What is an engine analyzer? How does it differ from an EGT gauge?
This is not an exhaustive review of EGT-CHT monitoring equipment. It is an attempt to give you an overview of what you can get for your money, and what you should get for your money.
Practically speaking, there are two main types of systems; a scanner-analyzer, and a simple display. The simple display can show all four cylinders at once, or can be manually switchable to each cylinder. Within these two styles, you can get EGT only, CHT only, both EGT and CHT, and some number of other sensors depending on the brand and model you choose (for example, oil temperature can be included on some of them, plus other options).
The scanner-analyzers clearly add some safety factor in addition to the operational benefits. For example, you can tell immediately if a spark plug croaks while enroute, when you otherwise would not know until the next run-up and mag check. The analyzer (and knowledge of your mag harness setup) also enables you to identify exactly which plug is bad, which can save you time and money. An analyzer with the oil temp option is a very good safeguard against an inaccurate factory gauge or sender, when you might not even know that your oil is overheating.
If money is a major object, and you need to pare the system to the very minimum (but want all cylinders measured), and you are willing to use manual controls, consider a KSA Mixture-Mizer. It is a quality instrument by a little-known but dependable company. You can get it with four probes and a rotary switch, and it will show the data for whatever cylinder you select. You can get it with EGT only, CHT only, or both.
Opinions vary on this subject, but consider this. Outfits such as GAMI have concluded that you cannot hurt a non-supercharged engine via a too-high EGT. Their testing has concluded that the point of about forty degrees rich of peak is where the cylinders will be most heavily loaded at a less than optimum rod angle, therefore a peak pressure spike will occur if the engine is operated there. If an engine is carbureted and leaned to roughness, then to smoothness, without a gauge, it is unlikely to be within 40 degrees of peak on any cylinder (though it is possible). If you are running a fuel injected engine without instrumentation, it is more easily operated at forty degrees without awareness, but it is also easy to avoid. If you lean to slight roughness, you’ll be close to (or just lean of) peak, on at least one cylinder. As far as the engine is concerned, that’s easier on it than being 40 degrees rich. If you lean to roughness and then enrichen to max power (highest RPM or airspeed), you should end up at least 100 degrees rich of peak, and perhaps a bit more.
What definitely CAN hurt any engine is too high a CHT. You can prevent many more problems by managing CHT than you can by monitoring EGT. CHT can even be used to control leaning, though modern EGT probes give a faster indication. Note that peak CHT typically does not occur at peak EGT; it typically occurs in the range of 50-100 degrees rich of peak, closer to peak cylinder pressure and best power. Also note that CHT will drop much faster as you go lean of peak, than it does as you go rich of best power. The primary drawback to lean of peak operation is the significant reduction in power. In our Aero Center planes, we can’t typically regain power lost to leaning via more manifold pressure, with our unsupercharged engines.
If I had to make the hard minimum-cost choice, I would choose switch-selected multi-cylinder CHT, and if possible, supplementary oil temperature. The next step would be to add switch-selected EGT, with the top tier being a scanning analyzer (like the JPI or EI products). The scanning analyzers are typically much more “expandable”, with added function and sensors.
My suggestion is that you list the capabilities you must have to make a change worthwhile. Then list the features you’d add if you could, in order of precedence. Then list the available equipment, its cost (in original form and with added capabilities), and which of the functions it provides (both basic and enhanced). See if you can afford the minimum that makes a change worthwhile. If you pass that hurdle, then see where your budget crosses your desired capabilities, and what equipment falls in that ballpark. You can’t go wrong with any of the quality products that have a long and proven track record.