GSRCRXsi

so im doing some electrical work, re wiring the whole car really. and as a part of this, im wiring in a master cutoff switch, switch panel, fuse box etc. im a little confused as to how to go about wiring up the switch. and i apologize for asking this, as i know its been asked many times over. i did search, but many threads are old (non working pics), or from the drag racing forum (which may not necessarily apply).

so after looking at the stock diagrams, i can see 2 scenarios in my head that would work

1. switch interrupts battery->fusebox feed AND fusebox->distributor (ignition) feed.
-OR-
2. switch interrupts battery->fusebox feed AND alternator->fusebox feed.

like this pic (just replace distributor feed with alternator feed for scenario 2)



so both ways will get the job done, right? is either way preferable to the other? is there a more elegant solution that is simpler and legal for NASA? does the starter HAVE to be switched out too? or can it stay a straight shot from the battery?

how are you guys actually doing it?

lastly, where do you guys buy racing electrical stuff? ive seen lots of posts like "buy x here, and y there" but id like to buy everything from one place. relays, master switch, switch panel, fuse box, etc.

known

iTrader: (1)

Up late too, either way I think is fine. Im going with daves photo you posted for my setup.

I got some of my stuff from pegasus auto like the longacre swith etc. I got my wiring for it all locally at a store called sky craft that sells by the foot but there are a ton of online places for wire.

I went with 32mm royal excellence welding wire

http://www.skycraftsurplus.com/weldingwire.aspx

naterpatater77

i would say that option 2 would be a better way to go cause the car will still be a live circut for a while while the alternator is turning. I believe in the gcr all power sources must be cut.

GSRCRXsi

thanks guys. anyone else?

any reason to go with the more expensive $60 switch over the Longacre $30 one?

known

iTrader: (1)

the load they can take ?

i just got the longacre 35 dollar switch with the plate which is pretty stout but my buddy is running a cheapo key style on his ITB scca car.

GSRCRXsi

i looked but it seemed like the one with the plate only had two posts (for cars without an alternator), link to the one with the plate and is a 4 post?

descartesfool

A good place to buy all kinds of automotive electrical supplies is Waytek Wire:
http://order.waytekwire.com/products...ches/Switches/

Search the site and you will find all kinds of connectors, wires, crimps, switches, relays, etc.

SCCA rule book says this: http://www.scca.org/documents/2011%2...lo%20Rules.pdf

Master Switch - All cars shall be equipped with a master switch
easily accessible from outside the car. Spec Racer Fords shall be
wired per RFSRII. The master switch shall be installed directly in
either battery cable and shall cut all electrical circuits but not an
on-board fire system, if so equipped. It shall be clearly marked by
the international marking of a spark in a blue triangle and mounted
in a standard location. OFF position shall be clearly indicated
at the master switch location. The standard locations shall be as
follows:
a. FORMULA AND SPORTS RACING CARS — In proximity to
the right-hand member of the roll bar, but in a location so that
it cannot be operated accidentally. It can be mounted on a
bracket welded to the inside of the upright member or mounted
so that the operating lever or **** is outside of the body panel
immediately inboard of the upright member.
b. CLOSED SPORTS RACING CARS, PRODUCTION CARS,
AND GT CARS - In front of the windshield on either the cowl
or on top of the fender, but close enough to the windshield to
18. MODIFIED CATEGORY — 135
be accessible if the car is overturned. Alternatively, it may be
mounted below the center of the rear window or on a bracket
welded, clamped or bolted to the roll cage or dash, easily accessible
through the open window. (Drilling of holes in roll cage
to attach the bracket is prohibited.)
c. OPEN PRODUCTION and GT Cars - May exercise a choice
among the above locations.

So I don't think you can leave anything connected to the battery when the switch is in the off position.

GSRCRXsi

thanks for that, ill check out that site. ill be with NASA though. ive seen lots of people mount it inside the cabin by the drivers window on the dash. seems like a good enough place. weird that the SCCA rules seem to all want you to mount the switch outside the car and not really operable by the driver.

known

iTrader: (1)

you dont have to mount it outside the car for scca.

it just needs to be accessible from outside meaning they can look at your sticker indicator and reach in and shut it down. a lot of people have them welded to a plate on the cage on the driver side.

descartesfool

You can also check out this switch with extra contact to connect alternator output to ground via a resistor when disconnecting battery:

http://www.pegasusautoracing.com/pro...asp?RecID=1464

descartesfool

Here is a pic I took last year of the interior of one of Realtime's TSX's. You can see the kill switch on the dash inside the car.

Next pic shows a rare exterior disconnect switch on a World Challenge Lotus from 2010.

GSRCRXsi

thanks again,

yea thats the switch i was talking about. curious if its worth double the price of the longacre one.

GSRCRXsi

a shopping list from that site:

5 - $3.2300 - Toggle Switch ON-OFF SPST 15A, 2 terminals
1 - $5.6900 - Toggle Switch ON-OFF DPST 15A, 4 terminals
1 - $14.930 - Fuseblock, 12 Gang w/ ground terminal
6 - $3.1700 - Standard Relays, 12V SPDT 40/20A, 5 terminals
4 - $2.4800 - 4' length, black heat shrink, 1/4" ID, 4:1 shrink, adhesive
100 - $0.0281 - female push-on .250 22-18ga, non-insulated
100 - $0.0422 - female push-on .250 12-10ga, non-insulated
__________
total - $72.74

i figure i can get wire locally, and reuse some of the looming from the stock harness. and im going to re-use some connectors in the chassis harness from the old harness. most likely i will re-use the under hood fuse box for the big fuses, and relocate it under the dash. besides the master switch (i didnt really like their selection), am i missing anything?

when you have a switch/relay setup, such as with the fuel pump and ignition circuits, do you have to fuse the switch portion? or just the relay portion? or both?

also what gauge wire do you think will be needed from the battery to the switch and back?

edit:

so i made this little diagram of a potential setup with the 4430 switch. figured its easier than trying to explain it in words. i would use two of these guys on the firewall



and do something like this:



any problems with this? note, i would still have the ignition on the second pole of the switch, i just didnt add it to the picture.

spAdam

iTrader: (1)

I've always been told that on an alternator equipped car that you need to use the method in your last post there to keep the still turning alternator from backfeeding and doing damage to the ecu or other components.

That being said, I know a handful of drag guys that still had alternators and did not use the resistor to ground and never fried anything, but I doubt that they ever operated the switch with any kind of revs (and therefore alternator output). Its not something that really I'd like to test though, so I'm going to assume that you need the resistor.

Anyone have any experience to share on that?

GSRCRXsi

so theres no problem with my above drawing? no issues with the alt, starter and fuse box being splits of the same lead?

also, is there an issue using a relay for the ignition switch, rather than having the full load going through the switch the whole time? seems most diagrams (and even stock) use a switch, rather than a switch and relay setup.

spAdam

iTrader: (1)

I don't see a problem. Not sure why you need to cut power to the starter though. That circuit is open unless the solenoid is closed, and the solenoid can't be closed if there is no available power to the signal side.

GSRCRXsi

yea, i dont either, but rules are rules i guess. maybe they dont want any possible shorts with the switch off? i dont know really.

spAdam

iTrader: (1)

I would re-read your rule book, maybe even shoot an email to someone in your sanctioning body for a clarification. The amperage that you starter can pull is a lot to run through any automotive grade switch (imho of course) and is the reason why starter cables are connected directly to the battery with as short as possible a cable from the factory. My most rigorous safety tech experience is with FSAE, and while they sent us back to the paddock to rewire our safety switch for not individually cutting a few circuits, they said nothing about the starter being run straight to the battery.

I'd also like to know for future reference. I'm all about passing tech on the first try.

GSRCRXsi

this is what the NASA CCR says about the master switch:

"An electrical master switch is recommended on all cars, and required on some, as listed in the class rules. It shall be mounted so that it is easily accessible from the outside. If mounted outside the cockpit, it should be mounted in an area where it is least likely to be damage (e.g. cowling near wipers). The switch shall shut off the motor and cut all power except to the on-board fire system and any other life support / medical device. The switch location must be clearly marked. Any marked switch must function as per this rule, or the indication decal must be removed."

HC rules just say: "a NASA CCR compliant masterswitch must be used"

so the question becomes, is this legal/aceptable? its a preferable setup IMO

spAdam

iTrader: (1)

Unless someone else with more experience chimes in here, I'm 98% sure that that is the way to do it.

GSRCRXsi

yeah, i PMed prkiller this thread. hopefully he can chime in.

raffaelli

that diagram is correct. dont forget to find a good ground for the resistor. i would also consider the terminals at the fire wall optional.

GSRCRXsi

yes, the terminals are optional. thats just my preference for an easy disconnect and would be covered by boots. thanks for confirming that the second diagram with a direct starter/battery connection.

what gauge wire would you recommend for the path to the switch and back? 8ga? 6ga? 4ga? larger?

any objections to my list? or using a relay setup for the ignition, rather than just a beefy switch.

5 - $3.2300 - Toggle Switch ON-OFF SPST 15A, 2 terminals
1 - $5.6900 - Toggle Switch ON-OFF DPST 15A, 4 terminals
1 - $14.930 - Fuseblock, 12 Gang w/ ground terminal
6 - $3.1700 - Standard Relays, 12V SPDT 40/20A, 5 terminals
4 - $2.4800 - 4' length, black heat shrink, 1/4" ID, 4:1 shrink, adhesive
100 - $0.0281 - female push-on .250 22-18ga, non-insulated
100 - $0.0422 - female push-on .250 12-10ga, non-insulated
__________
total - $72.74

Atmosfear

iTrader: (18)

I would say 4 ga. minimum. Have you done a battery relocate as well?

granracing

Mount it somewhere you and the corner worker both can access it. Sitting in the car seeing steam pour out, hoping it's not smoke while you can't reach the kill switch really sucks. I was sitting perpendicular just below a hill horizon on a track, couldn't get out as I watched cars swerve around me, and workers couldn't get close to the car quickly. After that totalled car, the kill switch was mounted in the same general area as the Real Time pic.

Awesome installation illustration.