Do Piston Engine TBOs Make Sense?

These are highly loaded engines being asked to produce more than 80% of rated, continuously. Even with excellent maintenance 1200 hours is probably about average between overhauls. But a huge amount depends on how it is flown.

I question the foo foo juice Camguard on an engine that is flown a couple hundred hours a year. I also question corrosion in an engine being run that often.
As the radio announcer says says "but wait, there's more to the story"
 
Dr. O said:
These are highly loaded engines being asked to produce more than 80% of rated, continuously. Even with excellent maintenance 1200 hours is probably about average between overhauls. But a huge amount depends on how it is flown.

I question the foo foo juice Camguard on an engine that is flown a couple hundred hours a year. I also question corrosion in an engine being run that often.
As the radio announcer says says "but wait, there's more to the story"
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Actually, I would argue that they are not highly loaded. They are in fact de-rated. They are this way because they are expected to be able to run at 100% power continuously. Some claim 100% all the way to TBO.

This is why a 320 cubic inch engine only makes 160 hp. My Jet Ski engine makes 160 hp and it's only 1500 cc. That's less than 92 cubic inches. I run my Jet Ski engine about 75% power continuously and I now have over 400 hours on it with no failures. It will not however, make it to 2000 hours without a rebuild. I know this for sure.

If you are flying a couple of hundred hours a year, you absolutely don't need Camguard to protect from corrosion. The makers of Camguard will tell you as much. It may help in terms of wear though. Camguard has people like me in mind, those that fly 50 hours a year or less.
 
I agree for the most part they are lightly loaded engines but there is more to the equation than HP/CI, you are neglecting to consider the 'time' factor. Your Jet Ski engine also turns almost 3.5 times the RPM for that same HP so it needs 3.5 times less ICP (inner cylinder pressure) to do so. The destructive 'load factor' on both engines is pretty much the same. High ICP s what begets detonation, and that is the primary destructive force on an engine.
 
Henning said:
I agree for the most part they are lightly loaded engines but there is more to the equation than HP/CI, you are neglecting to consider the 'time' factor. Your Jet Ski engine also turns almost 3.5 times the RPM for that same HP so it needs 3.5 times less ICP (inner cylinder pressure) to do so. The destructive 'load factor' on both engines is pretty much the same. High ICP s what begets detonation, and that is the primary destructive force on an engine.
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Henning, you are forgetting that his jet ski engine only displaces 94 cu inches which means he probably has high ICPs, in fact he probably is supposed to run a higher octane gas to keep pre ignition in check.
 
PaulS said:
Henning, you are forgetting that his jet ski engine only displaces 94 cu inches which means he probably has high ICPs, in fact he probably is supposed to run a higher octane gas to keep pre ignition in check.
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His Jet Ski also turns 7500 rpm at full power. They will run about the same ICP because that is what the fuel will take before detonation, and the verge of detonation is where you find the best performance for the fuel. It won't do it as efficiently as the big slow engine since drag is a non linear equation, but power to weight it wins.
 
I remember reading an article on ICPs. Aircraft engines had higher ICPs even than high performance sports cars at full power, as a rule.
 
Ted DuPuis said:
I remember reading an article on ICPs. Aircraft engines had higher ICPs even than high performance sports cars at full power, as a rule.
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Yep, because they have larger diameter pistons and longer rods, so they can take advantage of it. The expansion rate of the fuel is the limiting factor.
 
Henning said:
Yep, because they have larger diameter pistons and longer rods, so they can take advantage of it. The expansion rate of the fuel is the limiting factor.
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Yep. But that also debunks that "not run hard" part. What the engine considers hard vs the pilot is different.
 
Ted DuPuis said:
Yep. But that also debunks that "not run hard" part. What the engine considers hard vs the pilot is different.
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Well, 'hard' is still relative, and I was already 'debunking' the not run hard part. Even though the maximum ICP is higher, it is still not in the critical range unless one is really pushing an engine that is turbo charged and/or rating at greater than .5hp/CI/2500rpm.

The main advantage a person can give themselves operationally is to run LOP. Not only does it use less fuel, it's also kindest to the engine both in pressure and deposits. Carbon and lead deposits, especially on exhaust valves, are the major cause maint dollar output.

BTW, another proof they run hard is that they are more efficient than high RPM engines.
 
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Henning said:
There's either an electrolysis problem, potentially a condition charged by the magnetos through the drive gears, or it was a junk crank from the factory. I don't know where they got their steel from. If I was replacing a crank, I'd have Crower make me a SuperLight off a billet and supply it as an "Owner Produced Part" Considering what a Continental crank costs, it'll be about the same to have one custom made better and stronger, maybe even a couple bucks cheaper.

The thing is one needs to determine why the degraded steel? If there is electrolysis set up, it doesn't matter how good the crank is, it will degrade. That a 2002 Continental Crank is of junk steel wouldn't particularly surprise me. I would also be looking at the alternator, that engine has the geared Alt up front right? Is it grounding through the crank? I'd look hard at the alternator and installation.
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How much static electricity is produced by the prop?
 
bnt83 said:
How much static electricity is produced by the prop?
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It's a very interesting question, but unless it has an uncommon installation I would expect it to be more common an issue with an AD by now.

My suspicion lies in the alternator, bad diode or something, bonding wire insulated or missing...:dunno:
 
Another crapshoot.

IO360 Lycoming in a 177RG, exchange overhaul from a big name company,

The company said the cam was new when they assembled the engine


The engine was installed in 2008 with a reported 400 hours on it when metal was found in the oil filter.

Somehow they came to $20k to replace the cam, prop, governor and oil cooler inspection for metal. Seems awfully high to me.
 
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Henning said:
It's a very interesting question, but unless it has an uncommon installation I would expect it to be more common an issue with an AD by now.

My suspicion lies in the alternator, bad diode or something, bonding wire insulated or missing...:dunno:
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This one was a bit misleading, the io550 crank was a factory overhaul I believe and when the owner received it the crank was already at .010 under.
 
bnt83 said:
Another crapshoot.

IO360 Lycoming in a 177RG, exchange overhaul from a big name company,

The company said the cam was new when they assembled the engine


The engine was installed in 2008 with a reported 400 hours on it when metal was found in the oil filter.

Somehow they came to $20k to replace the cam, prop, governor and oil cooler inspection for metal. Seems awfully high to me.
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I'm sure the cam was new. It's corrosion that kills the cam and lifters. Doesn't matter if it's brand new, or 20 years old.

If you're putting on a new prop and prop governor, along with a IRAN on the engine, $20k isn't that far off. Why the new prop and governor? Do they need replacing independent of the cam issue? Going to a better prop?
 
Dav8or said:
I'm sure the cam was new. It's corrosion that kills the cam and lifters. Doesn't matter if it's brand new, or 20 years old.

If you're putting on a new prop and prop governor, along with a IRAN on the engine, $20k isn't that far off. Why the new prop and governor? Do they need replacing independent of the cam issue? Going to a better prop?
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No....not necessarily. Cams and lifters, by design, are very sensitive to hardness....and if not manufactured properly with the correct hardness will begin to spall (which looks like pitting).....and is often times incorrectly diagnosed as corrosion.

I'd bet most of Lycoming's woes are from process issues vs. corrosion.:dunno:
 
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