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So if I am running an isolated/floating ground for the EFI portion - I'd imagine that the wire size vs load requirement would be downsized quite a bit when compared to the wire size / load requirement for the starter, lights, pumps and fans.

I'm thinking I could get by with a #6 wire for the isolated/floating ground portion, then go with an 00 run up to the starter/chassis itself. All sensors and the standalone computer get their own dedicated grounds running to the bus bar isolated/floating ground.

Does that sound right?

The only place I see a conflict is with the crank and cam sensors. Won't they see both grounds just thru contact? And can that negate the "floating" part anyway?

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I would think your right with the wire size.. as
for the crank and cam I dont know.. maybe Monte will
tell you

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Are sensors powered hall effect, or two wire, or?

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One thing I dont know is... since the battery is a
filter... the flow goes from neg to pos and we are
trying to isolate the neg... HOW far up the neg is
the battery still acting as a filter... maybe this
is what our issue is.. just guessing.. I dont know

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I have been fighting issues like Monty talks about. My stuff is grounded to the battery and I still fight it.
Once you get agressive with the tune (over 20 psi of boost in my case) the plugs are hard to light. And that energy will go somewhere when the plug stops firing.
I'm still trying to figure it out lol

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I am not sure I agree, I would rather have one reliable, properly sized, tested/measured ground, then, unless in an in an emergency, a random selection of undersized, maybe good grounds, and let the electrical devices figure which one is best. IE, if a ground is thought to be not correct, then any additional backup grounds have to all be the same proper size, thinking you can "share" or combine grounds is unwise and asking for future problems.

"static straps", are primarily for grounding static charges, not grounds.

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My point was not to have a bunch of undersize grounds. My point was its nothing wrong with adding a ground of the correct size even if you already have a ground of the correct size in whatever circuit you are working with. Hence the saying .....you can never have to many grounds. Ron

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I believe I understand your overall point, but the problem I see is when one has multiple grounds, often for extra assurance/back-up/whatever, unless they are all sized for the largest possible current demand, when one of the redundant grounds becomes less effective (corrosion, intermittent, loose, disconnected in error, etc), the current will then seek another ground with less resistance, and IF that ground is undersize, issues arise. Therefore My concept is just to have a single "great" ground path, and if a problem with that ground arises, the effect is immediate and maybe very obvious, and likely in a single location. That's why having a "lot" of grounds is not a goal for me.

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Directly to the frame is ALWAYS your best bet - for grounding everything. Least # of attaching points for the starter / alternator. Next best is something that is welded to the frame. Worst is something that is bolted to the frame. Doing voltage drop tests are always in order when doing / checking grounds.

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Not close to correct...........in fact that is the WORST way to wire a ground system. Just because people do it all the time and it is passable, does not make it right. Work with a lot of EFI cars as I do and you will quickly find the flaws in this type system. Your frame or sheetmetal is a TERRIBLE conductor.

What I do on all the EFI and actually everything I wire now, is a "floating" ground system. I attach a copper bus bar on rubber isolators under the dash. I run the cable from battery to bus bar and run all high draw grounds to this bar, such as ignition, pumps, fans, etc. I also tie both heads together and run a ground wire to bus bar as well. The ONLY thing I ground to the actual chassis or sheetmetal is the lights

Monte

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So Monte, are you saying that the only stuff that is critical to have the floating ground is the electronic stuff and not necessarily the rest of the analog stuff like starter, lights, fan, water pump, etc...? That's a whole lot easier to swallow than a complete rewire of a car to add EFI. Them wires under the dash are hard to get to on my junk, and the dash isn't coming out without cutting bars.

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I have been fighting issues like Monty talks about. My stuff is grounded to the battery and I still fight it.
Once you get agressive with the tune (over 20 psi of boost in my case) the plugs are hard to light. And that energy will go somewhere when the plug stops firing.
I'm still trying to figure it out lol

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What plug wires do you have?


Monte

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I'm sharing my 5v referenced sensors with both the factory PCM and the MS3X - with power and grounds supplied by MS3X. I'm betting my noisy TPS signal is from the sharing somehow. How the heck do I clear it up?

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I'm sharing my 5v referenced sensors with both the factory PCM and the MS3X - with power and grounds supplied by MS3X. I'm betting my noisy TPS signal is from the sharing somehow. How the heck do I clear it up?

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I would do a ground bus, with the bus ground feed striaght to the bettery. Only have sensors grounded on the bus.

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Noise can be a problem on any EFI car, but you add noise to the incredible cylinder pressure that you have in some of these cars that make 3000+ HP and you have a SERIOUS issue.

This is a typical thing we see, especially on THIS site. Guys have always done things a certain way, it works OK and when something different is suggested, they attempt to shoot that theory full of holes. Just because you have always done something a certain way, does not make it the right way for EVERY car out there.

I changed the way I wired cars, because I DID have issues on some high HP EFI cars with intermittent noise. So common sense tells you that if the changes were BETTER for EFI cars, they were better in general. At least that's how I looked at it, plus to me the "floating ground" deal is clean and easy. So what you have to string a couple extra wires. It makes trouble shooting SO much easier, because things are contained in a specific area.

As far as factory cars........who cares......I don't, because we are not talking about factory cars. Plus, when I worked for Dodge, I know our ECUs were directly battery grounded. Are they still??.........don't know, don't care.

So, you want to ground your whole car through the chassis or sheetmetal...........fine, no problem, but no need to try and prove it's the ONLY way or best way to do it

Oh yeah, forgot something and this is FACT not here say. The Holley Dominator ECU is capable of running factory LS coils. Millions of cars out there with LS coils. However, in a HIGH hp application, with high cylinder pressures, the "flyback" voltage from the LS coild was horrendous. Bad enough in fact, that we had to put a stupid amount of filtering in our boxes to keep the junky coils from smoking our boxes. So the point......what the factory cars have don't mean squat in a race car

Monte

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Directly to the frame is ALWAYS your best bet - for grounding everything. Least # of attaching points for the starter / alternator. Next best is something that is welded to the frame. Worst is something that is bolted to the frame. Doing voltage drop tests are always in order when doing / checking grounds.

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Not close to correct...........in fact that is the WORST way to wire a ground system. Just because people do it all the time and it is passable, does not make it right. Work with a lot of EFI cars as I do and you will quickly find the flaws in this type system. Your frame or sheetmetal is a TERRIBLE conductor.

What I do on all the EFI and actually everything I wire now, is a "floating" ground system. I attach a copper bus bar on rubber isolators under the dash. I run the cable from battery to bus bar and run all high draw grounds to this bar, such as ignition, pumps, fans, etc. I also tie both heads together and run a ground wire to bus bar as well. The ONLY thing I ground to the actual chassis or sheetmetal is the lights

Monte

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So Monte, are you saying that the only stuff that is critical to have the floating ground is the electronic stuff and not necessarily the rest of the analog stuff like starter, lights, fan, water pump, etc...? That's a whole lot easier to swallow than a complete rewire of a car to add EFI. Them wires under the dash are hard to get to on my junk, and the dash isn't coming out without cutting bars.

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bet they are not anywhere as sensitive as race ignitions. and how many different filters are they using? how confined are they?

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I dont know about the filters but its the low voltage
stuff that your trying to protect.. your dealing
with 0-5 volts or even 0-2 volts and the auto companies
run the grounds as said above... are they keeping it
clean with filters or not.. I dont know... I know
I had to deal with millivolt stuff on the fuel tank
(mainly the filler tube when it was plastic)

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That is the way Toyota/Lexus vehicles get away with grounding most of their 20-30 separate ECU's to the sheet metal. Most of the sensing circuits operate on a 5 volt reference signal so a sheet metal body ground on even the most sensitive systems is adequate. I'm kinda ground crazy on all my components on the Savoy I run ground points all over and most all of them can be traced back to my ground strap from the battery.
All that being said I still ground my battery to the bar in the trunk

Gus

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I have been fighting issues like Monty talks about. My stuff is grounded to the battery and I still fight it.
Once you get agressive with the tune (over 20 psi of boost in my case) the plugs are hard to light. And that energy will go somewhere when the plug stops firing.
I'm still trying to figure it out lol

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What plug wires do you have?


Monte

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The 409 Taylor's. Plan on switching to fire core this spring.
I was running Autolites and new plugs helped some. So now I have NGK plugs but waiting on March to see if there a little better.

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