Programmable Ignition 253

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Page created by T Oct 21st 2007:

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Coil and Switcher. Click to Enlargen. Photo by LMH.

==Programmable Ignition 253:==

LMH has provided more fantastic info on Programmable Ignition. This time he's adapted the knowledge he applied on the EST VK to

a 253 V8 in an HJ.


Hi all out in old Holden land. I've been quietly working on the next project which was installing a Programmable Ignition on the 253 V8 in the Tonner. Good news is it's all installed and running now. After some tweaking things here and there, the results are starting to really show.
As you all might recall I first installed this on a VK EST Commodore, and the results were great. The 253 presented a few different challenges mainly as to what dizzy to use and how to modify it.


Distributor. Click to Enlargen. Photo by LMH.


More info on the Programmable ignition install.
Here's the Dizzy I used. You can see the rotor, and the slotted drum that spins through the Hall effect pickup. You can see the external connection to the distributor for the signal. I strongly recommend using quality shielded cable for the pickup signal, and the Map Sensor cable too.

===MAP Sensor:===

MapSensor. Click to Enlargen. Photo by LMH.

You need to install a MAP Sensor. This one is off a VK Commodore. 3 wires to it. 1)+5vdc 2)Signal 3)Ground. You really must use a quality shielded cable. I had access to a foil shielded cable which should be good in the electrically noisy environment of an engine bay. The vacuum line goes to direct manifold vacuum via a spare port on your plastic or brass tree. You may have to put a tee in if you have no spare ports on the manifold.

That relay next to the sensor switches between Alpha and Beta Spark Tables. The only reason it's next to the Map sensor is because I ran the wires up the same cable. (It's a 4 core + Shield)


===Rotor Button:===

Now Guys. Here's one you need to look at. I've modified this Rotor to have a longer leading edge. This is so as the spark advances it is still lining up with the appropriate post on the dizzy. It is possible to fire the spark before the rotor has reached the post in the dizzy. Remember I'm running Gas so I add plenty of early advance, more than you would originally have from factory. Some of you, depending on your Dizzy may not have to do this.

Symptoms of the nature of miss-firing under medium throttle are a sign your spark is missing it's mark.
I modified this one by taking the brass piece off another Rotor button, and drilling/filing it to fit. The donor brass part was from a Large Cap Blue/Black V8 Dizzy.


===Stock Rotor:===

Heres an image of the UN-modified rotor. If you look very closely you can see only the left half of the edge has blackened from arcing. It was a fair bet that at the higher advance levels the spark was having to jump across space to make it to the plug. (Not Good). The engine would mis-fire occasionally under these conditions. After the modification done above in the previous post, problem was resolved.



===Advance Plot:=== 

LPG and Petrol Advance Curves. Click to Enlargen. Photo by Shawn Goodwin.


Initial Thread






LPG and Petrol Advance Curve Chart


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