Garmin GPS Antennae

Time: 1 Hour

I had run the RG400 coax cable from the Garmin GTN-625 tray a year or so ago when I was doing all the wiring behind the instrument panel. It wan through the left side firewall pass through. I just had it coiled up waiting for its final routing and installation. The cable has a required length and was labeled “so not shorten” since I put it in. So no that I had almost all the work done firewall forward I decided it was a good time to finish this task. I needed a TNC cable connection that is required for this antennae and ordered it from Aircraft Spruce. Once it had arrived, along with other goodies, I un coiled the cable and followed the steps to crimp it on the cable. If you need help with this task has a great video online. After I had it crimped on and tested for any shorts between the pin and shielding and all was good. So then the routing was planned out and how I would coil up the extra length of cable. I just decided it would be best to creat a larger coil and secure it with an adel clamp as well as zip ties before it runs up to the antennae. Once that was complete I ran the Dynon gps serial wires along the coax cable to secure it as well. I secured the cable in several spots to prevent chaffing or movement. Overall I’m happy with this layout and hope it has a good signal. I won’t know for sure until I buy the Garmin GTN-625 down the road.

E-Mag Wiring

Time: 2 Hours

Another firewall forward wiring task was to finish up the E-Mag runs. This is my engines ignition source. In traditional Lycoming engines they use magnetos to provide the ignition source. The E-Mags use newer technology to control very precisely when the spark is delivered in reference to pistons compression stroke. Another benefit is they have their own internal alternator that provides power for the spark even if all ships power is lost. For these reasons I went with this setup. There are only four wires needed to go to each E-Mag, a 12 volt source, a ground, a p-lead and a digital tach reading. The 12 volt, tach and p-lead I had run a while ago so I just needed to add a ground to the mix. I made the appropriate extensions to the wires and figured the best path to run the wires to the E-Mags. They have a connector that plugs into the back and you just have to screw each of the wires to the connector. The 12 volt source provides power under normal operations, the ground provides normal ground and the tach will give me an RPM reading. The forth wire is the p-lead for testing the function of the E-Mag using a switch in the cockpit. In normal operations the power is providing spark using the ground of the engine with the p-lead switch(I labeled it ignition) in the on position. When you put it in the off position you are grounding the p-lead and denying the E-mag from creating spark which only allows half of the spark plugs to operate making the engine run rough and providing a positive test that the E-Mag is working when the ground is removed. The last test for the E-Mag will be to remove the 12 volt power to make sure the internal alternator operates. I will do this by turning the circuit breaker off on my Dynon screen. After running all the wires I secured them and plugged in the connector. If I did them all correctly when I put power on I should see a red LED followed by a green LED. My luck was good and that’s just what happened!

Smoke System Nozzles

Time: 2 Hours

I have had the smoke system installed for some time now and is located in the aft cargo area. All the wiring and plumbing was finished all the way to the firewall where it ended in a T fitting. From this T fitting the smoke oil splits into two lines that run to two of the exhaust pipes. Now was a good time to locate and install the spray nozzles and their associated lines to the T fitting. Just like the EGT probes you need to do some measuring and figure out the best spot for your given setup. Once I was happy with where I wanted to placed them I marked and drilled the required 3/8″ hole. Then it was just a matter of running the line and securing it from the T to the exhaust pipe. The spray nozzle is welded to a metal flange that gets secured with two clamps. As a back up the instructions have you safety wire the nozzle as well. I left plenty of slack to account for engine vibration. One more firewall forward task done. The tasks are slowly disappearing!

EGT & CHT Probes

Time: 2 Hours

Part of the engine instruments is the measurement of the exhaust gas temperature(EGT) and the cylinder head temperature(CHT). These take analog info in the way of a probe that gets heated up and will be converted to a digital signal via the Dynon engine monitoring system(EMS). These signals can then be read in digital form on either of my screens in the instrument panel. For the CHT’s there is a threaded port in all four cylinders that a adapter threads into. Then the probe can easily be inserted with a quarter turn. The exhaust gas probes need a 1/8″ hole drilled into the exhaust pipes somewhere between 2″ – 6″ down from the flange/cylinder. I did some measurements and alignment planning for these so that they won’t interfere with items like the engine cowl. The most important part of the measurement is that all four probes are identical in relation to the distance from the flange so they can be accurately compared to each other’s temp. All eight probes have a length of wire on them and these will get spliced to the EMS wires that I had run a long time ago to the firewall.

CHT & EGT Wiring

Time: 4 Hours

Now that I had the probes all installed I could finalize the wire routing and do the splices. I had a lot of extra wiring from the EMS and just had it curled up on the firewall. I figured out where I want the splices to sit as it needs to be an easily accessible area for future replacements. Ones that was determined I measured and cut each wire to the correct length and began the process of stripping each wire. I decided to use knife splices and cover them with shrink tube to help in the replacement process in the future. The probe wire are interesting as they have a fiber like covering versus the tefzel I was used to. So striping then took a little more time. I used shrink tube to cover the transition of the outer sheath to the exposed wires. Then with the knife spices connected I covered those with shrink tube. Then I covered the entire thing with a large piece of shrink tube to protect it. I organized all the wires and routed/secured them to the engine mount. I left plenty of slack to allow for engine vibration as well. I powered up the Dynon system and tested the probes by putting a heat gun on each one checking to see if the instruments showed a rise. I’m happy to say every one worked perfect. So I repeated the whole process on the opposite side with the same results.