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If you are building a serious performance car, race car or custom ECU harness in Australia, the wire you choose matters more than most people realise. Standard PVC automotive wire works fine for a stock vehicle, but in a high performance or motorsport environment it simply does not cut it. Tefzel wire, also known as mil-spec wire or ETFE wire, is the industry standard for professional wiring harness builds and has been used in aerospace, military and top level motorsport for decades. This guide explains what it is, why it matters and which specification is right for your build.

What Is Tefzel Wire

Tefzel is the brand name for Ethylene Tetrafluoroethylene, commonly referred to as ETFE. It is a fluoropolymer insulation material originally developed for military and aerospace applications. The wire you will commonly see referenced in motorsport is designated under the MIL-SPEC standard as M22759, and it comes in two main variants: M22759/16 and M22759/32. Both use a stranded tinned copper conductor, are rated to 150 degrees Celsius continuous operating temperature and are rated to 600 volts. The difference between the two lies in the insulation itself.

M22759/16 uses a standard wall non-crosslinked ETFE insulation. It is the most widely available variant and is used extensively in aerospace, defence and motorsport applications. It has a minimum insulation thickness of 0.013 inches and is available from 2 AWG through to 24 AWG.

M22759/32 uses a crosslinked ETFE insulation, also called XLETFE. Because the insulation is crosslinked it can be made thinner while maintaining the same level of abrasion and heat resistance. This results in a smaller overall diameter and a lighter wire compared to M22759/16 at the same conductor size. The minimum insulation thickness is 0.005 inches. M22759/32 is the most widely used specification in high end motorsport harness builds where weight savings and a smaller bundle diameter matter.

Both specifications share the same temperature rating of 150 degrees Celsius, voltage rating of 600 volts, tinned copper conductors and excellent resistance to fuels, oils, coolant and other automotive fluids.

Why Tefzel Instead of Standard Automotive Wire

Standard PVC automotive wire is typically rated to between 85 and 105 degrees Celsius. In a motorsport environment, wire routed near the engine, turbocharger, exhaust or other heat sources can easily exceed this. When PVC insulation overheats it becomes soft, brittle and eventually cracks, exposing the conductors and creating shorts or failures at the worst possible moment.

TXL wire is a step up from PVC with a rating of 125 degrees Celsius, but it is still below what is achievable with Tefzel. More importantly, TXL has a thicker insulation for its conductor size, meaning larger and heavier wire bundles for the same current carrying capacity.

Tefzel insulation is much thinner than both PVC and TXL while offering significantly better abrasion resistance, chemical resistance and temperature performance. This means a smaller, lighter harness that is far more capable in the conditions a race or performance car is subjected to.

Which AWG Size Do I Need

Choosing the right AWG size depends on what the wire will be used for and how much current it needs to carry. As a general guide for motorsport builds:

24 AWG is used for low current sensor signals such as temperature sensors, MAP sensors and other ECU inputs. 22 AWG suits sensor wiring, relay triggers and low current switching. 20 AWG is suitable for sensors, camshaft actuators, injector power wiring and other low current devices. 18 AWG suits higher current sensor circuits, relay control and accessories. 16 AWG is used for higher current accessories and switched outputs. 14 AWG and 12 AWG suit power feeds, fuel pumps and other higher current applications.

Keep in mind that wire in a bundle runs hotter than wire in free air, so it is always better to size up slightly when multiple wires are tightly bundled together inside DR25 sleeving.

Tefzel Wire and Your Harness Build

Tefzel wire works best when combined with the right protective and finishing materials. Raychem DR25 heat shrink sleeving is the standard choice for sheathing wire bundles in a motorsport harness. Deutsch connectors, milspec bulkhead connectors and quality crimp terminals complete the system. Using the right tools for stripping Tefzel is important as its tough insulation can be difficult to strip with standard strippers. A quality set of purpose-built Tefzel strippers such as the Knipex auto strippers will save you significant frustration.

Buy Tefzel Wire in Australia

12Volt Motorsports stocks M22759/32 Tefzel wire in multiple AWG sizes and colours. We are a Melbourne based motorsport wiring specialist and stock everything you need alongside your wire including Raychem DR25 sleeving, Deutsch connectors and milspec bulkhead connectors. Fast shipping Australia wide. Browse our Tefzel wire range or get in touch if you need advice on sizing or quantities for your build.