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Thread: Ground Bus

  1. #71
    Senior Member NckT's Avatar
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    Quote Originally Posted by Shep View Post
    God no, nonono no, don't encourage bad behavior, that's like brushing your teeth and leaving the cavities alone, then chowing down on a bowl of popcorn kernals mixed with ice. None of that is even remotely close to a good idea. It's more akin to a band-aid on a broken femur than a legitimate solution to a design flaw.

    I don't think anyone at any point in this thread has said that only cleaning up "high resistive joints" alone is a even close to a wise idea for good reason. The first post was about laying down new ground wires to compensate for the undersized OEM ones. Where the notion came from that the car's grounds are properly designed is beyond me but they are anything but.

    Steel is tolerable as a wiring path, but only if properly cared for. McFly himself saw exactly why grounding through the easily-rusted frame is a horrible idea. Modern manufacturers do it because unibody designs inherently mean that frame and body are one electrical channel. That's why batteries often ground to the mating section between unibody and frame. And it's also why said ground is physically built far away from potential sources of corrosion, which places it under the hood of the car.

    The DeLorean did a lot of things wrong with the electrical approach by design. First, the frame is the only stretch of wire front to back in some ground loops. This is a terrible idea when high current devices (headlights, fans) are using this very same path. A chain is only as strong as its weakest link. The mere fact that the weakest link needs occasional redoing to keep pristine speaks volumes.

    Bear in mind also that automatic frames have a different current capacity than manual frames thanks to the transmission shifter cutout. It's equivalent to a kinked pipe, there's an immediate loss in capacity at that spot. I'd personally estimate that section of frame gives an equivalent AWG size between 1/0 and 2 for copper wiring, given the difference in metal as well as conductivity of copper vs. mild steel, as well as a corrosion factor to accommodate most frame conditions.

    This was an area that DMC would have worked out had they been given adequate time and resources to do so. I'm convinced that Johnny Carson's infamous hitchhiking could have been at least partially alleviated with more focus on the electrical system. Some who have crunched the numbers have stated the alternator was more than capable of handling the load, and wondered why it didn't. What's forgotten is the current doesn't travel to the front that well, which is exactly where all the power was being used.
    With the greatest of respect, analysing and testing the existing wiring on mine and others cars is not "bad behaviour", adding additional cabling to compensate for existing faults is. The only way I see this is a gain is that a product is made to realise money that is easily fitted by non technical people to see a "result" afterwards.

    The only really undersized gauge wire is what Dave mentioned, this is the only one that needs a separate earth (ground) wire.
    Last edited by NckT; 10-29-2017 at 04:56 AM.
    RIP Rob van de Veer Top bloke

    I say Sir, I must be mad, one loves fixing K-Jet !

    Make sure there's plenty in the tank for the weekend chaps....

  2. #72
    Mr. Pickles-mobile Shep's Avatar
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    Quote Originally Posted by NckT View Post
    With the greatest of respect, analysing and testing the existing wiring on mine and others cars is not "bad behaviour", adding additional cabling to compensate for existing faults is. The only way I see this is a gain is that a product is made to realise money that is easily fitted by non technical people to see a "result" afterwards.

    The only really undersized gauge wire is what Dave mentioned, this is the only one that needs a separate earth (ground) wire.
    Okay, this is counter to how your prior post read. More than just fixing the high impedence grounds, visual + electrical inspection of related grounds as well as diagnosis / prevention of impedence is also required (yes, required in my book -- this doesn't have to cost money and really is preventative maintenance at that point). Omitting that was what I was calling "bad behavior", I'm getting the vibe now though that you were referring to that along and I misread that -- my apologies!

    I can tout the benefits of the Big Three all day long, but unless you're doing a lot of high current stuff, it's likely to not be terribly beneficial. But again, tackling this as a "while you're in there" hasn't stopped me before personally. Particularly if one ground cable has issues multiple times, it is worthwhile swapping it out and checking it regularly. I want to say there was some steel used in the DeLorean ground wires from the factory, I could be mistaken however. For a setup that sees corrosion, any chronically faulty high-impdence ground should be swapped with an equal or bigger wire of non-corrosive material.

    I will note that some of the vendors do this type of work, but don't sell the parts. Reason being, it's a niche inside of another niche, and wiring is available damn near anywhere. Just cut to length and install. It's also one that is highly a matter of preference for how it's done. They'd sell maybe ten sets at ten different sizes, why bother if we source it ourselves anyways?

    It was also news to me that the radio taps into the frame and out to the battery/alternator, but does make sense. That's the one stretch I would patch with a 4 AWG or higher ground cable if you upgrade the radio. Modern radios pull more current than stock, often come with amplifiers built-in, for the short distance you're also bypassing the transmission cutout and allowing everything up front to piggyback off it. There isn't much harm in this approach, and will suffice for 99% of drivers out there.

    For the extra 1%, beef up
    Last edited by Shep; 10-30-2017 at 11:16 AM.
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  3. #73
    Senior Member NckT's Avatar
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    If you're going to add cabling, don't forget to include for internal resistance of the cable based on the resistivity of the material used and the internal structure of the calling too ie number of stands/core diameter etc with your calculations.
    RIP Rob van de Veer Top bloke

    I say Sir, I must be mad, one loves fixing K-Jet !

    Make sure there's plenty in the tank for the weekend chaps....

  4. #74
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by NckT View Post
    If you're going to add cabling, don't forget to include for internal resistance of the cable based on the resistivity of the material used and the internal structure of the calling too ie number of stands/core diameter etc with your calculations.
    I ran a test way back when Bill suggested this ground buss. I remember reading the voltage drop over the frame with a known current flowing. With that result I computed the resistance and suggested only a 2 AWG wire or larger would make any difference.

    So what runs off the frame ground. Cooling fans and blower motor seem to be the only thing up front. So do you really need to add a few millivolts to those loads?
    Dave M vin 03572
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  5. #75
    Senior Member NckT's Avatar
    Join Date:  Jun 2011

    Location:  Yorkshire UK

    Posts:    127

    My VIN:    No. 4068

    Quote Originally Posted by Bitsyncmaster View Post
    I ran a test way back when Bill suggested this ground buss. I remember reading the voltage drop over the frame with a known current flowing. With that result I computed the resistance and suggested only a 2 AWG wire or larger would make any difference.

    So what runs off the frame ground. Cooling fans and blower motor seem to be the only thing up front. So do you really need to add a few millivolts to those loads?
    I'm glad you've got my point Dave and have done realistic computations.
    RIP Rob van de Veer Top bloke

    I say Sir, I must be mad, one loves fixing K-Jet !

    Make sure there's plenty in the tank for the weekend chaps....

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