Re: Grounding for battery in the trunck?
[Re: Duner]
#1722072
01/08/15 05:31 PM
01/08/15 05:31 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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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?
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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Re: Grounding for battery in the trunck?
[Re: MR_P_BODY]
#1722074
01/08/15 05:35 PM
01/08/15 05:35 PM
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Joined: Jan 2003
Posts: 5,765 Hot Rod Ridge
FastmOp
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Hot Rod Ridge
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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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Re: Grounding for battery in the trunck?
[Re: jcc]
#1722075
01/08/15 05:52 PM
01/08/15 05:52 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Are sensors powered hall effect, or two wire, or?
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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Re: Grounding for battery in the trunck?
[Re: FastmOp]
#1722076
01/08/15 06:04 PM
01/08/15 06:04 PM
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Joined: Nov 2004
Posts: 6,890 North Alabama
Monte_Smith
master
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North Alabama
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Quote:
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
What plug wires do you have?
Monte
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Re: Grounding for battery in the trunck?
[Re: jcc]
#1722077
01/08/15 06:34 PM
01/08/15 06:34 PM
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Joined: Jan 2003
Posts: 27,421 Balt. Md
383man
Too Many Posts
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Balt. Md
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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.
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
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.
I understand your point also. I guess what I like about having a second proper ground is I kinda look at it like back-up. Like an eng to body ground. If for some reason one is left unhooked or the bolts left loose then with a back-up ground everything will still work. And if both are done right and working with good clean connections even better. Not saying do it as a bandaid just that it cant hurt. I dealt with alot of body ground problems over the years working at the Dodge dealer where even with a good looking tight connection you could only find the problem doing a voltage drop test. We had problems with Dodge Vans doing some weird things and finding grounds through the strange places causing some trans and wheel bearing problems so I always made an additional ground and put it on them myself after cleaning the factory ground. Ron
Last edited by 383man; 01/08/15 06:37 PM.
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Re: Grounding for battery in the trunck?
[Re: 383man]
#1722078
01/08/15 06:40 PM
01/08/15 06:40 PM
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Joined: Jan 2003
Posts: 27,421 Balt. Md
383man
Too Many Posts
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Posts: 27,421
Balt. Md
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You know with the digital race ignitions and all the electronics on race cars its easy to understand about having good proper grounds.
I would say its why MSD tells you to ground the ground and put the red power wires on their units right to the battery. I see alot where guys dont do that and some get away with it but there is a reason they want the main ground and power wires put right to the battery. Ron
Last edited by 383man; 01/08/15 06:42 PM.
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Re: Grounding for battery in the trunck?
[Re: Monte_Smith]
#1722079
01/08/15 06:49 PM
01/08/15 06:49 PM
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Joined: Feb 2014
Posts: 655 Huntsville, AL
Airwoofer
mopar
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mopar
Joined: Feb 2014
Posts: 655
Huntsville, AL
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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.
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
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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Re: Grounding for battery in the trunck?
[Re: Monte_Smith]
#1722080
01/08/15 10:41 PM
01/08/15 10:41 PM
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Joined: Jan 2003
Posts: 5,765 Hot Rod Ridge
FastmOp
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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
What plug wires do you have?
Monte
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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Re: Grounding for battery in the trunck?
[Re: FastmOp]
#1722081
01/09/15 12:25 AM
01/09/15 12:25 AM
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Joined: Nov 2006
Posts: 733 jacksonville,FLORIDA
slammedR/T
super stock
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super stock
Joined: Nov 2006
Posts: 733
jacksonville,FLORIDA
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Mont is right, in factory efi vehicles the modules all have a seperate ground going to the battery. They are joined to gether with a splice comb. the body/frame is grounded and the starter and engine and fan motors, etc.. use frame/body grounds. On computer data lines they are ALL twisted pair and on the newer CAN bus sytems the ecm and bcm(some times the ebcm) will have a 120 ohm resistor in both modules, these resistors make the the data lines have even less noise. Also a sensor ground is not a standard ground, it will have an inline transistor to remove noise and it is a "higher ground threshhold" than a normal ground. Then when you get into 5v referenced systems and double redundant 5v reference systems your head starts to spin LOL!
Last edited by slammedR/T; 01/09/15 12:42 AM.
2000 Dakota R/T, 408 magnum, 727, Indy heads 1000cfm 4150 carb, 93 octane fuel. motor; 10.258 @ 132.78 200 shot; 9.262 @ 144.69 racemagnum
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Re: Grounding for battery in the trunck?
[Re: Duner]
#1722083
01/09/15 12:46 AM
01/09/15 12:46 AM
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Joined: Nov 2006
Posts: 733 jacksonville,FLORIDA
slammedR/T
super stock
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super stock
Joined: Nov 2006
Posts: 733
jacksonville,FLORIDA
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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?
I would do a ground bus, with the bus ground feed striaght to the bettery. Only have sensors grounded on the bus.
Last edited by slammedR/T; 01/09/15 12:51 AM.
2000 Dakota R/T, 408 magnum, 727, Indy heads 1000cfm 4150 carb, 93 octane fuel. motor; 10.258 @ 132.78 200 shot; 9.262 @ 144.69 racemagnum
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Re: Grounding for battery in the trunck?
[Re: slammedR/T]
#1722084
01/09/15 12:55 AM
01/09/15 12:55 AM
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Joined: Nov 2003
Posts: 1,969 Chandler, AZ
Duner
top fuel
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top fuel
Joined: Nov 2003
Posts: 1,969
Chandler, AZ
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Quote:
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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?
I would do a ground bus, with the bus ground feed striaght to the bettery. Only have sensors grounded on the bus.
I will be switching to rear mount battery this weekend. Simple enough to just run a #4 lead for the sensor grounds.
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Re: Grounding for battery in the trunck?
[Re: Monte_Smith]
#1722085
01/09/15 01:19 AM
01/09/15 01:19 AM
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Joined: Mar 2006
Posts: 9,982 MI, usa
dvw
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master
Joined: Mar 2006
Posts: 9,982
MI, usa
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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
Monte as much as I respect your knowledge sometimes I have to disagree. So the fact that a race car has more cylinder pressure make the injectors need a floating ground? Really? I agree that cylinder pressure could be an issue with spark. But what in the heck does cylinder pressure have to do with injector firing or coil triggering? Nothing that I can think of. I will go tomorrow and get some straight facts and report back. If I'm incorrect I will post that as well. The bottom line is that every electrical circuit needs correct sizing. Clean tight connections. And correct routing . We fight noise issues all the time. Fixes involve different routing, shielding and yes moving the feed or ground circuit to a different power or ground location. But saying "grounding at the frame/cage" (which was the original question in this post) won't work is a catch all, and I believe incorrect. Doug
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Re: Grounding for battery in the trunck?
[Re: Airwoofer]
#1722086
01/09/15 01:22 AM
01/09/15 01:22 AM
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Joined: Nov 2004
Posts: 6,890 North Alabama
Monte_Smith
master
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master
Joined: Nov 2004
Posts: 6,890
North Alabama
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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.
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
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.
You are asking for a MAJOR headache with what you want to do...........and if I recall correctly, is the EXACT reason that I am not wiring your car for you. I told that I WOULD NOT do it, unless you let me rip all that stock crap out and wire the car RIGHT and you were NOT on board with that. You are asking for a MAJOR headache. Been there, done that and won't do it again. We have HAD this conversation standing in my shop. I refuse to chase gremlins on a car with a modern EFI and 40 year old factory wiring. Not worth it
Monte
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Re: Grounding for battery in the trunck?
[Re: FastmOp]
#1722088
01/09/15 01:26 AM
01/09/15 01:26 AM
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Joined: Nov 2004
Posts: 6,890 North Alabama
Monte_Smith
master
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master
Joined: Nov 2004
Posts: 6,890
North Alabama
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Quote:
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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
What plug wires do you have?
Monte
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.
The Taylors and the Moroso blue wires are notoriously bad for EMI noise. The Firecores are an excellent choice for an EFI car. I seldom "drink the koolaid" on that type stuff........but they flat work.......period.
Monte
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