Charge System Wiring (Part 1)

Time: 1.5hrs

Well I was going to post all this once it was all done, but the parts are taking a bit longer then expected so I’ll post what I have so far.

I purchased a crimp tool for the large 6AWG cable so I was able to make up a few of the larger gauge cable. The crimp tool is a simple hammer crimper, not a squeeze crimper and seems to do a pretty nice job. The hand crimper does a better job because they form more of a hex shaped crimp, but they cost around $200. This one cost about $9 from Amazon and does a good job. I was thinking of maybe soldering the crimps as well, but I’d rather not because that can cause the wire to getting brittle which could lead to it breaking. I’m using 6AWG Tefzel for the bulk of the high amperage connections. A smaller gauge wire like 8 or 10 would have worked as well, but there’s no drawback to using the heavier gauge wire other then weight really and there’s not that much of it. And minimizing the different size wires make it a bit easier and cheaper in some ways.

I need to work on what I’m going to do for the firewall pass thru. There are a few things on Aircraft Spruce but because there is already a large 2″ hole in the firewall it makes it difficult to simply go with what you like. What I’d like to do is use 2 stainless steel pipe pass thrus (one for high voltage wires and the other for the engine sensors). However, I don’t want to make another large hole in the firewall. What I’m leaning towards is a split stainless steel flat pass thru that uses silicone grommets. I’m thinking I might be able to fit 2 grommets side be side and pass them through the large 2″ hole. The pass thru is made for 3 grommets so I’d have to cut the pass thru down to shorten it up. I had purchased a large stainless steel flange that would work, but it’s pretty heavy so I’m going to look for something else.

This is the crimer I purchased. I found that one good hit with at 1lb hammer tightens the terminal so you can get the wire situated. Then 3 more hits seems to finish the crimp.

Not a terrible crimp and the wire is very secure in the terminal. This is the first crimp I did. The next ones were actually a little better.

I purchased some Molex and some AMP terminals and I like the AMP/TE ones better. They have some ridges inside that should hold the wire very well.

I purchased these 2 size terminals from The 1/4″ (TE part # 321598) fits the 6mm terminals on the start solenoid OK, a little loose and the 5/16″ (TE part # 33466) is for the master solenoid.

Some photos of the master solenoid. I roughed in the cables to the battery. I have the SR560 Schottky Diode installed on the solenoid to reduce reverse current from going through the master switch when you switch it off. The starter solenoid has the same, but it’s wired a little different. I’m waiting on a terminal so I can wire that one. The ground lug passes thru to the Faston terminal (in the cabin) for the avionics grounds.

Some wiring run to the starter solenoid. I have to divide up the connections on the switched side of the battery solenoid so some things will connect to the starter solenoid (batt solenoid side). I’m trying to keep wiring neat as I run it because it’s getting confusing. I purchased some reusable zip ties to help keep wires bundled. There’s a 1k ohm 1 watt resistor wired into the cable that goes to the VPX for the starter annunciator.

This is the ALT2 regulator connector that I wired up a few days ago. The regulator is mount ed inside the cabin. The left side has a ring terminal that connect the large capacitor and the right side will connect to the ALT2 relay out on the firewall. I purchased some large Faston connector so I could crimp the 2 12AWG wires into one connector. The Faston connectors are a bit special in that they have a small tab on the back so that they click when inserted in to the connector. I suppose you could just us the PIDG type and then push them directly onto the regulator and not us etch connector.

I will be mounting the MAXI fuse holders on the firewall as well. I had purchased some Littelfuse fuse holders which I really like, but I don’t like how the terminals crimped on. I don’t have the correct tool and I’m not going to spend $300 on it just to crimp 4 connections. You also can’t just buy the terminals so I’d have to spend another $30 a pop on the holders if I want to redo them. I have some Blue Seas Systems fuse holders coming which use ring terminals. I’ll see how these work out. I have to mount them side by side on the firewall so it’s gong to take up some space. I also need to figure out where to mount the ALT2 relay.


Airbox Temperature Sensor

Time: 0.25hrs

Still waiting on some electrical parts so trying to find something to do on the plane. I received the VDO temperature sensors that I’m going to use for the airbox temperature sensor. The Rotax 914 comes with one installed already, but it’s connected to the TCU so you can’t feed it to the Garmin. You don’t really even need it, but I figured it may be good to have and seemed easy enough to install. There’s an extra 1/8-27 NPT hole in the airbox and you just need to remove the plug. The sensor wires just like the coolant and oil temperature sensors (single shielded 22AWG wire) and is only a few dollars. I purchased it off Amazon for around $19. It’s a VDO 323057 Temperature Sender. We’ll see if it works in a year or so 🙂

Used a little Loctite 577 on the threads and torque to 15NM.

Hopefully I will have the charge system stuff finished up soon and also the final install of the turbo servo. After that’s done I should be able to put the front top skin on and fit the dash.

I also ordered a 2″ stainless steel pipe stub to use for the firewall penetration wire all the wire run through. Hopefully its not too heavy and I can figure out how to mount it to the firewall. I figured I should get this installed before I run a lot of cabling through the firewall since it won’t be a split piece.

Turbo Servo Mounting

Time: 2hrs

I roughed in the mounting of the turbo servo. TAF typically puts it on the engine side of the firewall lower down on the pilot side. The Rotax manual says not to install it on the engine side because the case isn’t fire rated so if you were to have an engine fire you’d probably lose the turbo pretty quick. Personally I don’t think it’s a big deal because if you have an engine fire you probably will shut down the engine so turbo or no turbo isn’t going to make much of a difference. In any case after speaking to Jean at Torrance TAF he persuaded me to mount it on the cabin side of the firewall. Most of the time today was really thinking about where it should go and how the cable should be routed through the firewall. I ended up with a somewhat odd arrangement. Since I used the cable bushings to pass the cabling through the firewall I had issues with where to mount the servo where the cable coming into the servo didn’t interfere with the cabling going through the firewall. I ended up mounting the servo on a slant. So the bolts are level, but the servo itself is slanted. There’s no reason why the servo needs to be mounted level and putting the bolts in level (rather than the servo) was actually much easier.

One thing to note is you do need to disconnect the cable from the servo to pass it through the firewall. The tension on the waste gate is set at the factory, but I just marked the cable so I can put it back at the correct tension setting.

I’ve also been working on the alternator and solenoid wiring. Which I will post in a few days when it’s done. The big time sucker here has been waiting for parts and then realizing you need more or different parts. SO I end up working for 10 minutes and then having to stop. The combination of ring terminal size and wire size is driving me crazy. The PIDG connectors have 3 different sizes and am mainly using the red (22-16AWG) and Yellow (10-12AWG) size terminals, but then I must have every different size of wire lug on the planet… 5mm (which is also #10 BTW) for the starter solenoid, 5/16″ for the master solenoid, 6mm (which also 1/4″ works) for the grounding of the ALT2 regulator, etc… so there are many different connectors you need and you usually don’t have the one you need.

The Turbo Servo mounted slanted, not bolted in yet though. I found that mounting it slanted allows the cable entering the servo to miss the the cables passing through the firewall (blue fittings). It also creates a nice gentle bend around for the cable. I need to wait for some spacers to arrive before I can mount it. I was also thinking of maybe using M6 screws with rivets instead of the AN4 bolts which are kind of a pain to tighten if you’re a “one man” show.

After some time working out different pros and cons of where to run the cable through the firewall I decided to run it through low on the firewall. This is a bit cleaner on the engine side and also eliminates an extra bend if I were to run it up high and then through the firewall. The cable also isn’t that long so some thought needs to go into it.

The cable comes out between the rudder pedals. I’ll install a bracket with and adel clamp and that will pull it closer to the firewall and keep it out of the way of the pedals. I’ve been using the CableSAFE passthroughs (purchased from Aircraft Spruce) to run the cabling through the firewall. I need the kind that comes in 2 halts because the servo cable already has an end on it and it won’t pass through the normal closed type CableSAFE fitting… so now I wait for parts.

Misc Engine Work

Time: 1.5hrs

I didn’t do too much actual work on the plane today. I mainly did some research to understand the different sensors and what is needed. I did make the mount bracket for my fuel pumps, and alodined a few parts. Additionally I tightened down a few bolts of the alternator bracket that I figured wouldn’t need to be removed. I left the bolts on the arm loose since I will have to tighten the belt on the alternator and can’t do that just yet. I also found that my oil thermostat doesn’t have metric threads even though the firewall forward manual calls for 6mm (12mm long) bolts they’re actually 1/4-20 bolts. 6mm and 1/4 are very close and the 6mm bolt threads in a little, but the threading is different. Fortunately I had a few bolts lying around so I was able to find one that fit and now I just have to order them from Bolt Depot.

What I mainly did today was look through the Garmin and Rotax manuals to figure out the sensors that I need to get. The newer Rotax engines are referred to as “Suffix -01” this is because they have a -01 at the end of their model numbers, for example mine is a 914ul2-01. The reasoning was because Rotax made a change to the cylinder heads to make all the parts the same. So with that there are no longer cylinder heat temperature sensors on the bottom of the cylinder heads, rather there are now 2 coolant temperature sensors on the top. This caused some confusion for me since both are shown in the Rotax install manual. Garmin sells a Rotax kit for use with the GEA24, but there are a few things that you pay for that you don’t use on the 914 and you still need to purchase a few other sensors so I’m thinking I may just skip it and get everything separate. I have detailed my findings in the following table.

Sensor Part Number Comments Wiring
Coolant Temperature Rotax 965531 Supplied with engine (Located on cylinder #2&3). Use shielded single wire 22AWG cabling terminate with 250 Faston Connector
Coolant Pressure KAVLICO P4055-50G-E4A Saw this mentioned in Garmin manual, but not sure if it’s applicable to the 914, may be 912IS only Use 3 wire 22AWG shielded cabling
Oil Temperature Rotax 965531 Supplied with engine (Located on oil pump). Use shielded single wire 22AWG cabling terminate with 250 Faston Connector
Oil Pressure Rotax 456180 Supplied with engine (Located on oil pump). Use supplied cable and connector. Wiring is long enough to reach GEA24
Mechanical Rev Rotax ? Supplied with engine (Located on generator). Use pins  26&11 from TCU along with zener diode, diode, and 300ohm resistor (comes with Garmin kit or source yourself)
Manifold Pressure KAVLICO P4055-30A-E4A or P500-30A-E4A Can’t find this sensor, Also may be available from Dynon. Comes in the Garmin Rotax 912/914 kit. Use 3 wire 22AWG shielded cabling
Airbox Temperature VDO 323057 This is not required, but will try this sensor. Sourced from Amazon and looks like it should fit (1/8 NPT -27 threads). Use shielded single wire 22AWG cabling terminate with 250 Faston connector
Fuel Flow FT-60 Aircraft Spruce has these (part # 10-01196) Use 3 wire 22AWG shielded cabling
Fuel Pressure UMA N1EU07D Aircraft Spruce has these (part #10-00980) Use 3 wire 22AWG shielded cabling
EGT TYPE K TERMOCOUPLERS Aircraft Spruce has these (part #15-09438). They can be ordered with 6 or 9 foot wires so no need to buy special K type wire. Also should mount to M8 threads in exhaust. Use supplied wire

Engine and External Alternator Install

Time 2.5hrs

Today was a big day. I finally got my Rotax 914UL2 installed on the plane. I’d be lying if I didn’t say that I was extremely nervous seeing the engine hanging about 3 feet up in the air, but all went very well. I was even able the manage the install all on my own without too much trouble. The firewall forward manual says absolutely nothing about the engine installation, but the Sling 4 Maintenance Manual (available from the TAF web site) has some great info on this as well as a host of other things. A few important things to note are that the torque value you use which is 38Nm (28ft lbs) is the lubricated value because you use a bit of engine oil on the bolt, so don’t just assume a dry torque value for a M10 8.8 grade bolt. (EDIT 11/25/2018: One thing to add is only use engine only if you don’t want to calculate your own torque value this is because other lubricants may provide more or less friction while tightening). Another item to note is that the 130mm bolts that are provided are a little long. The maintenance manual says to shortened them to 122mm. I suppose maybe the top bolts would be fine, but the right bottom bolt is fairly tight and would be too long if you didn’t shorten it. Also I followed the recommendation for how to install the bolts, even though the bottom bolts are actually put in backwards (in regards to what the FAA says to do). There is also a note in the MM that you don’t use washers on the nut side of the bottom bolts, though the kit provides washers to do this.

The 130mm M10 bolts need to be shortened to 122mm as per the Maintenance Manual.( original on the right) I suppose that really the lower and mainly the right lower bolt needs to be shortened, but it doesn’t;t look a little nicer not have a lot of excess bolt sticking through. The job went pretty quick with the dremel.

I took the side off the box so that I didn’t have to lift the engine over the box and it was a bit easier to get to the engine to loop the ropes through.

I double roped it just in case. It really wasn’t an issue though. The engine is very light (only around 100 lbs.) and the ropes barely looked like they were holding anything. I gave it a quick test with the crate bottom still bolted to the engine just to make sure it was balanced and that the ropes would hold OK.

No washer on the nut side of the lower bolts because the exhaust bracket is there. I torqued it from the bolt head side so that I didn’t scratch up the bracket (in this photo the bolt isn’t completely torqued). The right side is a pretty tight fit on the nut side and probably was the most difficult to get on. I also removed the oil tank so I could get the torque wrench on the bolt.

Top bolts (not torqued yet). I rotated tightening the bolts rather than one bolt to full torque at a time.

And it’s on. Not too bad. I found it easiest to pull the plane towards the engine to get the bolts to seat in rathe then the engine to the plane. The hoist made it very easy to get the engine to the right height.


Well the external alternator didn’t come with any instructions so I used the parts list diagram to figure out how it goes together. I also found that the Rotax Install Manual has a sparse diagram as well, but the parts list is a bit more detailed. I want to alodine the arm bracket so I don’t put that on yet and I didn’t torque anything down because I’m not sure what I should torque it to. Jean alerted me to the thin washer (#14 in the diagram) and to make sure it’s put in the correct place, they had put it on the other side of the joint and the alternator mount actually broke over time because there was tension on the bracket. It’s a very thin washer so not really sure how that would cause that kind of issue, but I’ll trust him on that :-).

The two bolts in the front of the gearbox housing cover (I guess that’s what you call it) get replaced with longer bolts provided in the alternator kit (from Rotax). The original that was taken out of the engine is on the right.

These are the two bolts that need to be removed and replaced with the longer bolts.

It’s pretty much together. I want to see if there’s any special torque values that I need to know about. Maybe the two bolts that go into the gearbox housing cover need to be torqued to a certain value. Also a few bolts need to be safety wired. I also use two large black bolts that came with the alternator to temporally hold the large pull to the main engine shaft. I don’t know what these black bolts are actually used for since I can’t find them on the parts list diagram, but I’ll check around more.

NOTE (11/24/2018): I just found the following referencing the part list diagram. I found this from the California Power Systems site.

So there’s a few torque values.

NOTE (12/5/2018) Also found torque values for the two socket head screws that hold the alternator bracket to the front on the gearbox housing. Those are torque to 10NM or 90 in. lbs.

Master Solenoid and ALT2 Relay Wiring

Time: 1.75hrs

I received the Master Solenoid from Aircraft Spruce today. This was mounted above the Starter Solenoid so I can just run a short 6 AWG wire between them. I also wired up the ALT2 (Integrated Generator) relay wiring and fuse. The relay will be used to switch the alternator (generator really) on and off of the master bus. The external regulator for the generator has a “C” (control) terminal, but the Rotax manual says that you’re not supposed to disconnect the “C” (control) from the “+B” (Battery) terminal while the engine is running so a relay (or high current carrying switch) is needed to disconnect all these terminals from the main bus while leaving them connected to each other. There is also a 22k uF cap that is needed to protect the regulator from damage.

Master Solenoid mounted using M6 Screws and loctite.

Messed with wiring up the ALT2 relay, fuse and cap. The cap isn’t as big as some of the others I saw. It actually has a very high time to failure something like 12,000 hours where most I saw where around 10,000 hours. I ordered it from DigiKey for around $11 (part #B41456B5229M000).

The fuse is a 25A MAXI fuse. I’m going to go with the MAXI fuse because they’re very common so it would be easy to get a fuse at an auto parts store say I was somewhere remote and had to replace it. I was also considering a circuit breaker on the panel but if the circuit break pops it usually pops for a reason so resetting it really isn’t a viable option. The regulator is fed from the wires to the left of the cap. I was also considering moving the fuse to the left side  of the cap to keep the wires a little shorter, but it may get messy splitting the single wire into the three terminals (C, +B, and R) that feed the regulator. The 10 AWG wire attached to the fuse holder is a bit large to attach directly to the regulator terminal.

I will also feed the Main Fuel Pump and TCU from the wire that connects from the battery solenoid to the relay input, but Jean talked me into using circuit breakers for those so I’ll have to run a wire up the to instrument panel.

Still waiting on the engine mounts so I can’t mount the engine just yet :-(.

Misc Firewall Work

Time: 1.5 hrs

Did some miscellaneous stuff on the firewall today. I finished installing the TCU, Redid the install of the gascolator with the new bracket that finally showed up, and finally installed the Rotax fuel pump cover.

Jean from Torrance TAF and Jim G (a pilot friend who has built a Sling 2 and a Lancair) came by a few days ago to check out the progress. Jean and I spoke a lot abut the engine and various stuff I needed to do. They both were very happy with the work that I’ve been doing and were extremely encouraging. At times it’s been a struggle to keep the project moving forward from both a time standpoint and financially. So it was nice to be able to talk to seasoned builders to gain some prospective. Thanks for coming out and the spending time.

I had ordered an aluminum fuel pump bracket off Amazon a while ago and it finally showed up. I liked it better then the other bracket I had, so I decided to use it. The bracket was for a 2″ fuel pump, but with the rubber I added (from an Adel clamp) it fits very well. I like that it mounts to the end mount in 2 places so the gascolator doesn’t want to spin.

It was pretty quick mounting the TCU. I was going to use nylon type locking nuts to secure it to the mount brackets, but because of the rubber stand offs on the TCU being somewhat fragile, I ended up using standard nuts and washers and used Loctite (blue) on them.

Cut out done and M6 rivnuts installed for the Rotax fuel pump box. I’m going to use the case from the 912, Jean was able to find an extra one at the office. I was hoping that I could have just used the holes that were there for the original TAF fuel pump mounting bracket, but the holes were just a little off from lining up and I didn’t want to mess around with trying to elongate the holes and them enlarging them. I put the new holes in line with the original ones, just up about an inch. I also found that Goo Gone works well on removing the glue after the insulation material is cut away.

Now just waiting on the Master Relay from Aircraft Spruce which shipped out on Friday… Oh and the engine mounting hardware from TAF which should be here this coming week as well.

I still need to work on the mounting of the fuel pumps and the plumbing. I’m thinking maybe I can use the TAF plumbing and just add on an AN fitting to the in and out. I think that all the various tees and elbows that I’d need will be both expensive and too large to all fit in the pump box. For mounting I’m going to make a small stainless steel plate that fits in the pump box and use maybe 1/4 bushings to stand it off from the back of the case. I can then use Adel clamps to mount the pumps to the plate and the plate will get mounted using the same screws as the pump cover.