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Old 11-15-2009, 07:31 PM   #1
Bad Noodle
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Default DIY MAF Wire Extension ( diy shielded sensor cable )

I couldn't find correct gauge wires I needed to extend the maf wiring for a blow-thru setup. So I made some:

A shielded wire is nothing more than a Faraday Cage around the signal wire. The concept is simple, wrap whatever you want with some conducting metal and ground it. This is important because it prevents interference when power carrying wires are close to one another. In case of the MAF wires, it will produce a clean signal when routing the wire around the engine bay.

When you undo the harness, there will be some shielded wires that look like:



From what I've read, this is usually the yellow/blue wire. But on my car it was white. Either way, these two wires cay the maf signals so I decided to shield both.

So to make some shielded wires, stretch the wire, grab some spray glue, and cut a 1" thick strip of aluminum foil (the heavy dudty stuff) as long as the wire you will coat:



Spray the foil with glue, wait a second for it to get tacky, then wrap the wire with it:



Once that's done, get some dollar store twisty tie and cut and strip a piece the length of the wire. It looks like:


Run it down the length of the wire, then finish wrapping the aluminum foil around:


This wire will be used to ground the aluminum foil wrap. Now get some shrink tubing and coat the whole thing:



Next, solder some regular wire to the solid wire, this is the wire you will ground, The finish up with the shrink tubing:


Next, solder your extension to the original maf wire and make sure the ground can reach the firewall



You're going to do something similar with the wires that have shielding on them. I first strip them:


I then soldered the inner wires together and covered them with some liquid electrical tape:
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Last edited by Bad Noodle; 11-16-2009 at 07:54 AM.
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Old 11-15-2009, 07:32 PM   #2
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Then i wrapped the inner wires with a layer of foil and soldered the outside wires together: (kinda hard to see)



Then wrap that in some electrical tape. Wrap everything with some wire loom and run wire to where you will be putting the maf:



From here just strip wires, solder on plug and you're done. You don't do anything to the shielding on the maf plug end
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Old 11-15-2009, 10:46 PM   #3
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hope this harbness works for you.
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Old 11-15-2009, 11:23 PM   #4
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Yes, harbness.

I extended mine w/o shielding it and it worked fine (Yes I was aware it was shielded).

My motor has to come out for some other crap, though, so I'll probably go ahead and try this.
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Old 11-16-2009, 12:44 AM   #5
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Would shielded audio or video cable work? Chop connectors off, strip, solder... I'd think the the spooled cable would work pretty well for this, it's built with the assumption that someone's gonna want solder up to the conductor, and the shielding too for that matter.
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Old 11-16-2009, 06:50 AM   #6
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Quote:
Originally Posted by NSFW View Post
Would shielded audio or video cable work? Chop connectors off, strip, solder... I'd think the the spooled cable would work pretty well for this, it's built with the assumption that someone's gonna want solder up to the conductor, and the shielding too for that matter.
That was my first thought, but I haven't found audio cable that's the correct gauge unless it's a monster or something expensive. And I don't want to chop up a monster.

I tried to match the thickness of the wire coming out of the ecu.

I admit that this is probably overkill or maybe even unnecessary, but I didn't want to run into any strange issues. This was cheap to do as well. I think it was a total of like $6 for everything. I figured it was worth the piece of mind.
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Old 11-16-2009, 09:53 AM   #7
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McMaster carr has tinned copper braiding that works well for this. Simply push the braid together to get it to expand, put the wire through it, then pull the ends to tighten the braid. Ground one (or both) ends.

Part number 5537k26 is 1/4" ID copper @$1.13/ft, SS is part number 1478T1 and is $2.10/ft.
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Old 11-16-2009, 10:11 AM   #8
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For those of you who understand this stuff better, is there any reason I can't just shield the whole 6-wire bundle rather than taking it apart and shielding the single signal wire?
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Old 11-16-2009, 10:25 AM   #9
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Yes. You want to isolate that single wire by itself. Bunching it up prevents signals from outside the bundle from getting in, but doesn't prevent electrical noise occuring from within the bundle.
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Old 11-16-2009, 10:29 AM   #10
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Quote:
Originally Posted by Mechie3 View Post
McMaster carr has tinned copper braiding that works well for this. Simply push the braid together to get it to expand, put the wire through it, then pull the ends to tighten the braid. Ground one (or both) ends.
Usually it is inadvisable to ground both ends as this can give rise to current flow and induce error onto the signal wire. Ideally you ground at the source of the signal.

Quote:
Originally Posted by CKxx View Post
For those of you who understand this stuff better, is there any reason I can't just shield the whole 6-wire bundle rather than taking it apart and shielding the single signal wire?
Bundling the wires together will not prevent cross talk between the wires.
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Old 11-16-2009, 02:09 PM   #11
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Glad you got the kinks worked out.

Just to add some engineering notes--when a wire has current flowing though it it creates a small magnetic field around said wire. This magnetic field can induce currents in other wires in close proximity ie. 'cross talk'. To prevent cross talk you can twist the power wire and it's ground wire together. Take a look at how Ethernet cables are twisted pairs--same concept. They are twisted together to prevent cross talk and reduce noise.

This concept works since the same current flowing to the device on the power wire is flowing out of the device in the opposite direction on the ground wire. These magnetic fields actually cancel each other out.



Shielding a cable in the above manner does not prevent cross talk. It prevents RF and EMF from causing havoc with the sensors and ECU. Any wires lying around act as antennas that pick up a lot of noise from the background. The longer the wire run the more prone it is to such interference.
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Old 04-05-2012, 06:31 PM   #12
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Good thread. Thanks!
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Old 04-05-2012, 09:00 PM   #13
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does this work? Do you think I would get away with using shielded audio rca cable?
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Old 04-05-2012, 09:36 PM   #14
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probably not because rca cables are not the correct gauge on the inside. I did switch over to real shielded cable I got from www.aircraftspruce.com/ and didnt' notice any difference

Last edited by Bad Noodle; 04-08-2012 at 08:49 PM.
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Old 04-08-2012, 05:29 PM   #15
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Quote:
Originally Posted by Bad Noodle View Post
probably not because rca cables are the correct gauge on the inside. I did switch over to real shielded cable I got from www.aircraftspruce.com/ and didnt' notice any difference
which cable did you buy from there? Do you have a part number
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Old 04-13-2012, 07:22 PM   #16
Tlove subaru
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Hello I'm looking for the wire colors for the maf sensor for a 2010 subaru impreza can anyone help me figure it out?
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