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 2 conductor wire 22AWG cabling terminate with 250 Faston and ring terminal (for ground) onnector
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 2 conductor wire 22AWG cabling terminate with 250 Faston and ring terminal (for ground) 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 2 conductor wire 22AWG cabling terminate with 250 Faston and ring terminal (for ground) 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.