Is a 6 Cylinder Engine Monitor Overkill on a O-300A

How to keep the Cessna 170 flying and airworthy.

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pdb
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Is a 6 Cylinder Engine Monitor Overkill on a O-300A

Post by pdb »

I have about 500 SMOH on my engine which has performed flawlessly so far (with the exception of my overhauled to new specs Continental (Bendix) mags.)

Given the age (technology) of these engines and the inefficiency of the induction system, is it worth the time and expense to install a 6 cylinder engine monitor? If so, what would the crowd recommend?
Pete Brown
Anchorage, Alaska
N4563C 1953 170B
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GAHorn
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Re: Is a 6 Cylinder Engine Monitor Overkill on a O-300A

Post by GAHorn »

Anything more than an oil pressure, oil temp, and Tach is overkill…. :lol: :lol: :lol:

I have a single cyl CHT and a Manifold Pressure gauge… and that’s largely overkill, IMO.

Obviously this is a highly personal choice and there are certainly valid arguments for as much instrumentation as possible in an effort to keep close tracks on any engine performance…. and that’s certainly useful info on ANY engine….

An EGT gauge , even a single cyl EGT… is not “necessary” for this engine because of its’ crude induction and carburetor system..unless you are interested in your “leanest” cylinder…. but if all you need is a safe method of leaning…the Owners Manual method (Lean to max RPM, then enrich to first drop in Max RPM) is completely “up to the task” for this engine. (Personally I lean to max and continue to lean until first drop..then enrich back to max rpm and leave it there. It’s my personal method which I prefer and have had zero problems.)

But if the question is: What is the absolute necessity? and what is the most “bang for the buck”… this simple engine doesn’t need much more than oil press, oil temp, and RPM info….and those three are critical, IMO.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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mit
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Re: Is a 6 Cylinder Engine Monitor Overkill on a O-300A

Post by mit »

I have had a GEM for 30 years nice to have.
Tim
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darhymes
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Re: Is a 6 Cylinder Engine Monitor Overkill on a O-300A

Post by darhymes »

I guess it depends on what you want out of an engine monitor. I think it is really nice to have CHT on all cylinders no matter what. Beyond that, my monitor has proven to be a helpful diagnostic tool when it showed a dead cylinder after startup one time…and it also let me know when the problem was solved and the engine was operating normally. From the first flight with the monitor, it showed me that two of my cylinders were getting really hot during climb. While I haven’t fixed that problem (working on it and making progress) it has allowed me to confidently continue to fly the plane while managing throttle in the climb to keep the temps comfortably lower. Before that, I flew blissfully ignorant looking at one CHT thinking the rest must be fine.

As for leaning, I have found the end result to be nearly similar if I use the monitor, the book method, or the good ol’ first knuckle method. The monitor is helpful for making small adjustments in mixture during extended cruise and during long climbs and descents. I would have to look through my logbook to see if there has been any change in fuel usage but if there is, it is probably minimal.

I have the Insight G2, by the way. It was nearly the same price as a JPI but with a modern, easily readable display and an SD card that pops right out for easy data downloads. It also shows fuel flow, fuel usage, OAT and carb temp. Overkill? Probably...but I really like having it on board.
Dustin Rhymes
'55 170B N4410B S/N 26754
'06 G550 “The Silver Bullet”
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pdb
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Re: Is a 6 Cylinder Engine Monitor Overkill on a O-300A

Post by pdb »

Thank you all.

I don’t see the 6 cylinder monitor as a leaning too but rather as an tool to monitor CHTs, all of them, and to help analyze any engine problems that might start to crop up. Still undecided if it’s worth the expense. I have been able to keep my plane in the air for the last 25 years without but it would be nice…..
Pete Brown
Anchorage, Alaska
N4563C 1953 170B
http://farm3.staticflickr.com/2366/2527 ... 4e43_b.jpg
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DaveF
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Re: Is a 6 Cylinder Engine Monitor Overkill on a O-300A

Post by DaveF »

I've had an engine monitor and electronic fuel flow for more than 20 years. I like the data they provide. They don't keep the airplane aloft, but they've helped me see problems early and fix them quickly. And I can get more information on run-up than just mag drop and feel. But I understand wanting to keep things as simple as possible.
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Larry E
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Re: Is a 6 Cylinder Engine Monitor Overkill on a O-300A

Post by Larry E »

I have been using an engine analyzer in my other airplane for several years now, and have once more received a huge benefit from the information it provides.

The weekend was spent in Michigan and the flight home was just under 150 NM. After a stop half way to clear Customs, the final leg home was proceeding well, but I noticed that #2 EGT was not in it’s normal position as the warmest cylinder. I usually lean the mixture to set #2 at 1250 degrees F and all other cylinders are a little cooler than this. During this flight – after setting #2 to 1250 F – I noticed that #3 was 20 degrees hotter – it’s normally 20 cooler. #1 and #4 were in their usual place with respect to #3, so something might be happening to number 2???

All 4 CHT’s were exactly the same as always – within 10 degrees of each other, and the engine was running fine. Probably an instrument or probe error – no need to land right away. And with the 20 knot tailwind I would be home in less than 30 minutes. But I kept an eye out for good landing areas and decided to investigate after arrival. Nothing changed and we landed uneventfully.

This shows what I found on the #2 exhaust pipe. The crack was ¾ of the way around the tube. Without an analyzer I would not have been suspicious, and would not have gone looking for a reason to explain the anomaly . If it had let go on the next flight, I might not be writing to talk about the advantages of an engine analyzer.
Picture1.jpg
This is typical of the information an analyzer can give you. As Dave mentions above, it can sometimes save a lot of stress and money.

Our 170 has just got 6 new cylinders, a new camshaft, new bearings - and a EI UBG-16.

Larry
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GAHorn
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Re: Is a 6 Cylinder Engine Monitor Overkill on a O-300A

Post by GAHorn »

THAT’s a great post, Larry!
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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bgiesbrecht
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Re: Is a 6 Cylinder Engine Monitor Overkill on a O-300A

Post by bgiesbrecht »

darhymes wrote:I guess it depends on what you want out of an engine monitor. I think it is really nice to have CHT on all cylinders no matter what. Beyond that, my monitor has proven to be a helpful diagnostic tool when it showed a dead cylinder after startup one time…and it also let me know when the problem was solved and the engine was operating normally. From the first flight with the monitor, it showed me that two of my cylinders were getting really hot during climb. While I haven’t fixed that problem (working on it and making progress) it has allowed me to confidently continue to fly the plane while managing throttle in the climb to keep the temps comfortably lower. Before that, I flew blissfully ignorant looking at one CHT thinking the rest must be fine.

As for leaning, I have found the end result to be nearly similar if I use the monitor, the book method, or the good ol’ first knuckle method. The monitor is helpful for making small adjustments in mixture during extended cruise and during long climbs and descents. I would have to look through my logbook to see if there has been any change in fuel usage but if there is, it is probably minimal.

I have the Insight G2, by the way. It was nearly the same price as a JPI but with a modern, easily readable display and an SD card that pops right out for easy data downloads. It also shows fuel flow, fuel usage, OAT and carb temp. Overkill? Probably...but I really like having it on board.
I'll have to check yours out next time I'm up at CCB. I am pondering one as well. How do you get the CHT readings? gasket style sender or probe? I don't think my cylinders (millenniums) have the bosses for the probes but I might be missing something.
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IA DPE
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Re: Is a 6 Cylinder Engine Monitor Overkill on a O-300A

Post by IA DPE »

1955 C170B N2993D s/n 26936
1986 DG-400 N9966C
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Re: Is a 6 Cylinder Engine Monitor Overkill on a O-300A

Post by Larry E »

The article mentioned by IA DPE is an excellent article by Mike Busch, and I agree with everything in it - including the idea that exact numbers for EGT is not important.
What IS important is relativity - how each cylinder is behaving with resect to the others. I should have emphasized this in my post. However, I mentioned that I go for 1250 degrees on #2 cylinder. There is a reason for this. The engine is a four cylinder, inverted, in-line made for the Spanish Air Force in the 1950's using pre-world war II technology. There is no technical information or support available, and only 3 in service on this side of the Atlantic (and we all have engine analyzers). The exhaust valves and guides are VERY susceptible to high EGT's, and had caused so many failures for the Spanish military that they completely overhauled them at 300 hours. I have put over 700 hours on this engine without overhaul and all indications are it is still in very good condition. I have had zero exhaust valve/guide problems.
This could be luck. But it might also be that by respecting some arbitrary maximum value we are getting more life out of the engine. We are not concerned with efficiency. We just want to keep these antiques flying.

Larry
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Re: Is a 6 Cylinder Engine Monitor Overkill on a O-300A

Post by darhymes »

I'll have to check yours out next time I'm up at CCB. I am pondering one as well. How do you get the CHT readings? gasket style sender or probe? I don't think my cylinders (millenniums) have the bosses for the probes but I might be missing something.
I’d be happy to show you my setup. My cylinders are Continental with wells for probes. I’ll pm my contact info.
Dustin Rhymes
'55 170B N4410B S/N 26754
'06 G550 “The Silver Bullet”
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Re: Is a 6 Cylinder Engine Monitor Overkill on a O-300A

Post by GAHorn »

I’m (respectfully) not a true-believer in everything Busch.

As for the statement “What IS important is the GAMI spread”….. Mr. Busch does not reveal how we are to manage that particular regime in a carbureted engine. (And he creates that term “GAMI-spread” as a shortcut to describe the different relative mixtures experienced by individual cylinders…. very convenient term for him to promote since the GAMI injector people are also his supporters/sponsors.)

I’ve operated the 80-octane rated IO-470 in a Beech Debonaire as well as the 100-octane rated IO-470 in the Beech Baron….and I found the exact opposite to be true as regards EGT indications….the 100-oct Baron engine had hotter EGTs than did the Deb.
And, Since those are fuel-injected engines … I suggest them to be much more appropriate engines to use in any comparison of low vs high compression engines and their relative EGTs….and therefore do not agree with his conclusion on that. (The carbureted O470 engines he uses as examples are much less worthy test-subject-engines for either exhaust-gas-temps OR cylinder head temp comparisons …because of the disparate carburetors and induction systems of those engines being incomparable.)

Additionally, the comments regarding peak digital EGT readings being reached only 1/4 of the time exhaust-gas flow occurs…while certainly true…(the EGT probe/gauge system “averages” the actual gas temperatures)… THAT is still useful. It is also the exact same situation which occurs in the early Alcor “relative temp” gauges of which Mr. Busch seems to hold a higher opinion…. I.E. they also only see exhaust-gas as an “average” indication.

Further…the relative EGT indications are not all that different in reliability than the CHT indications upon which he places higher import…. because the CHT gauge ALSO is only an “average” of all four strokes of the engine…. The heat being displayed is that which is generated only during the power stroke…exactly the same as the EGT…. the difference being that CHT indications are influenced by more than simple combustion-gases, also being affected by engine-baffle condition, relative wind, angle-of-attack VS throttle-setting, etc etc. I.E. there’s no reason to award the two different indication systems unrelated levels-of-import for engine operation. I imagine everyone agrees a CHT instrument is more important than EGT engine-operations… but CHT is only required equipment for those airplanes that have cowl-flaps.

Mr. Busch is a proponent of LOP operations. This is exceedingly difficult to accomplish in carbureted engines due to the wide variations of induction-tube designs, lengths, and the well-known inaccuracy of carburetor-venturi/fuel-air distribution. It is very likely that when the 170 Owners Manual method of leaning is utilized that the leanest cylinder is operating at LOP and the rest of the cylinders are operating in a combination of Peak and ROP. (Mr. Busch expresses a belief (and has written in the past) that that ROP is a very dangerous regime because any irregularity that may occur which causes a cylinder to run leaner will bring that cylinder/valve-assy into a dangerous overheat condition. To me, that seems to contradict what he has written in the article linked in this thread …where he implies that EGTs are virtually unimportant.)

Further, since the C145/O300 engine is almost always being operated at or below 70% power there is very little likelihood that any damage will occur if the Owners Manual method is used…. and that method does not require any instrumentation beyond the tachometer.

IMO
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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IA DPE
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Re: Is a 6 Cylinder Engine Monitor Overkill on a O-300A

Post by IA DPE »

I read his columns sometimes and give his thoughts as much consideration as I give any other writer. Sometimes thought provoking, sometimes full of b.s.

The only opinion I personally have on precise mixture control/ EGT monitoring is that fuel injected engines with tuned systems may benefit from proper use of the data. Our crude engines with uneven fuel distribution systems likely would suffer if trying to run LOP or such but like George says, do fine using the tried and true old technique.

I've got an EGT, CHT, and Oil Temp gauges. I look at Oil Temp in hopes it gets warm enough to boil off moisture, but admit to paying little attention to the EGT especially. I lean every flight with just the Tach and it works fine.
1955 C170B N2993D s/n 26936
1986 DG-400 N9966C
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Re: Is a 6 Cylinder Engine Monitor Overkill on a O-300A

Post by DaveF »

And how do we know that carbureted engines don’t run well lean of peak? Because we have engine monitor data that tells us. Without a monitor you don’t actually know what each cylinder in your engine is doing.

I’ve heard of a few rare carbureted engines that have such even F/A ratios that they will run LOP. Without a monitor we wouldn’t know that. At some MP, RPM, carb heat, and other conditions, my engine has rarely come close. But I can’t reliably reproduce it.
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