Another 100-Hour Letdown, Comparing GA With Autos

[Aeric]

So the airplane goes in for a 100-hour yesterday and the mechanic calls me to tell me number 2 cylinder has very low compression. It's the exhaust valve. A couple hundred hours ago the same thing happened with number 1 cylinder. These are semi-recent (~500 hr.) Superior Milleniums. The first time I had asked a few people in the know if Millenium was a good cylinder, and the answer was always yes. I know that the original TCM cylinders were not so good, and there is even an AD out on most of them calling for a retarding of ignition timing to reduce the likelihood of cylinder cracks developing. The engine is an O-200 in a 150L. Here are some facts with a few questions for those of you in the know: The O-200 has a specific output of only .50 hp/cubic inch. My automobile engine has a specific output of 1.32 hp/cubic inch. The O-200 turns a max rpm of 2750, my car's engine has a redline of 6800. The O-200 has 4 exhaust valves, my car's engine has 12(more of 'em to have trouble with). My car's engine now has about 3500 hours on it (140,000 miles) with absolutely no problems whatsoever, and I would fully expect it to go another 140,000 trouble-free miles. My O-200 has about 1100SMOH and about 500STOH. Why does an seemingly understressed engine have such issues with burned exhaust valves? It would be even worse with the OEM cylinders and their "cracking". I fully understand that an O-200 spends more time at wide open throttle but given the fact that the displacement is so large in comparison to the power output, and that at cruise the engine is producing aroud 60-70 horsepower, loafing along at around 2200-2300 rpm, why the unreliability? There are quite a few times that my car is at wide open throttle, and at highway speeds it's constantly making a large percentage of what the O-200 is at cruise. Even given the fact that a lot of the time my car engine is not producing a lot of power, I don't understand the disparity, after all, I'd rather have the more reliable engine in something that puts me thousands of feet above the ground. Any thoughts?

 

[Skylane81E]

You car engine is ill equipped to handle the usage your O200 sees.

 

[MSPAviator]

I practically got tarred and feathered the first time I mentioned it, but I really wish more modern engine technology was available in the majority of the GA fleet. Seems to me like most of the powerplants we have are just glorified 1935 technology.

 

[Henning]

So the airplane goes in for a 100-hour yesterday and the mechanic calls me to tell me number 2 cylinder has very low compression. It's the exhaust valve. A couple hundred hours ago the same thing happened with number 1 cylinder. These are semi-recent (~500 hr.) Superior Milleniums. The first time I had asked a few people in the know if Millenium was a good cylinder, and the answer was always yes. I know that the original TCM cylinders were not so good, and there is even an AD out on most of them calling for a retarding of ignition timing to reduce the likelihood of cylinder cracks developing. The engine is an O-200 in a 150L. Here are some facts with a few questions for those of you in the know: The O-200 has a specific output of only .50 hp/cubic inch. My automobile engine has a specific output of 1.32 hp/cubic inch. The O-200 turns a max rpm of 2750, my car's engine has a redline of 6800. The O-200 has 4 exhaust valves, my car's engine has 12(more of 'em to have trouble with). My car's engine now has about 3500 hours on it (140,000 miles) with absolutely no problems whatsoever, and I would fully expect it to go another 140,000 trouble-free miles. My O-200 has about 1100SMOH and about 500STOH. Why does an seemingly understressed engine have such issues with burned exhaust valves? It would be even worse with the OEM cylinders and their "cracking". I fully understand that an O-200 spends more time at wide open throttle but given the fact that the displacement is so large in comparison to the power output, and that at cruise the engine is producing aroud 60-70 horsepower, loafing along at around 2200-2300 rpm, why the unreliability? There are quite a few times that my car is at wide open throttle, and at highway speeds it's constantly making a large percentage of what the O-200 is at cruise. Even given the fact that a lot of the time my car engine is not producing a lot of power, I don't understand the disparity, after all, I'd rather have the more reliable engine in something that puts me thousands of feet above the ground. Any thoughts?

It seems like you have it all figured out already so are you sure you want to be informed how wrong you are? If Toyota couldn't do it in over 3 years and millions of dollars, you think you're gonna with their product? Only if you cast the 2.8 Common Rail TDi in Magnesium or Aluminum. You'll want to add a 1.3:1 roots blower as well.

 

[Tom-D]

We all know the prop can only be turned so fast before it become ineffective, that is why the 0-200 only turns 2800 max, and must make its horse power from being over bored to make torque.

Your car engine has no restriction in that manner so it makes it horse power by high RPM.

we can reduce prop speed by a reduction gears box but that is a higher cost of production and more parts to fail.

Superior has lost its reputation for being the best cylinder on the market. Its first production runs were great cylinders, but not so much lately.

ECI has a major alteration to he 50 cubic inch Continental cylinders for the C-145/0-300 and the 0-200 in as much as they place a positive exhaust valve rotator on the cylinder which has pretty much solved the problem of burned exhaust valves.
It does require an STC to place them on an engine, it does come in the box, and is ready to be submitted to the FAA by your A&P-IA.

 

[Henning]

We all know the prop can only be turned so fast before it become ineffective, that is why the 0-200 only turns 2800 max, and must make its horse power from being over bored to make torque.

Please explain the O-200 as it is applied in a Formula racer then?

 

[Tom-D]

Please explain the O-200 as it is applied in a Formula racer then?

Highly modified.

 

[Henning]

Highly modified.

Please read the rules again. BARELY modified.

 

[DaleB]

I feel your pain... and share some degree of puzzlement. And in fact, if you look at the NEW aircraft being manufactured, you'll see there is a lot of newer technology being hung onto the 1930s vintage engine designs. Not nearly enough, but some.

The biggest difference is that your car engine isn't making 75% of its rated power ALL the time, with long stretches at 100% output. You accelerate at some fraction of rated HP, then cruise along not using anywhere near the power your engine can produce. Your airplane can't loaf along at cruise using 20% power. Well, not very well at least.

If you want to know why your airplane engine isn't as advanced as your car engine, think about this... HOW old is your airplane?

 

[Aeric]

You car engine is ill equipped to handle the usage your O200 sees.

I do understand that these are two very different applications, but the two engines are both reciprocating internal combustion engines with two even more different reliability records.

 

[Aeric]

I practically got tarred and feathered the first time I mentioned it, but I really wish more modern engine technology was available in the majority of the GA fleet. Seems to me like most of the powerplants we have are just glorified 1935 technology.

My thoughts precisely...

 

[Aeric]

It seems like you have it all figured out already so are you sure you want to be informed how wrong you are? If Toyota couldn't do it in over 3 years and millions of dollars, you think you're gonna with their product? Only if you cast the 2.8 Common Rail TDi in Magnesium or Aluminum. You'll want to add a 1.3:1 roots blower as well.

I definitely don't have it all figured out, hence my posting asking for viewpoints from others who are more knowledgeable than myself. I agree with your point about someone else not being able to do it better, although Rotax might have done it.

 

[Henning]

I definitely don't have it all figured out, hence my posting asking for viewpoints from others who are more knowledgeable than myself. I agree with your point about someone else not being able to do it better, although Rotax might have done it.

Rotax has not broken any molds with regards to aviation recip engines. I would build a 2 seat tandem twin ampib with twin 914s. I'm all for water jackets to provide heater core water.

If I can ever talk Ben into building a scale 7755 and scaling up the H-1 on Volpar 18 tri gear. Hmmm... Nose of a BE 18 A/F...

 

[Tom-D]

Please read the rules again. BARELY modified.

Just because they look like 0-200s doesn't mean they are.

 

[Aeric]

We all know the prop can only be turned so fast before it become ineffective, that is why the 0-200 only turns 2800 max, and must make its horse power from being over bored to make torque.

Your car engine has no restriction in that manner so it makes it horse power by high RPM.

we can reduce prop speed by a reduction gears box but that is a higher cost of production and more parts to fail.

Superior has lost its reputation for being the best cylinder on the market. Its first production runs were great cylinders, but not so much lately.

ECI has a major alteration to he 50 cubic inch Continental cylinders for the C-145/0-300 and the 0-200 in as much as they place a positive exhaust valve rotator on the cylinder which has pretty much solved the problem of burned exhaust valves.
It does require an STC to place them on an engine, it does come in the box, and is ready to be submitted to the FAA by your A&P-IA.

We've heard how well the GO-300 (I think that's the ID) went over :wink2: Funny how a large number of problems were caused by pilots operating that engine at too LOW rpm, being used to typical engines.
And yes, the O-200 is an oversquare design, but I thought that undersquare engines typically are the lower revving, torque-rich designs...now I'm really confused
I wonder if I can replace the Superior cylinder with the new ECI cylinder, one by one as they continue to fail, kind of like a mix and match (just kidding!).

 

[Tom-D]

I wonder if I can replace the Superior cylinder with the new ECI cylinder, one by one as they continue to fail, kind of like a mix and match (just kidding!).

Yes you can.

But I'd grind the exhaust valve and keep going.

 

[Aeric]

I feel your pain... and share some degree of puzzlement. And in fact, if you look at the NEW aircraft being manufactured, you'll see there is a lot of newer technology being hung onto the 1930s vintage engine designs. Not nearly enough, but some.

Couldn't agree with you more, especially when it comes to engine management, temperature(s) monitoring, etc.

 

[Henning]

Just because they look like 0-200s doesn't mean they are.

The difference is mostly the prop and jetting. They are very limited and are somehow managing to pull 5600 rpm and that's mostly the prop and pipe from my understanding (just quick observation) of how they are dealing with the rules. If they went half that and put it to a GO 300 foundation it would be nice, espec w/ TCM FI and CS prop.

 

[Aeric]

The biggest difference is that your car engine isn't making 75% of its rated power ALL the time, with long stretches at 100% output. You accelerate at some fraction of rated HP, then cruise along not using anywhere near the power your engine can produce. Your airplane can't loaf along at cruise using 20% power. Well, not very well at least.

If you want to know why your airplane engine isn't as advanced as your car engine, think about this... HOW old is your airplane?

I can see your point, however when my airplane is at 100% power (still only .50 hp/cubic inch), it's full rich, my car is probably only a bit rich at full throttle due to the ECU mapping. The rest of the time, even when it's producing a lot of power, the ECU is programmed to keep it right at the optimal stoichiometric ratio, which is not rich by any means.
The airplane is 38 years old, but the engine is definitely not.

 

[Henning]

I can see your point, however when my airplane is at 100% power (still only .50 hp/cubic inch), it's full rich, my car is probably only a bit rich at full throttle due to the ECU mapping. The rest of the time, even when it's producing a lot of power, the ECU is programmed to keep it right at the optimal stoichiometric ratio, which is not rich by any means.
The airplane is 38 years old, but the engine is definitely not.

What is your maximum full rich altitude?

 

[Aeric]

What is your maximum full rich altitude?

You got me on that one :wink2: I typically start leaning at 2-3000 ft, depending on throttle opening and OAT. It's what I was taught, I'm still kinda new at this.

 

[Tom-D]

You got me on that one :wink2: I typically start leaning at 2-3000 ft, depending on throttle opening and OAT. It's what I was taught, I'm still kinda new at this.

Don't worry about it, lean every time the VSI stops pointing up. I've had a 150 to 16k

 

[Aeric]

Don't worry about it, lean every time the VSI stops pointing up. I've had a 150 to 16k

How the heck did it carry that extra weight of the oxygen bottle?

 

[Challenged]

I wonder how much AVGAS the GA fleet would save over the course of a year if we all used FADEC.

 

[MBDiagMan]

The design goals for an aircraft engine and a car engine are completely different.

Don't overlook the fact that you do not measure horsepower. It is a calculation based on torque and RPM. With the horsepower being developed at a low RPM, you have an inordinately low calculated horsepower value. The same torque at twice the RPM would be more than twice the horsepower value.

Also, remember that this is an air cooled engine that above everything else, must be reliable! To do this it takes lots of cylinder and fin area to dissipate heat at a rate that contributes to reliability. If it were a motorcycle, you could stress it for all it's worth, and they do.

For ME, reliability is sort of important in the engine that pulls along the aircraft that my butt is sitting in.

 

[Dr. O]

Sounds like you are having mixture problems with those two cylinders running lean...
Or pilot problems with all of them running lean?
Or not getting proper airflow over those two cylinders...
Valve rotators are good...
Proper mixture is good - right jets, right carb, right manifold gasket, not leaks around the throttle shaft...
Proper airflow is very good...
Strictly limiting ground running time is even better... When the engine will take full throttle without hesitating, it is ready to fly no matter what the oil temp shows... By the time that oil is warm the exhaust valves are cooking - and coking the valve guides... Not saying you do this, but it is common...

Anyway, engine problems are a bummer - btdt...

 

[DaleB]

I can see your point, however when my airplane is at 100% power (still only .50 hp/cubic inch), it's full rich, my car is probably only a bit rich at full throttle due to the ECU mapping. The rest of the time, even when it's producing a lot of power, the ECU is programmed to keep it right at the optimal stoichiometric ratio, which is not rich by any means.
The airplane is 38 years old, but the engine is definitely not.

It's the prop that limits your engine's speed. I doubt your car engine is very far up the curve by 2700 RPM either.

You're entirely correct that going to port fuel injection (or even direct injection), FADEC, etc would save a LOT of gas, and probably prolong the life of the average engine considerably. Heck, just swapping out one mag for a unit that will actually (gasp) advance the spark, even with an open-loop best-guess algorithm, can make a significant impact.

You say your plane is nearing 40 years old, but the engine is newer... no, not really. You're putting the exact same engine in, rebuilt or not. If you want to make any changes it's going to take an STC - or I guess you could make it experimental, if you don't want to actually use the airplane for anything other than testing. I think the real reason you see this situation is twofold. First, the cost of getting regulatory approval and certification for something new is, from what I have heard, staggering. Second, and I'm guessing on this one... Lycoming's biggest customers by far are companies that make new airplanes. I doubt they are strongly encouraging Lycoming to come up with STCs to vastly improve the flyability and economy of 40 and 50 year old airplanes, which might adversely impact their sales.

There's still a lot of inertia among owners/pilots, I think. You'll still encounter people highly resistant to anything more technologically advanced than magneto ignition or a carburetor. Add to that the ponderous weight of the regulatory issues, and you have the situation we see now.

 

[MSPAviator]

I think it would be possible for a clean-sheet design with modern auto-diesel engine technology and materials to have a 12:1 compression ratio, turbocharged, intercooled, FADEC, and EGTs in the 1800F range.

Such an engine would make more power, less noise, less vibration, less weight, lower specific fuel consumption, higher specific output, and more reliability.... all running on JET-A.

Of course with the small volume of demand/production and certification costs, such an engine would probably cost $10 million each.

 

[dell30rb]

You got me on that one :wink2: I typically start leaning at 2-3000 ft, depending on throttle opening and OAT. It's what I was taught, I'm still kinda new at this.

I leave it full rich until I hit 3000 feet, then I lean but keep it well on the rich side of peak RPM until I reach 6-7k feet (and the engine is putting out less than 75% power) then I lean for about 50rpm lean of peak rpm. I also climb about 10kts over Vy for improved cooling.

Cruise power is typically 65% and as lean as I can get it without running rough.

I can't back this up by the years and thousands of hours i've put on aircraft engines, but I can tell you that if you follow the manufacturers instructions by leaning to PEAK RPM (as the manual instructs) when you are climbing at 3000 feet or above, you are operating at the highest cylinder temps with that setting. Instead, lean to peak RPM and crank the mixture in until you lose a bit of rpm. Reset every 1000 feet or so

 

[Skylane81E]

I think it would be possible for a clean-sheet design with modern auto-diesel engine technology and materials to have a 12:1 compression ratio, turbocharged, intercooled, FADEC, and EGTs in the 1800F range.

Such an engine would make more power, less noise, less vibration, less weight, lower specific fuel consumption, higher specific output, and more reliability.... all running on JET-A.

Of course with the small volume of demand/production and certification costs, such an engine would probably cost $10 million each.

DA-42...

There is also a STC for 182s to bolt one on. I was quoted ~70k for the upgrade at OSH 2006, for a new FADEC engine, mount, propeller, turbo and cowling it actually wasn't a bad price.

 

[steingar]

One of the greatest surprises of my life came when I realized that the aerospace activity in which I was participating mostly depended on cutting edge 50's technology.

 

[Henning]

You got me on that one :wink2: I typically start leaning at 2-3000 ft, depending on throttle opening and OAT. It's what I was taught, I'm still kinda new at this.

Figure it like this. Gasoline has an Upper Explosive Limit Mixture (Rich of Peak, more fuel, more lead more temp) and a Lower Explosive Limit Mixture (Lean of Peak, less fuel, less lead, less temp) for the same power. You decide for yourself.

 

[denverpilot]

Pilots aren't resistant to technological change as much as they're resistant to be the first to try something that costs more than the airframe to buy, not counting possibly specialized installation costs and God knows what paperwork for the FAA.

 

[Aeric]

One of the greatest surprises of my life came when I realized that the aerospace activity in which I was participating mostly depended on cutting edge 50's technology.

I wasn't so much taken aback by the age of the design as that would indicate to me rock-solid reliability. And again, I fully understand the different missions, it's just the difference in reliability that surprises me.

 

[Aeric]

On a related note, my parents owned a 1954 Volkswagen Beetle sunroof with the 36 horsepower flat four. That engine spent a large part of it's life at WOT, no problems.

The new cylinder/piston assembly is on order and is being Fedex'd overnight, the mechanic said it might be done by Monday

 

[denverpilot]

I wasn't so much taken aback by the age of the design as that would indicate to me rock-solid reliability. And again, I fully understand the different missions, it's just the difference in reliability that surprises me.

Mechanics were cheap back then. Everyone was one or was neighbors with one. You worked on your car every time you drove it almost.

Meant a higher number of them certified to work on aircraft too, I would think. Haven't been able to find any stats that show number of licensed aircraft mechanic vs number of actively flying aircraft though.

But everybody was a mechanic. That's for sure.

 

[Henning]

Mechanics were cheap back then. Everyone was one or was neighbors with one. You worked on your car every time you drove it almost.

Meant a higher number of them certified to work on aircraft too, I would think. Haven't been able to find any stats that show number of licensed aircraft mechanic vs number of actively flying aircraft though.

But everybody was a mechanic. That's for sure.

I don't find that analysis whole. 'Everybody' was never a mechanic; that's for sure.

 

[denverpilot]

I don't find that analysis whole. 'Everybody' was never a mechanic; that's for sure.

I could change to "almost everyone outside of a city".

 

[bbchien]

Aeric, there was a bad stretch in there in whcih continental cylinders were the pits. I would order facotry kits, have about half of them sent to G&N to make the exhaust valve fit in the race, before putting these into service (TWO yellow tags on each of these assemblies).

I identified them by pouring oil into the cyl in a cookie pan. The ones that were okay for service has a dry cookie pan; the ones that went to G&N were empty of oil - all of it in the pan...by morning. Quality was atrocious.

I hear they are better now. I have 12 cylinders between 2010 and the present on factory remans and have my fingers crossed.

I am thinking you have one of the rare situations where a four probe EGT might be the cat's Meow. But for an a/c with a 450 pound useful load, that would be an additional impingement.... sigh.

 

[Aeric]

Aeric, there was a bad stretch in there in whcih continental cylinders were the pits. I would order facotry kits, have about half of them sent to G&N to make the exhaust valve fit in the race, before putting these into service (TWO yellow tags on each of these assemblies).

I identified them by pouring oil into the cyl in a cookie pan. The ones that were okay for service has a dry cookie pan; the ones that went to G&N were empty of oil - all of it in the pan...by morning. Quality was atrocious.

I hear they are better now. I have 12 cylinders between 2010 and the present on factory remans and have my fingers crossed.

I am thinking you have one of the rare situations where a four probe EGT might be the cat's Meow. But for an a/c with a 450 pound useful load, that would be an additional impingement.... sigh.

Well, these are Milleniums, not TCM, I've been told the Milleniums are better. I actually have an EGT gauge, it's a single so it's fairly useless, one or more cylinders could be substantially richer or leaner than the one that's being monitored. And hey, I've got a 499 pound useful load!