Been talked about probably in 10+ threads, but figured why not experiment a bit more. I am doing an LS swap, but I figure this info would be useful for more than just my application.
Not here to debate fusible links vs fuse methodology, lots of opinions. I have ran this by a few EEs at my job and no issues, also ran it by a prior ford EE, also no issues when spec'd correctly (Wire margin, Temp in engine bay, etc).
Fuses/Fusible links protect wiring. Wiring is sized to meet loads.
Design Assumptions/Notes:
Wire Rating:
The Toyota stock wiring has 5 taps to the battery. AM1, AM2, HEAD, EFI, and ALT. All but ALT stay a single conductor for a generous length of their run to various destinations (usually ignition, fuse box, or a relay). ALT gets tapped fairly quicly into another ~10ga wire. I measured the cross sectional diameter to get close equivalents in AWG. Note the range, its hard to get this perfect. Then converted to mm2.
Fusible Link Research:
Some good links:
www.raso.name
SAE J156
www.jalopyjournal.com
Toyota Diagram for FJ62, note that the yellow wire has a larger fusible link than the other same diameter wires, odd...
Not here to debate fusible links vs fuse methodology, lots of opinions. I have ran this by a few EEs at my job and no issues, also ran it by a prior ford EE, also no issues when spec'd correctly (Wire margin, Temp in engine bay, etc).
Fuses/Fusible links protect wiring. Wiring is sized to meet loads.
Design Assumptions/Notes:
- 2%-10% voltage drop is common in these applications depending on criticality of circuit.
- SAE J1128 or similar was used by Toyota (hopefully GXL/SXL/TXL in engine space) 105C rating assumed
- 60C derating for engine bay temp. This varies by datasheet. 25%-40%. I chose 25% (0.75 )See Allowable Amperage in Conductors - Wire Sizing Chart - Blue Sea Systems - https://www.bluesea.com/resources/529/AllowableAmperageinConductors-WireSizing_Chart or Single Core | Tycab Australia - https://www.tycab.com.au/single-core/
- Bundle Derating. Again Varies, but all of these conductors end up in a massive bundle. Likely something close to 50% would be applicable, but this starts to kill rating.
- ABYC E-11, ISO 13297 , and SAE J1128 all vary in the above constraints. Pick your poison. Ford and Chrysler have standards also Types of Primary Wire | Allied University - https://www.awcwire.com/allied-university/informatic/types-of-primary-wire
- Another analysis here. DC cable selection guide - https://stephenstuff.wordpress.com/2016/06/11/dc-cable-selection-guide/
Wire Rating:
The Toyota stock wiring has 5 taps to the battery. AM1, AM2, HEAD, EFI, and ALT. All but ALT stay a single conductor for a generous length of their run to various destinations (usually ignition, fuse box, or a relay). ALT gets tapped fairly quicly into another ~10ga wire. I measured the cross sectional diameter to get close equivalents in AWG. Note the range, its hard to get this perfect. Then converted to mm2.
| Fuse (Link) | Conductor Diameter (mm) | Area (mm2) | Approx AWG | Approx Conductor length (ft) | Max Amp at 30C | Max amp at 60C | Bundle Derate? |
| AM1 | 2.5-2.25 | 4.9 | 10 | 9 | 40 | 30 | 15 |
| AM2 | 2.5-2.26 | 4.9 | 10 | 9 | 40 | 30 | 15 |
| HEAD | 2.5-2.27 | 4.9 | 10 | 9 | 40 | 30 | 15 |
| EFI | 2.5-2.28 | 4.9 | 10 | 9 | 40 | 30 | 15 |
| ALT | 3.4-3.5 | 9.6 | 8 | 13 | 75 | 56.25 | 28.125 |
Fusible Link Research:
Some good links:
Raso Tech - Everything you need to know about Fusible Links
A blown fusible link can leave you stranded on the highway without warning. Discover how to ensure your electrical system is protected.
www.raso.name
Wiring 101
Several members have asked for a 'wiring basics' thread to remove the 'magic' that seems to attach to it, so here goes... I'll do this in several parts...
www.jalopyjournal.com
Toyota Diagram for FJ62, note that the yellow wire has a larger fusible link than the other same diameter wires, odd...
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