MS3X wiring considerations

[Yves]

I'm trying to convert to MS3X from MS2. Currently I have MS2 setup via a relay board and I run a second EGO to one of the MS2 adc's and the other adc is occupied by the baro.

When going to MS3 I would like to use a maf. The maf I have is a GM frequency type. I'm also going to use LS1 coils with the factory wiring and some dedicated pigtails.
My third change will be the use of the Vortec 96-2005 distributor as a cam sensor with dedicated pigtail.

As far as the wiring scheme I found in the manuals, it seems that :
- I have to disconnect the grounds of the injectors and connect them to inj A-G respectively in the firing order. 12V+ for the injectors can stay on the power from the relay board as is now the case Correct ?
- I have to connect the sprk A-H wires to the respective pigtails of the ls coilpacks right ?
- I have to supply the coils with a fused and switched 12 V and ground. Currently I'm running an HEI 8 (tpi type) that gets it's 12V+ to the coil from the original 12V+ that supplied the single coil of HEI ignition that originally came with the car (mech+vacuum advanced). I assume that I can use the 12V+ fused source to supply the 12V to the coils and run the ground to the engine ?
- I assume that the signal from the Vortec distributor goes to the nr 32 wire of the ms3X harness which says that this is for the cam Hall sensor. The ground for this one says that it needs to go to the main DB37. Can I assume the ground for the old HEI 8 ign can be used as ground for this one and the 5V source from the same old HEI 5V supply ?
- Can the GM maf signal be connected to the PT4 ? On the wiring it says that this one is an output....if not which one to use ?
- Where do I connect the Hall sensor for the crank trigger wheel ? To the tach input on the relay board ?
- as for tach output, it seems that I use wire number 26 from the ms3x db37 to the tach. The explanation in the manual states that sometimes a coil is necessary. I use a VDO rpm gauge. Would I need that one ?

The the following :
As I currently I'm searching for a suitable crank trigger wheel, I was thinking of using my HEI untill the time comes to switch the ignition and fuel to sequential. If I install the wires for the injectors as per ms3X schedule. Can I still use batch fire in combination with the HEI 8 ?
I aslo have an issue that for the HEI 8 there is a jumper wiring running from the 5V pad under the ms2 daughtercard to teh number 3 pin on the JP1 on the main board. This interferes with the installation of the MS3 daughter card. Can I put this wire on PAD5 which seems to be 5V as well ?

I have 2 wires from the JS4 and JS5 running through 2 openings in the case. The spare SPR connections will be used for the 2 knock sensors. Can I run the wires from JS4 and JS5 via some other pin that is not used (28-30 on the ms3X for instance ) ?

Sorry if this may have been explained somewhere but sometimes it's frustrating to combine all of the info to a workable solution where other may have gone through this before.

Thanks in advance.

[Matt Cramer]

As far as the wiring scheme I found in the manuals, it seems that :
- I have to disconnect the grounds of the injectors and connect them to inj A-G respectively in the firing order. 12V+ for the injectors can stay on the power from the relay board as is now the case Correct ?
- I have to connect the sprk A-H wires to the respective pigtails of the ls coilpacks right ?

I'll assume that seven fuel outputs and eight spark outputs was a typo and not a very bizarre seven Stromberg intake manifold reworked for EFI. Other than that, this is correct.

- I have to supply the coils with a fused and switched 12 V and ground. Currently I'm running an HEI 8 (tpi type) that gets it's 12V+ to the coil from the original 12V+ that supplied the single coil of HEI ignition that originally came with the car (mech+vacuum advanced). I assume that I can use the 12V+ fused source to supply the 12V to the coils and run the ground to the engine ?

Yes. Best to ground the LS1 coils to the cylinder head they'll be used on.

- I assume that the signal from the Vortec distributor goes to the nr 32 wire of the ms3X harness which says that this is for the cam Hall sensor. The ground for this one says that it needs to go to the main DB37. Can I assume the ground for the old HEI 8 ign can be used as ground for this one and the 5V source from the same old HEI 5V supply ?

You will want to run the ground to sensor ground and not power ground, and supply 5V from VREF.

- Can the GM maf signal be connected to the PT4 ? On the wiring it says that this one is an output....if not which one to use ?

PT4 can be an input or an output. It will work with a frequency based MAF but not a voltage based one.

- Where do I connect the Hall sensor for the crank trigger wheel ? To the tach input on the relay board ?

Yes.

- as for tach output, it seems that I use wire number 26 from the ms3x db37 to the tach. The explanation in the manual states that sometimes a coil is necessary. I use a VDO rpm gauge. Would I need that one ?

Probably not, but it's not always easy to predict.

The the following :
As I currently I'm searching for a suitable crank trigger wheel, I was thinking of using my HEI untill the time comes to switch the ignition and fuel to sequential. If I install the wires for the injectors as per ms3X schedule. Can I still use batch fire in combination with the HEI 8 ?

Yes.

[Yves]

Matt,

As I run the gm hei 8 with the specific wirekit that you supply for it : can I use the 5V from the PAD5 ? The terminal for the 5V+ wire next to the ms2 daughtercard interferes with the ms3 daughtercard in that location. PAD5 would be a better alternative and the board says it's 5V.

[Matt Cramer]

If that's a V3.57 board, just rejumper it to use VR input and use the MS3 settings.

[Yves]

A couple of questions regarding the hall sensor and cam sensors.

I use the DIYautotune hall sensor and a vortec distributor 96-05 with cam sensor.

What power supply do these need and does the cam sensor need a pull up resistor ? If so how much and where is this place ?

[Matt Cramer]

Our sensor just needs 12 volt switched power and no pull up.

Unsure on the Vortec cam sensor.

[Yves]

I've tested it with a lab power supply at 5V and it seemed to work. Any reason to use 12 V ? Better resistance against noise ?

[dontz125]

Basically. A lot of users have reported improved resistance to noise, and there's been a few who've reported increased speed / frequency (going past a limiting speed).

[Yves]

Basically. A lot of users have reported improved resistance to noise, and there's been a few who've reported increased speed / frequency (going past a limiting speed).

Can I assume that the ms3 can handle the 12V and associated amps ?

[dontz125]

With the additional series resistor, yes. Like I said, the extra voltage gets dumped to the Vcc rail and then to ground, and the current is single-digit mA.