ground wiring question

[Yves]

MS3X, V3.57, relay board

I have an MS3X setup that has main power provisions, ground, tps, O2, CLT, IAT and such connected through the relay board. The relay board has 6mm² cable going to one of the cylinder heads on my engine that is grounded to the chassis, which has a connection to the Batt -.

I wired up the MS3X ground wires to the same cylinder head.

Some sensors ground go back to the same 6mm² ground wire of the relay board, as well as all the ground wires for the shielding of some sensor cables.

I'm currently having some issues, which are related to noise (I think at least).

My questions are the following :
- could the direct connection of the MS3X ground wires be causing the noise ? Would it beneficial to connect them to the same 6mm² ground cable of the relay board ?
- do I need to connect the shields of the cables elsewhere than the 6mm² ground cable to prevent noise ?

Thanks

[dontz125]

The sensor ground can be one wire, several wires, or several wires that combine into one - but all sensor ground wires should connect directly to the MS itself. Not the head, or the chassis, or the battery, or the relay box.

Please see the grounding scheme page in the manual.

[Yves]

My ground scheme is as follows : MS =>relay board => engine
and MS3X => engine

the standard sensors, CLT, IAT, TPS, iac, O2 have their ground at the relay board.

The sensors that have no direct available connection on the relay board pcb are connected directly to the ground wire from the relay board to the engine. So essentially those have the same ground.

Hope this explains it a bit better.

Are you saying that I should run the ground (12V and 5V) first to the ms and then back over the relay board to the ground ? I'm not sure if that would make a difference, but I might be wrong.

Also I have both the crank and cam sensor on 5V. Would I need to put those on 12V ?

[Yves]

I'm going to do the following : put all the 5V sensors over TPSreturn/CLT ret/IAT ret to ground.

The only question I still have is where do I put 12V ground to or doesn't it matter ??

Another remark:
I have been looking at the schematics of both the V3.57 and the relay board. The grounds of the relay board (top section of the DB37 go directly to the ground pins on the relay board and over the relay board pcb to the ground terminal of the relay board, where I have the 6mm² wire to the engine block connected. This has me wondering whether there is actually a difference.

More even, do the ground wires of the MS3X (which is seperate set of wires) have to go to the relay board first before going to the engine ground ? The cam sensor and others are connected over the ms3X so this could be an issue as well.

[dontz125]

If the cam and crank sensors are Hall types, I believe they should ground directly to to the MS. The MS3X wires should ground at the head; while there is no theoretical difference, the addition of a set of connections can cause issues.

[Yves]

I'm currently getting the sync loss warning that that the missing tooth is in the wrong location, so this could be the cause ?