Practical Wiring - Professional Motorsport: Step 3 - Documentation Detail and Concentric Layer Design
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Step 3 - Documentation Detail and Concentric Layer Design
39.20
| 00:00 | - The third step of our construction process involves finalising our design and documentation. |
| 00:05 | We complete these tasks at the same time since they'll usually be done together and there's usually some degree of back and forth since one element obviously affects the other. |
| 00:15 | We're going to be utilising the information that we've created during the last two steps for aspects like wire size and physical layout and add the necessary details required to use this as the basis of our construction. |
| 00:28 | We'll begin by finalising our connector specifications which is often a task that those new to working at this level worry about, particularly when it comes to the likes of Autosport connectors. |
| 00:39 | We have 3 separate considerations with this wiring job. |
| 00:42 | First of all, there are some connectors where the choice is driven by our choice of electronics. |
| 00:47 | What I mean here is that in the case of the MoTeC electronics, we already know what the mating connectors will be so it's just a case of sourcing these. |
| 00:56 | With the exception of the C127 dash which uses the superseal 1.0 connector, the remainder use autosport connectors. |
| 01:04 | When it comes to the 3UZ-FE engine, we have some options. |
| 01:08 | If we wanted to take our harness construction to extremes, then arguably the best option would be to pot each of the sensors and actuators on the engine with a flying lead and then terminate these with autosport connectors. |
| 01:22 | This is a little excessive for our particular application, hence we've chosen to deviate slightly here and fit all new genuine Toyota connector bodies instead. |
| 01:32 | This is going to be more than adequate for our application and will still provide great reliability and environmental protection and this can be further improved upon by booting some of these connectors with heat moulded boots. |
| 01:46 | This is an area where some understanding of the connectors you're working with can help drive your decision though. |
| 01:52 | For example there are some factory connectors that are known to be problematic and these can fail when subjected to vibration like we'll see in a motorsport application. |
| 02:02 | In other instances, it may be difficult or impossible to source replacement genuine connector bodies so in this case we may have no alternative but to pot these sensors or actuators and terminate in an autosport connector or something similar. |
| 02:17 | We also need to specify the remaining connectors that will form our harness. |
| 02:22 | We're going to be using a combination in this case of autosport connectors for the likes of the bulkhead connector and the interface to the PDM. |
| 02:30 | However we'll also be making use of DTM connectors too for some of the internal interfaces that don't warrant the expense of an autosport connector. |
| 02:39 | Let's have a look at how we can decide on the correct connector for our application. |
| 02:44 | Once we're comfortable we have all of our bases covered, we can finalise the wire allocation in our spreadsheet, listing out every conductor that will need to pass through the bulkhead. |
| 02:54 | In our case, we've got a total of 79 conductors required so we can use this to help select a suitable connector. |
| 03:01 | We know therefore that we need 79 positions at minimum and we also know that these will be size 22 contacts to suit our 22 gauge wire. |
| 03:11 | If we consult an online TE Connectivity catalog we can see this can be achieved with a size 20 shell with a 35 contact arrangement which provides 79 size 22 contacts exactly matching our requirements. |
| 03:27 | Let's dive a bit deeper into this though and see how some manipulation of our wiring design can be used to help suit the available connectors. |
| 03:36 | On my initial design I actually had 82 required positions which could be accomplished with a size 22 shell with a 35 contact arrangement as this provides 100 size 22 positions. |
| 03:49 | This is overkill for us though and we also couldn't source this particular connector set easily from our local supplier without a long lead time. |
| 03:58 | To reduce the required positions from 82 to 79, I simply merged the shield drains for the ref and sync sensors together and then did the same for the cam position sensors and again the two knock sensor inputs. |
| 04:12 | Now instead of requiring 6 individual shield drains to pass through the bulkhead connector, I can get away with just 3 instead, now meeting our target of 79. |
| 04:22 | This sort of manipulation is quite common and you'll find there's usually some level of flexibility in what you can do and what you can get away with. |
| 04:31 | Let's get back to our chosen connector and we need to consider that one half of this connector needs to be a 2 bolt flange to bolt it to the firewall and the other side needs to be a free plug. |
| 04:42 | We've also chosen the standard S designation for the keying of this connector which is the red colour. |
| 04:48 | So our firewall connector is going to be an AS020-35PN and the mating connector will be an AS620-35SN. |
| 04:59 | The 0 designates a 2 hole flange and the 6 on the mating half designates a free plug. |
| 05:06 | The P represents male pins while S represents female sockets for our contacts. |
| 05:12 | I will point out that usually I prefer to specify the 2 bolt flange side of this connector half as a socket not a pin however I already had the mating plug in stock in socket form so it made sense to save a little bit of money and just buy the one half of this connector instead, hence we're going with pins for that firewall side. |
| 05:34 | Deciding on a suitable connector is something I know that many worry about by a little understanding of the autosport designations and a bit of time with the online catalog makes it pretty quick and easy work. |
| 05:46 | The other autosport connector we're going to use for this harness is the interface between the engine harness and the PDM32 to supply power to everything in the engine bay as well as the ECU itself and the starter solenoid. |
| 05:59 | We've already considered the current draw and in the design document, we have another tab that lists out each of the 12 volt supplies required. |
| 06:07 | The total here is 16 and again we're dealing with 22 gauge wire so we can use a size 12 shell with a 35 contact arrangement giving us 22 positions which is obviously more than we need but sometimes this is unavoidable. |
| 06:23 | Specifically we're going to use an AS112-35SN and an AS612-35PN as a mating pair. |
| 06:33 | We don't require the 2 bolt flange for this particular connector so an inline receptacle and plug is what we want. |
| 06:40 | If you're going to end up with two or more connectors of the same style in close proximity, then it's sensible to choose different keying to avoid any chance of accidental connection being made. |
| 06:51 | The keying is visually easy to identify by the colour band on the connector body. |
| 06:55 | With the connectors specified we can begin to create our documentation by setting out a spreadsheet with sections devoted to each connector. |
| 07:03 | With this set up, the next step is to detail the pinout of each of these connectors. |
| 07:08 | Much like specifying the connectors, often this pinout designation is defined for us when we're making a direct connection to a component such as the M170 ECU for example. |
| 07:19 | In which case, this can be directly recorded onto your spreadsheet. |
| 07:22 | The situation is a little more complicated when we can define the pinout of the connector ourselves, such as our bulkhead connector. |
| 07:30 | In this situation we want to take into account our concentric twist layer design as much as possible. |
| 07:37 | What I mean by this is we don't want to design our concentric layers so that we require conductors from the centre layer to be broken out at a branch point right at the very start of the harness. |
| 07:47 | Admittedly it's not always possible to pefectly match the concentric layers to the harness branch points but doing our best during the design step here will streamline the construction process and you will be thankful later on. |
| 07:59 | At this point, I'll fill out the documentation section for each connector with the required wires but wait to finalise the pinout until the concentric layer design for that harness section has been completed which is the next step of our process. |
| 08:12 | With all of the connectors and circuits for the harness specified, we've now got all of the information we need to know exactly which wires are running through each section of the harness. |
| 08:23 | Once we know this, we can design the concentric layering for each section. |
| 08:28 | What we'll usually do is start with the largest conductors or in our case our shielded cables as the core, working outwards to the smaller wires in the outer layers including any filler wires that may be needed to complete a layer. |
| 08:41 | Of course all of our conductors in this instance are the same 22 gauge size so our only consideration here is the twisted pair for our CAN bus and the shielded cables for the likes of our engine speed, position and knock inputs. |
| 08:54 | With the concentric layer pattern for the harness sections detailed, we can now go back to the connector pinout in our design sheet and fill them out to match the layer pattern as far as possible. |
| 09:05 | This won't be possible in all instances, particularly in the case of the M170 ECU connector. |
| 09:10 | As we've discussed, this pinout is defined for us by MoTeC and it isn't something we can modify to suit our concentric layer design. |
| 09:18 | In this situation, the design process for the concentric twist pattern does not change but the area behind the ECU connector, usually beneath the boot, will end up a little untidy as wires will need to change locations around one another to get to the correct layer. |
| 09:34 | Developing this concentric layer design and in turn developing our pin designation, can be a bit of an iterative process with the design evolving as you progress. |
| 09:45 | Some good guidelines are as follows. |
| 09:48 | First of all, have your concentrically twist pattern design drive your pinout definitions as much as possible. |
| 09:54 | What I mean by this is that on our bulkhead connector, we want our centre layer to be terminated to the centre positions of the connector and so forth. |
| 10:02 | We also want to group wires that will branch out together in our concentric twist pattern. |
| 10:07 | Try to have these in the same layer and next to one another if possible. |
| 10:12 | What I mean here is that if we have a sensor such as fuel pressure, then we know that we're going to need 3 wires to run to that sensor. |
| 10:19 | An analog voltage input, a 5 volt supply and then a sensor 0 volt so obviously we're going to want all 3 of these wires in close proximity within the same layer. |
| 10:30 | We also want to try to have wires that will branch out early in the outer layers and wires that will run the length of the harness in the middle. |
| 10:38 | Again, this isn't always going to be possible but we want to try and meet this rule as much as we can as it's going to save us disassembling the whole harness to fish out a conductor from an inner layer that we needed on an early branch point. |
| 10:51 | We'll have a look at the documentation and the design for our FJ40 harness now and go over some of the key points. |
| 10:59 | This complete documentation is available below the module. |
| 11:03 | Let's just start by getting familiar with the spreadsheet. |
| 11:06 | It is, as we've discussed, a complex harness with quite a few elements so there's a fair few moving parts to this spreadsheet and not all of them are going to be focused on in depth for our worked example. |
| 11:19 | Also worth just mentioning here that while I'm using a Google sheet here and as you'll see some hand drawn elements, really there's no black and white solution that you must use, of course at the top end, we might be using software such as HarnWare for a lot of our design, Microsoft Visio's another option. |
| 11:36 | Really whatever suits, as long as your documentation is solid, robust and something that you can come back to. |
| 11:43 | So let's dive in here and what we can see, along the bottom here we've got various sheets for our different elements, for example our M170 which we're focusing on at the moment, the C127, the bulkhead etc and as I've said, there are a fair few elements, we'll just scroll along further, we've got our concentric lay up, our branching and our PDMs. |
| 12:04 | So again, lots of things there that we need to have defined and documented so that we always have a rock solid place to come back to when we are actually constructing the harness. |
| 12:17 | And usually the amount of time that goes into documentation at this level, probably won't actually be dramatically different to the time we'll spend building the harness but the time we spend here is going to save us the potential of any mistakes, we're going to also know exactly what we're doing when it comes time to build our harness. |
| 12:35 | Alright let's dive in in a little bit more detail here and we'll start by moving across to our bulkhead connector here. |
| 12:42 | I've already talked about how we've defined this particular connector, how many terminals or locations we need on it. |
| 12:50 | And so at the top here we can see that we've defined the connector that we are using and below this we've also got the boot that we will be using once we've completed the harness and again we've got a downloadable sheet that will guide you on the correct boot size or suitable boot size for the common connector shell sizes. |
| 13:10 | Here we've got a section where we can add some notes relevant to this particular harness or connector I should say as well, anything that we need to know. |
| 13:18 | In particular we've got a lot of splices going on here which we'll look at in a moment and we've got a note here that says we've got a 22 gauge green wire spliced to all of our shields beneath the boot and using a S01-03R solder sleeve. |
| 13:35 | On these sheets I also like to just add a image here of the actual connector body. |
| 13:42 | So that I've got a visual cue to the pin out. |
| 13:45 | Now this is quite important when it comes to designing our concentric lay up as well because we'll know which of the terminals are in the centre. |
| 13:53 | So while it's a little bit hard to see here, with this particular connector we start from the outside with our terminal connector position 1 or terminal position 1 and at the very centre we end up at position 79. |
| 14:06 | If you didn't have this information available, it would make it very difficult to correctly design your concentric twist. |
| 14:14 | Now this on the interior side obviously connects to our M170 ECU so let's just quickly head across to that connector and you can see that the pinout of the M170 ECU, the location of the pin numbers is very very different. |
| 14:31 | For example here we start on one side of the connector with locations 1 through to 3 and on the other side we end up with 64 through to 66 so this is something that's very easy to overlook if you haven't actually added these images into your design sheet or at least taken note of them while you are developing your concentric twist. |
| 14:53 | As we've discussed here, there's some complexity around our concentric twist with how we're going to do this at the bulkhead and out to the engine bay vs how we're then going to have to work with that design at the ECU end but there is no easy way around this. |
| 15:08 | It is just going to result in our ECU connector being a little bit messy behind that boot. |
| 15:13 | Let's head back over to our bulkhead worksheet here and we'll look at a few other elements. |
| 15:18 | So if we look here for a start we've got the pin numbers 2 and 3 and you can see that I've highlighted these in a grey colour. |
| 15:28 | Now this is simply because these are passthrough wires here that actually have nothing to do with the M170 ECU. |
| 15:36 | You can see that the destination for these is to the C127, digital 1 and digital 2 input. |
| 15:43 | And these are for our reverse switch and our 4WD switch and we have the specific destination pins here. |
| 15:51 | The reason I've just highlighted these grey is just so that they are a very quick and obvious visual cue as to what those particular terminals or contacts are going to and if we scroll down further here we're also going to see that we've got another couple again grey and these are our analog voltage input 2 and our sensor 0 volt from the C127 so just clarifies that these are not related to our MoTeC M170 ECU. |
| 16:22 | I just want to highlight some of the considerations we can make when we are choosing our connector body, we already know we've got a 79 position connector body here and we know if we scroll down we are using all 79 of those positions. |
| 16:37 | Now just looking at how we have modified that harness here or our harness design, if we look here at pin 75, we can see that we are actually connecting the shield drains for both our ref and sync together as opposed to running them through as individual positions. |
| 16:55 | Likewise, our cam position left and right bank, the shield for both of those is joined together and finally our shield up here for our knock sensors, our 2 knock sensors, those shields are joined together. |
| 17:10 | So if we hadn't done this, that would've required an additional 3 positions for our connector body which would need to jump up in our connector size. |
| 17:18 | Now ideally we would want to run these drains through together but in this instance, there really is no downside to doing this, particularly that the sensors, the shielded cables that we are running here, are essentially going to the same location so they're going to be subjected to essentially the same levels of noise so these are some of the little considerations we can make here to help us design our harness around the connector body that is available. |
| 17:42 | Let's head over and have a look at our bulkhead splices external, so obviously these are the engine bay splices and we'll start at the very top here and we can see we've got our sensor 5 volt and our sensor 0 volt. |
| 17:56 | We scroll down, we've also got our 12 volt supplies for our injectors, bank 1 and 2, for our VVT and we've also got some auxiliary 12 volt feeds as well as our battery negative and then we've got our C127 so we'll deal with a couple of these specifically. |
| 18:14 | And we'll start by talking about the 5 volt and 0 volt A and B and on the M170, MoTeC give us two 5 volt regulated outputs and 2 matching 0 volt. |
| 18:25 | It is important to make sure that when we are connecting to a MAP sensor for example, throttle position, whatever, something that uses a regulated 5 volt and 0 volt, that we want to make sure that we match the A 5 volt and the A 0 volt or B, whichever one we're using. |
| 18:42 | Generally while these sensors do draw very very low current levels, we want to basically load share across the A and B sensor 5 volt supply as best we can. |
| 18:54 | Let's have a look at our sensor 5 volt A for an example here. |
| 18:58 | And for a start, we've defined the splice, this is a TE Connectivity D-609-05 which is the one with the yellow coloured band. |
| 19:07 | We're going to be booting this simply with a small section of SCL which keeps everything nice and tight and simple inside the back of the connector body there, obviously we've got a few of these splices so things do start to get a bit bulky pretty quickly. |
| 19:22 | And in order to define that particular splice, we do need to add up the CMA values of each of our conductors, as we can see there we've got 4 conductors that are going into this splice, that'll give us our CMA value and then we can just match that to the particular splice that will fit that particular CMA value. |
| 19:44 | Now the actual wiring here, first of all from our ECU, we've got our sensor 5 volt A supply and we need to know where we are getting that from. |
| 19:57 | So the destination for that is pin B61 so that's pin 61 on our bulkhead connector. |
| 20:02 | And we can just go back across to our bulkhead connector, just confirm that, we'll scroll down to pin 61 and we can see that yes that does in fact match our sensor 5 volt A supply. |
| 20:16 | Also going a little further here for this bulkhead connector, we can see where that is actually coming from which is from our M170 ECU of course and that is pin 16, we could go a little deeper and look at that M170 connector and that would show us the same. |
| 20:32 | We'll head back to our bulkhead splices and what we can see is where we are actually connecting that 5 volt A supply to, we've got that going to our TPS, our MAP sensor and our oil pressure sensor supply. |
| 20:46 | Now as I mentioned, we want to make sure that we are matching that with the 0 volt A, and we scroll down and essentially we can see that's exactly what we've done. |
| 20:57 | Now we do have a little bit more going on here in that we've also got our power steering switch, that's not powered, it doesn't need a 5 volt supply but it does need a regulator or sensor 0 volt so we've got that connected there and we've also got our oil pressure and oil temperature combined sensor 0 volt that is going to be spliced into that 0 volt A as well. |
| 21:20 | Alright let's scroll down a little bit further here and essentially everything is just the same as what we've looked at, for example our 12 volt supply to our injectors. |
| 21:29 | So we've got 1 pin coming through that bulkhead connector there that's going to then splice out to the 4 injectors on each bank. |
| 21:37 | So for example here, the 12 volt supply, coming from our PDM, that comes through on the number 43 position on our bulkhead connector and that's going to all of our bank 1 injectors which is the injectors for cylinder 1, 3, 5 and 7. |
| 21:55 | If you're wondering about the ignition side of things, we are running 8 individual 12 volt feeds through the bulkhead connector for our ignition coils. |
| 22:04 | Now coming down here we've also got a 12 volt auxiliary supply here and that's going to be supplying other elements on the connector, on the ECU harness I should say, such as our fuel composition sensor, our lambda to CAN unit, our inlet flap actuator as well as our alternator ignition feed. |
| 22:24 | Coming down here further again, we've got some splices here on the engine bay side of this connector for our C127 passthrough, this is for the 0 volt. |
| 22:35 | Given that we do need a 0 volt reference for our reverse switch and our 4WD switch. |
| 22:41 | Now this is again colour coded grey for exactly the same reasons we've already discussed. |
| 22:46 | Just make sure that it stands out to us and we know that this is the C127, it's not related directly to our M170. |
| 22:55 | Alright let's move across here and we'll have a look at our actual engine harness design or our branching. |
| 23:02 | And what I've done here is just drawn this out by hand, which you've already seen, we've already discussed and we've then taken a photo of this and added it into our spreadsheet so this just makes sure that we're not going to end up losing track of a piece of paper, everything is contained in the same location and again as I've already discussed, this is not the only way of achieving this result but it is a relatively quick and foolproof method. |
| 23:31 | What we've got is that harness laid out, we start here at our bulkhead connector, we've got each of our branch points labelled here and this just also shows us what's going to be at the end of each of these sections of harness for example. |
| 23:45 | Here we've got our fuel composition sensor, we can see that that is coming directly from the bulkhead connector and we can see the length of that particular run there, 840 mm so it's just a case of going through and basically transferring everything from our rope harness, measuring it and then adding it into this design sheet so we can actually build our harness based off what we have here. |
| 24:10 | Next let's jump into our concentric layup design and this is really one of the more significant elements of our design and we really can't do this until we've got all of those other elements already dialled in and figured out. |
| 24:27 | Particularly the harness branching. |
| 24:29 | The reason that's so important with our concentric design is where possible we want to design our concentric layers so that as we've already discussed, we are not trying to branch out wires from the centre of the harness at our very first branch point. |
| 24:44 | Again as discussed, it's not always that simple which is what we will see here. |
| 24:49 | So let's have a look at how this works. |
| 24:51 | So what I've done is I've started from our bulkhead connector, the most obvious place to start there and for example here, right from that bulkhead connector, as we've just looked at on our branching design, we actually have a break out there for our fuel composition sensor. |
| 25:07 | Now for each of these break outs, so this might be the fuel composition sensor or an injector or an ignition coil for example, the colour coding that I've used is always the same. |
| 25:18 | Again as I'm going through this, it sticks out at a glance so I know that this is actually to a termination. |
| 25:25 | Now we've got the conductors here and this will play into this as we go further. |
| 25:29 | All of our conductors essentially are 22 gauge except for our shielded wires. |
| 25:35 | And we've got here, the function of these, we've got our fuel composition sensor signal. |
| 25:39 | This also requires a 12 volt supply and ground. |
| 25:43 | Important to note here this is an engine ground, this doesn't need to be a sensor 0 volt and that supplies a digital signal back to the ECU. |
| 25:52 | Relatively simple there. |
| 25:54 | Let's just quickly compare that to our engine harness branching and we can see that that is this element that we've just looked at already, there for our fuel composition sensor. |
| 26:05 | Alright let's look in a little bit more detail at our concentric layer design here for the section from our bulkhead through to our branch point A and if we just look at our harness branching, we can see that this is this section here, 260 mm long, we know that this is going to contain every single one of our conductors, with the exception of our fuel composition sensor which we've just discussed, that's already been broken out. |
| 26:28 | So let's have a look at some of the considerations that go into this and really the first is how are we going to design our core? We're in a situation here where we have our ref, our sync, our cam position bank 1, our cam position bank 2 and knock bank 1 and bank 2 so we've got 6, 2 core shielded cables that we need to run through here. |
| 26:54 | Now if we're going to use those as our core, unfortunately 6 shielded cables, we're not going to be able to neatly wrap those or lay those together, that's not going to work. |
| 27:08 | We've got the alternative here which we've used is that we can run a single 2 core shielded cable as our core and of course when we are designing our harness, we always want to really work from our larger conductors and our shielded cables always work really nicely as a core and then work out to our smaller conductors. |
| 27:28 | As we already know, every other conductor in our harness here is a 22 gauge conductor which makes the rest of our job pretty neat and easy. |
| 27:37 | Now this is where we are best to make up a test section of our harness and this gives us the ability to quickly and easy play around with a few different designs and see what is going to work neatest. |
| 27:49 | We'll get this under our overhead here and have a bit of a look at it. |
| 27:53 | And what I've got here is our single 2 core shielded cable as a core, it's a bit hard to see but we've got that in the centre there, and then we've got our 5 other 2 core shielded cables wrapped around it. |
| 28:08 | Now what we'll also remember from the concentric design elements of the body of the course is that if we're dealing with conductors the same size, we have a single wire or conductor, in this case 2 core shield, as our core and then each subsequent layer we jump up by 6 conductors, or a factor of 6 so our first layer on the outside there should have 6 two core shielded. |
| 28:32 | We don't have 6, we've only got 5. |
| 28:34 | So if we actually have a better look at this, it's a little hard to see but we do actually have a gap running through this. |
| 28:42 | We can see it for example through here, which is where that 6th 2 core shielded conductor should be running. |
| 28:48 | Now we can still take advantage of this though so let's jump back into our spreadsheet and have a look at what we've incorporated. |
| 28:56 | So we've got our core, one 22 gauge 2 core shield, we've got the diameter of that, 2.6 mm and we've got that defined as our reference sensor. |
| 29:09 | Reason for this is this one is going the full length of our harness so nice and easy there. |
| 29:15 | Now what we've also got in our second layer here is our sync, our cam position bank 1, bank 2, knock bank 1 and knock bank 2. |
| 29:23 | So again that leaves us a little bit short. |
| 29:25 | In this case we do also have our CAN wiring which needs to go to our lambda to CAN module and the CAN wiring as we know is a twisted pair. |
| 29:35 | Now this gets a little bit ugly and messy if we are incorporating a twisted pair of wires in an outer layer of our harness so in this case this actually fits quite nicely in that gap that's left here with our 6th twin core shield that is missing so that's where we're going to incorporate our CAN high and low. |
| 29:55 | Now a couple of elements here, first of all our diameters. |
| 29:58 | So this is important to define our subsequent layers when we drop down to our 22 gauge conductors In this case, we are simply best just to measure the outside diameter using a pair of vernier calipers and in this case, because it is a little difficult to get a definitive and reliable measurement, we're best to take 3 measurements and average these. |
| 30:20 | So we can see that we've done exactly that and our layer 1 diameter there is 7.8 mm. |
| 30:29 | Now one element that is worth mentioning here is we've got our CAN position bank 1 and bank 2 in the core, and that's the only place it really makes sense to run that but if we come back to our engine harness branching, what we'll see here is that we've got cam position needs to be broken out for bank 2 right at that branch point A. |
| 30:53 | There's no real easy way around this and this is where we can have the best laid plans and intentions but ultimately a lot of our concentric twist is going to be developed around what makes sense and also what we need to physically do with our engine harness design. |
| 31:11 | Likewise, our lambda to CAN branches out at branch point A and that requires our CAN high and low. |
| 31:18 | This is OK, what it simply means is that there's no point constructing our harness much longer than the 260 mm at this point we need to get to branch point A because we know that at that point we're going to essentially have to disassemble our harness to get our cam position bank 2 out of that harness and then reconstruct it. |
| 31:41 | It's not the nicest but unfortunately it is sometimes inevitable. |
| 31:45 | Let's head back to our concentric lay up and we'll talk about a few more elements. |
| 31:49 | So once we've completed our layer one here in our design, obviously we step up to our layer 2 and here what we need to use is our diameter that we've already measured, 7.8. |
| 32:01 | And you'll recall that we do have a look up sheet in our concentric design elements of the main body of the course here that will help you define how many conductors are going to be in a subsequent layer. |
| 32:13 | So if we bring up our calculator here quickly, and what we do is we take our diameter of the previous layer, in this case 7.8 mm and we want to divide this by the conductor size. |
| 32:26 | In this case a 22 gauge conductor is 1.12 mm so we'll divide by 1.12 and that gives us a value of 6.9, let's round that to 7. |
| 32:35 | We can use that in our lookup table and what that's going to do is show us that for our next layer, we're going to need 24, 22 gauge conductors. |
| 32:45 | We can also work out fairly easily what the diameter of that next layer is going to be and again if we just bring up our calculator. |
| 32:54 | If we go, in this case 1.12, that's the diameter you'll recall of the 22 gauge wire, and we multiply that by 2 because we've got that on each side of our core and then we want to add the diameter of the previous layer, in this case 7.8, we can see we get to 10.04 so this is how we can essentially work out what the outside diameter of our finished harness is going to be. |
| 33:23 | So what we've done here is essentially grouped as best we can, the conductors that we're going to be running as far in the harness as we can. |
| 33:31 | Again, we already know that we're going to have this complexity of dragging our CAN position out at that branch point A but for the most part we can still design the rest of our harness as well as we can with the location of the conductors in mind. |
| 33:47 | So for example if we scroll all the way down here to our layer 4. what we can see is that we are branching out elements that are going to be coming out at that first branch point A, we're combining those, including those I should say in our outer layer. |
| 34:04 | So for example, we've got the wires here for, conductors here for our starter solenoid, we've got our power supply for our lambda to CAN and our alternator, ignition auxiliary 12 volt and again if we come to our branching design, we can see that those elements, our starter and our LTC just for a couple of examples, are right there at branch point A. |
| 34:27 | Just talking about the number of conductors in our layers, because we are only using 22 gauge, we've already worked out using our lookup sheet that our second layer is 24 gauge. |
| 34:39 | We remember that we step up 6 conductors per layer so of course 24 plus 6, our next subsequent layer will have 30 and our final layer here will have 36. |
| 34:50 | What this does result in of course is that we do have a requirement for these filler wires. |
| 34:57 | And just like Zach's done, we are defining all of our filler wires in a specific colour, we choose violet, you can choose whatever you like, it just means that at a later point if you ever see a violet wire or your filler wire colour of choice, you're going to know that that is in fact filler wire and you're going to know the purpose of that wire. |
| 35:18 | Alright so that really covers the considerations of our concentric design here, particularly with a complex harness where we're sort of forced to drag that cam position out at that first branch point and then reconstruct the harness from there. |
| 35:33 | I'll just cover a few more elements quickly here. |
| 35:35 | We've got some more of our terminations here from branch point A. |
| 35:39 | So for example we've got what we're going to be running to our inlet manifold flap control actuator. |
| 35:46 | We've got 2 wires there, we know that we're going to need our inlet flap signal as well as a 12 volt supply. |
| 35:53 | Quite important here just to focus a little bit on our ground design. |
| 35:58 | So branch point A, we do have a ground that's going to go to a nice simple location on the back of he cylinder head here and we need to consider what's going to go into that. |
| 36:10 | So let's have a look here, we are concentrically twisting this so we have a core, in this case one 22 gauge wire and then we've got a second layer with of course 22 gauge 6 conductors in this layer. |
| 36:25 | Now looking at this, what we've got here is the grounds for our ignition coil, so this can be really easy to overlook. |
| 36:33 | Let's just jump back to our branching design for a moment. |
| 36:36 | Now for example here, we've got our ignition 6 and this needs 3 wires, 3 conductors going to it, we're going to have a 12 volt feed, this is coming from the PDM via our bulkhead connector here. |
| 36:53 | We're also going to need to have a signal from the ECU, again coming from the M170 through the bulkhead, through our branch point A out to our ignition 6. |
| 37:02 | So that's pretty straighforward, that's defined at our bulkhead connector pin out but we also need a ground and while this is pretty simple to understand, it can be easy to overlook at our design stage because this ground does not come from the ECU, it doesn't come through the bulkhead connector, this needs to be directly to the engine block or cylinder head. |
| 37:23 | So in this instance, the ignition 6 will also end up going to this ground point here. |
| 37:30 | So it's a bit of a convoluted design, essentially we're running back through this harness up to branch point A and then we're going to be coming out here to our ground and that's going to be the same for all of our ignition coils when we have exactly the same on the other bank of cylinders. |
| 37:49 | Why I'm mentioning this is because these ground wires, conductors, need to be incorporated within this section of harness between our branch point A and our branch point G so pretty straightforward, it's not rocket science here but it is something that we do need to think carefully about and make sure that we incorporate. |
| 38:09 | Another element there which I've already discussed briefly but our lambda to CAN, that also has exactly the same requirement for a ground wire, so that's going to be again running up to our branch point A and then out to our ground as well. |
| 38:25 | So we'll come back across to our concentric lay up and just see exactly how that all works. |
| 38:31 | So we are incorporating in this case two of our battery negatives as well. |
| 38:38 | These come from the M170 so these are the M170 power grounds. |
| 38:42 | So battery neg 4 and 5, those will be incorporated, we've also got our LTC ground and then we've got our 4 ignition grounds so really important just to make sure that we've got all of those dialled in. |
| 38:56 | The rest of this is simply a rinse and repeat of what we've looked at here so far. |
| 39:01 | But important to be really detail orientated, take your time and make sure that you haven't overlooked anything because once you've locked this in and you're ready to start construction, it's very difficult to come back from anything that you have overlooked. |
