Electrical System

The electrical system in this car is clearly split into two parts:

  1. The motorbike ECU and associated loom. This is pretty much left as is but I strip out all the unwanted wiring for things like lights, etc. From an electronics perspective, this is a closed system.
  2. The rest of the wiring system for the instruments, lights, horn, sensors, etc. This is a bespoke design and build by me, optimised to reduce weight and covered below.

The 'electrics' as defined here, do not include the digital instrument displays or the bike engine electrics. It does include the lighting.

The electrics are essentially very basic and simple, because there just aren't many things being switched and controlled in this car. Security is provided by a basic keyed ignition switch. There is no immobiliser (unless this comes as part of the bike engine package and loom).

The CAN Bus is an automotive bus developed by Robert Bosch, which has quickly gained acceptance into the automotive and aerospace industries. CAN is a serial bus protocol to connect individual systems and sensors as an alternative to conventional multi-wire looms. It allows automotive components to communicate on a single or dual-wire networked data bus up to 1Mbps. I quickly ruled out using a CAN Bus as it is simply overkill for a car with so few components in it. I also ruled out using ISIS for similar reasons.

The electrical system in my Fury R1 (engine electrics are covered separately) was designed from scratch and built by me. This enabled me to run the cables in the most direct route, use the thinnest cable I thought I could get away with (at the time) and crimp and solder the whole loom myself, to ensure excellent reliability. I also used my own wiring colour coding system, to simplify fault finding and repair if ever required. Each colour wire was only used for one purpose throughout the whole car.

I over-engineered my Fisher Fury R1 wiring loom though, as it was my first kit car build and I wanted to be sure it would work reliably. And it has. With this car I plan to be more clever with the number of wires used and the size of the wires used. In this new wiring loom I am confident that I can save 2Kg or more.

Location

One easy way that I can save significant weight in this car, is through more intelligent location of the various components and an electrical system design that clearly separates the high current and low current systems and wiring. Both will enable less wiring to be used and the latter will mean that more of the wiring is very thin (7/0.2mm), low current (rated at 1.4A) 'equipment' wire (which is also cheaper).

I also plan to not run individual power wires to all of the lights at the front of the car (especially as the battery will now be at in the engine bay at the rear of the car). I will run a single power cable from the battery to the front of the car and to have the relays switching power to the lights in close proximity.

In this car, all of the switch gear will be located close to the steering wheel and all of this will be connected using low current wiring.

Wiring & Standards

In my Fury build I used the following wires:

7/0.2 Wire

In this car, I'm also using lots of 7/0.2mm, 1.4A equipment wire (0.22mm²) as discussed above. This is significantly lighter than the above wires [3.5g per meter]. This wire is available in a range of colours, to enable a unique colour coding system: black, white, grey, brown, red, orange, yellow, blue, green, pink and purple. It will only be used for signaling and LED lighting but this constitutes the majority of the wiring in this car. The resistance and voltage drop are too high to use it for any other purpose.

Colour Coding

I plan to build my loom from scratch again and use my own bespoke colour coding system again. It's just easier to do this for me and it will save huge amounts of weight (and a some money). All sensors will use 2-colour (e.g. white/blue) wiring.

Battery

Yuasa YTX12-BS My Fisher Fury R1 uses a Yuasa YTX12-BS 10Ah lead-acid battery which weighs 4.1Kg with electrolyte (not the claimed 3.4Kg). It is quite a small battery (150mm × 87mm × 130mm) but, the first lasted for nearly 5 years. I do use a battery conditioner on it regularly though. If you use a battery this small, it is important that leave nothing electrically connected to it, which will drain it flat and damage it.

The McLaren MP4-12C uses a Lithium Ion battery to save weight and this is an option I'm planing as it is an easy (not too expensive) way to save a several kilograms. The Shorai Inc LFX14A1-BS12 is a Lithium Iron Phosphate equivalent battery that weighs just 851g and is much smaller.

Fuses

8-way fuse holder In the Fury I used this 8-way blade fuse holder. It weighs 64g without fuses. To save weight, I'm using two smaller fuse holders, one near the battery and the other near the ignition switch. This massively reduces the amount of wire required.

Ignition Switch Fuses

Main Fuses

Relays

30A relay Bike engine wiring loom aside, there are just three relays in the rest of the electrical system. These are for the headlights dipped beam, headlights main beam and the horn. Again, to reduce the amount of high current wiring used, these are located close to the headlights and horn. They also use a single common power feed wire.

To save weight, I don't plan to use fuse holders, just 6.3mm spade connectors onto the relay terminals. You can get compact relays but they don't weigh much less and are a lot more expensive.

Power Sockets

2-pin locking power socket On my Fury, I had a total of 5 bespoke, locking power sockets (Maplin part no. FM50E), for powering things like video cameras, sat nav, phones, etc. They needed to be locking to maintain electrical connection whilst exposed to vibrations and acceleration. They are also used to connect a battery conditioner to the battery. Whilst being very handy, they are additional weight (10g each). In this car, I will just have one at the rear of the car.

power socket I'll also have a single standard cigarette socket at the front. These all go via a 5A fuse to the battery. I found this marine grade one with a waterproof cover on-line. It weighs 40g and is rated to 20A.

Top • Last page update: 16 Apr 2014