Autosport Labs

Hi Guys

I'm also wanting to fit dual EDIS-6 to my V12 and am also researching the MLJR option. Obviously, one would like to get away with a single MLJR unit for ease of programming. Now, I can see that fitting one trigger wheel with dual VR sensors will keep the two EDIS-6 units happy and provide correct base timing for each of the banks.

I am however concerned about the <b>phasing</b> of the SAW signals for the two EDIS-6 units.

As I understand it, for EDIS, the SAW signal has to go high immediately as the PIP signal goes low.

Now I can see this being the case for, say the A bank EDIS system, but the SAW signal for the B-bank EDIS system has to phased correctly with respect to the PIP signal coming from the B-bank EDIS-6 (which should follow 60 deg after the A-bank PIP signal), which implies dual PIP inputs and dual SAW outputs for MLJR?

The idea is to have two MJLJ units.

You gonna have 1 trigger wheel, two sensors (mounted 60 degrees apart), each sensor goes to its own EDIS unit, each EDIS unit connects to its own Megajolt and coil packs.

That seems to be the reality of running 12 with something that is made to run 6. To use a single Megajolt I guess some electronic wizardry should be employed, Brent is good at that.





Maybe using Aston Martin computer would be easier? Megajolts would do the same thing, but you have to look at overall cost, cheaper is always better.

The phasing between SAW and PIP doesn't matter. The only requirement from the EDIS is that if it doesn't get a SAW signal for a certain number of revolutions, it reverts to 'limp' mode. I think a megajolt should drive two EDIS SAW inputs, but if not, a little buffer circuit should sort it out.

From what I have read, it seems that the absolute phasing of SAW relative to PIP is not critical, but there are certain times when SAW can't be transmitted.
See <A HREF="http://www.dainst.com/info/edis/edis.ht ... is.html</a>, in particular this bit:
<I>The Ford patent says that the SAW is communicated to the EDIS module approximately 10us after 10° ATDC. This is to ensure that there are no spark events occurring, since the SAW accumulator can not be set externally while it's being read or cleared.

The SAW can be communicated at any time other than during a spark event. Also, the SAW will be stored in the EDIS module so the advance does not need to be updated every cylinder event. The EDIS module MUST receive a SAW signal from the ECU within 5 cylinder events or the EDIS will default to LOS mode and 10° BTDC spark advance. </I>

So it may work with a single Megajolt, but only if the requirements for the timing of the SAW signal can be met for both EDIS units simultaneously.

mcleodjm wrote:Hi Bart,

Is it possible to get away with only one trigger wheel and 2 sensors?

Have you thought yet about where to install the trigger wheel? I have a GM alt in place of my airpump and an electric fan so I have two positions on my crank pully that are unused, I have been looking into haveing a custom pully made for the trigger wheel(s).

Justin

FWIW: Fitting dual EDIS systems on the Jag V12 (or possibly other engines) has now been done, with a single Megasquirt-2. However, the same solution can be implemented with a single Megajolt or any other ECU capable of controlling an EDIS based ignition system. The key is having a circuit to delay the SAW pulse to the second EDIS module until after its PIP falling edge.

Kind regards
Philip

The whole story is here: http://forums.jag-lovers.org/av.php?966641o15