ArVeeNiner

ArVeeNiner

Well Known Member
Hi all:

It seems the norm to have two holes in the firewall for passing wires through the firewall. One hole is for the thermocouple and sensor wires while the other one is for the stay alive power as well as BUS power (with a few other stray wires thrown in). Is there any reason why I can't put ALL wires through a single hole? I drilled a hole on the pilot's side and it's large enough the fit all the sensor wires as described above AND the power wires.

Thanks
 
Although I have two holes for wiring in my 9A (better logistics for my design), I see no reason why you could not put all wires through a single hole.

greg
 
Not a good idea

It is not good practice to route sensor wires and power wires together.

The current level in the sensor wires is very low, and can be influenced by inductive coupling when run in bundles with high current conductors.
 
And then there's me. I have 7 holes for my wiring. Power and sensor wires are not routed together (somewhere I read that 1/2" separation is optimal) but I also did not like the idea of having wires that went from one side of the firewall to an opening on the other and then back again to the equipment on the other side. So I kept the runs as short as possible and grouped them where I could. Alternator, solenoid and right battery share a hole. Upper Lightspeed coil wires have their own hole, as does the bottom set. The two Lightspeed sensor cables each have their own hole, but then I had to deal with getting the connector through the firewall and putting them both through the same opening (connector plus a cable, not two connectors) would have made the opening bigger than available shields. I did route most of the sensor wires from the panel to the Engine Pod through those openings, though. The Engine Pod cable to the EFIS got it's own hole and the left battery got one.

It's a neat idea to minimize the penetrations in the firewall but if you have too many wires in the same bundle you have the problem of sealing the bundle. Smaller bundles are easier to seal and, IMHO, a better way to go.
 
Lightspeed specifically tells you not to route the timing input wires with the ignition output leads for their Plasma ignition units..
 
Yikes, 7 holes? I suppose that is okay if each wire hole is sealed properly.

I've found two to be sufficient. i use the firewall penetration kits from EPM.AV that are made of stainless and are tube-like. I use a small one on the upper left for the sensor wires and a big one down low on the right side for the power and alternator wires. These kits come with firesleeve and a tube of fire retardant sealant. I've never needed more than that and I am running dual alternators, electronic ignition, and sensors for six cylinders. That doesn't mean that's the best way, it's just the way I did it. YMMV.
 
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The other partner is going to go it alone under a new company name

I talked with Paul Bowmar and he is getting everything in order to go it alone under a new company name. I think he told me maybe, Plane Enterprises ?. He said he would let everyone, on this forum and Rivetbangers, know of his new company once everything is finalized.

I called and ordered a heat control box for the firewall from him once I saw the other company was folding. He is making a newer version of the heat control boxes which will be lighter made of stainless.
 
Sensors vs Others

I work in the industrial controls industry. We never mix sensor conductors with any current carrying precisely because of the induced voltage problem. Sensor inputs to computers (in our case PLCs, DCSs, and hybrids) are so sensitive that, depending upon the critical nature of the systems being controlled, the slightest error introduced by induction can ruin your day. Then you get into wire types, twisted cable vs non-twisted, insulation ratings and so on. Many people think I'm nuts, but I love such things.

Bottom line, separate your sensor conductors from current carrying conductors.

My 2 cents and worth every bit.

Cheers from a long term wannabe!
 
Safeair1.com has a stainless steel firewall passthrough system that looks similar to epm.av--price is a little better too.
 
EPM is changing to Plane Innovations

Just got my heat box from Paul Bowmar. He is going to go in alone going forward and the company will be called Plane Innovations (not Plane Enterprises that I posted earlier). He will let us know on the forum once he gets everything in order legally.
 
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