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Practical Wiring - Professional Motorsport: Component Listing and Physical Mounting

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Component Listing and Physical Mounting


00:00 - In this section of the course, we will discuss the key design techniques required at a professional motorsport level and how we will apply them.
00:07 The main aim of our design process is to generate a plan of how we will construct our wiring harness to ensure that all parts of it are accessible, i.e. not booted or sheathed in heat strink, while we still require access to them.
00:20 Although the desire and temptation is to delve right into the physical wiring harness construction, we need to have completed the design process before we do this as it is possible that the very last design element we consider could affect the first.
00:34 And we need to have every step planned out before we begin.
00:37 The first step of our design process is to list out all of the elements our wiring harness will make connections to.
00:43 This will vary greatly with your application, but for a reasonably standard EFI wiring harness, we'll include the power supply relays, ECU, fuel injectors, ignition coils and various engine sensors.
00:55 A professional level race car will most likely have many many other electronic devices fitted to the vehicle however, such as a power distribution module, chassis sensors, loggers displays, and more.
01:07 By listing all of these elements we can ensure that none of them are missed during our design process.
01:12 With all of our devices listed, we need to examine their physical location and how they're mounted in the vehicle.
01:18 We do this early on to try and deal with any connection problems before they become an issue.
01:24 Along with ensuring that the electronics are physically present and actually mounted to the vehicle.
01:29 While it's not impossible to make an estimate of a connector's required location, without having the electronic device it connects to in place, it's much easier to guarantee a tidy result if its present and properly mounted.
01:40 When looking at each device's mounting, you need to visualise how the harness will connect to the device, at what angle the harness will approach the device, and any special strain relieving that might need to be undertaken.
01:52 A good example to illustrate what I mean here can be seen with an ECU that has multiple connectors along one edge such as the Motec M1 series.
02:00 The temptation is often to mount the ECU in such a way that the wiring harness meets the ECU at a right angle along the length of this edge.
02:09 This is usually fine at the modified street car level as the harness would not typically be booted to the connector and the natural flex of the harness wires would allow us to easily install and uninstall those connectors.
02:22 In the professional motorsport world though we're going to be using shrinkable moulded boots to seal and strain relieve our harness at these points.
02:29 And the shape of these may not allow for a tidy installation with the connectors meeting the device at certain angles.
02:36 In this situation the solution would be to move the ECU up its mounting position an amount, allowing us to then use 45 degree boots or even straight boots so the harness exiting one connector will not interfere with the next.
02:50 If this was not possible we would look at rotating the ECU to give us better access or routing our harness in such a way that although the branches still met our connectors at a right angle, they wouldn't interfere with one another.
03:01 Another consideration to make is if the device or group of devices our harness is going to be connecting to is required in the vehicle at all times or is only going to be used during the vehicle set up and qualifying.
03:13 If this is the case, it's connection might be better accompanied with a sub harness that can be removed when the devices are no longer required.
03:21 To explain what I mean here we'll look at a four channel analog sensor to CAN bus interface.
03:28 It could be set up for auxiliary logging of chassis parameters such as suspension displacement.
03:33 But only while the vehicle is being tuned.
03:35 Instead of integrating the connection of these four sensors into our main harness, a better strategy would be to build a sub harness that connects these four sensors to the interface unit and then have a single connector on our main harness that also connects to the interface unit.
03:51 By moving these four connections into a sub harness, we will have simplified our main harness design and created a distinct sub system that may be possible to share over several vehicles.
04:02 Related to sub harnesses is the subject of interface or break out boxes.
04:06 These are similar to sub harnesses in that they allow us to shift complex sections away from our main wiring harness simplifying its design and construction process.
04:15 A good example of breakout boxes can often be seen fitted to the engine on a high level single seat race car.
04:22 All the engine sensors and actuators connect to the break out box either directly or via sub harnesses.
04:29 The wiring inside the break out box then takes all of these connections into a single connector, also mounted on the breakout box to which a main wiring harness connects.
04:39 Along with simplifying our harness design and construction process, this also means the main harness now only has a single connection which needs to be unplugged if we're splitting the engine from the chassis.
04:50 Essentially breakout boxes move the complicated branch sections of our harness inside a sealed box.
04:57 The extra space inside this box can make branching much easier to undertake tidily along with being a great place to perform splicing operations as they're very easy to strain relieve.
05:07 I'll conclude this section by mentioning something that I have found to be common practice, and that's for mechanical race engineers working on a car to assume that wiring can be run absolutely anywhere and no thought needs to be given to its routing.
05:20 It's our job as the electrical side of the team to help them think through the basics of how the component will be wired, the orientation of the connectors, and ensure that they are aware that we really do need the component physically mounted before we can design our harness to ensure the best outcome.