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Wiring Fundamentals: Wire

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00:00 - The choice of wire we use to build an EFI wiring harness is a critical one.
00:04 Copper wire is available in a huge array of sizes, specifications, and price levels.
00:10 Luckily the types we use in an EFI harness, only cover a pretty narrow range.
00:14 Choosing which type to use in a particular application typically comes down to budget and will either be TXL or Spec 55.
00:22 From time to time you may also encounter PVC insulated wire.
00:26 This has a very poor temperature rating and will not withstand engine bay temperatures reliably.
00:31 For this reason it should be avoided and never used in an EFI wiring harness.
00:36 TXL which stands for thin wall cross linked, is the standard used by OEM manufacturers for wiring harnesses that enter the engine bay of a vehicle.
00:45 And as such is a great choice for our EFI wiring harness.
00:49 It's relatively cheap and available from many online resellers in a wide range of colour combinations and sizes.
00:55 It has an operating temperature range of minus 40 to 125 degrees celsius, meaning it can withstand use in an engine bay reliably.
01:03 Spec 55 is actually a term that refers to a complete range of wiring harness products developed by TE Connectivity.
01:10 However it is commonly used to refer to the type of wire used for automotive wiring harness construction at a professional motorsport level.
01:18 It's also sometimes referred to by the Dupont brand name of the material used as the insulation, Tefzel.
01:24 Spec 55 wire uses a thinner tougher insulation jacket than TXL wire, and can withstand temperatures of up to 150 degrees, plus almost any chemical likely to be encountered in a automotive environment.
01:37 It's thinner insulation results in a wiring harness with a smaller overall cross section and a lighter weight.
01:43 It quickly gets expensive when used exclusively for harness construction, but at a professional motorsport level, the weight and size benefits are worth the extra cost.
01:52 While we would love for there to be an endless budget for every wiring harness we construct, whether you're building it for your own project or for a customer, this will almost never be the case.
02:01 It's my experience that the cost of Spec 55 wire is typically around five times that of the same size of TXL wire.
02:08 While the overall cost of the wire we use in our harness may be quite low, so the savings made by using TXL wire over Spec 55 might seem insignificant, you have to factor in supplier minimum order quantities.
02:22 If your wiring harness uses 15 different colours and sizes of wiring, and there is a minimum order quantity of 50 metres for each size and colour, the costs benefits of TXL wire will quickly become significant.
02:35 If you're constructing more than one harness however, and you can be sure that you will use the excess wire on future projects, the extra cost of Spec 55 wire will become more justifiable.
02:45 A term we need to be familiar with when selecting wire to use is AWG, which stands for American wire gauge.
02:52 This is how the internal copper of the wire is sized.
02:55 And for our application it relates to how much current the wire can safely carry.
02:59 A smaller AWG number actually means a larger wire.
03:03 We'll cover in detail how to determine the size of wire required in a particular application later in the course.
03:09 It's worth mentioning that insulated copper wire is available with either a solid or a stranded core.
03:15 We will always use stranded wire as it's far more flexible and resistant to vibration when compared to solid core wiring.
03:22 Solid core wiring is used in building construction and has no place in an automotive application.
03:28 In my experience, for a modified street car, TXL wire is usually the better choice as its specifications are more than adequate, it's easy and cheap to purchase in small quantities.
03:38 As an example, my personal car has an EFI wiring harness built using primarily TXL wire and has been reliable for many years.
03:46 For a club day track car or a weekend warrior, the budget available will most likely be the deciding factor between using TXL and Spec 55 wire.
03:55 For a dedicated professional level race car, Spec 55 is really the only option, as its more rigorous specifications will provide a larger safety margin for continuous use in the harsh motorsport environment.

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