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Discussion Starter #1 (Edited)
Working on building my own custom wiring harness for standalone ecu in race car. I want to do a proper job and not have a ton of splices everywhere.

So I'm looking for a source where I can buy the factory original connectors and crimp terminals for all the injectors, ignition, all the sensors, etc, all of it!
Where can I buy that?

I think I found sources for pigtails for most things, but that's not what I want. That will require splicing everything, that's what I'm trying to avoid.
The fewer splices and the fewer connections, the more reliable it will be.

Also, I guess it would be helpful to know how to identify the terminal types/part numbers?
 

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No thanks on the trans offer.

Here are some other FF Forum areas that you should check out or create a new post within based on your race car modifications. ->

Builds
https://www.focusfanatics.com/forum/ford-focus-builds-general-showroom/

Duratec Performance
https://www.focusfanatics.com/forum/duratec-performance-2003-2007/

ECU Tunes
https://www.focusfanatics.com/forum/focus-tuning-chat/

Brakes & Suspension
https://www.focusfanatics.com/forum/brakes-suspension-body-chassis/

Racing Discussion (sub-forums)
https://www.focusfanatics.com/forum/#ford-focus-racing-discussions

Gd Luck
 

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Whoops! I forgot to say the obvious...

You do not need a new standalone PCM/ECU (or wire harness) within your race car design UNLESS you have a unique (more expensive) design idea.

The stock PCM can deliver most race car needs, with a Tune, and other mods, and especially if talking about a 2004 Focus.
 

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The 'no splice' idea becomes rather witless once one realizes that there are many hidden splices in OEM harnesses underneath the wrapping.

There is absolutely zero reason why a competently done group of splices should lower reliability at ALL. It lowered points directly at incompetent work.
 

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Discussion Starter #11
there are many hidden splices in OEM harnesses
Yeah I know, that's why I want to delete the OEM harness.
And reliability isn't the only issue. It's also an issue of serviceability and weight savings.

What I'm probably going to end up doing is a compromise. Since I don't think I can get all the proper connectors for every device. I'll probably keep the engine side of the harness, and cut the big connector off that sits over the transmission. Then I can crimp on a pair of 20-pin deutch connectors, and on the other side of that will be the flying leads from the new ecu. That's probably the best I'll be able to do.
 

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Discussion Starter #12 (Edited)
You do not need a new standalone PCM/ECU (or wire harness) within your race car design UNLESS you have a unique (more expensive) design idea.

The stock PCM can deliver most race car needs, with a Tune, and other mods, and especially if talking about a 2004 Focus.
Does the stock ECU do traction control? Launch control? flat shifting? data logging? Can the PATS system be fully deleted (since I'm not going to have a key cylinder in this car)?
 

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Why not go for a custom-flashed ECU? Delete PATS, rev limiter, etc...and you'll still be able to data log for troubleshooting.

I'm guessing based on my experience that a 4-cylinder racecar won't be allowed many mods, but that's one that's awfully hard to spot. You won't save more than a few ounces of weight by changing the harness, btw. Given its age, though, you're well-advised to pull the whole thing and inspect it anyway. Depending on your location, you may have corrosion at the starter and alternator connections.

Are you putting in a fuel cell or leaving the stock tank in place?
 

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Discussion Starter #16
Battery in stock position, or behind the seat?
TBD
Probably going with something lightweight, so it might be worth leaving it in stock location just to simplify wiring, and avoid the long high power run for starter/alternator
 

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FYI, the OEM splices will be likely 10X tighter than any crimp you can do with the commonly available crimping tools out there and garbage. Solder is what you do for the most reliability but crimping using like mini-visegrips to control the crush will crimp MUCH tighter than a crimp tool will.

I used to do lots of race car building.
 

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Does the stock ECU do traction control? Launch control? flat shifting? data logging? Can the PATS system be fully deleted (since I'm not going to have a key cylinder in this car)?
The short answer is, -I do not know. I am not the Droid you are looking for.

You need to create a new thread in the Tuning area (linked previously). There is at least one guy over there (Tom) who keeps an eye on those threads. Tom can answer these and other questions. However, you need to add more details, such as what type of race car are you planning? Est money now, and ultimately into it? Engine (HP goals?) and Trans plans too.

Lastly, consult the racing governing body and/or rule-book where you plan to race or compete within. These rules might impact your car design and build decisions.

Gd luck
 

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If you're leaving the battery where it is, make sure the roll cage bars are placed to protect it at least. Even if the track doesn't mandate it, put it in a marine-type plastic box for acid containment in case of fracture. Battery acid is not something you want to be contacting.

When I hit the end of the track wall, I destroyed a brand-new battery (and shortened the car 18" on that side). The rebuild included moving the battery behind the seat and adding the additional wiring. Should have started with that and I would have been out less $$$ on the repair. Never had an issue with getting power from the battery to the engine.

Also, I recommend not hitting the ends of walls.
 
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