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Tuesday, 15 January 2013 04:22

Look Inside Your Engine—From the Cockpit! Part 1: Installation Featured

Written by  Charles Lloyd
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January 2013

I thought about adding a full-featured engine monitor to my panel for a long time, but I didn’t make the decision to commit until Insight Instrument Corp.’s G Series graphic engine monitors grabbed my attention at EAA AirVenture 2012.

This monitor series uses a color LCD coupled with a microprocessor to provide a wide range of engine monitor information and diagnostics.

The cost of an engine monitor was part of my reason for waiting all this time—as was my wish for improved engine monitor diagnostics to identify and minimize cylinder over-temp conditions. On the bright side, putting off the decision for so long did allow me to install a leading-edge engine monitor that does more than any other unit on the market today.

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G Series Products

Insight’s G Series monitors include four models. The G1, G2 and G3 are 2.25-inch diameter instruments for four- and six-cylinder aircraft, and these three packages vary in capability and price. Insight offers basic engine monitoring on its G1 with a typical price of $1,365; the G2 offers more features than the G1 and lists at $2,275 for a six-cylinder engine; and the full-featured G3 system, monitoring more than 20 data inputs plus data logging, runs $3,367 for a typical configuration.

According to Insight, its larger model G4 (the unit uses a 3.125-inch LCD display) and G4 Twin have received Transport Canada approval. As of this writing, the FAA now has the documents and data for STC approval in the United States, which is expected in the near future—possibly by the time you read this article. (Refer to Insight’s online price book—the website is listed in Resources at the end of this article—to price the G4 system for your specific aircraft. —Ed.)

I was in for some surprises during my initial operation of the G3—my procrastination had placed undue stress on my airplane’s engine.

Part one of this series describes engine monitor operation, plus the G3’s unique diagnostic capabilities. Part two will give you details about the ordering, documentation and installation of an Insight engine monitor.


Starting up the G3 is similar to starting a personal computer. As the instrument quickly boots, first you see screens that are part of the boot initialization process. Then the Main monitor screen appears, with cylinder and exhaust digital temperatures at the bottom of the screen that should compare with the OAT number in the upper left. This is a quick check that these sensors are functioning normally.

The digital CHTs at the bottom of the screen give an indication of when to apply higher power settings and prevent excess wear to a cold engine on a cold morning. An OEM cylinder temperature indicator attached to one cylinder typically starts indicating at 200 degrees F; Insight’s digital readout is superior and shows digital numbers before the bar graph rises.

Engine runup will show a slight increase in EGT temperatures, which is normal due to less efficient combustion. Applying takeoff power indicates increased EGT immediately. CHTs rise slowly. If you have engine baffle problems, these will show clearly as the specific cylinder temperature passes through the warning limit and turns yellow.

Reaching cruise altitude, Insight’s LCD monitor continues to show its superiority over gas discharge type displays. All of the digital and bar graph information on the G3 is very easy to read.

Level off and allow the engine temperatures to stabilize. Press the lower Select button to reset Lean of Peak (LOP) operation. (You can reset LOP at any time after takeoff, such as during climb.)

As leaning starts, the individual EGTs will rise. Finally the first EGT to drop will capture its LOP fuel flow displayed in its bar graph. Above the bar graph, an “L” temperature will indicate the lean of peak temperature (Figure 01, left).

In a carbureted engine, one cylinder will typically lean significantly before the others due to poor fuel distribution in the induction system. Continuing the leaning process will show the lean and rich of peak temperatures for all engine cylinders.

My O-470’s leanest cylinder can maintain smooth operation below 50 degrees F LOP. An arbitrary 50 degrees F LOP is the target for the leanest cylinder operation. Insight is the only engine monitor with these LOP features.

Previously, I’d enter an estimated average fuel flow of 12.3 gph for fuel planning using my Garmin GNS 530/430. This number typically showed fuel consumption two gallons more that the amount to top off the tanks for a two- to three-hour flight. After numerous flights, the Insight fuel flow monitoring system is tracking within 0.5 gallons or less compared to the top-off amount.

The Fuel Onboard feature records higher climb power fuel flows (as well as variations for cruise altitude and power settings) to integrate total fuel consumption (Figure 02, page 25).

All of this is with Insight’s new, improved high wing low pressure (no fuel pump) Fuel Flow sensor. The feature works well, and I am now more confident about endurance with Insight’s Fuel Onboard display than I was when using manual estimates.

Changing My Habits

While in flight with the G3, I experimented with carburetor air temperature settings at cruise power. After using an OEM carb air temp gauge for 13 years, I’m inclined to keep the temperature above the yellow arc at 40 degrees F (5 degrees C) and no higher—even on days with no visible moisture. This operation allegedly improves mixture distribution to all cylinders.

With the aircraft in cruise configuration, adjusting the G3 carb air temperature showed interesting results. Varying the carb air temperature as high as 60 degrees F showed that the fuel distribution at approximately 55 degrees F reduced the EGT spread significantly for this carbureted engine (Figure 01, page 25).

Different altitudes and power settings will vary the temperature spreads, but higher carb air temperatures still improve distribution. This lower EGT spread implies improved fuel distribution to all cylinders.

Who would have made this prediction without the data logging feature and digital graphics on the G series? I learned that it’s essential to test various settings to see if there are any that improve engine operation.

Why is that?

Initial experiences with an engine monitor may show operating conditions that you never expected to see. After the first takeoff, the CHT for the middle two cylinders (numbers three and four) immediately climbed higher than the remaining cylinders. Cylinder four’s temperature bar turned yellow immediately as the temperature passed 410 degrees F and continued to rise, approaching the red bar display at 450 degrees F. (The cylinder temperature limitation is 460 degrees F.) This condition was not good!

A color change on the G3 display brings abnormal conditions to your attention so you may immediately respond. The number-four cylinder bar turning yellow caught my attention.  (Figure 03, right) gives you an example of this easy-to-spot color change. Keeping the mixture rich, cowl flaps fully open, reducing to climb power and increasing airspeed to 110 knots indicated reduced this cylinder’s temperature to the high 300s.

Reflecting back to my pre-engine monitor days with one Cessna cylinder temperature gauge on the number-two rear cylinder head I recognized the risk of relying on minimal instrumentation: all of my previous operations had run this cylinder at high CHTs. I never realized the abusive operation taking place under the cowl.

The Cessna cylinder and oil temperature gauges show only a green band with no intermediate markings. One hint of problems in the past was that the oil temperature gauge would indicate higher than normal operating temperatures at IAS climb less than 110 knots. Now, with the G3 installed, I was able to conclude that the oil was absorbing as much heat as possible trying to cool these hot cylinders.

Other previous indications that something was not right included the oil temperature increasing during touch-and-go operations; climbing below 100 knots indicated airspeed or slowing down to pattern speeds during the summer caused oil temperature to increase significantly. Seeing actual numbers in the Insight displays helps with troubleshooting an engine problem.

 “Why is that?” was my nagging question. Something was probably not right with the air cooling baffles, I surmised.

Inspecting the rear inner cylinder baffles showed a 5/8-inch gaping hole between the baffle and case. This opening was a two-square-inch cooling airflow short circuit (Figure 04, page 27). Air surged into these large openings and did not cool the cylinders efficiently.

Looking in the Cessna Parts Manual showed that these inner-cylinder baffles should have additional soft material between the baffle and the case (Figure 05, page 27).

Sealing these openings corrected this problem (Figure 06, right). All cylinder temperatures are now more uniform, and the two middle cylinders do not go beyond 370 degrees F during lower-speed climbs. In addition, the Cessna CHT gauge indicates significantly lower than I’ve ever seen before. What a difference proper engine baffling will make in engine operation.

Other Unique Features

Other diagnostic information unique to the G3 sensors and software design are the thermocouple Probe Diagnostic System display. This display will indicate when a thermocouple is failing—a useful thing, as a bad thermocouple may resemble an engine problem. Insight is the only monitor with this diagnostic feature.

The EGT Periodic Temperature Variation function performs a complex analysis on the EGT data. The result is the ability to reveal an exhaust valve problem undetectable by any other means. You will see valve problem indications before completely burning a hole in a valve or experiencing a catastrophic valve failure.

The Engine Vibration screen shows unique vibration harmonics. This diagnostic shows cam, crankshaft and generator vibrations that could be indicative of a failing bearing or other unsatisfactory condition that requires further investigation.

The SD memory card logs all variables every second that the G3 monitor is on. Remove this card periodically and import the data into an Excel spreadsheet and you will know more about your aircraft’s engine’s performance than you ever expected. The table shows all the information logged every second of engine operation.

How long will the two-gigabyte card last in your operations? “Longer than you will fly your aircraft,” is the answer from Insight.

If you want to see a graphic display of your engine data, upload this data to the Savvy Analysis website. This is the application I used to evaluate the impact of carburetor air temperature control versus fuel air distribution (Figure 06, above). The best temperature I found to improve operation was 55 degrees F.


The Insight G3 Engine Monitor offers more that just a way to properly lean an engine. For me, investigating high cylinder temperature conditions led to improved engine cooling.

Yes, you can look over your baffling and spot irregularities without an engine monitor. However, the monitor confirmed there was a problem—and the monitor confirmed that the baffle repairs resulted in cooler engine operation.

With the G3 installed in my aircraft, leaning is now more precise. I have better fuel distribution and incremental fuel savings using the EGT lean of peak information display.

Insight’s leading edge diagnostic technology can help justify the installation of the G3. Moreover, it will give you confidence about your engine’s proper operation and could allow for early detection of an engine problem before exceeding critical engine parameters.

Charles Lloyd has logged 10,000 hours since his first flying lesson in 1954. He worked for Cessna Aircraft for 16 years. Lloyd retired as captain of a Citation Encore Plus for a major fractional aircraft ownership company. He flies a tricked-out 1966 Cessna 182—also known as Bill—that is a great business tool for his real estate investment company. Send questions or comments to This email address is being protected from spambots. You need JavaScript enabled to view it..



Insight Instrument Corp.
P.O. Box 194
Buffalo, NY 14205-0194
(905) 871-0733
Insight’s Price Book
(For all G Series monitors) files/Insight Price.pdf

Savvy Analysis


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