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My battery has been relocated to the cubby behind the driver's seat. In order to pass tech at my local tracks, I need to install the NHRA required exterior master disconnect switch.
What I want to do is install the master switch in the recessed area behind the license plate. I will fab up a plate/mount and clearly label ON/OFF as required. This way I wouldn't have to drill any holes in the bumper cover or license plate. I will simply remove my plate when I am at the track.
My question is... Will it pass tech and satisfy the NHRA rule book?? I have seen people put them through the plate or in the sheet metal behind the plate but it is obviously a little different on C4s.
I'm not sure if the recessed switch idea would be a go with the NHRA. It has to be easily accessible. This was my answer to punching a whole in the bumper. My license plate didn't care.
Alright. I mocked it up tonight and this is what I have. Basically it's in the same exact location as yours except it is recessed about 3/4" compared to yours. My license plate will fit right back over it with 1/16" spacers and conceal it when I am not at the track.
So... Now do you think it will pass???
I'm not sure if the recessed switch idea would be a go with the NHRA. It has to be easily accessible. This was my answer to punching a whole in the bumper. My license plate didn't care.
I know whether you agree with the rule or not is irrelevant, but...
Does that bother you that NHRA rules say the + side of the wiring be connected to the switch?
i mean, someone rear ends you, the tank ruptures, and now the + side of your wiring is sparking against metal ground ....
That NHRA rule (requiring hot side of wiring ) be connected to the switch doesnt make sense to me.
All you have to do is start up your car and then pull the negative terminal and see if it continues to run. It will as the alternator is grounded through the chassis and pulling the negative cable off the battery will not break the circuit. In order to stop the engine in the case of an emergency, you have to be able to break the circuit and the only way to do that is to cut the power from the alt and battery at the same time. There is no way around it.
I know whether you agree with the rule or not is irrelevant, but...
Does that bother you that NHRA rules say the + side of the wiring be connected to the switch?
i mean, someone rear ends you, the tank ruptures, and now the + side of your wiring is sparking against metal ground ....
That NHRA rule (requiring hot side of wiring ) be connected to the switch doesnt make sense to me.
Or am I mis understanding something
That has crossed my mind. I am running a 5 gallon fuel cell which is farther away from the rear with a plate between the switch and the cell for some protection. However, if I do back into the wall at speed, I could have a problem.
All you have to do is start up your car and then pull the negative terminal and see if it continues to run. It will as the alternator is grounded through the chassis and pulling the negative cable off the battery will not break the circuit.
It's a bad idea to disconnect your battery when the engine is running. There's a good chance you'll damage the voltage regulator in your alternator! It doesn't matter whether it's the positive or the negative post of the battery, it's the same result.
As Krusty says, a Master Disconnect switch won't kill a running engine.
It's a bad idea to disconnect your battery when the engine is running. There's a good chance you'll damage the voltage regulator in your alternator! It doesn't matter whether it's the positive or the negative post of the battery, it's the same result.
As Krusty says, a Master Disconnect switch won't kill a running engine.
The NHRA tech will turn the switch to "off" when the engine is running. If the motor still runs, the switch doesn't work and you're out. The second post on the switch can be used to disconnect the alternator. In my case, I shut off the fuel pump.
The NHRA tech will turn the switch to "off" when the engine is running. If the motor still runs, the switch doesn't work and you're out. The second post on the switch can be used to disconnect the alternator. In my case, I shut off the fuel pump.
So in your car, the battery stays connected to the alternator? And that's considered a safe shut-off? And your engine starts okay with that extra +/- 25 feet of cable between your battery and your starter?
If you're running a carb, shutting off the fuel pump won't kill the engine for a while. Do they have a time limit?
Mine will have the alt power and battery going to one side of the switch. The other side will go to power distribution block. Flip the switch off and no power can get to the block and will cut ignition, fuel, ecm ...etc. Not certain how 383vett's is wired but maybe he isn't running an alt, just dual batteries and he is using the small post on a 4 post switch to cut off the fuel pump as well.
Currently mine has about 10ft of 2 ga wire between the batt and starter. After I am finished with this switch install it will have about 20ft of 1/0 gauge. It has no problems starting now and I assume it will start just fine when it is done.
So in your car, the battery stays connected to the alternator? And that's considered a safe shut-off? And your engine starts okay with that extra +/- 25 feet of cable between your battery and your starter?
If you're running a carb, shutting off the fuel pump won't kill the engine for a while. Do they have a time limit?
If the engine is off, the alternator is not charging. My battery is located 1 foot to the right of the switch so the hot cable headed forward is intercepted. I am running a miniram with an ACCEL 666 fuel pump. No power to the pump, the motor shuts down immediately. The reason for the disconnect is because it is mandatory with a relocated battery.
I know whether you agree with the rule or not is irrelevant, but...
Does that bother you that NHRA rules say the + side of the wiring be connected to the switch?
i mean, someone rear ends you, the tank ruptures, and now the + side of your wiring is sparking against metal ground ....
That NHRA rule (requiring hot side of wiring ) be connected to the switch doesnt make sense to me.
Or am I mis understanding something
The main purpose of NHRA rules are to make a car safe for drag racing.
In a car, set up for NHRA racing, being driven on the street, I would be much more concerned about my head hitting the roll bar in a rearend collision.....
IMO there comes a point when it is hard to make a car both safe for street and drag racing.
The main purpose of NHRA rules are to make a car safe for drag racing.
In a car, set up for NHRA racing, being driven on the street, I would be much more concerned about my head hitting the roll bar in a rearend collision.....
IMO there comes a point when it is hard to make a car both safe for street and drag racing.
On the street I dont I see a lawsuit risk - ie. No one is forcing you to use a rollbar.
on the track I do see a lawsuit risk (ie. You gotta have this dangerous switch or you ‘cant run’).
Especially when there is a safer way to do it (like maybe make the switch somehow connect to fuel pump or something that loses its power (due to the computer shutting it down with zero oil pressure) in an accident
and those little waiver papers you sign are meaningless..
On the street I dont I see a lawsuit risk - ie. No one is forcing you to use a rollbar.
on the track I do see a lawsuit risk (ie. You gotta have this dangerous switch or you ‘cant run’).
Especially when there is a safer way to do it (like maybe make the switch somehow connect to fuel pump or something that loses its power (due to the computer shutting it down with zero oil pressure) in an accident
and those little waiver papers you sign are meaningless..
ok ill back out of this post.
For you and me, the fuel pump may work being injected. But the majority of cars are still carbed, at least in bracket racing in my area.
Ill promise you, NHRA has had lawyers and engineers look at this......
FWIW you could probably get away with the FP switch..... Most inspectors are going to test the switch and that is it.
For you and me, the fuel pump may work being injected. But the majority of cars are still carbed, at least in bracket racing in my area.
Ill promise you, NHRA has had lawyers and engineers look at this......
FWIW you could probably get away with the FP switch..... Most inspectors are going to test the switch and that is it.
The reason for the switch is not only to kill a running engine, but also to cut the positive lead of the battery cable which is usually located in the trunk or back of a car. This decreases the chance of spark and fire caused by the cable coming in contact with the chassis after an accident.
. . . but doesn't do any good if your alternator is still connected to your battery.
But who am I to argue???
How is the alternator connected to the battery when the positive terminal is off the battery which essentially is what the master disconnect switch accomplishes?
Question about NHRA master disconnect
