Firewall Forward Wiring

The Engine Information System (EIS) I'm installing as part of the G3X package is fairly robust. The Sensor Kit came with;

• 6 Exhaust Gas Temp (EGT) probes
• 6 Cylinder Head Temp (CHT) probes
• Oil Temp probe
• Mag Sensor (In lieu of a mechanical one)
• Oil Pressure sensor
• Manifold Pressure
• Fuel Flow Transducer (Didn't realize this, had already bought one)
• Shunt

I started this out by looking at the harness I received from Stein.  There are a lot of wires which actually just lines up with everything list above.  I spent a good bit of time upside down under the panel dressing the harness wires and routing them to my firewall passthroughs.  Given the length of the cables I needed to route the EGT and CHT wires for heads 2/4/6 on the pilot side, leaving heads 1/3/5 the copilot side, along with the rest of the wires.  I also went ahead and installed some non-EIS stuff such as wires for my ramair servo and air conditioning compressor.

With all parts installed and the harness wires sticking through I worked from the firewall moving forward.  I did sections at a time and used a mix of adel clamps and cable ties.  I tried to only use the adels in the firewall area but I decided to go ahead and use some heat stabilized ties which I can easily inspect each year.  It also gives a much cleaner look.

From an EIS perspective the only items I have to wire still are the sensor wires for the two shunts. Now I had previously decided to not use shunts and was going to rely on the VPX to give all power info.  For the most part I'm only concerned with if the Alternator is working and if the battery is charging and I've flown plenty of airplanes which a voltmeter was my only monitoring tool. However, because my harness had sensor wires for both primary and secondary alternators and because I hung a number of things independent of the VPX, I decided to go ahead and install two shunts.

The only reason I hadn't wired them yet is because it's suggested that you put 1 amp fused at the end of each wire so in the case there's a short, it doesn't blow out any of your avionics. I went back and forth on how to do this.  Originally was going to use 4 inline fuse holders with 1 amp blades, but that seems cumbersome.  Then I was thinking of doing a fusible link, which is basically a small wire encased in a fiberglass sheath.  This idea is if it gets too hot it melts and breaks the link. Then on a suggestion I looked at these really small micro fuses that I'll be able to solder in similar to a diode and shrink wrap it.  Should make it all safe and give it a clean look.

Airhorn!

UPDATE: The engine area obviously gets much hotter than a typical motorcycle.  This causes some internal components to melt a bit, changing the tough train sounding horn more to that of a clown car.  I went through a few horns and ended up removing it at annual. It was fun for a bit but the novelty wears off.

What I've been telling people about the wiring progress is it's the little victories that make me happy.  One of those was tonight when I finally had a chance to wire up the Airhorn (Or is it 'air horn'). This device has been sitting on a shelve since I bought off Amazon a number of months ago. For $50 it's one of the cheapest components you can buy for your airplane.  I went with the Marco Tornado intended for Motorcycles, Cars & Trucks... so why not an airplane?

I originally was going to hang it off the VPX, but the larger 10 amps or more 'breakers' are at a premium. I decided to go ahead and hang it off the ANL feeding the VPX.  In fact going to use this same spot to connect my Air Conditioning Components and USB chargers.  I have breakers for the AC parts but for the rest I used in-line blade fuse holders.  I went with a 20A fuse to match the instructions and 14 gauge wire for all but the switch lead.

In normal operations I'm going to trigger this via the pinky button on the stick.  However I don't know if I'll have a tendency to hit it in flight so I went ahead and used the spare switch space I had for an Airhorn switch. If I find I don't need it and then end up needing a rocker switch for something else I can just remove it from the path later.

The airhorn is physically mounted in an open space on the firewall via one bolt.  It's a 5/16 hole, which like all the holes I have, get sealed up with some fire barrier stuff before placing in the hardware.  Wiring works off a relay and because it's built for car horns which rely on some voltage you need to jumper a smaller wire off the positive input over to another tab.  Then it works like any other switch where grounding it out triggers the relay and allows the larger amperage across.

With the help of my kids I decided to let my son flip the switches and my youngest daughter film.  Here's a video of the test, glad she didn't drop her phone!  Also pardon the mess of wires, it's still a work in progress.