Megasquirt controlled spark advanced with stock distributor?

[hacki81]

Hi,

First of all, i read up a lot on the different methods of ignition control with megasquirt, but to be honest, the more i read the more confused i got.

I want to build myself a 4 cylinder 4 strocke engine based on a VW 827 block with megasquirt injection & ignition control. For various reasons i'd like to use a distributor ignition.
I know of one Audi engine with a distributor based electric map ignition system. The distributor of said engine is fixed - it has neither a vacuum nor a centrifugal spark advance, so i'd guess it'd be perfect for megasquirt ignition control.

Problem is: it's got a bosch hall sensor with a 4-window rotor, but one of the windows is slightly larger than the others, so megasquirt would get an uneven signal. I read somewhere that this wouldnt work?

Now i'm wondering how i would get a good ignition advance control on that engine with said distributor. Do i need something like a 36-1 trigger wheel or would a TDC sensor be sufficient? Or would a modified rotor in the distributor do the trick? ( or would one of these things work?)

Regards

[trakkies]

It would be best to use a crank sensor as this removes the 'slop' of a dizzy drive and gives more accurate and consistent timing. The dizzy then just sends the spark to the correct plug.

[Matt Cramer]

You can use a distributor with unequal length vanes provided one edge - either leading or trailing - is the same for all the points. You just have to set the correct Ignition Input Capture edge.

[hacki81]

It would be best to use a crank sensor as this removes the 'slop' of a dizzy drive and gives more accurate and consistent timing. The dizzy then just sends the spark to the correct plug.

Thats what i read and thought.. A 60-2 trigger wheel with hall sensor should do the trick then?

You can use a distributor with unequal length vanes provided one edge - either leading or trailing - is the same for all the points. You just have to set the correct Ignition Input Capture edge.

Interesting. Thats the reason why i asked here. Something i havent read before while i was reading up on that topic. Unfortunately i dont have said distributor right here so i cant measure the vanes just yet. I'll keep that option in mind though, tanks.