Grounding my car. Lets start over.

So I caused some issues on my car by hastily installing the MS3 box. Lesson learned, don't rush.

Please share your ideas and set ups for how you've got your EFI car grounded. I need ideas.

Alex if you want some pics, i'll probably just go ahead and text you some pics lol!

Im gonna start with the engine grounds, in this pic you can see I have a cable from each head going to a common bellhousing bolt which then has a 1awg cable hanging off that then goes to a through firewall isolated junction stud. Also you can see another cable hanging by the starter, it is the charge wire for the alternator that went through a grommet in the firewall and connected to a 160A marine grade resetable circuit breaker. Those cables were all hand made out of 4 awg shielded cable I got from an implement pivot/generator ag business.

ok.. your engine block needs to be grounded directly to your battery, both heads should be grounded to each other and then connected to the ground on the block.. ALL modern electronics should be grounded to a wire that is touching the battery. direct grounded

Your right, but I was'nt finished. The pic below shows the through firewall junction on the dash side.

From there another 1 AWG cable goes up to my buss bar that is isolated from body. You can also see the alternator charge wire connection at the breaker to.

Here is the best pic of the buss bar itself, you cant see it but there is another identical 1 awg cable connection in the lower right corner of the buss bar and THAT cable goes directly to the battery in the trunk.

As far as the Gold box is concerned, you run both + and - wires for it directly to the battery posts.

Not a Gen 3 car but I have an MS3X on my car.

I originally wired it like the manual says, with the grounds going to the back of the cylinder heads. It worked fine or so I thought, I had issues with Datalogs not working properly and reseting all the time. I also had an occasional backfire on startup as well.

After speaking with a well known MS guy he told me the manual is wrong and to remove the grounds to the engine. I did that and ran them off of a dedicated 12 gauge wire that goes to the battery. The only thing on that ground is the MS3 and my Wideband unit(LC2). This took care of the data log problem and the backfire issue.

I initally had my MS3 grounded to my grounding block but then moved it to the heads just because the instructions said so.

I may try to move the grounds back to the grounding block so its a more direct path to the negative post, maybe lose some weight in the process

Highly suggest running MS3 + and - 12 awg wires direct to battery posts. Doing this decreases the current load on ALL the component inside that box, ie eliminates heat as much as possible. Im not gonna say my setup is the end all be all, its the first time ive went full retard on a ground strategy like this on one of my builds. One thing I might add to mine is another cable from the starter housing to the firewall stud. Having my battery in the trunk since this car was first ever fired in like 1997, when i did the Gen III swap I changed out all the old cables with 1 AWG hi strand solid copper GOOD cables, ran the 4 awg charge wire from the alt. and it terminates under the dash at my pos 12V junction bar and my pos cable goes from there to battery. Another pos cable goes from there to another through firewall isolated junction stud on the starter side of the firewall. Another 1 awg cable goes from there to starter stud. I have always had a pretty big discrepency between voltage reading at alternator output and at the battery post in the trunk. At one time it was so bad it 14v at the alternator and 13.1 at the battery post, and back then I even had a 8 awg wire that ran direct from alt to battery post. My current setup shows 14.5v at alt and 14.1v at battery post at idle. I did something right here.

I an important thing to remember is that devices feeding info to your ms need to share the same power and ground as the ms unit. A wide band controller is an example of that.

I gotta ask a dumb question so I can learn something. What is the reason you would use an insulated stud on the ground cable where it goes thru the firewall to the bus bar? Would you not want the body to have multiple ground points, such as a cable from the battery to a rear frame rail, along with the one you wisely provided all the way to the bus bar? Is this well thought out grounding system something that would benefit a factory ECU running the GenIII Hemi in my Duster? I haven't gotten to the wiring phase yet, and trying to learn all I can beforehand.

Monty did a good write up i the race section with lots of people chiming in.
I'll see if i can find the post.

Do a google search on 'ground loops'. Sometimes more is not always better.

Anything grounded to the body will then have the body as a giant amplifier of NOISE to contend with as a result. Only thing NOT grounded to my buss bar on my car are my marker lights and tail lights. Only reason a cars body was/is ever used as a grounding point was simply out of convenience, not because of better function. And in the good ole days pre EFI and DIS and ECU's, RF noise from body grounds would on their worst day maybe make a radio station static'y.

This is BMW's strategy [E70 X5] for localized grounding points. There is just one ground cable from the battery to the chassis on those vehicles, and they are about as loaded up with electronics as they can get. From one I understand, the same strategy still applies today.

Chassis grounding seems to work fine along with a few twisted wires to critical components [ABS/SRS] and shielded wiring for finicky sensors [wheel speed, Crank, Cam, etc.] to cut down on noise interference.

I think OE wiring/ECU/sensors etc. have WAY more shielding/isolation built into the components themselves than the aftermarket stuff. I went the route I did because I trust Montes experience with the exact same style of cars/components that I am using. That and a 45 yr old body that still is probably 95% original as the day it was stamped together except for the 45 yrs of rust that I know damn good and well is there in those places you cant see. Another thing that made my decision was this simple thought, how many times have you heard or even wondered yourself when you or someone else has an electrical issue or phantom gremlin with their car and said " I bet its a bad ground" or "something isnt grounding right"? Im happy to say I can look at every single ground connection on my entire car in about 53 seconds.

Found his thread.
Very good read!
Unlawful section "Car wiring"

What has worked well for me (also posted in the race section thread).

ECU and ignition box grounded to battery via heavy cable (#2). I run battery in trunk with a frame ground in the trunk plus a heavy ground cable to the left front frame rail. At that point I installed a stud just above the frame rail that catches the heavy flange of the rail. From that stud another heavy cable to engine block at the factory ground location. I clean the block at the ground location with a flat file and keep it greased and tight for good connection.

The ECU and ignition box are grounded to the stud in the engine compartment and have direct path to the battery via heavy cable. The unibody gets a solid ground front and rear that takes care of everything else.

No ground issues.

Makes sense, and thanks for the replies. I'm an old guy who thought Mopar Performance electronic ignition kits were a big upgrade......so this new stuff is fascinating to me!