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Last page update was 16 Sep 2011

Electrics

The electrics in my car can be split into two seperate sections. The only overlap between the two is the ignition switch and battery.
  1. The bike harness, ECU, starter, etc. (which is covered in the engine section). The R1 engine comes with a wiring loom for lighting and other bits but it is going to bear no relationship to the wiring required for a car. My approach is to retain the R1 loom for all engine related functions. Some people strip out the wiring not required for a car installation but this carries with it a risk that you cut a required wire by mistake. I do need to unwrap the bike loom though to ensure it can reach all the required places and some parts may need extending.

  2. The rest (lights, horn, fuel pump, etc.), for which I will create my own custom loom.

Creating a car wiring loom from scratch can be a daunting prospect and most kit car manufacturers will supply their own loom. As with all generic designs though, it isn't going to do exactly what you want to do and my view is that building the loom is going to give me a better understanding of the car. If it all goes wrong and I have to start diagnosing problems, I will be far better placed, having put it together myself.

In order to wire the car up from scratch, I've produced my own wiring diagram (Microsoft Powerpoint) to help me. This is now pretty much complete but may change slightly as I start wire up the car. There isn't actually that much wire involved though and there is nothing particularly complex about it. The key things are:

Before you can make up the car part of the loom, you have to fully understand what you have in the bike loom.

Battery

Richard  used a Yuasa YTX12-BS 10Ah bike battery from MDS Battery . Dimensions are 150mm (w) x 87mm (d) x 130mm (h), weight is 4.1Kg. I planned to use the YTX9-BS 8Ah battery as it was nearly 1Kg lighter but thought better of it in the end and also went for the YTX12-BS.

There are no permanently connected circuits to discharge the battery over time but, the recommended charger for these sorts of batteries seems to be the Optimate III . This device will automatically maintain the battery state during long periods of non-use. I plan to wire in accessory sockets, which will also be used to connect this charger.

Battery Clamp

Richard  made a custom battery clamp from some aluminium straight.

Battery Isolator

It is a popular misconception that you need a battery isolator switch for competition use but in reality an ignition switch with suitable labelling will do. To add one would mean modifying the bike wiring harness and cables and to reducue weight and the length and complexity of the wiring required, so I'm not fitting one. This also results in a less cluttered dash.

Wiring

All of the cables for the main car loom are from Vehicle Wiring Products  (VWP). VWP sell three grades of 'thinwall' cable:
  1. Thinwall 16/0.20mm, 0.5mm², 11 amps. 20p per M. 7.40 per 100M reel. - Typical applications: Side & tail lights, alarms, reversing & rear fog lamps, electric aerial, horns, general wiring.

  2. Thinwall 32/0.20mm, 1mm², 16.5 amps. 24p per M. 11.15 per 100M reel. - Typical applications: Side & tail lights, alarms, reversing & rear fog lamps, electric aerial, horns, general wiring.

  3. Thinwall 28/0.30mm, 2mm², 25 amps. 30p per M. 18.75 per 100M reel. - Typical applications: Headlamps, fog & driving lamps, rear screen heater, windscreen wiper motor.

The cable thicknesses and colours used are indicated on my wiring diagram. Basically, it is all 0.5mm² except:

Wiring Standards

There are wiring standards and colours codes that should be used but I've chosen my own colours to minimise the different colours of cable I need to buy. The only thing I have done, is made sure that no two wires of the same colour go to a single switch, lamp or relay. This makes fault finding a lot easier.

Wiring Protection

I've tape wound bits of the wiring but in most places I've used a plastic spiral wrap from Maplin to keep the wires together and to keep the wiring loom tidy. This also prevents possible chaffing of the wires.

Ground Points

The chassis is basically grounded and there are several grounding points to which earth wiring is run to reduce clutter and length of wiring. There is a rear ground point for the fuel pump and all rear lights and another at the front of the car for the front lights. There will also be one or two in the engine bay.

Wiring To Fuses

There are five fuses fed directly from the battery (unswitched) and each potentially carries a large current flow (e.g. headlights, horn, etc.). In order to handle the current flows I will use a tube battery connectory with five seperate 30A cables going from this to the five fuse spade terminals. To tidy it up these cables will be spiral wrapped.

For the other fuses a single wire runs from the ignition switch to one of the terminals and is then looped around to the others in series. I can do this as these carry little current. This side of the ignition switch also goes off to the bike loom. Power on the other side of the ignition switch also comes from the bike loom.

Fuses

The fuse box holds eight 6.3mm blade fuses and is mounted behind the dash.

Fuse 1 (3A) - Instruments And Relays

This provides power to the instruments (Digidash) and the three relays used to switch the lights and horn. These relays have in-built diodes to cut back EMF.

Fuse 2 (3A) - Brake lights

Power to brake foot switch and then on to the LED brake lights.

Fuse 3 (5A) - Indicators

2 x 21W + 5W = 47W or 4amps.

Fuse 4 (10A) - Hazards

4 x 21W + 2 x 5W = 94W or 8amps. The hazard lights must work when the ignition is off.

Fuse 5 (20A) - Head Lights And Fog Lights

2 x 55W + 21W (fog light) = 131W or 11amps. Only high or low beam are on at once. Fog light is connected to this circuit as it must only come on with low or high beam headlights. This circuit is switched via the ignition switch and goes to the lights on/off toggle switch, which enables the headlight relay. This relay switches power via the headlight fuse to the main/dipped relay. This relay is not energised until the latching, high-beam switch is pressed. If not energised power is switched via the relay to the dipped bulbs and if energised power is switched over to the high-beam bulbs. This means the light switches are only powering relays and not the lights themselves.

Fuse 6 (20A) - Horn

This provides power to the twin horns via a relay.

Fuse 7 (10A) - Side Lights

4 x 21W side lights = 84W or 7amps. For SVA, the side lights must work with the ignition off.

Fuse 8 (10A) - Accessories

For taking in-car video footage and powering PMR radio communications via two 12V power sockets on the rear bulkhead. These use locking XLR connectors with a waterproof, protective cap. These will not be switched via the ignition and this means I can also plug in a battery conditioner at this point.

Indicators / Hazards

For the SVA test, the hazard lights must work even when the ignition is switched off. The logic required is provided by a 7-pin hazard switch from Vehicle Wiring Products  (part no. 517202). This is fairly large switch 38mm in diameter and requiring a 30mm diameter cut-out.

The electronic flasher unit from Vehicle Wiring Products  has four pins labelled C (warning lamp), 31 (earth), 49 (12V supply), 49a (indicator switch). The advantage of an electronic flasher unit is that the flash rate is not dependent on the load. They do a wide range of flasher units but this one (part no. RFL5) meets my needs best.

The wiring of the hazard switch and flasher unit is shown below, based on the supplied instructions. Note that a single flasher unit is used for both indicators and hazards in this design. It is powered when the ignition (pin 1) is switched via pin 4 or when the hazard switch is enabled via pin 2. Because the flasher unit is powered all the time via the ignition switch, the Digidash indicator warning light cannot be driven by pin 'C' on the flasher unit. The hazard switch has its own internal bulb to indicate that the hazards are on. There are other designs that use two flasher units, one for hazard function and one for the indicator function.

I worked out a better way of wiring this though, that does not leave the flasher unit powered all the time the ignition is switched on. I can do this because my indicator switch is a double pole on-off-on switch and the spare pole can be used to only power the flasher unit, when the indicators are switched on. This also means that pin 'C' on the flasher unit could be used to drive an indicator warning light but, on the Digidash2 you need to supply seperate left and right warning feeds.

Other Stuff

It's not shown in any of the circuit diagrams but I've also run some other wiring for the in-car video recording and in-car comms system. There is a co-ax line running from the camera, down the centre tunnel and round to the recording device, sitting on top of the drivers side-pod.

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