engine monitor for carbureted O360?

GeorgeC

GeorgeC

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GeorgeC
Paging Ted...

I've read a number of posts on probe failure on this and other fora.

On a carbureted engine (assuming it is leaned aggressively at 65% power, no LOP ops), does the value of monitoring all four cylinders outweigh the cost of having 4 times as many probes to fail? Is a single EGT/CHT probe on the hottest (#3?) cylinder sufficient?
 
GeorgeC said:
Paging Ted...

I've read a number of posts on probe failure on this and other fora.

On a carbureted engine (assuming it is leaned aggressively at 65% power, no LOP ops), does the value of monitoring all four cylinders outweigh the cost of having 4 times as many probes to fail? Is a single EGT/CHT probe on the hottest (#3?) cylinder sufficient?
Click to expand...

I have one in my 1977 Cessna 172n with an O360. To be honest I would almost feel like I was flying blind without it. I have had it for 5years and never had a probe failure. I drove my A&P crazy with it at first because apparently when you upgrade the 172n to an O360 they have a habit of running warm. Especially in the hot Florida summers. But the trick is to reduce the throttle a little and lean properly. The engine monitor gives you the proper tools to lean it correct. And the monitor alerts you if any one cylinder is too warm.

I have caught battery and alternator problems before they grounded me in desolate places. And when all is running well, it is nice to know that too. Like yesterday and today when we crossed the Everglades. Or when we flew from Florida to Phoenix over the Rockies. We also have an FS450 hooked up to provide the fuel totalizer function. It is nice to know exactly how much fuel you are using, how much you have and how much you will need to finish the trip and how much reserve you will have. Or to be able to quickly find out out how much you will have if you divert.
 
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GeorgeC said:
On a carbureted engine (assuming it is leaned aggressively at 65% power, no LOP ops), does the value of monitoring all four cylinders outweigh the cost of having 4 times as many probes to fail?
Click to expand...
I think so, and I've put my money where my mouth is on three airplanes with a total of four O-320/360 engines.
Is a single EGT/CHT probe on the hottest (#3?) cylinder sufficient?
Click to expand...
I think not.

In 20 years of flying with JPI EDM-series engine analyzers on three different airplanes, I've found that the hottest EGT and hottest CHT aren't always the same cylinder, and that the hottest cylinder moves around a lot. They have also helped me identify and isolate various issues with ignition and induction. My experience tells me that if you really want to know what's going on inside your engine, you need all-cylinder EGT/CHT instrumentation. That may not have to be a full-blown analyzer, but it does mean probes on all four cylinders (or six if you have them).
 
If you are 'leaned aggressively' you will be LOP. I've had monitors on 6 engines I've owned over 25 years and over 2700 engine operating hours and I can't recall a probe problem except a carb temp probe that was not expensive to change. I like having all the information, and if you get one, don't forget the fuel flow, I hate flying without one.
 
Henning said:
If you are 'leaned aggressively' you will be LOP.
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In a carbureted O-360? Maybe on one cylinder, perhaps on two, but not more than that -- the engine will be too rough otherwise. For reasonably smooth all-cylinder LOP operations, you need really well-tuned fuel injection.
 
Henning said:
If you are 'leaned aggressively' you will be LOP. I've had monitors on 6 engines I've owned over 25 years and over 2700 engine operating hours and I can't recall a probe problem except a carb temp probe that was not expensive to change. I like having all the information, and if you get one, don't forget the fuel flow, I hate flying without one.
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+1 on the fuel flow now that I've done both. The one HP I fly that has no fuel flow indicator feels naked :)
 
Ron Levy said:
I've found that the hottest EGT and hottest CHT aren't always the same cylinder, and that the hottest cylinder moves around a lot. They have also helped me identify and isolate various issues with ignition and induction. My experience tells me that if you really want to know what's going on inside your engine, you need all-cylinder EGT/CHT instrumentation. That may not have to be a full-blown analyzer, but it does mean probes on all four cylinders (or six if you have them).
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I have only had my engine analyzer a short period of time so I can't speak to the probe failure issue. The bottom line is that probes are not that expensive and are easy enough to change out if I'm ever faced with that situation. We did a full engine overhaul with new cylinders this annual and after spending that much on my engine, I wanted to make sure I could take care of it. When I was researching the analyzer options out there, there just was not enough difference in the money to not put full instrumentation on each head, exhaust and carb. Like Ron said, I've seen my hottest cylinder shift. It is comforting to me being able to see what is happening with all cylinders. If money is tight for you, check out all of the options that Electronics International has. They have a variety of ways you can go and still be able to monitor all cylinders fairly inexpensively. Their CGR-30P monitor is a lot of bang for the buck.
 
GeorgeC said:
Paging Ted...

I've read a number of posts on probe failure on this and other fora.

On a carbureted engine (assuming it is leaned aggressively at 65% power, no LOP ops), does the value of monitoring all four cylinders outweigh the cost of having 4 times as many probes to fail? Is a single EGT/CHT probe on the hottest (#3?) cylinder sufficient?
Click to expand...

I'd wager that a large percentage of the posts you read about probe failures were an attempt to isolate a problem that a probe indicated. Checking to see if a problem is actually a probe failure does not mean the probe actually failed. It is just a step in the diagnosis. I have had several probes checked to see if it was a probe failure. It never was.
 
GeorgeC said:
Paging Ted...

I've read a number of posts on probe failure on this and other fora.

On a carbureted engine (assuming it is leaned aggressively at 65% power, no LOP ops), does the value of monitoring all four cylinders outweigh the cost of having 4 times as many probes to fail? Is a single EGT/CHT probe on the hottest (#3?) cylinder sufficient?
Click to expand...

I don't think probe failure is the major expense associated with engine monitors--initial purchase / installation cost is. Typically, when carbureted engine owners ask if an engine monitor is worthwhile, it's because one of the traditional "paybacks" on an engine monitor for FI engines is LOP operation, which is not guaranteed on a carbureted plane, so they're looking for other reasons to have one.

I installed an Insight G3 on my Lyc O360 last year, and am glad I did. I like the additional data available on my engine in flight, and the detailed data available on the SD card post-flight.

One day, it may help me identify or diagnose an engine issue before it becomes a critical problem in flight.

But until / unless it saves my bacon, it'll be hard to say that there's financial justification to the purchase.

Why spend $$ on Rosen sun visors, when you can tape gray plastic film to the window? Why buy a GTN 650 when you can get a KLN-89B for less?

For most of us recreational flyers, there's no financial justification to anything associated with aviation. You spend the money 'cause you want to. Up to you to decide if an engine monitor is something you want to spend money on.
 
BTW, in some 18,000 probe-hours flying with JPI engine analyzers, I've yet to have a probe failure.
 
I installed a JPI 730 with fuel flow for my carbureted O360 a couple of years ago shortly after I purchased my bird. I think it is definitely worth it and I would feel naked without it. The first immediate benefit is understanding my fuel situation PRECISELY. my fuel flow is accurate to within one gallon. I can now plan and monitor my fuel state in long flights and determine if I really need to stop for fuel. It definitely has helped me avoid unnecessary/overly conservative fuel stops. Secondly, it definitely has help me manage CHTs far better than I was. The single probe connected to #3 provided insufficient information and in fact my hottest cylinder is typically #4. I have modified how I climb after takeoff and can adjust that real-time depending on what I see in the JPI. I am definitely managing my temperatures much better and I like to think that will be helpful in terms of engine health and longevity. Finally, it goes without mention that leaning will be much more precise than using a single EGT specially when you realize the leanest cylinder does move around in my O360.


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On a carbed O-360, lean till rough, then clean it up, unless you want another TV screen to look at.
 
No two cylinders on any engine run the same. If you really want to know what's going on, you need multiprobe. EGT and CHT. It is an awesome diagnostic tool. When something does go wrong, you can get ample warning and also it speeds up diagnostic time in the shop. No guessing which cylinder is the problem. You know.

Get the monitor. You won't be sorry.
 
As mentioned while leaning aggressively isn't going to be easy on a carb'd plane (or even an injected plane unless the injetcors are reasonably balanced), there's still advantages to multipoint analyzers. It lets you know if something is wrong with one cylinder (and identifies which one) even if not otherwise readily apparent. It certainly beats the trial and error method of finding a fouled plug.
 
flyingron said:
As mentioned while leaning aggressively isn't going to be easy on a carb'd plane (or even an injected plane unless the injetcors are reasonably balanced), there's still advantages to multipoint analyzers. It lets you know if something is wrong with one cylinder (and identifies which one) even if not otherwise readily apparent. It certainly beats the trial and error method of finding a fouled plug.
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I found that out. I thought i had a bad mag, but the engine analyzer showed me exactly which plug was causing the problem.
 
Ron Levy said:
In a carbureted O-360? Maybe on one cylinder, perhaps on two, but not more than that -- the engine will be too rough otherwise. For reasonably smooth all-cylinder LOP operations, you need really well-tuned fuel injection.
Click to expand...

I had two of them on analyzers, when I would have the turbos online I could get the temp spreads inside a dot, with the turbos off line, I'd have to crack the carb heat.
 
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