Time to start wiring the car!

General Chat About Electrics, And Ignition Systems.

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unstable load
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Post by unstable load » Sun May 14, 2017 1:51 am

Do you have the regulations for the class of racing you want to go into? There may well be something in there that is specifically required, and, guidelines to put kill switches here, here, and there.


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Post by stevieturbo » Sun May 14, 2017 10:34 am

The cutoff switch there...doesnt actually kill the alternator line.

So if the alternator is still spinning when you cut it, it will still be providing power to the accessories

Don't forget, the battery does not power things when the car is running, all power comes from the alternator and any excess re-charges the battery.

That's why there seems to be some calling it different things. Your diagram would isolate the battery, but not necessarily kill all electrical systems as some remain attached to the alternator.

Although by cutting ignition power to coils etc too it should also kill the engine which should stop the alternator charging and providing power elsewhere.

So it should be ok...
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Post by DaveEFI » Sun May 14, 2017 11:23 am

Also, if you disconnect the battery from a running engine, the volts can go sky high. which could fry any electronics.

I'm surprised there's not a suitable schematic out there for all the basics?
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Post by stevieturbo » Sun May 14, 2017 11:30 am

There should be a dump path for the alternator via the resistor on that kill switch for that.

Although never really looked into it much
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http://www.youtube.com/watch?v=XgWRCDtiTQ0

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Post by chodjinn » Mon May 15, 2017 6:36 am

OK well this is why I am asking for advice, I have read around a lot and done the best I can but I don't know if it is right or what needs changing. Yeah Dave I was surprised that I couldn't find a diagram or diagrams to try and help me.

The point of the fia kill switch is that it kills everything, so yes the alternator needs to go through it or whatever, but like I say I don't know how to do this. That diagram was my first attempt at sketching it out.
Last edited by chodjinn on Mon May 15, 2017 6:40 am, edited 1 time in total.
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Post by chodjinn » Mon May 15, 2017 6:38 am

unstable load wrote:Do you have the regulations for the class of racing you want to go into? There may well be something in there that is specifically required, and, guidelines to put kill switches here, here, and there.
MSA Blue book regs. Need to run an FIA kill switch with external/internal pull cords, and a rear rain/warning light. Nothing else is required specifically so I just need the wiring loom to run the engine and associated bits, plus a mini internal fan/heater and wipers/washer.

I'm ok on the individual circuits for rad fan, fuel pumps etc. It's the main part I am stuck with.
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Post by stevieturbo » Mon May 15, 2017 9:22 am

chodjinn wrote:
unstable load wrote:Do you have the regulations for the class of racing you want to go into? There may well be something in there that is specifically required, and, guidelines to put kill switches here, here, and there.
MSA Blue book regs. Need to run an FIA kill switch with external/internal pull cords, and a rear rain/warning light. Nothing else is required specifically so I just need the wiring loom to run the engine and associated bits, plus a mini internal fan/heater and wipers/washer.

I'm ok on the individual circuits for rad fan, fuel pumps etc. It's the main part I am stuck with.
MSA rules not always so clear...as a lot just ask for a fuel supply etc kill switch....which in many cases is the ignition switch ( and that it is reachable by the driver and labelled from outside. )
Not 100% sure which classes insist on an external kill switch

wiring diagrams for switch,

https://uk.images.search.yahoo.com/yhs/ ... e=avastbcl
9.85 @ 144.75mph
202mph standing mile
http://www.youtube.com/watch?v=XgWRCDtiTQ0

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Post by chodjinn » Mon May 15, 2017 10:02 am

For reference the race series is the BARC CNC Sports & Saloons Championship, my car fits under Class A rules. The rules are very open, but for electrics it only states that the brake lights need to work. And then standard safety features e.g. the rain/warning light and fia kill switch:

"One electrical circuit breaker must isolate all electrical systems on the car as defined in the MSA Yearbook section K(8) and Q(19.11.1). This circuit breaker must be accessible from outside the car and also by the driver."

The problem is Stevie, all diagrams relating to FIA kill switches indicate the use of an ignition switch, I am not using one of these which is why I am getting very frustrated/annoyed and not being able to figure out the wiring! I appreciate the help guys but I really need to get this sorted asap short of spending thousands of pounds for a professional to do it is there anywhere I can go for advice or anything else I can read etc?
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Post by stevieturbo » Mon May 15, 2017 7:28 pm

Any vehicle will need some sort of switch to kill the engine, call it what you will. Ignition switch is a fairly generic term and of course your car will need one.

it may not have a key, it may not be on the steering column...but it will still be doing the same job.
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202mph standing mile
http://www.youtube.com/watch?v=XgWRCDtiTQ0

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Post by chodjinn » Tue May 16, 2017 6:22 am

Right, well Richard has kindly sent me an email with a bit of an explanation which has helped a lot, sorted out a few things I was confused over. Which has made things a lot better. Relatively busy this week but will try and get something done later on and report back!
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Post by Ian Anderson » Tue May 16, 2017 5:21 pm

If you have a plumbed in fire system.
It has to work even if the kill switch is pulled

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Post by chodjinn » Tue May 16, 2017 5:33 pm

Ian Anderson wrote:If you have a plumbed in fire system.
It has to work even if the kill switch is pulled

Ian
It does, it's entirely mechanical and not related to the electrical system. There are two pull chords, one outside and one next to the driver (same for the kill switch). Also have a separate hand held extinguisher. Pretty standard for most track racing/hillclimbs.

Although I will have to wait a while to actually race in the series I want. New regs for 2017 mean I need a National A Race Licence, it used to be a National B. Guess I will have to do a few hillclimbs or something first.
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Post by chodjinn » Mon May 22, 2017 12:11 pm

I know there are mistakes in this but it's as far as I have gotten, but I don't know where to go from this. Some people tell me a 100amp breaker is fine, others say I need a 300amp for the starter and 100amp for everything else, but no one actually says where they need to go .... Rich has already said it wont work as it'll overload, but I don't understand why/what. The bottom four read lines from the fuse board go to the fuel pumps/rear lights/warning light - although I have just changed the twin fuel pump feed to a single as will be running both pumps off one relay.

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Post by stevieturbo » Mon May 22, 2017 5:09 pm

Overcurrent protection of any kind should always go as close to the power source as possible because largely this is to protect the wiring run thereafter.

Whether your breaker can work for starting current...depends on the breaker, its type and rating. Even if a started pulled say 200A...the initial hit might be much higher. Certainly in the mains voltage world, you get specific motor rated breakers designed not to trip with these brief surges.
I'm sure any car specific unit would be the same.

As for source of power...again, when running this will be the alternator, not the battery so that may need factoring in for any fuses or protection. 100A local to it should be fine.

You have a 75A fuse...then a relay. What size of relay that you're using a 75A fuse ? That'll need to be a 70A if you're expecting that much load.

Most...all ecu's trigger stuff via ground, not live as per your fan relay.

Some of the other 12v ign relay feeds....all of these are very low current so you could easily fuse these quite low. Your ignition relay trigger is almost unfused here.
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http://www.youtube.com/watch?v=XgWRCDtiTQ0

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Post by chodjinn » Tue May 23, 2017 5:54 am

Yeah, didn't really understand most of that Stevie. The diagram was cobbled together with a little help from Rich. I'm still struggling to find any useful/consistent information. I would have thought there would be a lot out there for beginners but apparently not!
RIP MGB V8 .... served me well as a learning curve.

R32 Skyline V8 .... this one is gonna be a monster!

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