ELECTRICAL SYSTEMS INSTALLATION

• Chapter Introduction
• ECM Mounting
• Battery Box Construction
• AUX Boost Relay Mounting
• Ground Plate
• Circuit Diagrams, Sheets 1 through 7
• Switches & Circuit Breakers
• Creating Good Cable Connections
• Primary System Wiring (Step by Step)
• Secondary System Wiring (Step by Step)
• EXPBUS Options & Voltmeters
• Engine Sensor Wiring & Calibration
• Propeller Hub Wiring
• Inspection Checklist - IV - Electrical System Test

1. High-quality wire strippers (20AWG through 10AWG) AWG = Average Wire Gauge or just Gauge for short.
2. Terminal Crimping Pliers
3. A large gauge terminal crimping tool for 8AWG through 4AWG cable ends.
4. A sharp razor knife such as an Exacto knife.
5. A good soldering iron or soldering station and high-quality electrical solder.
6. A bottle of alcohol or solvent for removing soldering flux.
7. A propane torch (propane or MAPP gas). Get a self-lighting model; you'll never regret it.
8. A good assortment of shrink-tubing (various sizes and colors, including clear) and an electric heat gun to shrink it (not shown).
9. A good assortment of tie-wraps.
10. 2 or 3 rolls of high-temperature (orange-red) silicone tape.
11. A can of white "Liquid Electrical Tape".
12. An assortment of Teflon aviation wire and cable. Sizes are denoted as we go, or refer to the master parts list.
13. An assortment of protective rubber terminal boots (approx. 8 large ones and 12 small ones).

Don't forget to track your time spent in each of these steps if you care about such things.

Your engine uses a small, rugged, computer to control ignition, timing, and a wide variety of sensors. This computer is known as the Engine Control Module or ECM. It is also commonly referred to as the Engine Control Unit or ECU. We will use the correct term, ECM.

The ECM is a standard Subaru part. In a car, the ECM controls the engine as well as an array of other functions from transmission to door locks. Some modifications have been made to its wiring to eliminate unwanted circuitry and adapt it for aircraft use, but the ECM itself remains an off-the-shelf part.

The ECM has metal mounting tabs. These can be cut shorter, although we prefer that you keep the unit as-is to retain the direct-fit in the unlikely even that it should ever need to be replaced. The ECM must be mounted inside your cabin, away from sources of heat and vibration. The ECM wiring harness was adapted from its automotive counterpart and is approximately 48" long. Because of its length, we recommend that the ECM be mounted on the RIGHT side of the cabin in the forward-most bay as shown below. This allows the ECM harness to be routed across the inside of the cabin without resorting to large coils of wires. It is not strictly required that you mount the ECM as described, but we think you'll find this convenient and we have crafted the wiring harness with this location in mind. Harness length and shape will change with different engine models.



Close-up view of rubber shock mount on shoulder-bolt.



The ECM can be oriented horizontally as shown, or vertically. In this example, we have taken advantage of the slots cut in the stock mounting tabs to install the ECM on rubber bushings. However you choose to install the unit, try to provide a similar shock-mounting to lessen the effects of vibration. Be sure to orient the connectors in a manner that allows easy access. In this case, the connectors are facing rearward to facilitate access from under the panel.

To reduce the chances of static damage, the metal case of the ECM should be grounded to the airframe with a short ground wire or braided ground strap.

OK, you probably want to peek inside, so I'll save you the trouble... it's a very well made module.



We will return to the ECM when we are ready to install the wiring harness.

1. 60A - Main Battery to EXPBUS (May also use an ANL-Type fuse if desired)
2. 50A - Alternator to EXPBUS
3. 20A - Aux Battery to Bus Master switch
4. 15A - Starter Solenoid and Optional Cabin Heater
5. 15A - Optional Pitot Heater and/or Optional Cabin Heater

Additional fuses include:

1. 10A - ATO Type - Main Fuel Pump
2. 10A - ATO Type - Aux Fuel Pump
3. 3A - ATO Type - Auto-Failover circuit and additional critical equipment.
4. 3A - ATO Type - Backup Gyro (size as needed)

The exact location of these breakers and fuses is up to the builder and can vary depending on what equipment you choose to install on your instrument panel and in your cabin. Many conventional aircraft place their circuit breakers on the instrument panel itself. There is much debate over whether this is worth the lost panel space, particularly on an already crowded instrument panel. Human nature says that a pilot will always attempt to reset a blown circuit breaker in flight. This can be very destructive to the equipment being protected and can even lead to electrical fires. It is always better to land the plane and investigate the cause of the tripped breaker rather than risking a potentially lethal cockpit fire.

Placing the breakers in a location which is easily accessible makes good sense, but not necessarily on the panel itself. In my own RV, I have chosen to install the breakers on the solid bulkhead behind the instrument panel. Placing them along the bottom edge allows me to easily reach them with one hand to check their status. You could also fabricate a bracket to orient them vertically so the breaker knobs will protrude downward when popped, thus becoming visible. Different builders have different ideas about their breaker positions. The decision is yours, but be sure to label thier location well for pilots.

Placement of the fuses is another matter. The whole reason for using fuses instead of resettable breakers is that if these circuits blow, you never want to reset them in flight. For example, if you blow a fuel pump fuse, never attempt to replace it in flight. You will be running on your Aux pump and landing should be your primary concern. Fuel pumps don't blow fuses unless they are seriously shorted out and you don't want to risk an in-flight fire.

The EXPBUS provides most of the secondary circuit switches required by a typical installation, however, yours is not a typical installation. A few additional switches are required to support the redundant system design. Do not cut corners on switches. A pretty switch is not necessarily a good switch. The switches we specify are high-quality Honeywell aviation switches found on everything from 747's to Space Shuttles. These are very specialized switches, so don't try to replace them with off-the-shelf lookalikes. Stick to the part numbers we provide.

All Honeywell/Microswitch products can be obtained from www.onlinecomponents.com or through the vendor search feature of www.honeywell.com

Here's a photo which identifies the major switch components



When you're ready to start, you should have a pile-o-parts like this, plus much more wire.



The EXPBUS unfortunately, comes with silk-screened labels for all of the switches. These are not appropriate for our installation, so you will need to consider making new labels for them, or as shown in the photo below, mount the EXPBUS behind the instrument panel with the banks of switches protruding through rectangular openings. This actually looks very good if you bevel the edges of the openings. If you look carefully, you will see ControlVision's optional diode module mounted on the bulkhead behind the panel. This option provides a few extra power taps and helps to protect avionics equipment from voltage spikes (although most modern equipment has internal spike protection already). The second photo below shows one last view from behind the panel before we start wiring.

Refer to diagram sheet 7 for typical EXPBUS switch assignments and labeling.

1. Note the time.
2. FIREWALL PASS-THROUGH: Aircraft Spruce p/n NMCS45A-13 - Nylon Bulkhead Seal 3/4"



3. Drill holes as needed in the firewall to install a 0.75" nylon firewall pass-through fitting as shown below. The exact location may vary depending on where you choose to install your batteries and Aux Boost Relay. The photo below shows this fitting 3.5" below the upper right engine mount bolt and 2" in from the right fuselage skin.
4. Loosely fasten the firewall fitting with two stainless steel screws for now. We will apply some sealant and tighten it down when all the wires have been run. It is helpful to place washers under each nylon "wing" of the fitting to prevent crushing it when you tighten the screws down.
5. BATTERIES:
6. Install both batteries in their mounts. Note that the location of your batteries is a critical Weight & Balance decision. The batteries provide your best bet for adjusting your CG. Builders have used the firewall, center console floor, baggage compartment, and even tail section to suit their individual airframe balance. It would be wise to discuss your options with those who have gone before you as this will affect the entire electrical installation. For the remainder of this guide, we are assuming a firewall battery installation.
7. FIREWALL GROUND CABLES:



8. Construct a pair of 8AWG ground cables, one from each battery ground post to the firewall Ground Plate bolts.
9. Secure the ground cables as needed with Adel clamps to prevent chaffing and loosening of the brass ground bolts. This particular installation places the cables inside the firewall recess box. You can position your Ground Plate wherever it is convenient to access from inside the cabin.
10. LEFT-AUX ENGINE BLOCK GROUND CABLE:



11. Construct an 8AWG ground cable from the leftmost (Aux) battery's ground post to the lower-left side of the engine block as shown.
12. Sandwich the battery end of this ground cable with the one going to the firewall as shown below, using a section of shrink-tubing and a silicone rubber boot. Notice how one terminal lug is upside down to allow the loops to lay flat against each other. This technique is useful throughout your electrical system installation. As an alternative to this method, you could insert and solder both cable ends into a single larger gauge terminal lug.





13. Install the paired cables on the Aux Battery ground post and secure with a flat washer, lock washer and nut. Some like to use a drop of blue LocTite, but I feel this interferes with good electrical connection. Do not over-torque the brass battery studs! If the cables are properly secured and strain-relieved with clamps, the bolt should not come loose.
14. Pull the boot over the connection.
15. Route the engine ground cable along the engine mount and gracefully curve it to meet the chosen ground bolt location. Secure with Adel clamps along the engine mount tube.
16. Secure the ground cable to the engine block with an appropriate METRIC bolt, flat washer, and lock washer.
17. RIGHT-MAIN ENGINE BLOCK GROUND CABLE:





18. Construct a 6AWG ground cable from the Main Battery's ground post to the upper-right side of the engine block as shown.
19. Sandwich the Main Battery end of this ground cable with the Main Battery Firewall Ground cable (the one going to the firewall) in the same manner as you did with the Aux Battery, using a section of shrink-tubing and a silicone rubber boot.
20. Install the paired cables on the Main Battery ground post and secure with a flat washer, lock washer and nut.
21. Pull the boot over the connection.
22. Route the engine ground cable along the engine mount and gracefully curve it to meet the chosen ground bolt location. Secure with Adel clamps along the engine mount tube.
23. Secure the ground cable to the engine block with an appropriate METRIC bolt, flat washer, and lock washer. Note in the photo how the Main Battery ground cable is routed alongside of the Starter cable and Alternator cable as they leave the engine and pass over to the engine mount tube. A single grouping of cables is better than having each cable take its own path. Note also in the photos how tie-wraps and silicone tape have been used to help secure and protect the Cam-Angle sensor and Fuel Injector connectors.
24. LEFT-AUX POSITIVE CABLE:



25. If you have not yet installed your AUX BOOST RELAY on the firewall, do so now.
26. Construct a 6AWG cable to run between the Aux Battery positive terminal and the left side terminal of the AUX BOOST RELAY. This is the large relay terminal NOT labeled "BAT". The length and path of this cable will vary depending on what type of battery tray/s you are using. The above photo shows two separate battery trays, thus the cable must run across the firewall to the relay. If you use the factory battery tray, this cable will be much shorter. Note also in the above photo, the firewall ground cables and the aluminum heater hose support brackets. We'll talk about these later.
27. Loosely attach one lug to the relay terminal. Finger-tight will do for now.
28. Insert a silicone rubber boot over the battery end of this cable and wrap the battery end lug with electrical tape to prevent it from shorting to the battery post for now. Place the lug next to the Aux Battery positive post but DO NOT CONNECT IT YET. We don't like sparks!
29. Route the cable across the firewall and secure as needed with Adel clamps.
30. RIGHT-MAIN POSITIVE CABLE:



31. Construct a 6AWG cable to run between the Main Battery positive terminal and the right side of terminal of the AUX BOOST RELAY. This is the large relay terminal labeled "BAT". In the above photo, the Main Battery positive cable is the short cable with the red shrink-tube label. The slight dip is provided for strain-relief and maintainability. Notice how sections of blue silicone tube and white boots are being used to protect the relay terminals. If you look closely, you'll see the Aux Battery positive cable running along the firewall to the other side of the relay, and the Main Battery ground and Oxygen Sensor (braided shield) cables running diagonally along the engine mount tube. The green bracket on the firewall is a battery hold-down.
32. Loosely attach one lug to the relay terminal. Finger-tight will do for now.
33. Insert a silicone rubber boot over the battery end of this cable and wrap the battery end lug with electrical tape to prevent it from shorting to the battery post for now. Place the lug next to the Main Battery positive post but DO NOT CONNECT IT YET.
34. STARTER CABLE:



35. Construct a 6AWG cable to run between the BAT side of the AUX BOOST RELAY and the Starter Motor Terminal Post.
36. This cable should run along the right engine mount tube like the ground cable does, but continue under the intake manifold, through the opening in the engine mount plate next to the radiator hose, and to the starter motor. Use care in routing the cable to avoid chaffing against any sharp edges. The photo above also shows the Starter Solenoid wire which we will install shortly.
37. Slip a silicone rubber boot over the starter end of this cable and secure the lug to the starter motor. If you prefer, apply some "liquid electrical tape" to this connection to help resist water penetration.
38. Pull the boot over the connection and tie-wrap the cable as needed.
39. Loosely attach the relay end of this cable to the relay terminal marked "BAT". It shares this terminal with the Main Battery positive cable.
40. EXPBUS MAIN BATTERY CABLE TO MAIN BREAKER PANEL:



41. The above photo shows one method of mounting the supplementary circuit breakers and auto-failover relay. The builder used a short section of aluminum angle to fabricate a bracket along the bottom of the bulkhead behind the instrument panel. This positions the breaker knobs downward where they can be quickly checked without consuming valuable panel space. Construct an 8AWG cable to run from the relay terminal marked "BAT" to the Main Battery Circuit Breaker. This cable shares the relay post with the Main Battery positive cable and the Starter Motor cable. Leave this cable about 12" longer than you think is necessary inside the cabin to facilitate routing and installation of the circuit breaker. Don't bother installing a terminal end for the breaker just yet.
42. Sandwich the relay lug with the starter motor cable using a section of shrink-tubing.
43. Install and tighten down the relay terminal nut using a flat washer and lock washer. There should now be three cables on this terminal post.
44. Protect the terminal post with a short section of silicone rubber hose split along one side and secured with tie-wraps as shown in the reference photo from step 30 above. Optionally, you can apply liquid electrical tape to further prevent moisture penetration.
45. Route the other end of this cable through the nylon firewall fitting. Continue routing and securing the cable as needed to mate with the 60A Main Battery circuit breaker. We will be installing another section of 8AWG cable between the circuit breaker and the EXPBUS "BAT" terminal later. The circuit breaker can be located anywhere it is convenient inside the cabin. We will cover this in more detail a little later.
46. ALTERNATOR CABLE:
47. Construct an 8AWG cable to run from the Alternator Terminal Post to the 50A Alternator circuit breaker inside the cabin. Put a lug on both ends of this cable. Alternators are notorious sources of radio noise. If you prefer, you can use shielded cable, or cover the alternator cable with braided copper shield, grounded at one end, to help reduce electrical noise.
48. Install a silicone rubber boot over the Alternator end of this cable and attach the cable to the Alternator terminal post with a flat washer, lock washer and nut.
49. Route the cable towards the firewall and across the rear of the motor to meet up with the right side ground cable and starter cable. The three of these cables can be tie-wrapped together and should follow a graceful curve out to the engine mount tubes where Adel clamps will secure them. These cables must have a small amount of slack at this point since the engine is rubber mounted and will vibrate a little (very little, it is a Subaru afterall!).
50. Continue routing the Alternator cable through the nylon bulkhead fitting and to the 50A circuit breaker location.
51. Install an appropriate sized lug on the end of the Alternator cable and secure it to one side of the 50A breaker with the supplied screw and lock washer.
52. AUX POWER CABLE:
53. Construct a 10AWG cable to run from the left AUX BOOST RELAY terminal post (the post NOT labeled "BAT") to the 20A Aux Battery circuit breaker inside the cabin.
54. Install the relay side lug to the relay and secure with a flat washer, lock washer and nut. This cable shares the relay post with the Aux Battery positive cable.
55. Protect the terminal post with a short section of silicone rubber hose split along one side and secured with tie-wraps as shown in the reference photo from step 30 above. Optionally, you can apply liquid electrical tape to further prevent moisture penetration.
56. Route the other end of the cable through the nylon bulkhead fitting and over to your 20A Aux Battery circuit breaker location.
57. Install an appropriate sized lug on the end of the Aux Power cable and secure it to one side of the 20A breaker with the supplied screw.
58. EXPBUS MAIN GROUND:
59. Construct a 14AWG wire to serve as the main ground for the EXPBUS. This wire should run from the EXPBUS "Ground" terminal to your Ground Plate. A flat blade type connector is used on the EXPBUS module end. You can use another blade-type connector on the Ground Plate end or use a ring-type connector here if you prefer. This ground is for the EXPBUS internal circuitry only, and does not carry a lot of current. Short sections of shrink tubing over the exposed end of the blade connector can help prevent a short.
60. Note the time.

 

Congratulations! You have just completed the wiring of your primary power distribution circuits. At this point, your major cables are finished but your positive battery posts should still be disconnected for safety. We will create a few more short cable sections to connect the circuit breakers and fuses to the EXPBUS and tie up the loose ends during the installation of your secondary power distribution circuits in a moment. Take a break!

1. Adding a dab of high-temp RTV silicone sealer to the back side of connectors
2. Tie-wrapping connectors to prevent their accidental removal
3. Use of orange/red silicone tape to protect any exposed wire bundles
4. Further use of tie-wraps to secure the harness and relieve strain
5. Custom brackets for the main harness connectors.

None of these items are required, but builders are a fussy lot... We want you to be happy with your installation. If you choose to add or replace any of the corrugated tubing, be sure to use the high-temperature type. Often this will have a gray strip along one side of it. Secure your harness well since it will be exposed to a lot more wind than it would in a car, unless you drive awfully fast.

Being a wire-nut, here's what I did with my engine harness. Do as much or as little as you feel comfortable with. The harness as shipped is perfectly airworthy as is.

1. Note the time.
2. ENGINE HARNESS CONNECTORS:

    

3. The two large connectors that mate your engine harness to the main ECM harness should be secured to a bracket using large tie-wraps or other clamping mechanism. You may want to fabricate a small aluminum bracket, like the one shown above, to hold these connectors. Because of the number of wires involved, and the fact that this harness spans the gap between the motor and firewall, you want to have these connections protected against vibration as much as possible. The connectors should be oriented such that they are facing the firewall. It is obviously easier to do this if you first disconnect these connectors. NEVER PULL ON THE WIRES THEMSELVES!!!
4. Give the engine harness a good inspection to make sure all engine connectors and wire bundles are secure and not chaffing against anything sharp. Add tie-wraps or clamps as needed.
5. If your engine sensors are already installed and wired by the factory, jump to the step titled "ECM Harness" now. Otherwise, continue with the next step below.
6. ENGINE SENSOR INSTALLATION:
7. If you have not yet obtained your engine sensors, do so now. Which sensors you chose are up to you, but consider the following list. NOTE: On newer motors, the location of the Oil Temperature and Oil Pressure senders will be swapped.
   • Oil Pressure Install on top-front as marked. (See note above).
   • Oil Temperature Install in top-rear by alternator. (See note above).
   • Coolant Temperature Install in left radiator.
   • PSRU Temperature Install in PSRU as marked (avoid gear contact!).
   • Fuel Pressure (Active type shown) Install in pump outlet plumbing.
   • Fuel Temperature (optional) Install in pump outlet plumbing.
   • Coolant Loss (we will discuss this one separately)

    

   These sensors are readily available from any good parts supplier. Most use a 1/8" NPT thread side, although some may have a 1/4" NPT thread which must be adapted using a reducer fitting. Your engine will have labels indicating where these sensors go. The exact location of these sensors is subject to change with engine models and years. The important thing is to get to know where they are on your engine.

8. Install all of your sensors now. Be sure your PSRU sensor does not interfere with the gears. Use a small sensor and if needed, use a fitting to extend it out from the case to prevent contact with the gears.
9. All sensor wiring should be 20AWG Teflon insulated wire. Obtain a good length of this wire since it will be used for most of your radio installation too. It's cheap.
10. You may choose to cut some of the tie-wraps securing the existing engine harness and snake the sensor wiring through the existing tubing, or you may create a separate harness specifically for the sensors, it is up to you. Whichever way you go, be sure to use the high-temp tubing and ample tie-wraps to secure the harness when done.
11. Some builders will prefer to use a Cannon-plug, or other pin connector at the firewall for these additional wires. We advise against this practice however, because it creates additional connections and impedance which can interfere with the sensitive sensor circuits. Instead, our preferred method is to install another nylon bulkhead fitting and run the sensor wires nonstop from the sensors into the cabin. For now, you can just leave ample length of wires and trim them to fit as we move into the cabin part of the job. For now, we are only concerned with finishing the engine side of the installation.
12. Most sensors will have a single "signal" wire and use the engine block as their ground. Some will have both a "signal" wire and a "ground" wire, in which case, you will need to run two wires and attach the ground to your Ground Plate inside the cabin or a ground stud on the engine block. Some sensors, such as fuel pressure, are available in an "active" design. This type of sensor will have three wires, "signal", "power", and "ground". About the only difference, aside from improved accuracy, is that these active sensors require power, in which case, you will run three wires to them.
13. Install 20AWG wires for each of your sensors now.
14. Route the wires carefully across the engine to avoid chaffing and contact with hot objects. Bring the wires together near the large engine connectors and leave plenty of length for continuing their journey into the cabin.
15. Secure the wires with tie-wraps, Adel clamps, or tuck them inside the corrugated tubing as needed.
16. Use silicone rubber boots (typically the small size boots about 1" long) or apply liquid electrical tape to protect the connections from moisture.
17. If you are planning on using a propeller with electric hub, you may want to run two additional 14AWG wires out to the PSRU. Leave about a foot of extra wire at the PSRU end for attaching these to the servo brushes later.
18. Label all of your wires at the firewall end for easy identification as we proceed. Simple masking tape tags will do the job.
19. ECM HARNESS:





22. The ECM Harness will connect the engine harness with the ECM. Most of the length of this harness will be inside the cabin, but about a foot of it will extend from the firewall to the engine harness connectors. Note that the above photo shows the harness without any protective covering. In your installation there will be corrugated tubing and silicone tape to protect the wiring. If you add wires, you will need to reapply the protection.
23. The first step for this harness will be to determine where it will enter the firewall and construct a suitable nylon bulkhead fitting.
24. For my own RV installation, I have located the fitting approx. 8.25" to the right of the upper left engine mount bolt (right and left as viewed by a seated pilot of course, NOT as facing the firewall) and 5" down from the top of the firewall. A 1.125" (inside diameter) nylon bulkhead fitting will be used. Four stainless steel screws will attach the fitting to the firewall. Adjust the location as needed to avoid falling on top of existing rivets or other components. The general idea is to locate the fitting such that the wire bundle will run nearly straight to the firewall from the engine. It's not that critical.
25. You will find that the 1.125" ID nylon fitting is just the right size for the large corrugated tubing, but a better seal can be had by removing the corrugated tubing from the section of the harness between the nylon fitting and the engine connectors. Wrap the harness with high-temp silicone tape and use a pair of rubber grommets to adapt the nylon fitting to the harness. You will need to make a slice in the grommets to install them around the wire bundle. The grommets will fit into the grooves of the nylon fitting. Once the nylon fitting is secured, the grommets will grip the wires tightly and form a good weather resistant seal.



Aircraft Spruce p/n NMCS45A-11, Grommet p/n AN931-11-16 (you need 2 grommets)

26. Before installing the harness through this fitting, decide whether you are going to run any additional wires through this fitting or a separate fitting. On my own installation, I chose to create three separate harnesses. The ECM harness, an engine sensor harness (I wired my own sensors), and a fuel pump and fuel-related sensor harness. In my installation, I cut three holes in the firewall for these harnesses and use Cannon plug shells to protect the smaller harnesses as shown below (fly-market items). Note in this photo I used a stainless hose-clamp around the large nylon fitting (can't hurt...).



27. The ECM harness engine connectors will just fit through the fitting hole before the halves of the fitting are installed. Insert these connectors through the firewall and forward to their mates on the engine. Go ahead and connect the engine connectors.
28. Now assemble the nylon fitting/s. Stainless steel screws are recommended on all firewall fittings. Stainless steel is very difficult to work with. It quickly dulls your tools and slices your fingers. A fairly quick and bloodless way of cutting large holes is to drill a chain of small holes, punch out the center (twisting segments with needle-nose pliers works good), and smooth the final hole with a drum sander. The following photos show the full sequence of building the large bulkhead fitting.

    



29. Inside the cabin, thread the ECM harness across the forward fuselage and under the panel support ribs (F-7107/7108 on an RV9A).
30. Suspend the harness under each panel support rib with Adel clamps. Note that I have chosen to wrap the entire length of the ECM harness in high-temp orange silicone tape. The photo below shows the harness as it enters the cabin and threads across to the ECM. The white wires are the engine sensor wiring, fuel pump wiring, and misc ECM wiring heading to the switches on the instrument panel. These wires will run along the pilots side (left) of the fuselage, to your control switches. You can drill a hole for a snap bushing in the bulkheads as needed, or suspend these wires with Adel clamps. The wires should be long enough to reach the instrument panel in the vicinity of the Start, Bus Master, and Aux Boost switches.



31. In the center of the ECM harness (in the vicinity of your Ground Plate) you will find the main ground wire for the ECM. Attach this ground wire to your firewall Ground Plate. The critical nature of this ground suggests that you use a ring type wire connector and place it on one of the ground bolts rather than using a flat blade type connector. The photo below shows how the ECM harness (in orange) takes a sharp turn towards the instrument panel, then again towards the ECM (shown in the next photo). In the vicinity of the Ground Plate, you can see a white wire attached to the ground bolt. This is the main ECM ground. The other white wire grounds the metal shell of the ECM itself.



32. The wires which exit the ECM harness on the passenger side (right), will connect to your Oxygen Sensor or Starter Solenoid. Just tuck these out of the way for now.
33. Fasten the three ECM connectors to the ECM.



34. OXYGEN SENSOR:
35. The O2 Sensor/s is/are located in your exhaust pipe/s. If your pipe is not installed, do so now. If you have a need to remove it again for cowling work, etc. simply install the nuts finger-tight for now.
36. The O2 Sensor wiring harness consists of three or four wires depending on the model being used. Ideally, these wires should be covered with a section of braided copper shield to prevent spurious signals in this very low-voltage circuit.



37. The O2 Sensor harness can be routed through the right side nylon bulkhead fitting shared by your large cables.
38. Using crimped splice (aka butt) connectors, connect the O2 Sensor wires to their counterparts as labeled on the ECM harness. Use sections of shrink-tubing over the splices to keep out moisture.
39. Note: Early motors may not have run the O2 sensor wiring as shown and described above. Early wiring harnesses had the O2 sensor entering on the left side of the firewall. If you would like to reposition the wires and add connectors, you will need to open up the harness and splice in connectors as shown in the next two photos. This change will already have been made on later wiring harnesses. Refer to the earlier photo that shows the finished harness connected to the ECM.





40. STARTER SOLENOID:



41. One of the larger, long, wires near the ECM will be labeled for the Starter. This wire is to be run through the right nylon bulkhead fitting and should follow the path of the Starter Cable to the Starter Motor.
42. Fasten the wire to the flat blade connector of the Starter Motor Solenoid using a flat blade connector and a section of shrink-tubing.
43. Fold this wire over (do not bend the connector itself) and tie-wrap it to the Starter to prevent it from vibrating loose.
44. TIMING PARAMETER BOX:



45. On some early engines, there was a small black box dangling near your ECM that contains a proprietary circuit board which helps to tune the operation of your engine for aircraft use. Simply tuck this box in a safe place and secure it using tie-wraps or double-sided foam tape. You can tape it right on top of the ECM if you like. This photo shows it foam-taped to the side of a panel support rib.
46. OBD-II CONNECTOR:
47. The final dangling wires near the ECM are the On-Board-Diagnostic (OBD-II) harness and connector. This connector allows you to install a diagnostic troubleshooting computer to your engine. This option is available from the factory. Position this connector somewhere under or behind the panel that can be accessed for diagnostic use if needed.
48. BAROMETRIC SENSOR:



49. Returning to the pilots side of the ECM harness, locate the small Barometric Sensor near the nylon firewall fitting. This sensor can be mounted to the firewall using two stainless steel screws on either the engine side or cabin side of the firewall. We prefer that it be mounted on the cabin side to keep it in a calm, reasonably temperature-controlled, area. Builders have mounted it in on either side of the firewall and have not reported problems with it.
50. RPM WIRE:
51. The wire labeled "RPM" or "Tach" provides a tachometer signal for whatever instrument you are using for this purpose. Route and install it as needed.
52. ECM POWER & MEMORY WIRES:
53. Locate the wires labeled "ECM Power" and "Memory". These will be connector to your fuse panel or circuit breakers. Route them forward to the vicinity of these parts and leave them long for now. We will connect these later.
54. ECM WARNING LAMP:



55. Locate the pair of wires and round red indicator lamp labeled "ECM Warning". This lamp is akin to the "Check Engine" lamp in a car. We find it to be a very useful indicator, worthy of a position on your panel or within eyesight of the pilot. Route and install this lamp as needed. The photo shows the substitution of a "Legend Light" from Aircraft Spruce, with a "Caution" label.
56. This completes the installation of your ECM harness and related circuits. All that's left is the final wiring of the switches, breakers, fuses and EXPBUS.
57. EXPBUS POWER:



58. Construct a short 8AWG cable to run from your 60A Main Battery fuse or breaker to the EXPBUS "BAT" terminal. Use an extra-flexible type of cable (i.e. fine strands, large strand count) if available. Regardless of the cable used, be sure to provide shallow "S" bends between the EXPBUS and the bulkhead and circuit breaker to relieve strain. The photo shows a pair of cables (Main Battery and Alternator) with extra layers of shrink tubing to protect these connections from accidental (and potentially catastrophic) short circuits.
59. Route, install, and secure this cable. Use extra care when attaching the cable to the EXPBUS terminal with fiber lock nuts and flat washers. Secure and protect the cable such that it cannot vibrate loose and short out to the EXPBUS housing (creating a really big spark!).
60. EXPBUS ALTERNATOR POWER:
61. Construct another short 8AWG cable to run from your 50A circuit breaker (Alternator) to the EXPBUS "ALT" terminal.
62. Route, install, and secure this cable as you did in the previous step. Again, use extra care to prevent any shorts at the EXPBUS.
63. EXPBUS ALTERNATOR FIELD CONTROL WIRE:
64. Construct a 16AWG wire to run from the EXPBUS "Field" terminal to the field control wire of your Alternator. The EXPBUS end will use a 1/4" flat blade type connector, while the Alternator end will be spliced with the field control wire at the Alternator and covered with shrink-tubing.
65. Route the wire through the right side nylon bulkhead fitting and follow along side the Alternator cable installed in the previous step.
66. PITOT HEATER & CABIN HEATER BREAKER/S (Optional):
67. If you are installing a Pitot Heater or Cabin Heater, now would be a good time to construct a 10AWG jumper wire between the Main or Aux breaker and a 15A Pitot Heater breaker. A similar breaker can be used for your Cabin Heater. Whether you choose to power these optional loads from your Main or Aux bus is your decision to make. If you intend to use these relatively heavy loads often, I would favor putting them on the Main Battery Bus because the AUX Battery is only charged through the small charging circuit on board your EXPBUS.
68. AUX BATTERY TO BUS MASTER WIRE:
69. Construct a 10AWG wire to run between the 20A Aux Battery breaker and the Bus Master switch pin 2 as shown on Sheets 1 and 4.
70. Attach the breaker side of this wire to the breaker and the other side to the switch, but leave the Bus Master switch side loose for now.
71. EXPBUS BBAT TO BUS MASTER WIRE:
72. Construct a 10AWG wire to run between the EXPBUS "BBAT" (Backup Battery) terminal and the Bus Master switch pin 1 as shown on Sheets 1 and 4.
73. Attach the EXPBUS BBAT side of this wire and loosely fasten the other side to the Bus Master switch for now. The wires that run between the EXPBUS and Bus Master switch can be routed across the top of the EXPBUS. It's a good idea to protect the wires from the sharp edges of the EXPBUS's metal chassis using clamps or a strip of plastic pinch molding.
74. FUEL PUMP WIRING:



75. Construct four 14AWG wires for your Fuel Pumps to run between the pumps and the instrument panel in the vicinity of your Bus Master, Pump Select, and Auto-Failover Relay. Note the Auto-Failover Relay will be mounted to the bulkhead behind the instrument panel. Just leave these wires extra long for now.
76. Attach the wires to the Fuel Pumps. Use extreme care to assure that the wires cannot short against the Oetiker clamps on the Fuel Pump hoses. Silicone rubber boots or liquid electrical tape help here. You can also install a short section of corrugated tubing over the fuel hoses to protect them from shorts as shown in the photo. Note also the auto-failover pressure switch wiring in the photo (an old version of this switch is shown).
77. Route these four wires through one of the nylon bulkhead fittings to the instrument panel. Leave them long and unterminated for now.
78. FUEL PRESSURE & TEMPERATURE SENSOR WIRES:
79. If you haven't already done so, construct and install 20AWG wires for your Fuel Pressure and (optional) Fuel Temperature sensors.
80. Run these wires to whatever instrumentation you intend to use for these.
81. AUTO-FAILOVER PRESSURE SWITCH WIRES:
82. The Auto-Failover Pressure switch has two terminals labeled "NC" and "C". Refer to the prior photo and to Sheet 6 for details. Note: this description may vary with different models of switches.
83. Construct a 20AWG wire to run between the "NC" terminal of the pressure switch and the instrument panel.
84. Construct another 20AWG wire to run between the "C" terminal of the pressure switch and your Ground Plate.
85. Attach both of these wires to their respective pressure switch terminals. Protect them with silicone rubber boots or liquid electrical tape.
86. Route these wires through one of the nylon bulkhead fittings. Fasten the ground wire. Leave the other one long for now.
87. NOTE: The new "preset" Auto-Failover pressure switch is factory set to 28psi.
88. EXPBUS FUEL PUMP AND IGNITION WIRES:



91. The above photo shows a nearly complete installation of the EXPBUS. The three wires running across the top-center of the chassis are the BBAT, AUX1, and AUX2 wires heading to the Bus Master switch. Note also the "S" bends in the ALT and BAT cables that connect the EXPBUS and bulkhead-mounted circuit breakers. You can clearly see the optional diode module and six connecting wires in this photo. Notice also the use of a strip of mylar tucked between the switch lugs to help prevent potential shorts. A similar loose fitting mylar cover will be added over the entire unit when the wiring is done to prevent any stray nuts or screws from causing trouble. Be sure to retain adequate cooling airflow. A tiny 1" computer fan can be tie-wrapped to the side of the chassis if necessary. USE CARE INSERTING THE FLAT TERMINALS ON THE EXP SWITCHES. THEY ARE NOT ALL THAT STRONG. REMOVING THEM IS VERY HARD TO DO.
92. The EXPBUS "AUX2" terminal and switch (S9) will provide power through your Bus Master switch to the EFI Fuel Pumps. The EXPBUS "AUX1" terminal and switch (S10) will provide power through your Bus Master switch to the ECM-ignition circuit. The AUX1 and AUX2 terminals are the only outputs supported by the automatic backup feature of the EXPBUS. Do NOT wire your EFI Fuel Pumps to the EXPBUS terminal labeled "Fuel Pump" (S6) as this is for Lycoming installations that use an electric boost pump which is non-critical and not backed up! You can use the switch labeled "Fuel Pump" for your optional EIS engine monitor, or EFIS.
93. Construct a pair of 14AWG wires to run from the EXPBUS to the Bus Master switch. Use 1/4" flat blade type connectors for the EXPBUS ends of these wires and leave the other ends unterminated for now. Wires which run between the EXPBUS and Bus Master switch can run across the top of the EXPBUS as shown in the photo. Note the protective plastic pinch molding applied to the metal chassis edge to prevent chaffing the wiring.
94. Connect one of these wires to the EXPBUS "AUX1" terminal and the other wire to the EXPBUS "AUX2" terminal.
95. This completes the EXPBUS engine-related wiring.
96. INDICATOR LAMPS:



97. The above photos show one method for wiring indicator lamps. Because these lamps are mounted through the instrument panel, it is helpful to be able to remove them without resorting to soldering. The top photo shows how to construct short "pigtails" with 2-pin Molex connectors. The second photo shows a row of Molex panel connectors for three of the indicator lamps. A forth one is further to the center. The Molex connectors are just small enough that they fit through the holes in the instrument panel and the lamp mounting nuts. Be sure to use quality connectors. Cheap Molex immitations are best avoided.
98. We strongly suggest the use of four status indicator lamps to keep the pilot abreast of any changes in the critical systems. 1) Low Fuel Pressure, 2) Aux Pump On, 3) ECM Caution, 4) Bus Override.
99. The auto-failover feature of the fuel system can respond to a failing pump faster than a human can even perceive a problem exists. Therefore, these indicator lamps will provide you only means of knowing if you have lost your main fuel pump. You can use any 12 volt DC lamps. Aircraft Spruce sells nice "Legend Lamps" which allow you to customize the labels or select from a number of preprinted labels. These also come in red, green, and blue colors. As a general philosophy, we prefer red as an indication of an emergency condition such as low fuel pressure, while we use blue as an indication of a less critical condition. In our case, we recommend blue lamps to indicate that the Aux fuel pump has come online, and that your Bus Master switch is in OVERRIDE mode. Neither of these constitute an emergency, but rather, things that the pilot should be aware of.
100. Obtain your lamps and determine their position on your panel. We suggest that the Low Fuel Pressure (red) lamp, and Aux Pump (blue) lamp be located next to your Pump Select switch. This assure that the lamps will draw your attention to the vicinity of the switch. We suggest the OVERRIDE (blue) lamp be located next to the Bus Master switch. Leaving the Bus Master switch in OVERRIDE is not an emergency in itself, but it defeats the purpose of having redundant primary electrical systems and unless it really is an emergency, this can run down your Aux Battery in short order.
101. The lamps draw very little current. You can safely use 24AWG wire for these. Most lamps use soldered connections. Construct and attach wires for all of the lamps and run them all over to the vicinity of the Bus Master switch and Auto-Failover Relay. Leave these ends unterminated for now, or install suitable connectors if you prefer. Note that these lamps may not have bulbs installed when you purchase them. Check yours and install bulbs if needed.
102. At last, it's time to install the four control switches.
103. AUX BOOST SWITCH WIRING:
104. Refer to Sheet 1. The SPST (Single-Pole, Single-Throw) Aux Boost switch controls the Aux Boost Relay coil. The relay coil gets its power from internal relay connections. To activate the relay, the terminal labeled "coil" is grounded through the Aux Boost switch.
105. Construct and install a 16AWG wire to run from the center terminal of the Aux Boost switch to the Ground Plate. Use a flat blade connector at the Ground Plate and a ring connector at the switch.
106. Construct another 16AWG wire to run from the bottom terminal of the Aux Boost switch to the Aux Boost Relay's "coil" terminal. This is the small terminal. It is always "live" when the battery cables are hooked up.
107. Attach one end of this wire to the Aux Boost switch and route it out the right side nylon bulkhead fitting to the Aux Boost Relay's "coil" terminal.
108. Protect the relay connection with a small silicone rubber boot or liquid electrical tape.
109. This completes the wires which will be run through the right nylon bulkhead fitting. You may seal the remaining space in this fitting with high-temp silicone sealant or comparable potting compound.
110. STARTER SWITCH WIRING:
111. Refer to Sheet 1. The SPST Starter switch controls power to the Starter Solenoid. We derive power for the starter solenoid from the Aux Battery in order to preserve the capability of starting the motor in-flight during an electrical emergency (although you can also source this circuit from the Main Battery bus (prior to the EXP) if you prefer, knowing that the AUX BOOST switch will still provide power to it when the busses are parallelled anyway).
112. Construct a small 16AWG jumper wire to run between the input side of the 20A Aux Battery circuit breaker and the input side of the 15A starter breaker.
113. Construct and install a short 16AWG wire to run between the output side of the 15A breaker to the center terminal of the Start switch.
114. Identify the "Start" wire, run previously, and attach it to the bottom terminal of the Start switch. Trim away any excess length first.
115. The EXPBUS and the optional diode module, both contain an optional circuit which disables the avionics bus during engine start (when voltages can sag below what some avionics equipment can tolerate). If you wish to use this circuit, construct a 20AWG wire to run from the output side of the Start switch to the EXPBUS "Start" terminal using a flat blade connector.
116. If you trace the entire path of the Start circuit, it runs from the Start breaker, through the Start switch, to the EXPBUS Start terminal, and Start terminal on the optional diode module, and a Start signal at the ECM, and finally to the Starter solenoid itself. Seems like everybody wants to know what's crankin!
117. BUS MASTER SWITCH WIRING:



118. The above photo shows the Bus Master switch in the foreground. Note the bundle of wires passing over the top of the EXPBUS chassis and the plastic protective pinch molding on the metal chassis edge. Note also the "S" bend in the bundle of wires running between the Bus Master switch and breaker panel. "S" turns provide important relief for mechanical strain on the switch terminals. The screw terminals of these high-quality aircraft switches are remarkably strong. Tighten the screws with a flat-blade stubby screwdriver so they are not likely to come loose.



119. Refer to Sheet 4. Connect one side of the 24 AWG OVERRIDE Indicator Lamp to Bus Master switch PIN 3.
120. Connect the other side of the OVERRIDE Indicator Lamp to your Ground Plate with a flat blade connector.
121. Construct and install four small 14 AWG jumper wires on the Bus Master switch as shown above. PINS 2 to 6 to 9 to 12 and another between PINS 10 and 12. If you use larger ring terminals on PINS 6 and 9, you can double-up the wires and reduce the number of terminals involved.
122. Construct a 10AWG wire to run between the output side of the 20A Aux Battery breaker and PIN 2 of the Bus Master switch.
123. Identify the 10AWG wire, run previously, from the EXPBUS "BBAT" terminal. Attach this wire to Bus Master switch PIN 1.
124. Identify the wire from the EXPBUS "AUX1" terminal and connect it to the Bus Master switch PIN 4.
125. Identify the wire from the EXPBUS "AUX2" terminal and connect it to the Bus Master switch PIN 7.
126. Refer to Sheets 4 and 1. Construct and install a 16AWG wire to run between Bus Master switch PIN 5 and the 3A fuse panel for the "Critical Equipment" circuit.
127. Identify the "ECM Power" wire from your ECM harness. Connect this wire to the same 3A fuse panel connection as in the above step. Note that the ECM Power does not actually pass through this 3A fuse, it is merely a convenient place to obtain switched power. This Critical Equipment fuse terminal is normally sourced from the EXPBUS AUX1 (IGN) switch when the Bus Master is ON. When the Bus Master is in OVERRIDE, this terminal is sourced from the Aux Battery bus.
128. Install a 20 AWG jumper from the input side of the 3A fuse and the input side of the 3A "Backup Gyro" fuse as shown on Sheet 1. The other side of this 3A fuse will go to whichever electric gyro you have declared to be your backup gyro. The "backup gyro" circuit provides backed up power to drive a single gyro, typically your attitude indicator or turn-and-bank, when under emergency power. We call for a 3A fuse here. A slightly larger fuse can be used if you need a little more power, but keep it absolutely minimal please!
129. While we're in the area, identify the "ECM Memory" wire from your ECM harness. Connect this wire to the output side of the 20A Aux Battery breaker as shown on Sheet 1. The ECM Memory circuit is always live, allowing the ECM to retain its internal history of engine performance parameters. Pulling and resetting the Aux Battery breaker will reset the ECM.
130. Construct and connect a 14AWG wire between Bus Master switch PIN 8 and the 10A fuse for the Main Fuel Pump.
131. Construct and connect a 14AWG wire between Bus Master switch PIN 11 and the 10A fuse for the Aux Fuel Pump.
132. Secure the switch and wires as needed. This completes the Bus Master switch and ECM power wiring!
133. PUMP SELECT SWITCH & AUTO-FAILOVER RELAY WIRING:



134. The first photo above, shows the completed Pump Select switch wiring. The second photo shows the completed (but not entirely pretty yet) fuse panel, auto-failover relay, and circuit breaker installation. Note how the wire bundle to the Bus Master switch emerges from the gap between the relay and circuit breakers. It is clamped to the mounting angle and runs behind the components. If you look closely, you can also see the braided copper shield over the Alternator cable at the upper right corner of the photo.
135. If you have not yet mounted your Auto-Failover Relay, do so now. It can be mounted to the bulkhead behind the instrument panel. Theoretically, relays will last longer and be less susceptible to vibration if they are mounted with their base on the bottom. This would suggest the use of a small angle shelf against the bulkhead for it to sit on.
136. Refer to Sheets 2, 5, and 6. Construct a small 14AWG jumper wire to run between Pump Select switch PIN 2 and PIN 4. This jumper configures the internal switch functions for our purposes.
137. Identify the Main EFI Fuel Pump power wire (marked "+" on the pump body) run previously, and connect it to PIN 7 of the Pump Select switch.
138. Construct a 14AWG wire to run between the output side of the 10A fuse for the Main Pump and PIN 8 of the Pump Select switch.
139. Construct a 14AWG wire to run between the output side of the 10A fuse for the Aux Pump and PIN 5 of the Pump Select switch.
140. Identify the Aux EFI Fuel Pump power wire (marked "+" on the pump body) run previously, and connect it to PIN 6 of the Pump Select switch.
141. Identify both EFI Fuel Pump ground wires (marked "-" on the pump bodies) run previously, and connect them to your Ground Plate using ring type connectors under one of the ground bolts.
142. Construct a 14AWG wire to run between Pump Select switch PIN 6 and Failover Relay PIN 6.
143. Construct a 14AWG wire to run between Pump Select switch PIN 3 and Failover Relay PIN 8.
144. Construct a small 20AWG jumper to run between Failover Relay PIN 8 and Failover Relay PIN 1.
145. Construct a small 20AWG jumper to run between Failover Relay PIN 0 and Failover Relay PIN 4.
146. Construct a 16AWG wire to run between Failover Relay PIN 2 and your Ground Plate. Use a flat blade type connector on the Ground Plate.



147. Your Ground Plate should be filling up rather nicely by now. The photo above shows quite a few grounds making their way back home. Notice how the more critical grounds are attached to the Ground Plate bolts using ring terminals. The black box with two white wires feeding into it is the power supply for a Blue Mountain EFIS unit. The fat orange bundle is the main ECM harness. The wire bundles will be laced neatly when the installation is completed. There's a number of avionics equipment grounds to be run yet.
148. Refer to Sheet 2. We need to install a 1N4004 Diode between Relay PIN 0 and our Fuel Pressure lamp and Fuel Pressure switch. To be activated, the Failover Relay is looking for a ground on PIN 0. This ground is achieved when the Fuel Pressure switch closes. The same ground will allow the Low Fuel Pressure lamp to be illuminated. Once the Failover Relay closes, its "S1" contacts create a second source of ground to latch the relay closed. The "S2" contacts fire up the Aux Fuel Pump. When good fuel pressure returns, the pressure switch opens again, but the relay stays latched in the closed position so the Aux Fuel pump will continue to run. See the problem yet? Since we now have good fuel pressure, we want the Low Fuel Pressure lamp to extinguish. This is where the diode comes in. The diode will not allow current to flow backwards through it, thus the only suitable ground for the lamp is through the now-open fuel pressure switch, hence, the lamp turns off. All of this happens so fast it is easy to miss. An auto-failover operation causes the Low Pressure lamp to flick on then off an instant later as the Aux Pump and lamp come on and stay on. Note that if your Main Fuel Pump has not blown its fuse, it will also be on during an auto-failover operation. It may still be able to contribute some pressure, but you can turn it off to let it cool down by selecting the AUX position of the Pump Select switch. We will run through all of this during our checklist at the end of this chapter. Back to the diode...
149. IMPORTANT - Orient the diode so the end WITHOUT the white-stripe is on Relay PIN 0. If you get this backwards, the diode will conduct when power is applied and the Low Fuel Pressure lamp will always be on. Best to get it right the first time!
150. When connecting diodes, you can crimp a ring type connector to their leads as you would with any wire end. You can also insert a piece of shrink-tubing over their entire length to protect them. They will not run hot enough to melt the shrink-tubing.



151. The above photo shows our Failover Relay diode. The ring terminal attaches to PIN 0. Note the clear shrink tubing over the entire length of the diode and leads. The white-strip of the diode is on the side facing the crimp-splice, where our two wires attach.
152. Connect the 16AWG wire from the "NC" (Normally Closed) terminal of the Fuel Pressure switch to the diode splice connector.
153. Also connect a short 24AWG wire from this splice connector to the Low Fuel Pressure lamp.
154. Connect another 24AWG wire from the other side of the Low Fuel Pressure lamp to the output side of the 5A Critical Equipment fuse.
155. Connect one 24AWG wire from the Aux Pump lamp to Failover Relay PIN 6.
156. Connect the ground wire from the Aux Pump lamp to your Ground Plate using a flat blade type connector.
157. This completes the Pump Select switch and Auto-Failover circuit wiring!



158. While we're working with diodes (selfish as they may be), let's install one to help the Aux Boost Relay out on the firewall. This is not strictly necessary, and is not shown on the diagrams, but it can help to extend the life of the switch by clipping spikes that occur as the relay coil voltage collapses. The first photo above, shows the construction of a short 1N4004 diode-jumper with a pair of ring terminals. Construct this jumper to be about 4" long. Cover it with shrink tubing.
159. Install the diode between one of the mounting screws that holds the Aux Boost Relay to the firewall and the Aux Boost Relay "coil" terminal (the small terminal). Orient the diode so that the end marked with the white stripe is attached to the "coil" terminal. If you get this one backwards, the relay will immediately activate. This diode is there to prevent voltage spikes from being generated as the relay contacts open. It will prolong the life of the control switch.
160. Note the time.
161. HEY EDISON WE'RE DONE!

 

Carefully go over your accomplishment to make sure you didn't leave anything unhooked. Contact us if you see that we forgot to document something or did something obviously wrong (we're only human and it's a real pain in the neck describing wiring like we have just done). Anything you can suggest to improve the way we have written this manual would be greatly appreciated.

At this point, you can elect to hook up your Main and Aux Battery positive cables if you like. You should pull the 60A, 50A and 20A circuit breakers before hooking up your battery cables. If all is done right, and everything is turned off, there should be no sparks. If you do get a spark when you hook up the batteries, stop immediately and double-check the primary system wiring.

When you reset the 60A breaker, power will be available to the EXPBUS and all circuits it supports. When you reset the 50A breaker, the Alternator will be available. When you reset the 20A breaker, power will be available to the fuel system, ECM, and starter circuits. Note that a small amount of current will always flow to the "Memory" wire of the ECM to maintain it's internal performance map. Over many months of nonuse, this can drain your Aux Battery. If you intend to park your plane for more than a few months, you may want to pull these breakers to eliminate battery drain, or better yet, hook up an external power source (i.e. trickle charger, solar panel, etc.). You can wire-in an external booster connector if you like.

If you detect problems when you apply power, you can pull fuses and trip breakers systematically to isolate where you've gone astray. If everything is fine, complete the installation of your engine monitoring instrumentation then complete the Inspection Checklist at the end of this chapter. If you're really stumped, give us a call.

Once you're happy with things, you should disconnect the batteries again until you have finished the rest of your avionics, instrumentation, and airframe wiring.

EXPBUS Options & Voltmeters

ControlVision offers an optional enunciator module for the EXPBUS. This option provides a small indicator panel containing lamps for each circuit to show when one has tripped. It also provides an ammeter, and switch panel lamp dimmer control. This is a good option to have at a reasonable price. To install it, a single ribbon cable plugs into a socket on the EXPBUS.

REGARDLESS of whether you use this option, you will want to install a voltmeter on your essential equipment fuse clearly displayed on your instrument panel. This engine requires a reliable electrical system, so a voltmeter should be included in your engine instrument scan.. You can optionally add a second voltmeter for the Aux bus, or a single-pole-double-throw switch to allow one voltmeter to work with either selected bus. If you prefer dual voltmeters, you can add wires to the EXPBUS "BAT" and "BBAT" terminals for the Main and Aux bus (respectively) voltmeter taps. Personally, I find that if I just wire the single voltmeter to the essential equipment fuse, it will display the most important voltage, that of the ignition circuit, regardless of which battery is feeding this circuit. Closing the AUX BOOST switch briefly, shows me that both batteries are equally charged (if the voltage remains steady).

Another EXPBUS option is a small diode module to help protect your avionics from voltage spikes. Most modern avionics have fairly good power filters already, but it never hurts to add further protection. This option also provides a function for disabling specific avionics busses during engine cranking which is when you are most likely to experience significant, and potentially damaging, voltage sags. Keep in mind that if you are in the habit of preprogramming your flight plan into your GPS unit before starting your engine, and you wire your system to disable the avionics bus that your GPS uses, you may inadvertently perform a reset on your GPS and lose your flight plan.

Refer to the manufacturers instructions for installing and using these options.

Engine Sensor Wiring & Calibration

Your engine is equipped with a separate set of sensors used by the ECM for engine operation. These are already calibrated and continuously monitored by the ECM. No further work is required for basic engine operation.

The second set of sensors installed by the factory (if you ordered the Grand Rapids EIS option) or by the installer (if you didn't) may need further wiring and calibration.

Depending on what engine instrumentation or monitoring system you have chosen to install, you will have additional wiring to do before your engine sensors are fully functional. In addition to the wiring, many such systems will require calibration of the sensors before accurate readings can be had. We cannot possibly describe the wide array of instrumentation that exists, therefore, we refer you to the documentation from your specific instrumentation to complete the wiring and calibration of these sensors. If you've come this far, we have full confidence that you can accomplish the remaining tasks. We strongly advise you to have fully functioning engine instrumentation before starting your engine.

The EXPBUS "MB1" and "MB2" terminals provide ample power for your engine monitoring and miscellaneous airframe functions such as flap motors and electric trim. The MB1 terminal will already have a wire attached to it for the EXPBUS internal battery charger circuit. Use the MB2 terminal first and if you need more than the 5A it provides, you can tap into the MB1 or INST connections. The INST terminal is for gyros and other goodies on the instrument panel. These are not backed-up power sources, so keep in mind that you will lose these function in a serious (albeit unlikely) electrical emergency. Avoid adding more circuits to the backed-up "AUX1" and "AUX2" terminals as this would impact the power loads we have designed for. Consider that in an electrical emergency, you really don't care about much more than landing the plane, so watching your engine instruments is of relatively low importance. You will continue to have the use of the ECM Warning Lamp in all modes of operation. Note also that the EXPBUS provides two Landing Light switches and circuits (one is labeled TAXI). These have special circuitry to provide a slow fade-in of power. This is great for saving light bulbs, but don't use these for electronic equipment which is less tolerant of voltage changes.

• PRIMARY WIRING CHECKS
• [ ] Disconnect both positive battery cables.
• [ ] Remove all fuses and pull all circuit breakers.
• [ ] Turn your Bus Master switch to the center "OFF" position.
• [ ] Turn your Fuel Pump Select switch to the "Main" position.
• [ ] Turn all of your EXPBUS switches OFF.
• [ ] Reset your 60A breaker (if it is the resetable type). This restores Main Bat circuits.
• [ ] Lightly tap the Main Battery positive cable to the battery post. No appreciable spark should be seen.
• [ ] Install the Main Battery positive cable to the Main Battery positive post.
• [ ] Reset the 50A breaker. This restores the Alternator circuits.
• [ ] Reset the 20A breaker. This restores the Aux Battery circuits.
• [ ] Lightly tap the Aux Battery positive cable to the Aux Battery positive post. An extremely tiny spark may be seen because the ECM Memory circuit will be receiving power.
• [ ] Install the Aux Battery positive cable to the Aux Battery positive post.
• AUX BOOST & STARTER CHECKS
• [ ] Reset the 15A Starter breaker. This restores the Starter Switch and Solenoid control circuit.
• [ ] Briefly lift and release the Aux Boost switch. You should hear your Aux Boost Relay engage and disengage.
• [ ] Clear the area around the engine and propeller (if installed).
• [ ] Briefly lift and release the START switch. You should hear your Starter Motor engage and disengage. Do not attempt to start the motor just yet. If the Starter Motor did not engage, double check the cable connections at the batteries, starter, and grounds.
• EXPBUS CHECKS
• [ ] Turn on your EXPBUS Master switch.
• [ ] Observe any indications on your optional EXPBUS enunciator panel. You should see no charge from your Alternator since the motor is not running. You should see a Low Voltage indicator since the Alternator is not charging, and your voltmeter should show approx. 12 volts. All Avionics Bus circuit failure LED's should be lit. These will go out once you turn on the Avionics Master switch.
• CRITICAL SYSTEMS CHECKS
• [ ] Note: We are about to test your Fuel Pumps. We assume you DO NOT HAVE FUEL in your system yet. Proceed with these next tests quickly to avoid running your pumps any longer than necessary. Try to limit these tests to no more than 30 seconds. Your pumps depend on fuel to remain cool.
• [ ] Install your four ATO blade type fuses or reset your pump circuit breakers.
• [ ] Raise your Bus Master switch to the ON position.
• [ ] Turn on the EXPBUS AUX1 (IGN) switch. This enables your critical engine control systems. Your ECM Warning Lamp should be ON. Your designated backup gyro should be spooling up. Your red Low Fuel Pressure Lamp should be ON.
• [ ] Turn on the EXPBUS AUX2 (Fuel) switch. Your Main Fuel Pump should be ON. Note the sound of the pump.
• [ ] Put the Pump Select switch into the AUTO position. Your red Low Fuel Pressure Lamp should remain lit (assuming there is no fuel in your system yet, otherwise it should be OFF). Both Main and Aux Fuel Pumps should be ON. Your blue Aux Pump Lamp should be ON. Note the sound of both pumps.
• [ ] Lower the Pump Select switch to the Aux position. Your Main Fuel Pump should be OFF. Your Aux Fuel Pump should remain ON. The red Low Fuel Pressure Lamp should be ON (again assuming you have no fuel in your system, otherwise it should be OFF). The blue Aux Pump Lamp should be ON. Note the sound of the Aux pump.
• [ ] Turn the EXPBUS AUX1 (IGN) and AUX2 (Fuel) switches OFF.
• [ ] Turn the EXPBUS Master switch to the OFF position.
• [ ] Turn the Bus Master switch to the center-OFF position.
• [ ] Raise the Pump Select switch to the MAIN position.
• EMERGENCY OVERRIDE CHECKS
• [ ] Lower your Bus Master switch to the OVERRIDE position. Leave the EXP Master Switch OFF. The blue OVERRIDE Lamp should be ON. The Main Fuel Pump should be ON. The red Low Fuel Pressure Lamp should be ON (assuming you have no fuel in your system, otherwise it should be OFF).
• [ ] Put the Pump Select switch into the center-AUTO position. Both Fuel Pumps should be ON. The red Low Fuel Pressure Lamp should be ON (assuming no fuel is in your system). The Aux Pump Lamp should be ON.
• [ ] Lower the Pump Select switch to the Aux position. The Main Fuel Pump should be OFF. The Aux Fuel Pump should be ON. The red Low Fuel Pressure Lamp should be ON (you know about fuel). The blue Aux Pump Lamp should be ON. The backup gyro should be spooling up and any other critical equipment you have wired up should be active.
• [ ] Turn the Bus Master switch back to center-OFF position. All pumps, fuel system lamps, and critical equipment should be OFF.
• EMERGENCY OVERRIDE ENGINE RESTART CHECKS
• [ ] Remove your four ATO type fuses again to prevent the Fuel Pumps and backup gyro from running.
• [ ] Lower the Bus Master switch to the OVERRIDE position.
• [ ] Briefly lift and release the Aux Boost switch. You should hear the Aux Boost Relay engage and disengage.
• [ ] Clear the area around the propeller and engine.
• [ ] Briefly raise the START switch. The Starter Motor should engage and disengage.
• [ ] Return the Bus Master switch to the OFF position.
• [ ] Turn all EXPBUS switches OFF (they should already be OFF).
• [ ] Congratulations Sparky! She's working fine.
• [ ] Note the time.

  Before you are ready to actually start and run the engine, you will need to do the following:

  1. Complete your engine sensor wiring and perform any required sensor calibration.
  2. Hook up your fuel system (i.e. you might want to add wings to your airplane or at least a gas can and some hoses).
  3. Leak-test your fuel system.
  4. Check your Auto-Failover Pressure switch.
  5. Add fluids to your motor if not already done.
  6. Review the operational procedures section of this manual and your videotape.
  7. All of this will be covered in Chapter 11. Before then, Chapter 10 will cover your cowling installation.

   

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