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FORD Expedition 98 5.4L 2 Pin Coil on plug wiring help

Practical Motorsport Wiring - Club Level

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HI all. I hope you can help me as this is my first time wiring this type of coils. I'm Piggy back wiring an EMU Black ECU to the car and I used 22 awg wires for the trigger pin on the coils and didn't touch the stock 12V 18 awg wires going to the coils. I'm not sure if this type of coils will need a bigger size wire for the ignition trigger pin on the coil going to the EMU Black Ignition output terminals. Usually there's a power supply pin, at least one ground pin, and one ignition trigger pin but these coils only have 1 pin connected to 12 V and the other connected directly to the stock ECU so I'm afraid that using 22 awg wires will damage the ignition output terminals on the EMU black or worse

Also since the EMU black wiring will splice into the sensors' signal wires and will only control 8 ignition coils and 8 injectors, I wired the primary power supply to the ECU and ECU ground of the EMU black using 20 awg wires. As for all power grounds and the switched 12V pins, I used 22 awg wires. Should I have used bigger size wires?

I appreciate all the help I can get and Thank you in advance

Hello Ahmed,

If the coils have only two wires, they are passive (dumb) coils. If one has constant 12V and the other goes straight to the ECU this means the factory ECU has the required ignition drivers built in. According to the EMU Black documentation the ECU is only capable of driving six of these style coil directly, not the 8 you require; running 8 directly will damage your ECU. The ECU can support 12 coils with in built igniters (smart) coils or 12 passive coils via a separate ignition module. Both wires for the coils will need to be 18 AWG but trigger wires from the ECU to a separate ignition module only require 22-20 AWG.

According to the EMU Black documentation, it has two H bridges and a wideband controller on board, so the 12V power supply & the power grounds would want to be 18-16 AWG depending on what is being utilized. I don't see any recommendations in the EMU Black documentation for their recommendations, however I have attached some documentation from a Motec M150 which has some helpful recommendations for wire sizing (see page 3).

Attached Files

Hi Callum. Thank you so much for your response. It was extremely helpful. After I read your response I got LS1 Coils to use instead as they are smart coils which I can easily run In a wasted spark setup using EMU Black.

However, I can't find enough data online regarding the LS1 coils. In stock form, each four coils seem to have one 18 AWG wire supplying 12V spliced into 4 18 AWG wires heading to each coil.

I wanted to make sure if its safe to supply all 4 Ls1 coils with 12V using one 18 AWG wire?

Hello Ahmed,

You will be able to run the 8 coils individually which will be even better than waste spark. Using the coils in a waste spark set up will require larger gauge wire than the factory set up because you will have 2 coils dwelling simultaneously, whereas the factory direct fire will only have 1.

If you are staying below 7000rpm and dwelling the coils for no longer than 4ms, 4 coils being fired direct fire will only have one coil dwelling at any moment. The LS1 coils peak current draw is about 10A, from memory, of which has to build up from 0 so they will average about 5A. If running direct fire this will mean you only have 5A of continuous current draw required for the 4 coils, whereas waste spark will require double that.

TXL 18AWG would be okay running direct fire (depending on the distance and ambient heat it's subject to), but not if you are running waste spark. M22759/32 (Tefzel) 18AWG could do 10A (depending on the distance and ambient heat it's subject to). Keep in mind, if you plan on running higher than 7000rpm or dwelling the coils longer than 4ms (from memory, the LS1 coils are damaged if they are dwelled for longer than 4.5ms), there will be a higher current draw.

Thank you for your quick response I appreciate your help greatly. I won't be able to run the 8 coils individually as EMU black has only 6 ignition outputs

Since I have to run the coils in wasted spark and Since I have 4 coils on each bank, I am wondering if I can wire the 12V pin on the connector which groups all 4 coils using one 18 AWG wire? I understand that wasted spark means that 2 coils will be dwelling at the same time, but they'll be on opposite banks. Lets assume the coils that will fire together are called X and Y

Coil X will be on the left bank with the 4 coils that are powered with 18 AWG and Coil Y will be on the right bank with the other group of 4 coils wired with another 18 AWG wire.

P.S, the engine won't exceed 7000 RPM

Will this work? Assuming as you said that each coil has an average current draw of around 5A, and in each group of 4 coils, only 1 coil will be dwelling at a time, Will one wire of 18 AWG be sufficient to power all 4 coils ?

I see, they don't let you select an auxiliary output for the other ignition coils; that's unfortunate (also a little misleading as in the sales literature suggests it can support 12 cylinders direct fire). Yeah, depending on the length and ambient temperature it is subject to, one 18AWG conductor will do, provided that only one coil is dwelling from a single 12V supply at a time. If using TXL wire and the ambient temperature is high, or the conductor length is more than 2 metres, consider bumping it up to 16AWG.

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