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Master Cut Out

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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Hello again. I´m working on my instalation and I want to install the master circuit braker according with FIAAppendix J – Article 253 Art 13 which says:

"The general circuit breaker must cut all electrical circuits, battery, alternator or dynamo, lights, hooters, ignition, electrical controls, etc.) and must also stop the engine. For Diesel engines having no electronically controlled injectors, the circuit breaker must be coupled with a device cutting off the intake into the engine. It must be a spark-proof model and must be accessible from inside and outside the car. As for the outside, the triggering system of the circuit breaker must compulsorily be situated at the lower part of the windscreen mountings for closed cars. It must be marked by a red spark in a white-edged blue triangle with a base of at least 12 cm. This outside triggering system only concerns closed cars"

I attach my circuit design, so please help me with location. As yo can see, If I set circuit braker between pdm and rest, starter engine continue being feed by alternator. If I set circuit braker between battery and rest, then the alternator continue feeding me the PDM and starter...

Attached Files

There should be a terminal for the alternator output to be connected to that incorporates a diode - this allows the alternator to 'dum' it's current and avoid damaging voltage spikes, while preventing current from the battery to pass through it.

What model circuit breaker are you using, or are you using the ECU to control the electronics - different motorsport bodies may have slightly different requirements.

I´ve been looking this days about this problem. I have several options:

Option 1: Using mechanical 6 pole battery isolator, File:"Fia_isolator_wiring_1024x1024.png". This option is the easiest but I don´t really like using this days mecanic cables to external isolation etc. I would conect + battery to one main pole, and then alternator, PDM, and starter on the other. Then number 1, is used to alternator protection derivation to ground, and number 2 is used to change PDM IGN channel from 12V to GND when isolator is activated.

Option 2: Using a power relay (I learnt this on Motec Webinar) I don´t really know if this is suitable for my application: As you can see on picture "AIM PDM Ignition.PNG" (and user guide), when PDM is connected to 12V it is ON, and when is grounded it is off. It is a non configurable Pull Down digital input. In the image attached "Motec Webinar High Power Isolator Relay.PNG" , when External or Internal switch are opened, then relay main power is opened. Here the question is what isolate trigger states does it takes when the switches are opened or closed.

Option 3: Using a Cartek or EcuMaster similar solid state Battery Isolator. But it is really expensive and I would like using option 2 if posible

I hope you understand me...

Thank you

Attached Files

I finally did 2 different designs. (Attached)

Now I need to know which one would you chose and what type o surge protection would you use


Attached Files
  • WhatsApp-Image-2021-03-30-at-11.43.21.jpeg
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