Killswitch inside the Car / Ferrari 348

There is a kill switch inside a 348 Challenge so someone has already ... done it from the factory.

 

Done everyday for racecars. Look up how to do that. Best are not key based like the 348 challenge car but solinoid based. The esthetics of this can be a mounted low power switch or hidden extra security switch.

 

If you just wanted to turn off the motor, the ignition key would do the same job. The point of a kill switch is to kill all the electrics. If you have a solenoid-based kill switch, you still have electrics and a relay the size of a small planet.

 

the Kill switch kills the ground connection...

 

What device would you use for the remote control of a circuit breaker? If you used a regular relay which relaxed to the open position and if the small gauge wiring burnt through, it would re-engage the contacts.

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This type would be constantly using the battery.

Some contactors are mechanically latched with a momentary power input, but you would have to manually reset them at the contactor.
Some contactors need to be unlatched with reverse polarity.
Some contactors are the rotary type and cycle through various states after each switch input.

 

not true at all. Solenoid is the way modern race cars are done. The challenge method is 1994 using long hot wires that can spark a fire or remain hot even if the cut off is used.

 

that does not work

 

How does the solenoid method work?

 

This is how the FP350S mustang racecar is wired. But all modern cars have a junction box that is powered by battery or alternator. You can put the junction box in place of the battery in the diagram below and then you kill power there and everything including the alternator dies so the car can't run on alternator power when battery disconnected. This allows no high power wires to a high current carrying dash cut off switch like the one in the passenger foot well of 348 challenge cars. This solinoid method uses just a ground wire as a trigger so no chance of arching or fire if displaced in a crash. The relay is fabricated to be close to the junction box like right nest to it. That keep a displacement short out unlikely and keeps heavy big load carrying wires to a minimum. If you put an old school cutoff switch in the cabin at driver's reach that could be 15-20ft of heavy 4G wire in a 348 Ferrari and it is not safe by today's standards but still acceptable in amateur racing but not pro racing. Also, there is voltage drop the longer the wires. Using a solinoid relay is safe cheap and light weight. Solinoids use power when switched and motor not running. So it will eat a battery in a day just on but not car running. Today there are more expensive solid state solinoid relays that you can leave on without using power. They are used today more for when people make mistake not shutting off power to racecar. But I have used these for some many years the 1st thing I do when I exit my racecar is kill the power. When you have a crash or engine blow you don't always know what the problems are so the 1st thing you do is cut power. Second might be to activate your fire system if you see flames. Then look around for an escape being mindful that all the other cars around you on track are closing on you at 100mph and you could be in an impact zone.
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So looking at your diagram, the cutout is wired directly into the positive lead rather than the normal cutout switch.

Usually the junction box (PDB?) is powered by the battery or alternator, so if you don't wire the "dash master switch" directly to the battery and activate the switch, the solenoid will relax and reclose the master relay.

It makes more sense to me to have the ignition energising/closing the relay all the time until you need to cutoff the power. If you lose power or the 18gauge wire gets damaged in an accident/fire, the relay relaxes and opens.

What is Jannik using his car for?

 

your last question is most important. Is the goal to cut power say to save a battery while going on a month vacation or protecting the car from electronic source of fire seen in racecar crashes? Safety is why power is cut on the positive side closest to source to minimize the length of hot wire that can arc and also why the solenoid is on off not constant on until you turn it off and why solenoid does not “relax” it is either on or off.

 

One way of installation of a battery cut-off can be what I did on my 348. As it is a 1991 model (no factory battery isolation switch) with the battery at the back, it was easy to insert a latching relay at the battery, for the two red wires that go from the battery "+" to the bus bar, which cuts power to everything except the link from the battery to the starter motor and the alternator (see Ian's diagram below). In this way, I did not need a robust relay as it did not have to deal with the very high amps to the starter. My installation was primarily to eliminate battery drain if parked for a long time but it could also be used to "kill" the engine.

I used a compact Tyco (V23130-C2021-A412) latching relay, 200 Amps continuous, which needs two momentary (push-button) switches, one for "on" and one for "off". The good thing is that the relay does not consume any power when left either "on" or "off". The last picture below shows my installed push-button switches. I also installed a remotely (fob) operated switch, wired in parallel to the push buttons, to be able to operate the Tyco relay from outside the car.

According to the Tyco datasheet, this relay could also handle the starter motor current as it is good for 600 Amps if limited to 5 sec., then wait for 60 sec. before the next crank (not very good if you have a problem starting the engine and you have to crank it repeatedly).

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