Trigger Disk in a Distributor

There is nothing more stable, in terms of an electronic ignition system, triggering system; than a "crankshaft mounted", iron toothed, or "flying magnet", trigger wheel.  Stable, because there is no need, at all for a C.A.S. (Camshaft Angle Sensor), if You use a trigger wheel with a missing tooth, & run the ECU in a "Wasted Spark" ignition only, or EFI Ign & Inj mode.There is plenty of room usually, down on the crankshaft pulley, to mount quite large diameter wheels, which results in good clean On/Off spacings for either VR or Hall Effect sensors.

However, I must admit; that if You are a novice, & going to carry out this mod from scratch, with the engine in the car, It could be a lot more difficult, than with the engine out.  Wouldn't be nice, if You could just pull out the original easily accessible distributor; & replace it with a a distributor, that has been internally gutted, & actually has a multi-toothed wheel, & a CAS signal, therein.

Now that concept is nothing new; as some early Nissan distributors had such an arrangement, with a stainless steel plate, with slots punched through them, with a LED light souce on one side, & a photo electric diode or transistor, on the other side. 

http://datsun1200.com/modules/mediawiki/index.php?title=Nissan_Optical_CAS

I know years ago, I played with them, but ultimately gave the idea away, as "oil fog", coming up the dissy shaft, would create fogging of the light sensor, which resulted in missing & the like.  I know Simon, down in Tassie used to play with these, like me; as I researched the subject on Rollaclub, & came across Simon's original threads & pics.

So Altezzaclub had a problem on His 4AGE engine where the dissy, hangs out over the side of the engine, very close to no: 1 exhaust header, resulting in it getting pretty hot. (actually bloody hot)

The particular dissy He had, had the early Toyota ignition system which used two VR (Variable Reluctor) sensors) to sense 4 off teeth on one trigger wheel, & 24 teeth on the rotational speed & positional wheel.  The whole concept, was to use the 4AGE dissy, as an input device to a Haltech Sprint 500 ECU, & use COP ignition coils, removing the need for distributor cap, & HT spark plug leads, altogether.  Now It was a tight ask, but as the pictures atest, but I was able to get two smaller, robust commercially available, Hall Effect sensors in there, from a ATV.  I ground 3 of the teeth off the four (4) tooth wheel, to produce a single CAS signal for the ECU, from the remaining single tooth. The 24 teeth, then produced a clean pulse train for the ECU input, to determine crankshaft RPM, & position.

Note the temperature sensor, to see how hot it gets in there, once it's back in the car, & running.

Here is the output of the Hall Effect sensors.  Nice clean sharp 5V DC pulses.

Actually, at one stage, I was hoping to get a magnet disk in there using assymetrical Rare Earth magnets, with the Hall sensors poking down through the lid on the top of the 4AGE dissy, but working with the assymetrical rare earth magnets, is a steep learning curve, I discovered. (assymetrical magnets have their N & S poles, on the "curved" outside of the magnet, rather than on the conventional round ends).

Cheers Banjo

Edited March 19, 20251 yr by Banjo