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Pilots are able to customize CGR equipment by completing a Marking  and Configuration Requirements (MACR)  document with their order.
Pilots are able to customize CGR equipment by completing a Marking and Configuration Requirements (MACR) document with their order.

Trading Six Instruments for Two: Cluster Gauge Replacement

(1 Vote)

July 2015 -

You can monitor engine and electrical system parameters, fuel flows and quantities and OAT in two 3 1/8 inch instruments using CGR-30P and the CGR-30C from Electronics International.


I recently moved into the 21st century and upgraded my instrumentation by installing my first glass panel—a tidy engine monitor package from Electronics International (EI) consisting of two round instruments; the CGR-30P and the CGR-30C.

Each of these two instruments fit in a standard 3 1/8 inch instrument hole and together make up the CGR-30P Premium package. The Premium package is designed to provide full systems data and can be configured to suit the application and pilot’s needs. (EI also offers a Basic package that consists of a single CGR-30P instrument. The Basic package is pre-built and configured to display CHT, engine RPM (tachometer), fuel levels and volts. —Ed.)

IMG 1526 

These engine instruments are approved for installation in a wide range of single and twin engine aircraft by STC. Twin engine aircraft require two CGR-30P instruments. In most cases, a single CGR-30C has the capacity to display other needed data.

CGR, as you may have guessed, stands for Cluster Gauge Replacement. I’m now monitoring my engine and electrical system parameters, my fuel flows and quantities and OAT in two 3 1/8 inch instruments. The CGR-30P (“P” for Primary) is on top of the two-gauge stack; the CGR-30C (“C” for Cluster) directly below. I replaced six discrete instruments with two, and my panel is much cleaner.

CGR instruments have active TFT (thin-film transistor) displays with 262,144 colors and are sunlight readable.

The CGR system is almost infinitely programmable. For instance, the RPM channels can display data from engines with as few as two and as many as 12 cylinders. A few wiring changes allow the CGR combo to accommodate LASAR and Light Speed Engineering Plasma II and Plasma III electronic ignition systems.

In order to upgrade to the EI CGR system I removed an old analog manifold pressure gauge; a nice Horizon P-1000 electronic tachometer (a good instrument); a JPI EDM 700 with fuel flow (another good instrument); and three Aerospace Logic instruments: a fuel pressure/ammeter-voltmeter; a left and right fuel quantity gauge; and an oil pressure/oil temperature gauge.

I’ve been flying with the EI CGR-30P and -30C gauges for a month now, and although I’m still going back to the manual to learn all the capabilities of these instruments, I am very happy with my new glass panel displays.

I like the brightness and clarity of the displays; I like that the engine data that I consider critical is on the front page of the -30P and all the other engine data is concentrated in one spot and is very easy to access.

I like the fuel/trip planning and tracking feature; I like the comprehensive programmable alert and warning system; and I like… well, the list goes on. There are a lot of features packed into these two instruments.


Easy leaning

The leaning algorithms in the CGR instruments make it exceedingly simple to perform lean-of-peak (LOP) and rich-of-peak (ROP) mixture setting chores.

When leaning, I’ve found the EI display and data feed very easy to decipher.

In cruise I lean until what EI calls a “telltale marker”—I call it a white line—appears above the first cylinder to peak. The number-two cylinder on my Lycoming O-360 always peaks first. The white line and a numerical readout appear across the EGT portion of the EGT/CHT bar graph at that peak temp.

Since I’ve selected ROP leaning (carbureted engine) with the select knob, all that’s left for me to do is leave the mixture where it is (peak EGT) for maximum economy (at 75 percent power or lower in Lycoming engines, and at 65 percent power or less for Continental engines); or richen the mixture slightly until the digital readout indicates 80 to 100 degrees for a best power fuel/air mixture.

How do I know what percent power I set? Prior to installation of the CGRs I had to do it the old-fashioned way by referring to the power chart in my owner’s manual. Now it’s simple—after programming a page with data gathered from the owner’s manual and one short flight, a percent power number is displayed.

The first step: filling in the MACR

The first step in ordering an EI CGR-30P is to determine how you want to configure the pages of the instruments; then you can fill out the Marking and Configuration Requirements (MACR) document.

Pilots also have the option of selecting five non-primary functions to customize the CGR installation for their airplane. These functions include OAT, horsepower, volts, carburetor air temperature, fuel flow, hydraulic pressure, g meter, cabin altitude, induction air temperature, turbine inlet temperature (TIT), compressor discharge temperature—there’s even a carbon monoxide detector option.

Primary instruments

The first (main engine) screen of the -30P always displays RPM and CHT/EGT data for up to six cylinders. There’s also room on that page for three additional data points in the form of strip gauges.

The gauges that Piper configured in a small cluster in my Comanche are termed primary gauges. These primary gauges are specified by FAA regulation for each airplane. The applicable regulation for my Comanche—and for most piston-powered Pipers—is Civil Air Regulation (CAR) Part 3. Most piston-powered Cessna aircraft are also certified under CAR 3.

The primary gauges in my Piper Comanche are fuel pressure, oil pressure, oil temperature, left and right fuel levels, and amps. Since my Comanche has a constant speed propeller, the regulations also mandated a manifold pressure gauge.

There isn’t room to display all of the primary gauges on the -30P main engine screen. I chose to display fuel flow, fuel pressure and oil pressure along with the EGT/CHT bar graphs and the tachometer and manifold pressure displays the main engine page. (Since I could display the other primary gauges on the -30C, I chose those functions for the main page display of the -30P that I thought were most important.)

The other primary data that’s required as well as other operationally important data is in full view just below the -30P on the -30C. This list includes left and right fuel quantity (referenced to fuel level senders in the tanks), oil temperature, outside air temperature (OAT), carburetor inlet temperature, vacuum, volts and amps.

As I filled out the MACR, I wrote in the instrument face markings (red arc, green arc, yellow arc, redline) for each instrument by reference to the owner’s manual or POH. (This is typically something the installing shop will do. —Ed.)

The second screen is used to display functions that don’t need to be displayed continuously such as tach time, engine time, flight time, local and Zulu time.

The third screen in the -30P is the fuel quantities screen. This screen displays estimated fuel levels for different tanks—up to four tanks can be displayed—or total fuel quantity. Provisions for adding fuel and K-factor adjustments for the fuel flow display are on this page.

The fourth screen is the fuel data screen where trip- or leg-specific information based on fuel flow and GPS information is displayed. This data includes range, distance to destination, fuel reserve, time to empty, fuel used during flight and even fuel economy (in mpg). The information on this page is dependent on an RS232 data feed from the airplane GPS.

Since the fuel data screen is tied to the GPS and the fuel flow data, a change in any part of the fuel/time equation (such as a change in destination airport), power settings or mixture strength instantly updates important flight planning data such as, “Do I have enough fuel with my personal fuel minimums to get to my destination at this power setting?”

The big install

EIBox Steve

As I worked my way through the installation checklist I ran into a few hiccups but was always able to get support from Michael Roberts, Dave Arata, Daniel Bennett and Tyler Speed at EI.

The installation was straightforward. All the wires from all the data probes, the fuel flow transducer, the manifold and oil pressure transducers, the electrical system shunt and the resistive fuel level module (RFLM) are fed into three plugs that connect to and feed the engine data converter (EDC).

I mounted the EDC, the vacuum and manifold pressure (MAP) modules and RFLM on a shelf on the cabin side of the firewall. A single serial data wire moves the data stream from the EDC to the -30P and -30C.

The EI CHT probes are different from JPI probes in that they aren’t spring loaded to insure contact against the bottom of the hole. According to Arata, EI can supply the spring loaded probes if the customer desires.

This difference in probes is the reason the CHT numbers differed between the JPI system I removed and the EI system I installed—by approximately 30 degrees F. (The EI CHT readouts are cooler.) The hottest cruise power CHT I’ve seen during the last month is number four, at 343 degrees F.

Since my CHTs were never very hot—I’ve never seen 420 degrees F, the bottom of the yellow warning arc—with either system, this difference is not a big deal on my airplane. To me, the most important function from sampling EGT and CHT is detecting gross engine problems quickly. These problems always show up first on EGT systems. It’s critical to respond quickly to rapid temperature deviations from the norm.

The CGR system has two systems that do this automatically. The first system consists of setting normal operating ranges on both EGTs and CHTs. For instance, if your normal full rich low power EGT readout is 1,100 degrees F, set the range low limit at 1,000 degrees F. If your peak EGT is 1,500 degrees F, set the range upper limit for 1,150 degrees F. A variance outside either limit will cause the EGT bar in the graph to turn white and blink. Whenever a CHT falls outside the upper or lower range limit, that cylinder bar will turn red and blink.

There are four modes of operation used to display CHT/EGT information. Select mode is used to select the EGT and CHT for one cylinder. The temperatures are then displayed numerically at the bottom of the display.

Other modes include the Diff mode that displays the difference between the hottest and coldest CHT and EGT. These numerical values are shown at the bottom of the display as EGT-D and CHT-D.

Then there’s the Scan mode where EGTs and CHTs are continually scanned; the rate of scanning is configurable.

Finally there’s the Hottest mode where the hottest EGT and CHT are shown numerically.

The second way to spot deviations is to use the normalize mode. After setting cruise power, the normalize function can be selected by pushing and holding the Select knob for four seconds or by pushing the rotary knob to activate a cursor above the EGT/CHT bar graph display, then rotating the knob to select “normalize,” and pushing the knob in to select that function. Either method causes the bars of the CHT and the bars of the EGT of the current flight to be compared to bars recorded during a reference flight in the past. Differences are easy to spot.

Like other EI engine monitors, the CGR system incorporates microprocessors that analyze engine data as it is collected. When a deviation from normal operating levels is sensed, the device immediately triggers warnings so pilots can evaluate and take action if necessary.

The master nag

EI CGR Warning system

Each EI CGR system also has a sophisticated warning system that keeps an eye on aircraft systems—engine, fuel flow, electrical, fuel quantity, etc.—and alerts the pilot if these parameters stray.

Since I decided not to rearrange my panel to install the -30P and -30C within eight inches of my vision centerline (as recommended by Advisory Circular [AC] 23-1311), I installed the EI master caution and master warning lights in a row with the “Alt Inop” warning light slightly to the left of my airspeed instrument.

Caution and warning flags also appear on the faces of the instruments. A voice alert and warning signal that’s wired to the avionics audio panel (with panel-mounted on-off-acknowledge switch) is an option.

Each of the strip gauge displays will blink in tandem with the remote caution and warning lights if any function varies from the green arc. Pilots need only push the “E” (escape) button on the face of the instrument to acknowledge the alarm and stop the blinking.

Pilots can toggle between the EI CGR-30P between a variety of EGT/CHT data displays including ROP leaning; LOP eaning, EGT digital operating mode and CHT digital operating modes. The LOP leaning display show the first cylinder to peak, where all cylinders are in relation to the first to peak and the number of degrees the first to peak is lean of its peak.

Fuel transducers

To obtain the most accurate fuel level data, CGR buyers are urged to install EI’s P-300M magnetic fuel level sensors (only one moving part) since these sensors provide a linear voltage output and are extremely accurate; the original resistive-style float sensors can’t provide the same degree of accuracy.

In order to calibrate the arm length and arm travel of a P-330M, the original level sensor must be sent back to EI.

My resistive level sensors had been rebuilt and calibrated recently, and since I was installing a fuel flow transducer to monitor my fuel flows, I elected to connect my existing resistance-type senders to the EDC through the RFLM.

There are also provisions to use capacitive fuel level senders. An interface module such as the RFLM is not required for either magnetic or capacitive level sensors.

The after-installation calibration procedure was very easy (four levels) and the levels displayed on the -30P are consistent with my dipstick readings.

 Basic tech facts

Over Lap Connectors OLC 1

EI uses overlap connectors (OLC-1) throughout the installation wherever two (20 gauge or smaller) wires must be connected. The OLC-1 connector consists of a reddish colored nonconductive barrel. Wires are connected by tightening a tiny Allen head set screw after inserting each wire into opposite ends of the barrel.

EI developed the OLC-1 to resolve dissimilar metal corrosion problems and issues related to mis-crimped and/or poorly crimped wiring. At first I was flummoxed because it seemed like I needed a third hand to hold two wires in position and the barrel of the OLC-1 while carefully manipulating a tiny Allen wrench to install the set screw, but before too long I had it down.

The total electrical load for the CGR-30P, -30C, EDC, RFLM, all the pressure (and vacuum) sensors and the fuel flow sensor is less than two (12 VDC system) amps. This low electrical load insures that the pilot will be able to continue to monitor engine, fuel and electrical system health without the need to shut these systems down to preserve battery power in the event of a charging system failure.

Configuration screens

EI checklist screen

The EI CGR-30 system permits many configuration options. Fuel flow K-factor, EGT and CHT bar graph range settings, USB and data recording rates and fuel alarms—I set my fuel alarms to signal when my total fuel gets down to 10 gallons—and units (gallons, liters, etc.) information can also be configured.

Much of these configuration chores are done by the installing shop and except for the instrument face markings (red arc, green arc, yellow arc, redline) referred to earlier, these values may be changed as necessary in the field.

In addition, there’s a page on the CGR-30C for checklists. Checklists can also be configured for the airplane and pilot’s personal preferences. All monitored data can be downloaded and displayed on a spreadsheet or graphed. (Contact Electronics International for more information on this activity. —Ed.)

Daniel Bennett at EI’s sales and support department told me that installation times on Piper singles are reported to be between 12 and 18 hours. That seems about right for a savvy technician and well-equipped shop.

The hardest part for me was waiting for the box from EI to arrive after sending in the MACR. Now that the installation is finished and working well, I’m impressed.

I’m considering making a few more 21st century changes in my Comanche, but right now I’m just happy going to the hangar so I can continue to learn more about the features of my new glass panel engine monitor.

Steve Ells has been an A&P/IA for 43 years and is a commercial pilot with instrument and multi-engine ratings. Ells also loves utility and bush-style airplanes and operations. He’s a former tech rep and editor for Cessna Pilots Association and served as associate editor for AOPA Pilot until 2008. Ells is the owner of Ells Aviation (EllsAviation.com) and the proud owner of a 1960 Piper Comanche. He lives in Templeton, Calif. with his wife Audrey. Send questions and comments to .


Electronics International, Inc.



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