Wiring - Big Relays in a race car - Why this way?
03-22-2021, 06:34 PM
#1
Wiring - Big Relays in a race car - Why this way?
I've been going through my cars wiring, most of the factory wiring was removed and replaced with a bare minimum. No key, just a Power switch and a start button. etc.
I am trying to understand the rationale behind the wiring of two big relays.
There is a big Relay in the passenger footwell , it takes the Pos cable from the battery.
There is another 200amp relay in the engine compartment, its output feeds the engine (starter i think)
Basically, the power switch is a Double pull/double throw.
The Neg Side Seems to control the relay in the engine, the positive of the switch controls the relay that sits immediately after the battery
Flip the switch both are on or off
Looking at how the relays are wired, the negative of the Engine Relay then goes to the negative of the battery relay.
The positive output of the battery relay ends up as the main input to the engine relay.
Is this redundancy normal in wiring auto relays or because race car? if it is a racing safety feature, what is the thought process behind it? ( I heard they dont use switch fuel pump power on dragsters using a switched ground because an accidental ground wire contact could reactivate the fuel pump in an emergency situation... so that is why i am asking if this is a safety thing)
.. try to stay on topic please.
Thanks
I am trying to understand the rationale behind the wiring of two big relays.
There is a big Relay in the passenger footwell , it takes the Pos cable from the battery.
There is another 200amp relay in the engine compartment, its output feeds the engine (starter i think)
Basically, the power switch is a Double pull/double throw.
The Neg Side Seems to control the relay in the engine, the positive of the switch controls the relay that sits immediately after the battery
Flip the switch both are on or off
Looking at how the relays are wired, the negative of the Engine Relay then goes to the negative of the battery relay.
The positive output of the battery relay ends up as the main input to the engine relay.
Is this redundancy normal in wiring auto relays or because race car? if it is a racing safety feature, what is the thought process behind it? ( I heard they dont use switch fuel pump power on dragsters using a switched ground because an accidental ground wire contact could reactivate the fuel pump in an emergency situation... so that is why i am asking if this is a safety thing)
.. try to stay on topic please.
Thanks
03-24-2021, 04:01 PM
#2
Nordschleife Master
I would assume it isolates the battery 100% of the car if u flip the main power swich. Basically your "kill" switch.
