine.

By using a solid state device like a transistor to switch the primary side of the coil the life of the points is greatly increased and the performance of the engine (well ignition system at least) should be more reliable.

[bassy]

thaks for the information earlyrolla, do you know how these things actually work? internal components ect? Would anyone know any sites that could expalin, and provide a wiring diagram.

thanks, matt

[gearb0x]

Adding to what early rolla said its possible it will increase the dwell time as well as create a stronger spark.

As for how that particular module works, i have no idea. http://www.siliconchip.com.au/cms/A_105632/article.html has details on their now updated HEI box whichs does pretty much the same thing though. The "older" kit which i just installed on my 2TG was "transistor" based, i assume that one has an IC to make it slightly smarter. That said, the old one i put on my 2TG seems to have made a noticible difference (that, or i have a case of modders denial)

[Earlyrolla]

The exact operation and circuit diagram will be somewhat unique to the manfacturer. If you want to know the circuit of the one you have then it will mean tracking down a suitable circuit diagram.

If it is a straight forward transistor assisted ignition it may or may not have dwell control. If it is a little more complex like the Silicon Chip one it could have a heap more features like the battery voltage compensated dwell control or the anti-theft device. In each of these cases the circuits will be quite different. However the basic coil switching circuit will be the same, unless you go to capacitor discharge ignition (CDI).

There is a diagram in the PDF of a very basic transistor assisted ignition kit. (9)
http://www.electronics123.net/amazon...nual_K2543.pdf

Without going into too much depth the operation would be as follows:

Case 1 - Points Closed
When the points are closed the pin 2 will be pulled to ground, this means the base of T1 will be at ground and the transistor T1 will be off. If T1 is off then base of T2 will actually be high meaning T2 will be turned on. This means that the primary side of the coil will be charging (storing energy in the coil's magnetic field) as there will be a closed circuit between the positive side of the primary coil and the negative side of the primary coil via T2 to ground. This is the dwell period - here you can see it is still determined by the operation of the contact set and not modified by any intelligent circuit.

Case 2 - Points Open
When the points open the base of T1 will go high as a result of the pull-up resistors. When the base goes high T1 turns on, the collector (where the diode D3 is connected) will be pulled low due to the current flow through the transistor. This in-turn turns off T2 as the base goes low, thus interrupting the current flow in the coil. The interruption of the current flow and consequently the collapsing magnetic field in the primary coil results in a high voltage being generated across the secondary coil - the ignition spark.

Hopefully that kind of answers your question

As for what is in the box you have I am guessing something probably pretty basic like the circuit above.

[timbosaurus]

As rolla said, The module is there to increase the lifetime of the points, and possibly increase dwell as well (but not likely).

Ignition systems need in the vicinity of 5-10amps of current to charge up the coil for 10 to 20 ms. Contact points can flow this current easily when fully closed but tend to spark/arc upon opening/closing which leads to burning out of the surfaces on the points. The condenser (capacitor) on the side of the distributor is designed to slow the instantaneous current flow when contact is first made but isn't always the most reliable method. The transistor is used to reduce the current flowing through the points all the time. Some transistors can allow up to 10amps to flow, with a base current of only 200mA, acting like a fast and reliable relay! Needless to say, if the current through the points is reduced by a factor 50(ish) the points will last a lot longer.

Without looking back at ur pics I would guess there would be 3 wires on the unit, one will go to the floating contact on the points, one will go to the primary side of the coil, and the other to ground.

If you are so inclined, it's much more fun and exciting though to use an Atmel and a map sensor (which you can conveniently get samples from freescale ) with the said transistor unit and make urself a programmable advance ignition module!

T.

[timbosaurus]

Oh, and as for what is actually in the box, most likely a BJT transistor... prolly a darlington pair of them. FET's are often used these days, but this unit looks too old to be using a FET. There would be some sort of over voltage protection to prevent damage to the transistor from the flyback voltage ( > 300volts between collector and emitter! ) which is normally a zener diode array. And a resistor or some sort of base drive circuit to limit the base current into the transisor. Nothing complicated i'd imagine.

Cheers
T.

[RWDboy]

Yeah i found one of those once in a friends garage. Didn't work though. I have a wiring diagram lying around somewhere, i'll try and dig it up for ya sometime.

[Tham]

I was using this one in the late 80's to early 90's
in my Isuzu Gemini. A friend had been using it in his
KE70 and gave it to me.

Ultra is one of the third-party transistor-assisted
ignition boxes made sometime in the 70's or so.
I remember I hooked up a dwell meter to it, and it
did extend dwell several degrees.

It's Japanese, I believe. Mitsubishi also made one at
that time, but had five wires and had a far better
and sophisticated casing/heat sink design. Two wires
went to each contact of the ballast resisitor. I used it
before the Ultra. Gave out after a few years though.

Nippondenso also made one with a simpler stainless
open-type box.

Looking at your first photo, it is a bit fuzzy. But I think
red goes to the coil positive, black to coil negative,
blue to the distributor and green to any good earth.

Mine gave out after a couple of years, but it does
improve points life a lot, just like the HEI unit.

[Tham]

You can try swapping the blue and black wires
if it does not work.