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I have the GMPP engine mangement kit for my LS3/480 crate engine. My main question is, do I need to go straight back to the battery, or can I get power from another source? The reason why I ask is, my battery is mounted in the trunk.
 

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Trifive Automotive Electrical Wiring Expert
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I have the GMPP engine mangement kit for my LS3/480 crate engine. My main question is, do I need to go straight back to the battery, or can I get power from another source? The reason why I ask is, my battery is mounted in the trunk.
Is your starter battery post always hot? The alternator output would be the next alternative.
 

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Keep in mind that you're powering your computer, fuel pump, and cooling fans with the power input to the panel. So you need to be able to supply the full amperage for all those loads. So yes, all the way to the battery, or to a terminal you supply that can carry that current.
 

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Dave....As Don said....Is the Battery terminal on your solenoid hot at all times?
 

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Discussion Starter #6 (Edited)
Dave....AS don said....Is the Battery terminal on your solenoid hot at all times?
Yes, but my fuse panel will be mounted to the inner fender on the driver's side, and the starter is on the passenger side. As you can see in the picture below, my alternator charge cable goes to a feed-thru terminal stud. It would be very convenient to connect to that terminal stud, but, I've always heard that EFI should always get power straight from the battery, to avoid any random, phantom issues. Any truth to this? I carefully read the instructions that came with the engine management kit, and it doesn't specifically say to run the wire directly to the battery.

 

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Trifive Automotive Electrical Wiring Expert
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Yes, but my fuse panel will be mounted to the inner fender on the driver's side, and the starter is on the passenger side. As you can see in the picture below, my alternator charge cable goes to a feed-thru terminal stud. It would be very convenient to connect to that terminal stud, but, I've always heard that EFI should always get power straight from the battery, to avoid any random, phantom issues.
It's not a problem if the wires are sized correctly and the connections are tight. Most vendors recommend "straight off the battery" so there is not 3 or 4 bad connections before it gets to their computer.
 

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Dave here are a few things to consider.
1. the fuel trims are cleared every time the battery is disconnected.
2. the ecm doesn't like power surges
3. the ecm doesn't like it when voltage drops below 1.5 volts.

wire directly to the battery.
 

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Discussion Starter #11 (Edited)
Keep in mind that you're powering your computer, fuel pump, and cooling fans with the power input to the panel. So you need to be able to supply the full amperage for all those loads. So yes, all the way to the battery, or to a terminal you supply that can carry that current.
Rick and John, I have enough 4 AWG on hand to run straight to the battery. Now, since I'm doing that, I feel I should add a Megafuse on that wire, close to the battery. I'm thinking a 125 amp fuse should work.
 

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If you're using Vintage Air w/electronic controls that also needs to be connected straight to the battery. I didn't on my '57 Handyman & had to go back & change the wiring after the car was finished. The A/C blower was acting crazy, changing speeds on it's own.
 

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Discussion Starter #13
If you're using Vintage Air w/electronic controls that also needs to be connected straight to the battery. I didn't on my '57 Handyman & had to go back & change the wiring after the car was finished. The A/C blower was acting crazy, changing speeds on it's own.
Thanks for the tip! Yes, I'm using the Gen VI setup with the 3 knob electronic control.
 

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Rick and John, I have enough 4 AWG on hand to run straight to the battery. Now, since I'm doing that, I feel I should add a Megafuse on that wire, close to the battery. I'm thinking a 125 amp fuse should work.
more than enough
 
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