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Combining fuses

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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Hello! Hope you haven't had enough of me yet this week. My project's wiring is almost all done (the theoretical stage), so shouldn't be much more of this.

Below are all the loads that need to go through a fuse. There's simply more of them than there is fuses.

I have two power distribution type fuse boxes. 10 and 4 position ones. They are rated at 100A per box, 30A per circuit. Smallest wire size is 0.5mm2, rated for 11A.

Next stage of planning is to divide the loads into the two fuse boxes so that neither does more work than the other. The loads need to be cut down to 13 fuses. I want to keep a slot open. If you like a challenge, give it a go please.

Brake Lights, LED 4A

Fan 80W oil cooler Relay, 10A

Fuel pump Relay 1, Bosch 044, 20A

Fuel pump Relay 2, Bosch 044, 20A

USB 5V charger, 2A

Alt lamp "L" 7.5A

Starter solenoid 20A

IGN coils Relay, 30A

Solenoids Relay (VVTi, WBO, MAC, VSS, Injectors), 10A

ECU, 3A

Alt "IG", 7.5A

LED front lights, 10A

Wiper Relay, 20A

Fan 80W water rad Relay 1, 10A

Fan 80W water rad Relay 2, 10A

Ign. switched relay control circuit 2A

4 Slot Box:

20A FP1

20A FP2

20A Starter Solenoid

30A Ign Coils

10-Slot Box

20A Both Fan Water Rad

5A Ign Switch Relay & USB Power

3A ECU

5A Brake Lights

10A Headlights

10A Alt Lamp & Alt "IG"

10A Fan Oil Cooler

10A Solenoid Relay

20A Wiper Relay

Hi David!

That's very close to what I had in mind. I still wanted more experienced people to chime in.

A few questions regarding your choices

Water fans had 2 circuits for better control (both are ECu controlled). To decrease the effects of inrush current I was going to turn them on staggered. Granted they aren't ridiculously high draw items, one relay probably suffices. Tell me though, would you go straight into two 1.5mm2 wires from the relay, or rather have a 2,5mm2 going to the front and then splice?

Do you have any Experience with Amazon USB chargers (I read ina thread somewhere that they are fine and I couldn't really find a more reputable one)? Do you know, are they known to fail in any particular way, taking down the IG.sw circuit with them, rendering the car useless? That was my concern.

Maybe join the USB with brake lights instead?

Solenoid relay powers Injectors, VVTi, VSS and MAC and WBO. It's only there because the Ignition relay is protected by a much larger fuse and I didn't want to have a fuse larger than the wiring solenoids use (we established that in one of my other threads).

Do you have a different solution for that, one that saves a Fuse and Relay slot?

Thank you for your time

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