How many grounds to engine are needed MS3X?

oldskool · Post by **oldskool** » Fri Apr 11, 2014 2:51 pm

Hi, I'm in process of routing all wires to engine compartment thru firewall with 41 pin bulkhead connector. MS3 harness has 15 wires needed without the 13 grounds from pins 7-19, MS3X harness also has 15 wires needed without the 5 grounds in diagram. I'll be running sensors, IAC, HEI 7, relays, bank 2 bank injectors(V8), with the 8 MS3X injector wires for possible future sequential. Thanks,
David

Post by **muythaibxr** » Fri Apr 11, 2014 10:01 pm

Run as many as you can. You need everything you can get from the ms3x board as well as the mainboard. Run them separately all the way to the ring terminal that you connect to the block.

oldskool · Post by **oldskool** » Sat Apr 12, 2014 8:50 am

muythaibxr wrote:Run as many as you can. You need everything you can get from the ms3x board as well as the mainboard. Run them separately all the way to the ring terminal that you connect to the block.

Thanks for reply, since I have more grounds than available pins left, I'll run all grounds together to a heavier gauge wire, to a pass thru terminal at firewall, then to ground at engine.

rabid · Post by **rabid** » Sat Apr 12, 2014 3:00 pm

I would actually try to run them separately to a common point in the engine. I've seen stuff like that on the oem. I don't know if it is for cost or because it is better. One less splice at least.

Post by **muythaibxr** » Sat Apr 12, 2014 8:23 pm

oldskool wrote:
muythaibxr wrote:Run as many as you can. You need everything you can get from the ms3x board as well as the mainboard. Run them separately all the way to the ring terminal that you connect to the block.
Thanks for reply, since I have more grounds than available pins left, I'll run all grounds together to a heavier gauge wire, to a pass thru terminal at firewall, then to ground at engine.

I specifically said run them separately because it works better. Also, do not ground at the firewall and then the engine, that can cause ground loops. Ground only to the engine.

Ken

dontz125 · Post by **dontz125** » Sat Apr 12, 2014 8:53 pm

He's using a pass through terminal, the electrical equivalent of a bulkhead tubing fitting. It's insulated and isolated, so he isn't grounded at the firewall.

S.Bretz · Post by **S.Bretz** » Wed Apr 16, 2014 5:40 pm

muythaibxr wrote: run them separately because it works better.

Ken

I will take note of this. I think I put a few wires together and ran a couple larger grounds out the engine on my last setup. I never had issues, but I'm sure I probably got lucky then. My very first install had some "sloppy" grounds and it got better when I cleaned it up some, but it still wasn't separate wires all the way to the terminal...but if you say to run separate wires for each ground, it can only get better right?
What is the reason/theory to separate them? What makes it "better?"

elutionsdesign · Post by **elutionsdesign** » Wed Apr 16, 2014 5:50 pm

Individual wires have a higher current handling capacity. Research has shown that electron transfer is a surface thing, not a bulk thing, so the more surface area (wires) you have the better.

S.Bretz · Post by **S.Bretz** » Wed Apr 16, 2014 6:16 pm

makes sense. Thanks

Megasquirt Support Forum (MSEXTRA)