Tale of Two Air Filters

Time: 0.75hrs

Quite a few months ago when I has ordering a few things from Aircraft Spruce I also went ahead and ordered the engine air filter. It’s a standard filter made by K&N. Aircraft Spruce had listed one for use on the Rotax 914 so that’s the one I purchased and a quick test fit showed that is seemed to fit fine. Later I received the fiberglass airbox that fits around the air filter which has a hose connection to it that ties into a NACA duct on the cowling to bring in fresh air to the engine. A fit of the airbox onto the air filter revealed that the filter was too long. After a little research it seems there are 2 filters that will work on the 914, the K&N RU-0800  (4″ height) and the K&N-RU-0810 (5″ height). The one Aircraft Spruce sells is the 5″ height so that’s why it was too long for the TAF supplied airbox.

With that figured out and the correct filter ordered I installed the filter and hose. Installing the filter is a bit tricky because there’s a few hoses in the area and not much room to work. I was able to get the clamp for the air filter tightened down using a ratchet wrench rather then using a flat head screw driver. The hose was fairly easy to install after cutting it to the correct length.

The 2 air filters I have. Both are 2 7/16″ at the throat, but the RU-0800 (on the left) is 4″ in height while the RU-0810 is 5″. The one on the left is the one that fits into the TAF supplied air box.

The RU-0800 fits nicely into the airbox.

Hose is installed. There’s a few hoses in the area so I’m glad it fit in there without too much hassel.

Oil Cooler Hose Rework

TIme: 1 hr

I started doing a little rework of the hoses connecting to the oil cooler. The original hoses I had made up have 90 degree fittings on both ends, but then the clocking of the fittings have to be exact. Since I decided to run both hoses on the right side of the prop shaft rather then one one each side it made the clocking off. It ended up still working but the hoses had a bit of twist tension in them and it also pushed down on the oil cooler and the cowling a little.. I came up with an idea to instead use 90 degree fittings on the oil cooler so that the hoses could have a straight fitting on one end and not need to be clocked. It wasn’t easy finding an M14x1.5 male to 3/8″ NPT female fitting though. I originally wanted an M14 to -8AN 90 fitting to replace the straight one that came with the oil cooler, but that seemingly doesn’t exist… well at least in steel. So the M14 to NPT fitting was installed and then I have an NPT to -8AN 90 degree fitting . The angle can be adjusted to it’s pretty flexible to get it how you want the hose to run. I will need to get the current hoses cut and straight fittings put on. The only issue I see is that having to use 2 fittings has made the connector come up higher and the hose will be closer to the alternator belt. I can turn the hose a little more straight to get more distance, but I think it will have enough clearance.

Got the old M14 to -8AN straight fittings out without damaging the oil cooler. and put in the new fittings. The M14 to NPT fitting seals with an O-ring and I tightened that to 26 ft lbs same as the other fitting that I removed. The 90 fitting is a tampered NPT so I used Loctite 567 which is for high temperature

The new fittings are angled and the hoses are marked. I’ll have to send them back to Steve at Aircraft Specialty to cut and put the new ends on.

Engine Work Complete

TIme: 6.75 hrs

Over the past week or so I worked on getting the engine finished up. I’m sure I’ll still have a few things to do on the engine, but I wanted to get as much finalized as possible so I can move onto other things. There’s just too many open projects going on at once and I’m starting to lose track of where things are at when I come back to them.

I took a bunch of photos so I’ll just describe what I did after each of the photos. I know I still have a few pending things firewall forward but the bulk of the engine work should be finished. Items remaining are:

  • Purchase and install EarthX battery – I don’t want to by this too soon since it will just need to be charged periodically and should be pretty easy to wire up.
  • Adjust alternator belt, torque bolts and safety wire – I need to get the prop installed before doing this
  • Finalize the throttle and choke cables – I need to wait until the panel is installed or I at least have a good idea where the choke knob will be mounted so that I can cut the cable to the correct length.

I installed the External and Internal Alternator fuses in the engine compartment. I know some people have used circuit breakers in the cockpit, but I didn’t like the idea of running long high current wires unfused and if the breakers were to blow you’re not really supposed to reset it anyways so I decided I’d just put them closer to the source. I also uses a braided ground strap rather than just a wire. It’s easier to see if it’s broken.

Here’s what I ended up doing for the left side coolant hose. NOTE: I should get a picture of the bracket that’s mounted to the exhaust. In any case the hose is supported by a bracket that mounts on the exhaust and then attaches to that using an M8 bolt through the adel clamp. I used a very flexible silicone hose for the coolant hoses. For this side I had to also fit a 60º bend to this main hose since I wasn’t able to get this main hose to bend that tight into the radiator.

You can also see I wrapped the exhaust which I found a few other people doing and one of the guys at Torrance TAF had said was good to do. And you can also see the EGT sensor which I only ran to the rear mounting holes on each side. I had read that doing all four is not really necessary.

I ended up replacing all the nylon locking nuts for the engine mount with all metal locking nuts. I also did this for all the various clamps, etc. You’re not supposed to use nylon locking nuts firewall forward, though I see a few on the Rotax engine (from the manufacturer) so I would expect they should hold up OK.

Just a overview photo of the wiring routing and fuel lines in/out of the fuel regulator.

I’m using silicone and stainless steel teflon hoses so that I have minimal hose replacement when I have to do the 5 year rubber swap outs. The only rubber hoses left are what’s on the engine and in the fuel pump assembly. When that time comes I’ll try to replace those with appropriate non rubber hoses. The one silicone oil hose (connected to the oil tank) is special and is fluorosilicone lined to hold up the the oil.

I used adel clamps to hold the oil and fuel drain lines… kind of overkill I guess. I also combined the left and right side fuel drains so I only have one hose fuel drain exiting the cowling. I still need to cut the drain line hoses a bit shorter.

Another overview photo. I made a few short clamp extensions from stainless steel sheet. One was used to connect the 2 adel clamps for the main oil line that runs from the oil tank to the thermostat. The other connects the 2 adel clamps that are used to hold the fuel line from the fuel flow sensor to the right carb. I also made a bracket to hold the fuel flow sensor.

I ended up running both the oil lines between the thermostat and the oil cooler on the right side. There was just no good place to secure the hose if I ran it on the left side and it comes very close to hitting the cowling and alternator.

Just a shot of the rear portion of the engine. You can see the red wire that runs to the starter and quite a few adel clamps that were used.

UPDATE (09/05/2019): Adding below photos that I forgot to take and some more info.

I was able to get the extension loom from Air Master for about $100 with DHL shipping. This is an extension cable so there are connectors on both ends and Martin (at Air Master) said to leave about 20″ from where the slip ring will be installed which on the Rotax 914 in the center of the engine on the top where I believe the vacuum pump is mounted if you had that option. Having this cable allowed me to close up the firewall for where all the cabling goes through. It’s made from 2 pieces of 1/16″ stainless steel that screw onto the firewall there are grommets also in there for the cables to pass through. Then I put the stainless steel grommet guards on.

Here’s what I ended up doing for the left side cooling hose. I purchased a stainless steel exhaust hanger (9″ JEGS 309002) from Amazon and bent it at around the first hole. I also purchased a stainless steel 1.5″ U clamp to clamp the bracket to the exhaust. It seem pretty sturdy so should work well. This keeps the cool hose away from the exhaust manifold and secures it from moving around.

I didn’t have a photo of how I did the fuel flow sensor. I made a bracket to mount it to the same mounting holes as one of the engine sensors. The hose coming off the regulator is split and feeds the flow sensor and will also the pressure sensor which is mounted on a plate on the engine mount. My only worry is that the 90º bend it pretty close to the inlet of the sensor and the Red Cube manual said not to do that. I spoke to a few people about it and they think that because I’m only pulling 5 gallons an hour it shouldn’t matter, it might matter with a higher volume of fuel since the bend can create some turbulence in the flow and mess up the sensor readings. If I get inaccurate readings I have an alternate idea of how to run the hose so will have to see.

On the ride side of the engine it’s a tight fit for the exhaust manifold, cooling hose and oil line. I probably should add something to hold the oil hose to the cooling hose to keep it from touching the exhaust.My other worry is that the box that goes around the air filter will hit the cooling hose so I’ll have to move it… will have to wait to see when I get the air box.

Exhaust Shroud Heater Inlet Tube

Time: 2 hrs

I finally cut the hole in the cowling for the heater inlet to the exhaust shroud. It’s a bit tricky because you can’t see it and you need to mark the hole somewhat accurately. Of course after some frustration of trying to mark the hole and getting something reasonably accurate so I could drill a starter hole I figured out that if I would have removed the radiator I would have been able to see in a bit better through the front of the cowling. Still a somewhat impossible task, but it would have definitely made it a bit easier. To get some idea of where the inlet pipe would intersect the cowling I cut down a toilet paper tube to fit in between the exhaust shroud and cowling. This worked well to be able to mark one edge with a marker so I could drill a 1 1/4″ hole as a starter hole. After the starter hole was done I put the lower cowling back on and used the Dremel with a sanding drum to open up the hole so the tube would fit. After achieving a pretty nice fit I remove the lower cowling so I could more easily clean up the hole and cut back the heat shield. I also cut and riveted the inlet tube onto the exhaust shroud. Unfortunately once the tube was riveted is seems that the angle had changed a bit and the near perfect hole I had made was now a bit off. I was able to bend the inlet tube a little the get a better fit, now at least I can live with the way it is… not perfect but pretty good.

Using a cut down toilet paper tube I was able to mark one side of where the hole needed to be cut. I used a 1 1/4 hole saw to cut the initial hole an then used the Dremel with a sanding drum to open it up.

The final hole. The pipe used to be centered in the hole, but after riveting it changed the position a bit. Not a bit concern for me. I don’t want to widen the hole to make it equal all around so I’ll live with this.

Fuel Pumps Finished

Time: 2.5 hrs

Well finally I got the fuel pumps installed. There was a lot of trial and error to get everything worked out. Fortunately the pumps all fit in the Rotax box and the placement of the mounting screws worked out as well.I also have all the fuel and oil lines in (just need to torque the fittings).

I decided to change the way I had mounted the pumps to the mounting bracket. I was using the two adel clamp that came with the pumps, but I change to using for stainless steel zip ties instead to make the pumps a bit more secure and save some room. I just needed to drill a few holes in the mounting bracket so that the ties could loop around to secure the pumps. I purpose some ratcheting ties which worked great. it was much easier to get a nice tight pull on the ties.

I like the zip ties better better than the adel clamps and then don’t take up as much space either.

It’s mounted and wired up. I also put in the Capacitors using some crimp on ring connectors. Negative is a M5 screw and positive is M4.

A few photos of the fuel lines (all stainless steel). Everything is roughed in. I just need to make sure all is good and the I can torque the fittings and secure any wiring like for the fuel flow sensor.

Fuel Pump Assembly and Pressure Test

Time: 1.0 hrs

The fuel pumps went together quickly. I purchased some Oetiker ear type clamps from Belmetric. I purchased 14.5mm and 19.8mm size clamps which seemed to fit well. The 14.5 were a tad tight over the fittings, but I was able to get them to work. After I had the pumps assembled I used a differential pressure tester that I purchased from Sky Geeks as well as some extra fittings and a hose that has quick change connectors on the ends (the hose that comes with it one has quick change on one end). This pressure tester can also be used to test the pressure drop on the 914 cylinders using a 12mm adapter to connect to the spark plug hole which may be handy in the future when I do my annuals.

I tested the fuel pumps for leaks up to 30 psi. I found that the Rotax docs for the rubber rebuild on the IS (fuel injected) type engines tests the pumps up to 87psi, but the carburated engines don’t run at as high a pressure, the normal fuel pressure is around 2-5psi over the airbox pressure (which is max around 18psi). I didn’t want to damage anything so I figured 30 psi would be reasonable. The only leak I had was on one of the adapters I used to get the tester connected to the -6AN fitting on the pump. I’m happy that the 5/16″ hose barb to -6AN converts I found don’t leak. Now I have AN fittings on the pumps and don’t need to use rubber to run out of the pumps to connect to the stainless steel hoses.

Just a quick check I ran the tester up to 10psi and set the slow fill back to off. I noticed the pressure dropped off on the second gauge after a few minutes so I knew there was a leak. It turns out the leak was between the M14 adapter and the M14 to -6AN fitting. I was able to tighten that up again and ran the test up to 20, then 30 psi. I left it for about 5 minutes with no noticeable pressure drop and a check with some soapy water on all the fittings just to make sure.

Fuel pumps all assembled and fit into the Rotax fuel pump box. I’m going to check with TAF to see if they have a been made bottom plumbing manifold. I noticed from Craig’s build log that his has a better, tighter bend to it that would fit much better in the Rotax box than the one I have. Also I may work on a better way to attach the pumps to the mounting plate. I’m currently using the clamps that came with the pumps, but I don’t like that I had to mount them towards the ends of the pumps to avoid the screw from hitting the check valves. It’s such a tight fit to get all this stuff into the box. I would prefer more centered so the pumps are more secure or using 2 clamps per pump.

A photo of the differential pressure tester (model E-2A) I got. Aircraft Tool Supply has them as well, but they were out of stock and it wouldn’t have been available for 3-4 weeks. This is the 0.040 orifice one with no master orifice. The hose is the ATS extension hose which has quick disconnects on both ends so I was able to purchase a 12mm (for the cylinder compression checks) and a 14mm (to make the conjoin to the fuel pumps) with quick disconnects that can be swapped out easily. I chose a 14mm adapter just because I was able to find an M14 female to -6AN male fitting.

Fuel Selector and Exhaust

Time: 4 hrs

My fuel selector that I ordered from Andair in the UK came a few days ago so I figured I’d get that installed. I also finished up the mounting of the exhaust and exhaust shroud.

I ordered my fuel selector with AN fittings instead of the NPT fittings that the TAF one comes with. It turns out there isn’t a whole lot of room in the dash where the fuel selector mounts (what else is new). I ended up having to swap the -4AN with the -6AN fittings around on the fuel selector (Left/Right tank connections) and then I had to use my heat gun to heat up the fiberglass on the dash so I could bend out the flanges a bit to make room for the 90º AN fittings. I got all the fuel lines cut and the AN hose ends put on. I still need to install the M4 rivnuts in the fuel selector and torque down the hose fittings.

The exhaust went quick. There’s really no photos in the manual on how to mount the shock mount and adel clamp so it took some experimentation to make sure the exhaust didn’t hit the engine mount or anything else. For the exhaust shroud I used some large hose clamps to hold the shroud closed tight so I could drill the holes for the rivets. I also put an adel clamp on the heater hose that runs up to the heater box to secure the hose.

My Andair FS2020 fuel selector valve. I ordered it with -6AN fittings on the top for the fuel feed and return and -4AN (return), -6AN (feed) for the connections to the fuel tanks. This photos was taken before I swapped the -6AN and -4AN fittings around (on the sides). I did this because the -4AN fittings are smaller so they fit better closer to the dash.  I also got the clear anodized faceplate so that it matches my vents and other hardware… hey it’s got to match.

Exhaust shroud installed. I used a few large hose clamps to get it all held closed tight so that I could drill the holes for the remaining rivets. This uses the stainless steel/steel mandrel rivets.

This is what I came up with for mounting the exhaust. I couldn’t find any photos of mention of it in the manual, but this seems to work. The clamps holding the exhaust to the engine and other clamp are the Rotax exhaust clamps (Rotax #951 550) which I ordered from Lockwood Aviation Supply.

Well it all fit. I couldn’t run the hoses directly down, they run up a little and then down. I also couldn’t use my 60º fittings on the return and feed (on the top) because the one closest to the dash hit the dash, but the 90º fitting fit OK.

The fuel selector basically installed.

My faux dash in place… working on some ideas for where everything will go. I need to start thing about who will cut the panel. If I can get a hold of some CAD software I can get most of it designed and so it should make the cutting a bit cheaper.

My upholstery should be here any day now so hopefully that came out OK. I also purchased the wings so I’ll have to go pick that up and start working on those soon.



Fuel Pump Connection

Time: 0.25hrs

I purchased a few of these adapters that convert a hose barb into an AN fitting. The only ones I could find came from a company in Australia called Aeroflow. The seem to fit well so  I have high expectations that they’ll work. I just order a differential pressure tester so that I can check the fuel pump assembly (and these fittings) for leaks. I’m also thinking of switching to the Oetiker type clamps instead of the fuel hose clamps I’m using mainly to save some space so that things fit a little better and so I can more easily get the nuts onto the posts to secure the pumps.

The fitting has an O ring that helps the fitting tighten on the hose barb. I guess I’ll have to replace them when I replace the other fuel pump hoses every five years.

I hope these work. It’ll be nice to just attach the braided hoses directly to the pumps rather than having to use intermediate rubber hose in between. I also need to see if I can better place the clamp for the left pump. It’s a bit high, but any other place the mounting bolt hits the check valve.


Time: 3.0hrs

Over the past few days I did a few miscellaneous items on the plane. I’m waiting on a few small parts so that I can make better progress, but there’s still lots to be done even without the needed parts.

Things done today:

  • Mounted GEA24 and TCW battery backup
  • Finished up carpet on copilot and pilot areas
  • Torqued bottom oil pump bolt
  • Torqued a few of the oil line fittings
  • Installed safety wire on fuel pump bolt
  • Cleaned up some wiring
  • Made up a small circuit board to hold the components needed for the RPM and Oil Pressure sensors
  • Cut and clecoed the heater shroud input tube onto the heater shroud.

I mounted the battery backup under the shelf so that it’s a little easier to get to. The batteries will need to be changed sometime plus there is a fuse that may need to get replaced if is every blows.

The GEA24 is mounted and I also finished up all the wiring to it (not shown in the photo). I made up a small circuit board that has the diodes and resistors that’s needed for the RPM and oil pressure sensor to interface to the GEA24.

This is a very simple pre-done board that I bought from Sparkfun. The board internally has every set of 3 holes connected so you can lay things out to connect to each other without having to run wires. I used the captive screw terminals so I can connect the RPM wires from the TCU on the one set and the signal wire from the oil pressure sensor on the other set (only one of the two is used). To install it I connected the wires to the captive screws and then just wrapped it with some silicone tape and the tie wrapped it to the J243 connector of the GEA24.

Firewall Forward Work Continued

TIme: 3hrs

I had a productive day today getting a few things done on the engine. I worked on putting together the exhaust shroud for the heater and also finished up the radiator/oil cooler bracket. The exhaust shroud needed all the holes drilled in the large clamps that hold the shroud cover onto the exhaust. There’s quite a few holes that need to be drilled, but once you get set up it goes along quickly. I used RTV to seal up the mating surfaces and also filled the area where the inlet and outlet tubes attach to the shroud. I’m waiting on the bolts and a longer tube for the front (the one I had was too short to reach past the cowling.

On the radiator/oil cooler mount I just needed to install the cam locks. I’ve been getting the hardware from Skybolt. I purchased a simple non adjustable, non floating receptacle and had a few of the -6 length studs already. I just need to put some kind of rubber on the part that presses against the oil cooler so it doesn’t wear and scratch the cooler.

Oh yeah and also my Andair fuel check valves came in so I test fit them into the fuel pump assembly. It’s tight but they fit. I had to order these from Andair in the UK since they seem to be the only ones that have the check valves with the 5/16″ hose barb.

All the holes drilled in the exhaust shroud. The last row of holes needs to be after it’s fitted onto the exhaust when the clamps have been tightened. TAF supplies stainless steel rivets with a steel mandrel to use on the shroud.

A few photos of the shroud installed on the exhaust. I order some 1.5″ (0.065 wall) anodized aluminum tube for the front inlet. I needed a bit longer tube so that it will stick out from the cowling (will need to cut a hole in the cowling for that) Also to get the shroud on I had to remove the bracket that attaches to the exhaust. You just need to remove one of the engine mount bolts and an M10 Allen screw to get the bracket off.

Radiator and oil cooler brackets are done. I had to modify the camloc receptacle a little so that it would fit flat on the bracket. I just had to file one edge a bit.

Well it all fits. The sides of the box bow out slightly, but should be fine. And yes I know I have the fuel pumps reversed (I think I have the check valves in the right direction, but I’ll check it out before I install them). It seems like they fit better in the box this way and the box is labelled “in” and “out” so I wanted to make it so the labels are accurate. It shouldn’t really affect the hose braided lines.