Building A Cosworth Powered Kit Car
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Building A Cosworth Powered Kit Car
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WiringA Birds Nest of Wires!The next section in the build manual was the wiring loom. The wiring loom supplied with the kit was specifically designed for a Pinto engine with a carburettor. As I was fitting a Cosworth engine with fuel injection, I had the complication of fitting an ECU, extra sensors in the engine bay and the associated wiring to make it all work. Luckily the Cosworth engine has its own wiring loom which was retro fitted on top of the Sierra loom. This loom had its own relays, fuses and required little interfacing with the Quantum supplied loom. Only 4 connections were required. Fuel Pump - The Quantum loom already has a fuel pump feed travelling to the rear of the car. Coil – I decided to use the Cosworth wiring for the coil but the rev counter required a feed. Power – To minimise connectors at the battery, The Power to the Cosworth loom is supplied via the direct feed +12v from the Quantum loom Ground – Again to minimise connections to the battery, It seemed sensible to connect the Cosworth loom to the same ground point as the Quantum loom. To complicate things further, I had taken the ABS wiring loom from the Cosworth donor as well as I intended to use the wheel speed rotors for the Racelogic traction control system. The only cables I really needed from the ABS wiring loom was the shielded cable from the wheel speed sensors. The complication doesn’t stop there, the Racelogic traction control system has its own ECU and a mass of wires to interface with the wheel speed sensors, the fuel injectors, the coil feed, power and ground. A separate loom is also included which connects to the slip adjuster switch and launch control button. Finally, one more item was added into the melting pot before I start fitting the wiring. As I used to fit Thatcham approved Alarms and Immobilisers. I acquired a Cobra Thatcham Category 1 alarm and immobiliser. This consisted of a Battery backup Siren, a central control unit, a separate immobiliser module and a hyperfrequency sensor. Loom Wiring to back of ChassisThe first thing I did was fit the rear part of the Quantum supplied wiring loom. This fed through a grommet into the top of the transmission tunnel. At the same time, I included the shielded cables for the rear wheel speed sensors and an extra blue wire for the alarm boot switch. This part of the wiring loom terminated at a non waterproof multiway plug in the rear subframe. As I needed more connections and I did not like the fact that this multiway plug was not waterproof, I replace this multiway plug with a larger Waterproof multiway plug. While I was in the process of changing the multiway plug, I realised that the fuel level sender would not work if the boot tub loom is disconnected. It was relatively easy to change this so the fuel level sender was connected to the chassis side of the multiway plug rather than the boot tub side. I also wanted to fit an inertia switch to the fuel pump just on case I have an accident. I took the inertia switch from the donor Sierra and decided to mount it in the boot tub. This meant I needed to modify the rear loom so that the fuel pump feed was fed through the multiway plug to the boot tub loom and the returning fuel pump feed on the boot tub loom is connected to the fuel pump via the multiway plug. Loom Wiring in Engine BayThe number of wires which needed to feed into the engine bay from the Passenger footwell would never fit through the existing laser cut hole in the chassis. The easiest way around this was to cut a second hole next to the existing hole to allow the Cosworth loom to enter the engine bay. This was a very neat solution as the Cosworth loom did no have to interface with the Quantum supplied loom in the engine bay. The dressing of the looms was the next issue, I never liked the cable ties supplied with the kit, which secure loom to chassis. As I would be doing a lot of experimenting, I required reusable loom clips similar to what the major manufacturers use. I ended up acquiring a mixed selection from Vehicle Wiring Products which do the job perfectly. Alarm and Immobiliser WiringBefore starting to connect the various wiring looms together, I needed to make sure all the module were mounted in place. This meant mounting the Siren and immobiliser modules in hard to get places and dressing the wires along with existing wiring to the passnger footwell. Traction Control WiringLike with the Alarm system, the traction control unit was mounted in a secure dry place behind the scuttle and the injector cut, tacho feed, wheel speed sensor and power wiring were dressed along existing loom wiring to the passenger footwell. The Control loom from the Traction control unit was then dress along with the Scuttle Wiring loom to exit the scuttle through the large hole in the middle of the metal scuttle. I added a multiway connector to the control loom at this point to assist easy removal of the scuttle. Scuttle WiringThe Quantum supplied loom already separated the wiring loom which sits behind the scuttle from the part which comes from the passenger footwell. This made life fairly easy except I had decided to use Greengauges dash instruments meaning extra wiring was required to run the Greengauges Tacho and Greengauges electronic speedo. The supplied wiring looms which came with the greengages Tacho and Speedo simplified matter greatly except I was one wire short. I needed to add a wheel speed sensor feed from one of the wheels to the speedo. This was an easy task as all four wheel speed sensor wires were sitting in the passnger footwell. As I had a fair excess shielded wheel speed wiring, I dressed a shielded wheel speed sensor feed from the passnger footwell to the scuttle. As this is a shielded cable, a shielded connector was required meaning this wire could not be part of the multiway connector already present. Passenger Footwell Wiring
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