Just joined? Please introduce yourself.
Classic Edge Designs, LLC Prime Custom Cars, LLC MadMooks
Page 21 of 23 FirstFirst ... 111920212223 LastLast
Results 201 to 210 of 229

Thread: Nomad final assembly

  1. #201
    Registered Member 55 Rescue Dog's Avatar
    Join Date
    Nov 2015

    Member #:2775
    Posts
    887
    Quote Originally Posted by chevynut View Post
    My research shows that the coil can draw upwards of 20-25 amps. I'm actually using a MSD Blaster coil (no ignition box) with a GM computer-controlled distributor and I'm feeding it from a 25A fuse with 12 gauge wire. Virtually nothing of any significant power on my Nomad goes through the ignition switch. The starter solenoid, IGN power, and ACC power are all switched by 50A relays. The ignition switch itself will be on a 5A fuse.
    Don't forget when it comes down to fuses, that the instant pull-in current of a relay is 300-500% higher than the constant hold-in current. A 5A fuse might not be enough, but time delay fuse would handle it though. A fuse is suppose to protect constant current for the wire size is all, not just the device.
    Last edited by 55 Rescue Dog; 05-14-2019 at 05:06 PM.

  2. #202
    Registered Member
    Join Date
    Apr 2012

    Member #:571
    Posts
    3,835
    The typical automotive relay pull in current is really low, but as you point out the holding current is even lower. 5A is way generous.

  3. #203
    Registered Member 55 Rescue Dog's Avatar
    Join Date
    Nov 2015

    Member #:2775
    Posts
    887
    Quote Originally Posted by Rick_L View Post
    The typical automotive relay pull in current is really low, but as you point out the holding current is even lower. 5A is way generous.

    http://www.industrial-electronics.co...n_Current.html

  4. #204
    Registered Member
    Join Date
    Dec 2018

    Member #:4017
    Posts
    53
    Quote Originally Posted by chevynut View Post
    My research shows that the coil can draw upwards of 20-25 amps. I'm actually using a MSD Blaster coil (no ignition box) with a GM computer-controlled distributor and I'm feeding it from a 25A fuse with 12 gauge wire. Virtually nothing of any significant power on my Nomad goes through the ignition switch. The starter solenoid, IGN power, and ACC power are all switched by 50A relays. The ignition switch itself will be on a 5A fuse.
    By you using 12 wire on the coil at 25 amp draw is that overly conservative? Maybe worded another way, is 16 or 14 gauge wire adequate? I like the idea of a relay.

    Another question is fuse on the coil line required and wouldn’t that reduce the current? I’ve not seen any older cars with a fuse in this line feed as OEM. I do appreciate you sharing the electrical on your car as this is an area that I have lesser knowledge.

  5. #205
    Registered Member
    Join Date
    Apr 2012

    Member #:571
    Posts
    3,835
    Chevy used a minimum of 12 gauge wire on HEI ignitions, I think I've seen 10 gauge also. They do it for a good reason.

    Fuses won't reduce current unless they do their job and blow when there is a wiring fault, which is what they're supposed to do.

    You're right, most cars with a standalone ignition system don't have a fuse on the ignition on the switch feed. On the other hand most EFI stuff often has multiple fuses on the switch feed.

  6. #206
    Registered Member chevynut's Avatar
    Join Date
    Nov 2011

    Member #:115
    Location
    Fort Collins, CO
    Posts
    9,882
    Quote Originally Posted by Rick_L View Post
    The typical automotive relay pull in current is really low, but as you point out the holding current is even lower. 5A is way generous.
    Yes, the 50A relays I'm using draw about 140mA coil current each. The ignition switch only triggers 2 of them when starting (solenoid, IGN) and only two when running (IGN, ACC) for a total of 280mA for the relay coils. So a 5A fuse is really overkill for that purpose. I may be using HALO DRLs and they will be powered off the ACC terminal of the ignition switch as well (off during start). They draw 350mA each for another .70A. So total current through the ignition switch is only like 1A. If I decide to power something else with it, it's simple to change a fuse. I used a 12 gauge wire for the ignition switch power just in case. LOL!
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

    You can see my 56 Nomad build here http://www.picturetrail.com/chevynut

    For affordable C4 Corvette Suspension conversions for your car, visit http://www.classicedgedesigns.com

    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax

  7. #207
    Registered Member chevynut's Avatar
    Join Date
    Nov 2011

    Member #:115
    Location
    Fort Collins, CO
    Posts
    9,882
    Quote Originally Posted by Gmvette View Post
    By you using 12 wire on the coil at 25 amp draw is that overly conservative? Maybe worded another way, is 16 or 14 gauge wire adequate? I like the idea of a relay.
    Part of the reason you use a wire larger than you need is to reduce voltage drop. The 12 gauge wire is overkill for 25A but GM used 12 GA for HEI, and I read that AAW uses 10 gauge for the coil circuit. So I just followed their lead. I also read where a lot of guys used 14 gauge with no problems. I actually think my Holley EFI harness was 14 gauge but it was too short so I cut it off shorter and used 12 gauge wire to extend it, which was the only large pink wire I had.

    Another question is fuse on the coil line required and wouldn’t that reduce the current? I’ve not seen any older cars with a fuse in this line feed as OEM. I do appreciate you sharing the electrical on your car as this is an area that I have lesser knowledge.
    Fuses don't reduce current, they're basically a "short circuit" and are just a piece of metal that melts at a specific current. I read somewhere that you shouldn't fuse the HEI circuit, but saw no justification for that and it's actually protected by the fusible link at the starter.....so there really is a fuse. GM probably wanted to eliminate a large fuse. Why wouldn't you fuse everything you can? I see no downside as long as the fuse isn't blowing all the time. I could have just connected it to one of my 50A breakers too but decided to go with a fuse. Typical HEI coil current is much lower than 25A, which looks like worst-case. I think what I did is conservative, while still protecting the wiring which is what a fuse is supposed to do.

    Pretty much everything I have is double or triple fused.....power comes into the car from the starter via a 4 gauge cable, and goes through an 80A fuse to my amp, and a 100A fuse to multiple 50A breakers and one 30A breaker. The 50A breakers supply power to the cooling fans and the fuse panels which are broken up into sections for constant power, IGN power, ACC power, and retained ACC power. The 30A breaker supplies power directly to the A/C, starter solenoid, and seats. Since the seats rarely get adjusted, I think that's safe. Yes, it's overkill, but I didn't want to use one power distribution block with all the wires stacked on it. I could easily have gotten away with one breaker for the fans, and one or two for everything else but again it's hard to put a lot of 12 gauge wires onto a breaker stud. And I would rather have room for expansion if needed.
    Last edited by chevynut; 05-15-2019 at 09:20 AM.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

    You can see my 56 Nomad build here http://www.picturetrail.com/chevynut

    For affordable C4 Corvette Suspension conversions for your car, visit http://www.classicedgedesigns.com

    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax

  8. #208
    Registered Member 55 Rescue Dog's Avatar
    Join Date
    Nov 2015

    Member #:2775
    Posts
    887
    A fuse adds resistance, and a voltage drop to a circuit which is how they work I think. That's the difference between a 1 amp fuse, and a 100 amp fuse is the current capacity of the element and melts when current is too high. If it had no resistance it would never blow. It is the resistance of the fuse that causes it to heat up with current, and melt the element. With no fuse, then it would be the resistance of the wire that melts instead. Every electrical issue always comes down to OHM's law. He was a very smart guy 192 years ago named George.
    Last edited by 55 Rescue Dog; 05-15-2019 at 03:58 PM.

  9. #209
    Registered Member
    Join Date
    Apr 2012

    Member #:571
    Posts
    3,835
    Well that's true because a fuse heats up as the current increases and eventually melts. But in the big picture the resistance and voltage drop of a fuse is rather small. Just as the current draw on a relay coil.

  10. #210
    Registered Member chevynut's Avatar
    Join Date
    Nov 2011

    Member #:115
    Location
    Fort Collins, CO
    Posts
    9,882
    Quote Originally Posted by 55 Rescue Dog View Post
    A fuse adds resistance, and a voltage drop to a circuit which is how they work I think. That's the difference between a 1 amp fuse, and a 100 amp fuse is the current capacity of the element and melts when current is too high. If it had no resistance it would never blow. It is the resistance of the fuse that causes it to heat up with current, and melt the element. With no fuse, then it would be the resistance of the wire that melts instead. Every electrical issue always comes down to OHM's law. He was a very smart guy 192 years ago named George.
    Of course a fuse adds resistance....every inch of copper wire adds resistance......every connection adds resistance. But the resistance of a fuse is small in the whole scheme of things in a circuit. The point is they're made of a low melting point metal so a small amount of heating melts it. I don't know how many watts it takes to heat up the fuse to where it melts, but from a practical point of view it's irrelevant.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

    You can see my 56 Nomad build here http://www.picturetrail.com/chevynut

    For affordable C4 Corvette Suspension conversions for your car, visit http://www.classicedgedesigns.com

    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax

Page 21 of 23 FirstFirst ... 111920212223 LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •