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914World.com _ 914World Garage _ installing new wiring harness thru firewall

Posted by: jkeyzer Apr 2 2006, 04:28 PM

I am working on a Megasquirt conversion and I need to pass a 1" diameter harness and a smaller vacuum line into the passenger compartment to my ECU box which will sit in between the seats.

I am looking for advice on where to punch thru the firewall. I am hoping to keep the stock backpad in place with as little modification as possible.

One question I have, is where is the firewall a sandwich of 2 layers of metal, and where is it single layer? Does it roughly correspond with the crease just over 3/4 of the way down? I would like to avoid this area if possible.

My current plan is to drill a hole in the center between the seats, a few inches above the sharp ridge shown in the picture, and then run the cable down under the backpad to my ECU box. That should allow the harness to come in from the engine compartment without having to go down through the engine tin.

Comments or suggestions?

Can anyone draw a line where the sheet metal goes from 1 layer to 2 on the photo?

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Posted by: jkeyzer Apr 2 2006, 04:30 PM

Here is the ECU box.

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Posted by: jkeyzer Apr 2 2006, 04:31 PM

contents of the box...

Megasquirt V2.2 board and a Tech Edge WBO2 controller.

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Posted by: jkeyzer Apr 2 2006, 04:33 PM

AMP Mate-n-lock connectors used for the harness.

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Posted by: jkeyzer Apr 3 2006, 01:36 AM

bump

Posted by: jonwatts Apr 3 2006, 01:49 AM

Jeff, I have a center tunnel with some of the firewall still attached. I'll take a look at it tomorrow and see if I can give you a definite answer.

Posted by: yarin Apr 3 2006, 05:18 AM

Wow... excellent work! I Really like how clean and thought out your install is. Great choice of connectors too, your connections should be 100% reliable!

The factory hole is about 1.5", but its 1/2 occupied. I managed to route my MS bundle through there, unterminated though.

Posted by: crash914 Apr 3 2006, 05:51 AM

I drilled my hole in the dented circle shown in the lower left of your picture...Yes it is two thicknesses of metal, but it works.

I also mounted the ms box to the fire wall behind the passenger seat and put the tech edge box under the passenger seat...works ok...

Posted by: tdsmoonchild Apr 3 2006, 07:01 AM

QUOTE (jkeyzer @ Apr 2 2006, 04:33 PM)
AMP Mate-n-lock connectors used for the harness.

Looks real nice!

Posted by: McMark Apr 3 2006, 11:34 AM

Double walled below the line. Single wall above. I would try to pop the lines through in the center, just above the center tunnel.

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Posted by: jkeyzer Apr 3 2006, 12:56 PM

Thanks for the illustration, Mark. Looks like in order to avoid having to deal with the 2 layer section I will have to run the cables down the firewall a few inches on the inside of the cabin. Should be no problem if I modify the backpad a little bit.