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Cranking, charging and gauge wiring loom

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I need help creating a wiring loom from scratch which solely operates the cranking charging and possibly one gauge for my drag build not sure how I need to start and what items I need ie fuse box relays fuses wire thickness fr battery ect any help will be greatly appreciated.

I never wired a whole car by my self and wish to wire it all including the motor but not sure how to start with the cranking/charging loom...

Im going to honest, there's a lot to go that needs to be considered.

- what ecu

- what car, do you know if the crank is Hall or VR?

- how many devices are you trying run

- what sensors are you running on the engine

- what's your budget

- are you familiar how to wire fuse, switch, relay setups

- not sure what you mean by using one gauge? like a sensor gauge? those are easy :)

- figure out amperage draw of all your components with Amps=Volts/Resistance or Amps=Watts/Volts

- Are you going to be using PWM controlled devices? i.e. thermo fans or boost solenoid

I'm not telling you that you can't do it, but start going through forums and basic schematics for ideas on how the electrical system works. I hate to sound negative, though im not trying to be, it's just hard to answer a very vague question about such a broad topic

I will say use 4awg for battery :)

Hi Ryan,

I have basic knowledge in wiring but as I said I have never wired a car completely, here are the answers to the questions,

- what ecu Haltech E8 with flying lead loom

- what car, do you know if the crank is Hall or VR? Toyota Celica GT4 ST205 using a reluctance sensor from haltech

- how many devices are you trying run Devices? This is a drag build will only be running a RPM and wideband gauge as devices no head light no tail lights nothing of the sort.

- what sensors are you running on the engine Wideband, Coolant temp, 4 bar map sensor, Air intake temp, crank reluctance sensor

- what's your budget No idea

- are you familiar how to wire fuse, switch, relay setups not a pro but I done in the past id say novice

- not sure what you mean by using one gauge? like a sensor gauge? those are easy :)

- figure out amperage draw of all your components with Amps=Volts/Resistance or Amps=Watts/Volts I have not calculated this as I am not sure where to start from.

- Are you going to be using PWM controlled devices? i.e. thermo fans or boost solenoid yes but will all be done through the haltech flying lead I also have a boost solenind by gready which will have a separate harness all I need is power and ground to make it run not will not be using the ecu to control this device.

I am not sure you understood me in my first message so here is to re structure;

I will be running a haltech e8 ECu which has a flying lead so all I need to do here is wire it into the sensors fan fuel pumps ect this will make the engine tunable. My query Is how to make the engine start and charge, how to wire the alternator and starter motor to make the car crank and charge I would like to fabricate a separate harness apart from the haltech flying lead. This harness will be very small and shouldn't be hard to fabricate just not sure what components to use and how to wire them in harness in my eye I am seeing as follows;

From battery to a relay obviously fused then connected to the alternator to charge the battery, and for the starter motor the same thing but obviously would only crank the engine I obviously would like to connect the cranking to a switch panel for ignition on and push start botton and the 2-3 switches which will be wired to turn fuel pumps on and off an have an extra switch or 3 just in case I need to add more fan devices ect.

Just unsure how to wire it all in I mean I can do it alone or just pay someone to do it, I have dont the wiring fundamentals course also but there was nothing about the cranking and charging system and how to wire this loom. Want to learn to do it myself and be confidant in what I am doing. Just looking for some guidance before I proceed with the wiring.

I have attached a pic of my engine bay Just fitted the motor this week.

The target is 700AWHP for drag use only !

Attached Files

So is there no one at all that can help me out in this?

You mean something like this ?

Attached Files

Hey Ludo Yes like this exactly this was just what I was looking for bro something simple but it helps a lot, is that a 4 gauge wire? and maybe abit more detail like is one relay enough to control all the current and how is the relay wired exactly which are the trigger terminals and which is the high current terminal ?

can I hi jack slightly,

with the st205 alternator, it has 4 connections a large charge one about 4 gauge.

then a 3 wire connector, one goes to the charge light on the dash. one of the other two goes to the ignition switch and the third goes back into the fuse box but after the fuse.

whats the purpose of these two small guage (about 18 gauge) wire?

The third one is for the voltage output regulation.

Hey Ludo Let me see if i go this correctly The terminal L will be connected to the dash as a warning light 18-20 gauge wire. The B terminal will be connected to the Ign Switch fused by a 100amp fuse and also connected to the ign switch and starter motor by another wire and also connected to the 12v batt + terminal. Terminal G is a direct 12v bat connection with no fuses or relays or switches. and terminlal I will be connected to the Ign switch which is connected to a 30amp Relay and grounded with a 3ohm resistor. Alternator will be grounded to the block/head and chassis

Is this the proper way of wiring the alternator?

Ryan,

You would use 4 AWG for battery even for a trunk located battery?

Or in this case 3 AWG would be better?

4 awg @ 150 A (crank) (4.5 meter lenght) would be about 5% voltage drop @ 12v

Allan,

Did you get it sorted?

Im doing very similar, just excuse me while i jump on board :-)

Personally (Like Alan i believe) plan to have the 'car loom' seperate to the rest, however i will have lights, indicators etc and the charge loom can be independant.

Then the engine loom with all my modules can be tied into one loom.

I was always told you needed to run a 250 amp fuse on the battery as when cranking it is possible to draw this?

and also to run 0 gauge for battery to boot installations? seems like drastic over kill compared to what you guys recommend.

what about using a 130 amp relay instead of the switch?