2-Cylinder Engine Monitor: Installation and Operation Manual

The Wapsi Aero 2-cylinder engine monitor was designed to be a direct drop-in replacement for legacy GRT EIS 2000 installations. The DB-25 connector is compatible with the existing wiring harnesses. The panel cutout and mounting holes are also identical. This means that the installation process can be as simple as unplugging the old GRT EIS and plugging in the new Wapsi Aero engine monitor.

The faceplate of the Wapsi Aero engine monitor is 3/16" taller than the GRT EIS. In most cases, this difference is negligible. However, if the GRT EIS was originally installed near the top/bottom edge of a panel or in proximity to another instrument, special care should be taken to ensure that there is sufficient clearance.

The functional differences between the GRT EIS and the Wapsi Aero engine monitor are detailed in the table below.

A premade wiring harness is available for purchase from Wapsi Aero. For those who want to construct their own harness, it is important to understand and adhere to standard aviation wiring practices. This is beyond the scope of this manual, but a list of helpful resources is included below.

Aircraft Wiring Guide by Marc Ausman

FAA-H-8083-30B, Aviation Maintenance Technician Handbook – General

FAA-H-8083-31B, Aviation Maintenance Technician Handbook – Airframe

FAA-H-8083-32B, Aviation Maintenance Technician Handbook – Powerplant

AC 43.13-1B - Acceptable Methods, Techniques, and Practices - Aircraft Inspection and Repair

SAE Aerospace AS50881

NASA-STD 8739.4A

Avoid using electrical crimper and stripper tools available from automotive stores. The correct tools are available from Aircraft Spruce and are listed in the table below.

The wiring harness should be built with 20 or 22 AWG M22759/16 wire for all inputs except for the EGT/CHT thermocouple wire. This wire uses ETFE insulation which is resistant to hear, moisture, chemicals, and abrasion and is flame resistant.

For the EGT and CHT sensors, we recommend using FEP thermocouple wire pairs in a FEP jacket. FEP insulation (Fluorinated Ethylene Propylene) is resistant to heat, moisture, chemicals, and abrasion. This wire can be purchased from Wapsi Aero. The EGT sensors require K-type thermocouple wire and the CHT sensors require J-type thermocouple wire.

D-sub connectors come in two common forms: crimp pin and solder cup. The solder cup style is not recommend for this installation because thermocouple wires do not solder well.

Both diagrams are viewed from the mating side of the connector. From this perspective, the pins and sockets will be visible. Generally, the pin numbers are lightly etched on the plastic face of the connector.

The connector on the display head is female.

The engine monitor uses type-K thermocouple probes for measuring exhaust gas temperatures. EGT probes come in two different styles: clamped and threaded. Consult your engine manual for the appropriate style of probe and mounting location.

The engine monitor uses type-J thermocouple probes for measuring cylinder head temperatures. Cylinder head temperature probes comes in a variety of diameters. On most 2-stroke engines, the CHT ring is installed underneath the spark plug. Consult your engine manual for the appropriate style of probe and mounting location.

On Rotax 2-stroke engines with Ducati CDI ignition systems, the tachometer should be connected directly to the gray tachometer pickup wire.

On Rotax 2-stroke engines with points-style ignition systems, the green and green/black wires can be used. One of the wires should be tied directly to ground and the other should be connected to the engine monitor tachometer input.

The lighting coil can also be used as a tachometer source. If the lighting coil is already connected to a regulator/rectifier, the engine monitor can be spliced into one of the lighting coil wires (generally yellow).

If it is not connected to a regulator/rectifier, one wire should be tied to ground and the other to the engine monitor.

Connect ground wire to same location that the instrument is grounded.

Any fuel probe that provides a linear 0-5V output can be used. These sensors require external power, often 5V or 12V. The sensor power outputs from the engine monitor can be used. Many fuel level sensors will require a multi-point calibration after installation. Refer to the manufacture documentation for details specific to your sensor.

The coolant sensor is connected to ground through the engine block. Poor engine grounding can result in erroneous or erratic sensor readings.

It is important to provide proper wire support between the point where the wire exists the harness and where it connects to the sensor. Failure to do so will often lead to a broken wire.

Proper grounding is vital to correct operation and is often one of the most overlooked aspects of aircraft wiring. Poor grounding will lead to erratic behavior at best and damaged avionics at worst. Often, these problems will be unpredictable and undiagnosable by customer support.

A proper installation should use a centralized grounding location. On simple installations, this can be the negative terminal of the battery. On more complex systems, this should be a bus bar (see below). All ground wires should be run directly back to this point. Ground wires should never be attached between avionics. Doing so can create a condition called a “ground loop” that often leads to damaged electronics.

Be careful when using your airframe as a grounding point. If the airframe is specifically designed with grounding studs, these can be used. However, these points do not exist on many ultralight and light-sport aircraft. Many of these planes are made from a collection of anodized and power coated metal parts. Anodized or power coated surfaces are both poor conductors of electricity and will not provide a reliable ground. A raw aluminum surface is also a poor selection for a grounding point because it will develop a non-conductive oxide layer over time. In these installations, a grounding block should be installed. Grounding blocks are cheap and can be purchased through many aviation, automotive, and marine sources. They are commonly made from copper alloy with a tin plating which helps to preserve their electrical conductivity. The block can be mounted to the frame near the battery. The negative terminal of the battery is attached to one point on the block and any other ground wires are attached to the remaining points using ring terminals. It is important to use a large-gauge wire to attach the grounding block to the battery.

The engine block also needs to be grounded properly. Many of the engine probes rely on the block as a ground return path. In most installations, a 2-4 AWG gauge cable between the engine block and battery is sufficient. The quality of the ground should be tested after installation using a voltmeter. With all equipment powered on, the voltage differential between the engine monitor and engine block should be no more than 20mV (preferably less than 5mV).

For accurate EGT and CHT temperatures, it is vital that the appropriate type of thermocouple extension wire is used.

The thermocouple operates on the thermoelectic properties of two dissimilar metals. In order to make an accurate measurement, the engine monitor must know the temperature at the point where the thermocouple wire transitions to copper wire (called the cold junction). If this thermocouple/copper wire junction is placed at point other than the d-sub connector, the reading will initially appear correct while the EIS and cold junction are at the same ambient temperature. However, as the temperature of these two locations begins to diverge in flight due to cooling from airflow or heating from the engine, significant error can be introduced into the readings.

The engine monitor is designed to accept a wide range of input voltages from 8V to 30V. On simple installations, a switch should be installed between the battery and the unit power. On electrical systems with an avionics power bus, the engine monitor should be connected to this bus.

The warning light pin should be wired to one side of a bulb or LED. The other side of the bulb should be attached to the same switched power bus that is used for engine monitor power. Do not power the light directly from the battery.

If a LED light is used, ensure that the correct in-line resistor is used to keep the current within an acceptable range. Consult the LED datasheet to determine the maximum operating current.

The connections to the pitot and static ports should be made with 1/8-3/16” (0.125”-0.1875”) tubing.

When installing on an aircraft with a static port, the static ports should be teed together. Many open-cockpit ultralights do not have a dedicated static port. In these cases, the static ports on the engine monitor can be left disconnected but should be shielded from direct airflow.

A wide variety of tees and adapters are available through industrial supply stories such as McMaster-Carr and Grainger.

The engine monitor provides the same serial data output stream as the GRT EIS 2000. As a result, it is compatible with the same Grand Rapids EFIS systems. Refer to the associated GRT EFIS manual for more installation and configuration details.

The engine monitor provides two auxiliary power supplies to provide fuel-level sensor power when needed. The 5V supply is available on pin 23 and is rated for up to 500mA current draw. The 12V supply is available on pin 6 and is rated for up to 200mA current draw.

Reference the drawing below for panel cut-out dimensions. All units are in millimeters. Ensure that there is adequate room behind the unit to allow for the wiring harness to be attached. A DXF file is available upon request.

The main menu can be opened by pressing any of the six buttons on the bezel. This will display labels next to each button. These labels are context-sensitive and will change as you navigate through the menu system. Selecting EXIT will close the main menu.

To open the setup menu, select the SETUP button on the upper-right hand corner.

The six buttons in the setup menu have the following functions unless otherwise noted:

From the main menu, select SETUP → QUICK SETUP

Although this setup is not necessary, it will save a lot of time by automatically configuring the tachometer, coolant, EGT, and CHT limits to values specified by the engine manufacturer. It also configures the battery limits for a 12V battery and the fuel level limits to a 0-100% scale regardless of tank size.

Use the up and down keys to find your engine in the list. Then select LOAD to use the parameters from the selected engine. If your engine is not listed on the screen, the parameters can still be configured manually. See Quick Setup Ranges in the appendix for more details on what values are assigned during quick setup.

It is recommended to use the quick setup option to perform the initial configuration. Once this has been completed, individual sensor limits can be adjusted. Selecting SETUP → SENSORS will populate a list of sensors that can be configured. Select the desired sensor from this list and a menu similar to the one below will appear.

MIN DISPLAYED and MAX DISPLAYED set the range in which the needle/arrow will move. These are comparable to mechanical stops on a steam gauge. The needle will not move until the MIN DISPLAYED value has been met and will stop moving once MAX DISPLAYED has been exceeded. These values should be set to as narrow of a range as possible while still including the entire normal operating ranges (green), the caution ranges (yellow), and a small portion of the over-limit ranges (red). Using a narrow ranger will increase the resolution of the graphical display, making it easier to visually detect minor anomalies.

The RANGE[1-5] submenus allow the user to adjust the position of the colored bars on the gauge

ENABLED must be set to true for that range to be active.

Five color options are available: RED, YELLOW, GREEN, BLUE, WHITE.

Yellow should be used to indicate a range in which the parameter is close to exceeding its minimum or maximum value. Any time the needle on the gauge enters a yellow region, the text will also turn yellow.

Red should be used to indicate a range in which a parameter has exceeded its minimum or maximum value. Any time the needle enters a red region, the text will turn red, the gauge will flash, and the warning light will flash.

The table below helps show how each sensor setting relates to the graphical ranges displayed on the screen

The tachometer operates by measuring the timing of the pulses from the engine ignition system. Different types of engines produce a different number of pulses per revolution so this must be configured. The setting can be found under SETUP → SENSORS → TACHOMETER and is called PULSES/REV. This value is automatically configured if the quick setup option is used. Otherwise, it should be set according to the following table. Please contact us for any engine type not listed below.

Fuel parameters can be set under SETUP → SENSORS → FUEL

The fuel gauge can display fuel quantity in two different formats: gallons or percentage.

When using Quick Setup Ranges, the tank is automatically configured for percentage. This can also be done manually by the user by setting TANK CAPACITY to 100. To display fuel quantity in gallons, set TANK CAPACITY to the number of gallons that your tank holds. It is recommended to set MAX DISPLAYED to the same value as TANK CAPACITY

From the main menu, select SETUP → TIMES → HOBBS

Using the plus and minus buttons, adjust the ENGINE TIME parameter in increments of 0.1 hours (6 minutes). Pressing and holding the plus or minus buttons will adjust the time in 1.0 hour increments.

From the main menu, select SETUP → TIMES → FLIGHT

The flight timer can be configured to trigger off of the tachometer or the airspeed reading. The flight timer only runs when the selected trigger source is above a certain threshold. The TRIGGER options selects the source. The TRIGGER THRESHOLD setting adjusts the value which the selected parameter must exceed before the flight timer starts (e.g. airspeed greater than 50)

The pressure sensor calibration menu is accessible under SETUP → CALIBRATION.

The unit has been calibrated at the factor and it is not recommended for the user to modify this setting.

Unless otherwise indicated the following units are used in the display software:

Press any button to open the main menu. Select BARO on the left side. Use the ▲ and ▼ keys to increase and decrease the barometer setting. Select EXIT to close the menu.

Press any button to open the main menu. Select DIM on the left side. Use the ▲ and ▼ keys to increase and decrease the brightness setting from 1 to 10. Select EXIT to close the menu

When a parameter enters into a range designated with a red color, the associated gauge will begin to flash unit that parameter leaves that range. Any flashing gauge will also cause the external warning light to flash.

The flight timer runs whenever the configured trigger threshold is exceeded (see installation manual). The timer is reset when the unit is turned off.

The engine monitor is able to detect with the connection to certain sensors has been disconnected or broken. This includes the following sensors: coolant temperature, CHT, EGT, OAT. In the case that the sensor is disconnected or broken, three dashes (---) are displayed instead of a number.

The airspeed indicator is displayed in miles per hour. For airspeeds lower than 28 MPH, three dashes (- - -) are displayed.

The engine monitor officially supports the following engines:

It may work with other engines but compatibility is not guaranteed.

The current software version can be found in the setup menu under UNIT INFO.

The unit must be returned to Wapsi Aero for any software updates. Software updates are free, but the user is responsible for all shipping costs. Software bug fixes are covered under the warranty policy.

Sales: [email protected]

Support: [email protected]

Wapsi Aero LLC warrants this product to be free from defects in materials and workmanship for one year from date of shipment. Wapsi Aero LLC will, at its sole discretion, repair or replace any components that fail in normal use. Such repairs or replacement will be made at no charge to the customer for parts or labor. The customer is responsible for all associated shipping costs. This warranty does not cover failures due to abuse, misuse, accident, improper installation or unauthorized alteration or repairs.

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