Fuel Pressure/Manifold Pressure Sensors & the “Red Cube” (Fuel Flow) and Throttle Cables

6. 5 Hours

Had a good productive day in the hangar.

Started out working on the cable to the heater box.  I have been avoiding it as I knew it was going to be difficult and sure enough it was.  I only took one picture as I was irritated with the thing.  Below is a pic of the cable going to the heater box.  I think this will be a first for me saying something like this regarding this entire experience.  The whole heater cable/heater box mechanism is not well engineered and I see issues with it going forward.  If you recall I had used a solid cable holder (Cable Safe) to secure the cable where it passes through the firewall.   That did not work as it held it securely at a 90 degree angle to the firewall which made the bend to get to the heater box so tight the cable would not move in the casing.  I replaced it with a rubber grommet with allows the cable to angle through the firewall but is not very secure.  I thought the existing screw to hold the cable to the heater box door was very small so drilled a hole through an AN-3 bolt and used that to secure the wire.  Even with the reduced angle coming through the firewall the end of the casement would push out of the cable adjuster as there is still quite a bit of pressure when trying to actuate the cable.  I even found the end of the cable fitting on the cabin side was moving/sliding as the crimp was not holding it in place.  Grrrrrrrr.  After 2..5 hours I decided I needed to think about this further.

IMG_3894.JPGI really only have a the fuel pressure sensor, the manifold pressure sensor and the fuel flow sensor to wire to the harness but I can’t do that until I get those sensors mounted so dove into those.  In the below pic I highlighted the manifold pressure sensor and the hose I installed.  You can see it connects to the manifold crossover tube.  The hose from the crossover tube is only a 1/4″ and I found I do not have an 1/4″ NPT to a 6mm/ 1/4″ barb fitting to fit into the sensor.  Drag.  Have to order one.  This will have to wait.

IMG_3897.JPGNext I moved to the fuel pressure sensor.  It turns out I have all the parts needed so was able to move forward with putting it together.  In the pic below you can see the banjo fitting at the top, the 5/16 fuel line and the pressure sensor.

IMG_3900.JPGI then worked some fire sleeve over it.

IMG_3901.JPGIn order to install this i need to complete the install of the “Red Cube” which is the fuel flow sensor.  This is much more involved and has be a bit nervous.  What you need to do is cut a 110mm section out of the hard stainless steel line that leads from the fuel regulator to the right carb and install the sensor in that cutout section.

IMG_3903.jpgDon’t know if you can read the instruction in the top right of the above pic but it tells you you need to cut off a barb off a brass fitting and silver solder it onto the stainless line.  Hmmm.  I have not done any of that….  I am going to noodle on that tonight but right now I think I may have a professional do that as it has to be done right.  If it is weak and it cracks….. That sounds like a bad day.  I can at least get the parts ready.  That is what you see below.

IMG_3905.jpgFYI I just used a tubing cutter from my plumbing tool box to cute the stainless steel fuel line.  You do have to clean up the inside of the line as it really creates a burr that shrinks the diameter rather significantly.  That is ready to go (I think).

As I am focused on getting the firewall set that means that I need to look at getting the throttle cables through the firewall too.  I pulled out the throttle quadrant and went over the unit tightening up the cable adjusters that were on this side of the cables.

IMG_3906.jpgIn order to drop the throttle quadrant in place I have to install at least one side of the center console but I noticed that I had not cut the leather away from the rivnuts on the sides of the cubby box, so did that.  The center console panels cover those so they will not be seen.

IMG_3907.JPGDarn razor blades.

IMG_3909.JPG I still need to pass the two throttle cable through the firewall but this ended the day.  Looks kind of cool !!!

IMG_3910.JPGYesterday I got notice from UPS that my propellor should be here Friday !!!  That contains the last puzzle piece regarding the firewall as their is a small harness that needs to pass through to the prop controller on the panel.

Engine Wiring (Continued)

4.0 Hours

I recently received two pieces of “How to” literature form the EAA (Experimental Aircraft Association).  The first is the guide to getting your aircraft registered & certified.  It looks really good with step by step instructions on the various pieces of paperwork that need to be submitted (there are numerous ones).

IMG_3870.JPGThe second is a structured guide to going through the first 40 hours of flight in which you have to thoroughly test the plane.

IMG_3871.JPGAS far as work goes I managed to get some time in the “hangar) yesterday afternoon.  It would have been more but my wife made me cut some trees down in the back yard…  Yard work is getting less and less appealing as I grow older.

First I was able to complete the wiring of the fuel pumps.  The first thing was to complete installing some capacitors between the ground and power wires.

IMG_3874.JPGI was then able to install the pins that come with the fuel pumps and then install the connector which also comes with the fuel pumps.  Once that was down it was simply pushing them together.  The pump themselves are not parked with polarity signs so you need to leverage the Rotax Install Manual.  The connectors only go on one way thus I could mark the connector with a “+” as you can see below.IMG_3876 2.JPGNext I worked on cutting out a huge amount of extra wire between the TCU and the Turbo Servo.  That is the way it comes from the Factory.  I literally cut out 5′ of extra wire.  The below pic just shows it cleaned up.  Behind the bottom tube you can see I still left a small service loop.

IMG_3877 2.JPGNext I needed to tackle the wires still left that come from the TCU.  Here they are.

IMG_3878 2.JPGBelow is a pic of the wiring diagram you need to reference in the Rotax Install Manual.  The boxes show which wires need to be used to connect the turbo warning light that is on the panel.

IMG_3879.JPGI am going to share with you builders that the Rotax Installation manual is not a well organized document.   You have to do a fair amount of searching.  For example, the above pic tells you which wires to use for the warning light but it does not tell you which one is the ground/positive.  That ends up being on a different page.  I guess you get used to it but at first it can be confusing.

I continued prepping to connect wires by pinning the remainder of the wires from the harness.  In this case I am using female connectors.


I realized that in this pic you can see that I replaced a cable tie with a 1.6″ adel clamp to secure the heater hose (highlighted).  I like that much better as there is no chance it will slide now.  I was concerned it could make contact with the Turbo servo on the firewall.

I wrapped up the day connecting the electronic rev counter (rpm) wires from the TCU to  the wire harness.  FYI polarity does not matter with those two wires.  Thanks for the reassurance on that Steve (from Midwest Panel Builders).


Engine Wires Continued

3 Hours

First, hopefully this update finds the friends and family who follow along healthy.  For those of you building planes, take advantage of our current circumstances and lock yourselves away and make some progress !!   Sunday I focused on completing the 16 pin connector that will reside between the wire harness and the engine.  In this 16 pin connector I routed the four EGT  sensors, the two CHT sensors and the two mags (each has a ground totaling 16 wires).  Taking my time, I re-lableled the wires as I had to cutoff the extra length of wire which is where the current labels were.  I then pinned all the wires from the engine and started installing them into the connector.

IMG_3866 2.JPGLooks good.  As this is very new to me I took my time.  I did have a question on the way the connector works and texted Steve O’Connor at Midwest Panel Builders (they built my panel and harness and recommended these connectors) and he called me right back even though it was a Sunday.  I am really impressed with both Steve and Adam and their approach to service.  Thank you gentlemen.  With that sorted out I completed the wire labeling on both sides of the connector, installed the pins into the two sides and brought the two sides together.  I know the below pic looks busy due to the back ground but I am really pleased with how neat it all looks sitting against the motor mount.  I have to figure out how to secure it all down to the motor mount tubing but overall I am really happy.

IMG_3868 2.JPG

In fact I am so impressed with how it cleans up all the wiring I am going to add a second connector to accommodate the other wires (Oil pressure, oil temp, manifold pressure, fuel pressure, etc.)  I will use a 14 pin connector which should leave two empty ports just in case.  Once completed it will make removing the engine a much simpler task as the two connectors will represent all of the wiring except the internal generator wires which go directly to the regulator/Rectifier on the cabin side of the firewall and the wires that go to the external alternator.  I could have routed those through a connector as well but they attach to the external alternator with a plug as well so thought it would be overkill to run them through another connector.  Another benefit of using these connectors is if a EGT sensor goes bad all I have to do is remove it for the exhaust pipe and de-pin it from the connector and replace it with a new sensor after I put a couple pins on.  Hopefully I will complete this task this coming weekend.

2nd Set of Eyes, Pinning wires and Choke Cables

5.0 Hours

Yesterday was a good day in the hangar even if I do not have as much to show for it based on the amount of time I was in the “Hangar”.  That is because I had an A&P mechanic from Lawrence airport stop by and look over the build.  He owns a maintenance shop right on the field and is also a certified Rotax mechanic.   We spent a significant amount of time talking about what he was willing to do with me and looking over the project.  Basically he has agreed to be my second set of eyes on the build, particularly on the firewall forward and fuel system.  To me this is a home run as an experienced set of eyes looking over the work is maybe the biggest best practice we can do as builders.  He shared that he liked what he saw from a workmanship perspective which is what opens the door for additional consults.  He shared that he had started something similar with an RV-6 builder and told him he would not be able to help him after his first visit as the builder’s work was so poor.  Too much liability.

As far as actual work goes, I started pinning wires that will go to the connector I mentioned in an earlier post.  The Connector I am using, and the connectors that Midwest Panel Builders used, are Delphi GT150’s.  You have to have the proper crimper to do the job, which I do.   Below are wires that I have pinned that are coming from the engine that will go to the connector.  The white “skirt” is a seal to keep moisture out of the connector.  I think they look pretty good.  I also labeled all the wires so there is no mixup when installing them in the connector.

IMG_3863.JPGHere is the 16 pin connector I will be using.  I think I am going to need to get another 12 or 14 coin connector to accomplish the entire task as there are not any bigger connectors in the GT150 series.


Thought I would show the crimper used for these pins.  It is a really sweet item that securely holds the pin in place making it easier to put the wire and skirt where they need to be before you crimp.


Here is interesting one…  If you recall I was having trouble with the lug that goes on the choke cable wire.  The screw the secures the wire to the lug would not tighten up.   I thought that a M4 tap should do the trick and rant that through them that but it still did not allow the screw to seat all the way to the bottom.  As I looked at the tap, it is obvious it is tapered at the tip so it was not the same diameter all the way to the bottom.  I took my Dremel and cut it off about a 1/4″ from the trip.  That helped though it was still not perfect.  I still had to work to tighten the screws up which maybe is a good thing as it will act a lock on the screw.  They are in and working.

IMG_3865.JPGThe last update for today is a bit annoying.  In the below pic I am pointing to a plate that is used to install the forward canopy lights to the canopy itself.  They (there are two) never came with the lights kit I purchased from The Airplane Factory.  They now have to be shipped from the factory in South Africa.  I have plenty of other things to do but still frustrating due to the time it will take to receive them.


CHT & Oil Temp Sensors and Fuel Selector

3.0 Hours

Spent time on doing the final install of the fuel lines to the fuel selector.  Was not hard but took my time to make sure I was attaching the lines in the correct locations.  I used Loctite 577 on the threads as that is the variety that is resistant to petroleum products.  I then used torque seal to show I had tightened each line.

IMG_3856.JPGI then moved back to engine wiring.  I have been getting my head wrapped around what I need to do to move forward by reading the Rotax Installation Manual, the Airplane Factory Electrical manual and talking to Steve at Midwest Panel Builders.  I think next weekend I can really start to make some headway.  In the mean time I started running wires from the various sensors up to where they will connect to the wiring harness behind the engine.  Below is a pic of one of the two Cylinder Head Temp sensors.  There are two, one on cylinder 2 and one on cylinder 3.

IMG_3853.JPGAnd below is what is used to make the connection to the sensor.  Pretty simple.

IMG_3854.JPGThere is one more of these same types of sensors and that is for the oil temp.  It is on the left front of the engine by the oil filter.

There were a couple of ground wires that I needed to run from the harness to the top of the engine block.  FYI for you builders, those are M8 bolts that goes into hose two holes.  You can see I have two small wires running to one bolt and the other holds the 4 gauge wire that runs back to the grounding bolt on the firewall.



Paint, Choke Cable, Heater Cable, Magneto Wiring, & Fuel Selector

7 Hours

I was able to spend most of yesterday in the hangar though I was not as productive as I had hoped for the amount of time I was in there.  Numerous items took a significant amount of time and a couple I could not complete.   I started the morning out meeting with a bodyshop man.  I had mentioned going to his facility in an earlier post but he wanted to see the project in person in order to give me a honest quote.   A real knowledgeable guy who knows his products and knows aluminum.  I will now wait for his quote.

From a work perspective I started on what I thought would be an easy job,  which was hooking up the choke cables.  I had picked up some ferrules at Aircraft Spruce (they go over the end of the cable).  That is what you see in the pic below.

IMG_3833.JPGYou slip some heat shrink over the cable and brass fitting and shrink it down.  That will hold it all together but it is the wires connection to the carb itself that holds the cable housing in place.  Below is what it looks like with the heat shrink in place.

IMG_3834.JPGGoing good.  Now on to the challenging part.  In the below pic you will see the plug that goes on the end of the wire itself which drops into the armature on the carb (will get a pic once I get them installed).  Sounds easy.  See the screw in the end…..  I could not get it to screw all the way in so it would contact the wire.  There are two of them and they both act the same.   I figure that maybe the threads at the bottom are intentionally not finished down at the bottom to act as a lock.  Maybe i am making things up…..  I spent 1.5 hours trying to slowly work a screw all the way in.  No dice.  I was afraid I was going to break off the screw in the fitting as I had it is the vice and used some pliers to work the screw in.  I need a new plan of attack.  Need to noodle on that some more…

IMG_3835.JPGOn to the heater cable.  This turned into an even larger challenge.  The primary thing I am concerned about is the tight bend the cable has to make coming out to the firewall into order to get to the heater box.  It turns so sharply that the cable really has a hard time moving in the cable housing.  In the below pic you can see I turned the firewall fitting around (compared to the one right next to it) so that the cable (the one to the right) does not have to bend as tightly.


I think I need to get it all together see if it is going to work okay.  I cut off the housing cable and some of the internal wire to get it close.  Also this is what the kit comes with to secure the cable to the heater box door.  Seems pretty weak.

IMG_3840 2.JPG

When I get a little anxious I forget to take pics thus not much to show here….yet.  More to come.

On to another challenge except that I was a bit more successful on this one.  Below is a pic of the two fittings that I had to get apart in order to install the magneto wires from the wire harness.  The engine has dual mags.

IMG_3841.JPGI worked for a good hour trying to figure out how to get the fitting apart.  There is the main tab on the top but there are also ones on each side.  It took quite a while using a very small screwdriver to push on all three tabs in order to get it to move.  I certainly did not want to break these fittings.  Once I was able to get it apart I needed to determine what pin I needed to attach to the wire as the engine comes with both male and female pins.  As you can see in the below pic it is a male pin and you can also see that the one I will install goes into the empty slot on the lower left.

IMG_3845.JPGI have not done much pinning in my life so was a bit anxious but the finished product looks to be good.

IMG_3846.JPGAll back together.  Check.

IMG_3848.JPG Because I am focused on getting the firewall as far along as possible in the hopes that the propeller harness will be the last thing that has to pass through I thought I should start looking at the throttle cables which means I have to get the center console in a position to accept the throttle quadrant assembly as the cables are integrated into it.  All that means is I have to get the fuel lines connected to the fuel selector and organized in a way that does not conflict with the rudder cables.

These next couple pics are going to look busy, but there is a lot going on in the center console.  Below is a pic with top feed and return lines attached.

IMG_3849.JPGAnd this one shows the feed and return lines to the wings attached.

IMG_3850.JPGThe fuel selector will be seated into the bottom of the dash.  I did not torque anything yet as I wanted to verify how all the hoses were going run and that I had angled the fittings properly.  From the picture angle below I like what I am seeing as I have the fuel lines angled into the center away from where the rudder cable will be.

IMG_3851 2.JPGI have to tighten and secure all of the lines but think I can accomplish that today.

Choke and Heater Cables, Back Seat & Canopy Lights

12.0 Hours

Put in a good effort this weekend with twelve hours spent in the hangar.  As I look at the the build sequence I really need to get everything that passes through the firewall in place in order to move forward with the build.   That includes the heater, choke and throttle cables and the remaining wires that still need to pass through the firewall.  That includes the harness for the constant speed prop,  I had placed the order in December for the AirMaster Propellor so thought it was time to reach out and get a status.  Perry at the Torrance factory checked and I should have it somewhere around 4/1.  That is quite a lead time so to those building a Sling 4 or TSI make sure you place your orders early.  That is going to slow things down a bit but at the same time there is still plenty of other things to do, like wiring the engine.  Deep down I think I am chicken of the wiring.  Definitely not my comfort zone.  So with the firewall pass throughs on my mind I started with the heater cable and fished it through the hole in the firewall.  I had purchased pass  through cable holders from Aircraft Spruce over a year ago and was anxious to try them out.  The brand is called “Cable Safe”  My understanding was that I needed to purchase one that had two halves as a whole one would not be able to slide over the cable.  See the below pic of the Cable Safe fitting, and both ends of the cable.

IMG_3810.JPGI really thought I was was being smart by purchasing the split case.  However if you look at the above pic you may realize that there is are two nuts that also have to slide over one of the cable ends as well.  As I sat looking at this wondering how to tackle it I thought it sure would be great if that black cable end pulled off….

IMG_3812.JPGSweet !!  For those builders out there, please take note.  One thing to note is that the cable is way too long and I have not been able to figure out how to attach the cable end to the heater box cable bracket.  I will have to noodle on that a while.

Next I fed the two choke cables through the two holes in the firewall.  The 914 has dual carbs thus the dual cables.  There is a single pull knob controlling both cables.  Below is a pic of me holding the choke cables and you can see the heater cable behind.

IMG_3831.JPGOnce I had the cables through and was ready to tighten down the Cable Safe fitting that would secure them I realized I really should put the Dash and Panel in place to see how much cable I need to have on the cabin side of the firewall in order for them to meet the panel correctly.  FYI after I fished the choke cables through through the firewall they looked like they were way too long as well then thought if I crossed them it might take up the extra length.  That seems to work really well.  Below you can see where the cables mount (circles).


I put the dash on a table and was going to mount the panel with just a couple of screws and realized it would not fit due to a UBS power socket hitting the dash. Not a bog deal, I just needed to trim the dash a little bit.  Below you can see the small cutout i made with the Dremel.

IMG_3814.JPGI was then able to screw the panel to the dash and put it in the plane.  Pretty cool pic.   The two circles show where the cables come through the dash.

IMG_3816.JPGIt worked well in helping me determine how much cable I needed to have.  I did notice that there was a spacer in the parts for both cables but could not figure where it went. It certainly did not go in front (covers the laser etching) but the whole was the wrong size to fit over the cable if it is supposed to go to the back.

IMG_3820.JPGFinally I just drilled it out and it makes sense for it to be on the back as it then allows the nut on the front to tighten up.  While I had the panel fitted to the dash I noticed that the dash was missing four rivnuts.

IMG_3821.JPGIMG_3822.JPGSo I went ahead and installed them.  It was tricky getting the rivnuts to lock in place through the thicker fiberglass.  You just need to take your time and ensure they are fully seated before pulling them.  Below is the technique I use.  I screw a rivnut on upside down which allows me to know where I need to cut the leather out in order for the rivnut to seat against the fiberglass.

IMG_3823.JPGI next moved to finishing the rear seat installation.  That has been a long time coming.  I had to get a different set of camlock studs (purchased at Skybolt.com) as I had purchased the adjustable receivers  (adjust the depth to accommodate different length studs) which I will discourage others from doing.  Sounds like a good idea at first but it is a pain to figure out where the depth should be.  After a couple hours I was able to figure it out.  I also realized I needed to countersink the rivets holding the receiver otherwise the seat would not sit flush against the seat extension frame.

IMG_3825.JPGBelow is the final product.  I do like these quarter turn Camlocks and I really like the wings.  Not tools needed to remove the seat.

IMG_3827.JPGShe is in.

IMG_3828.JPGWith a much better place to sit now I started wiring the canopy lights.  The back ones are white light push-on units.  I wanted to use quick connects in case I ever need to replace them so added those to where the lights attach.   I did solder on leads to the main power/ground wires that go to both rear lights as well as to the potentiometer that controls the from red lights.

IMG_3829.JPGBelow is a pic with the rear lights installed.  I have to say I do not like the white housings.  They just look stuck on.  I am going to see if I can paint them something different.

IMG_3830.JPGI tested the potentiometer I had which is used to adjust the brightness of the front seat red lights and discovered it did not have an off position.  Bummer. Back it goes so could not finish that job.

One last thing to note is I signed up for a four day class on servicing and maintaining my Rotax 914.   It is put on by Lockwood aviation down in Sebring Florida.  Really looking forward to that experience!!