Megasquirt Support Forum (MSEXTRA)

Hi I have an 89 911 3.6l. I am trying to set up my initial settings in tuner studio. I am trying to find information on my cars cranking dwell, cranking advance, normal dwell and spark duration. I cannot seem to find this information any where. Could someone help me out on how to find this info or how to measure it myself or can I just use the settings that are preset in tuner studio




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maych87,

Change "Fixed Advance" setting to "Use Table". I would lower "Cranking Dwell" to 5ms. All the other dwell settings should work for you. Are you using the stock trigger wheel (on flywheel) and cam sensor? I am not familiar with those settings, but if you do a search on the MS3 forums I know this has been talked about. There is long post by Pelican member "billjam" who did MS3/MS3X install on 3.6L Porsche. He used Toyota cop's for a dual plug setup, which would not apply to you, but I believe he used the stock triggering setup for engine RPM's and cam input.

What sort of coil(s) are you using? It can be difficult to determine optimal dwell without knowing the primary resistance and primary inductance. If you're not sure, 3.0 ms is typically a good guess.

Matt Cramer wrote:What sort of coil(s) are you using? It can be difficult to determine optimal dwell without knowing the primary resistance and primary inductance. If you're not sure, 3.0 ms is typically a good guess.

Thanks for the input.

I am using the stock triggers on the flywheel and distributor. I am also using the stock coil which I cannot seem to find much info on. Is there a way to measure the primary resistance and inductance?

If I just use 3.0ms could this potentially cause damage and will I need to adjust this later or does it not make much of a difference?


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He used Toyota cop's for a dual plug setup, which would not apply to you,

The Porsche 3.6L engine is dual plug, and BillJam set it up that way with Toyota COPs. MayCh's engine would be dual plug unless he built it up from a smaller engine.

Ya, I forgot that the 3.6's were dual plug. My bad. I just assumed pencil coils were being used.

So, How are you going to connect your two coils to MS so you can control spark advance? What version of the MS main board do you have? The coils would have to be triggered together and the charging current would be quite high. I am not familiar with how Porsche controlled these. I wonder if the stock ECU just sent 12vdc to them or just grounded them (like MS would), or if the voltage was bumped up like a CD ignition. I did some checking and these coils are also used on 84' - 89' 911's; 944's; 968's and 928's.

As best I can remember from BillJam's thread on Pelican Parts BBS, the MS3X he used was capable of firing his COPs two-at-a-time as required by twin plugging. That uses the 5v circuits for switching the charging ON/OFF. The settings for charging dwell, etc, are all taken care of by TS and the MS ECU.

Actual charging is done by 12v which is where the additional capacity is required to charge two coils at once. The 12v circuitry must be modeled (I did it with Excel) to ensure that the total current required is within the capacity of the system being used. My LS2 truck coils charged sequentially used maximum of 7A per coil and 10A simultaneously if on the same circuit. Using two circuits to charge twin plugs should stay within that same amperage for EACH circuit, or 20A simultaneously from your central source. (Of course, with your coils the amperage may be higher or lower than my amperage, so adjust accordingly.)

I used 5 degrees of cranking advance, 4.3ms cranking dwell, and 4.3ms nominal dwell. (LS2 coils suffer from premature discharge if dwell is set at or above 4.5ms.)

Brian,

Yes, I drive two LS2 coils per cylinder for my twin plug setup directly from the MS3X spark outputs, but the input impedance is high for the 5vdc smart circuit that controls the coil. My settings a very similar to yours. I am using the D514 version, not the D585 truck version, which seems to have the over dwell issues. I had my nominal dwell set to 5.5ms and had no issues. But after all the reported issues I lowered mine to 4ms.

"billjam" went to all the trouble to build an interface circuit to drive two Denso/Toyota pencil coils per cylinder. But other people have done without an interface circuit, "xbmwguy" on Pelican Parts forum has done it with no issues for some time. And if you go to MS3Pro, the spark outputs can withstand even more current. I have been thinking of converting mine to Toyota COPs to free up some space in the engine compartment as 12 LS2 coil

My question to maych87 was how he was driving those two large coils for the 3.6. He would need to modify the 3.xx mainboard (if he has that version) or use an external igniter box to drive two coils at once.

I am very new to this and learning as I go. I have learned a lot in the last month. As far as I can tell on the original ecu the switched positive is pin 37 which powers two igniter control units. I am using a breakout box and have pin 37 wired to pin 28 on db37 connector.

Also, on the stock ecu pin 1 is an ignition pulse to output stage which appears to ground both ignition control units simultaneously, which I think is the way the ms3 works. I have pin 1 of the stock ecu hooked up to pin 36 of the db37.

If someone could let me know if that is going to work that would be great. I will attach the wiring diagram and connector.










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