SDS - Hall Sensor & Injector Wires over the top of the Engine / MAP hose routing

The hall (crank) sensor wires need to run from behind the flywheel back to the firewall passthrough, as do the power and ground wires for the injectors. A logical route for these is over the top of the engine, however this means they need to pass through the baffles. 

I had already pinned the 9 position Dsub connectors at the SDS ECU for the hall sensor wires, and at the front of the engine the hall sensors are already wired (and potted in epoxy). This meant i needed to cut the wire at some point in order to run it - so i elected to install a CPC connector at the aft baffle to make this connection, and will include the injector wiring in the same connector. 

Protecting the Hall Sensor Wires

I had previously made up a little bracket and a length of 3/8 fuel tube to protect the hall sensor wires. I attempted for a couple of hours to make the existing fuel tube bend correctly to pass through the front left baffle, but frustrated, gave up and started again. The second time around i started with the hole in the baffle, and worked backward. This worked a lot better and i had the tube bent in an hour.

The purpose of this effort was to reduce the liklihood of an alternator belt breakage causing the loss of the crank sensor, and potential loss of the engine. 

Since the wires are connected to the hall sensor at one end, and the baffle CPC at the other, this would have made the removal of the baffles impossible. So i elected to trim a small channel to allow the baffles to be removed. I will make a small cover plate later to go over this gap, and to strengthen the baffle in this area. 

The baffle was trimmed to allow the baffles to be removed.

This took many hours!

Running the wires across the top of the engine

The first step in completing the wiring was to work out where the CPC connector would go in the baffle. After much head scratching, i made a decision and drilled a hole to mount the CPC. 

To run the wires across the top of the engine, i started by installing a bunch of different sized ADEL clamps - the holes in a standard ADEL are 3/16, but the engine case bolts are 1/4, so i used a step drill to enlarge the mounting holes in the clamps. Where the bolts were not long enough, i either swapped the washers for thin ones, or increased the length of the bolt.

When a bolt was undone to install an ADEL, i re-torqued that bolt before undoing another one.  

Each case bolt was torqued as i went.

I used some white WCH (high temp silicone) ADEL clamps on the pushrod tubes, to support the injector wires until they could join the main bundle travelling aft. 

The bundle was laced together with lacing tape. 

Once it was all bundled to my satisfaction, i cut the wires to the correct length. Here i did a stupid thing! There are 2 identical Hall Sensor cables - these are 4 core shielded cable. When i rough cut them, I had marked them with sharpie becuase i figured the engine won't run very well if i mixed up the primary and secondary hall sensors! Anyway, despite this careful marking i went ahead and snipped all the wires at the aft baffle in one go - totally forgetting about being careful. Doh! 

Ended up having to buzz out the wires from the hall sensors themselves to make sure i pinned each one in the correct location. I connected a multimeter to the shielding at the baffle end, then used a razorblade connected to the probe at the hall sensor end to make sure i had the correct one in the correct spot! 

Sockets were then installed on the wires. I followed my wiring diagram to pin the connector.  

Of course, i had half pinned the connector before realising i had forgotten the backshell. Always.

A normal DSUB pin can take up to a 20 AWG wire. I had elected to keep the SDS 18 AWG injector wires, as the pins for the injector connectors are apparently fairly hard to crimp properly, plus i thought 18AWG was much more sturdy in the environment on top of the engine. This meant i needed to remove a couple of strands from each pin, so the wire would fit. 

Everything was labelled as normal, then pinned. 

The following photos are mostly for me own reference (just in case). 

To protect the wires further, they were wrapped in nylon spiwrap (2 different sizes), then covered in this product. This is a self closing flame resistant nylon. I covered the whole wire run, then used lacing cord to secure it. I liked this approach as it means i can open the loom later if i need to, without having to remove the loom, or de-pin any connectors to install heatshrink etc. 

The manufacturer lists the following specs:

Temp rating: Operating         -50° to 150°C
                      Melting point     240°C+

Flammability: meets UL94, FMV SS302 test < 100mm/min

The finished product:

The Aircraft Side

I also pinned the aircraft side of this harness, although i will likely have to cut these pins off later as i won't be able to determine the proper length for this harness until the system is installed into the airframe. Photos again for my own reference:

MAP Hose Routing

ADEL clamps were installed onto the sump bolts in a few locations and the MAP hose was run roughly to the back of the engine. 

Next up will be to install the fuel block, and run the fuel injector hoses.