Coil Pack Project

Parts List from Jegs:

1) 555-40166 Coil, LS Gen IV Years 2005-2013 Unit Price: $52.42 x4

2) 555-402026 8.5mm Plug Wires LS1 Years 97-04 Unit Price: $53.99 x1

Subtotal: $263.67

Free Shipping

Tax: $18.46

Total: $282.13

Parts List from RockAuto:

1) ACDELCO Part # 357A Ignition Coil Wire Unit Price: $22.79

Subtotal: $22.79

Shipping: $5.46

Total: $28.25

The part numbers listed above are a Jegs private label, more than likely

someone like Accel or MSD are making the coils and wires for Jegs, as they do not

have a manufacturing division. I will discuss this farther in the project out line.

I took some time looking through other platforms on this subject. The Supra

platform likes the 555-40162 part number. At first I was thinking that it was more

of a robust coil pack, but it turns out that once the mounting bracket is removed

the round coil pack will fit into the stock valve cover opening for the spark plug.

Then a boot has to be sourced from a Lexus I believe, and then there is no real

way to secure the coil pack. On the subject of what coil pack is better, I found no

real conclusive proof that one style is better than the other. GM seems to have

changed the mounting options for the different generations of engines. The 555-

40166 is a lower profile than the other generations, and might fit better into the

small confines of the Mazda engine bay. I will know more once I get into

fabricating the bracket.

Here is a cross reference list of the coil packs, Jegs, Accel, and MSD are

listed.

Jegs claims their coil packs are rated higher than the OEM. This snap shot

was taken right from the website.

Wiring the Coils

The cost of one half of the ignition coil wiring harness was much cheaper

than sourcing individual pig tails with the correct plugs for the GM coil packs. If I

remember correctly it is something like 4 times the price to purchase individual

pig tails then it was to buy one half of the OEM harness…go figure! This is what I

started with.

I was thinking that it would be nice to be able to install a Mazda connector

for the main harness plug, that way the end user could remove the factory coil

pack harness and install this one. Well, once I was under the hood I realized that

the Mazda coil pack harness does several sensors, unlike the GM harness in the

above picture, it only supplies the coils.

I then started stripping the GM harness down so I could access just the

plugs with a pig tail attached. Item #1 is 555-402026 plug wire, #2 is the 555-

40166 coil pack, and #3 is the AC Delco 357A harness after the tape and plastic

cover was removed.

The next step was to see if the plug wire would actually fit into the valve

cover without modification. Sure enough, it fit almost like it was made for it.

Now it was time to figure the pin out from the Mazda to the GM coil plug. I

started with the #1 spark plug. Mazda plug pin one is the ECU signal, blue with red

trace. This is attached to the red wire on my particular GM connector, or pin C on

the GM connector. Pin two is coil ground, black with blue trace (this color

combination is the same for all four Mazda coils) I attached this to the brown and

black wires on the GM pig tail (this is also common on all the GM connectors) pins

A and B. Pin three is 12 volt power, solid green and this one attaches to the pink

wire in the GM connector (same color on all the connectors) pin D. Refer do the

following picture and diagrams.

At this point I only have the one GM coil wired and running. I have no

reservations in thinking that the other three will work just as expected. I would

like to fabricate the bracket before I cut the other wires and splice in the GM

connectors.

While digging into this project I noticed something odd. I measured the

voltage on pin 2 and 3 on the Mazda coil connector, to my surprise it was almost a

full volt less than the battery voltage. So, I am wondering if I add a relay to pin 3

and bring in full battery voltage to supply the coils if I would not get a more

constant supply vs. going through the engine wiring harness. It might just be a

marginal increase, but any little bit will help. This is something I will explore once

all the GM coils are up and running.

Remember earlier in the discussion about the possibility of a private label? I

really think if you are going to the trouble of making this a plug and play kit the

coils need to be made with Mazda specific connectors. I say this because the

Mazda ignition harness shares the main wiring connector with other parts of the

engine harness. It would not be as easy as just dropping in a new harness and go

from there; it would have to be routed to the other parts of the engine bay.

Cutting and splicing wires would not be an option for the general customer. I

think that would just cause a nightmare. The last option I have is to have a short

pig tail made. One side would plug into the Mazda OEM connector and the other

end will plug into the GM coil. I am not a fan of this option for the fact it does not

look like a finished, or an OEM application.

I am open to options, and discussion for other ideas on the project.

This is all I have for now. The bracket is the next step, and hopefully will be

ready to bolt up January 4th.