IO-360 at reducted RPM for 160 hp

[jj_jetmech]

[quote=grubbat;944299]My ford 2000cid engine ran about 9800 rpm for three races till I had to pull the bottom end. In the corners we were pulling about 7500rpm. What does this have to do with the discussion?

This Ford engine has nothing to do with this, you're right. RPM became part of this discussion because this agency decided that an RPM limitation is appropriate.

I was Crew Chief for a Formula One Reno racer for years. We ran an 0-200 over 4000 RPM. Time Between Overhauls about 100 Minutes. This was preventative not absolutely necessary. We never had a failure it was pretty happy up there in that range.

Prop it for 4000+ RPM see if it stays together. Yep seemed to work lets try it again.

I just think that it's important to acknowledge that were essentially doing the same thing here.

I trust No Engine! I always have an LZ in mind its part of my scan!

[mannanj]

Following this thread, I suppose that running my angle valve IO-360 200hp Lycoming with a constant speed prop at 2300 rpm and 23 in. mp. giving me about 120-130 hp. (And about 160kts TAS) Will require me to have to rebuild it at 500-750hrs. Is that the consensus?

[Mike H]

Originally Posted by mannanj

Following this thread, I suppose that running my angle valve IO-360 200hp Lycoming with a constant speed prop at 2300 rpm and 23 in. mp. giving me about 120-130 hp. (And about 160kts TAS) Will require me to have to rebuild it at 500-750hrs. Is that the consensus?

I think you must have read something wrong!

[lr172]

Originally Posted by jj_jetmech

The fact that they take off with 2700 is doing nothing to enhance their longevity.

Larry[/Quote...

Can you explain why this is true? Can you show the data or provide the math and physics that prove this particular crankshaft's frequency is happier at 2100 rpm than it is at 2700 rpm with no mention of what propeller its swinging, its inertia , the compression ratio, it's timing and the resultant power pulses.

Why do you believe that crankshaft failure is the chief enemy of the lycoming. I hear much more about glazed cylinders, valve failures head cracking, bearing failure, etc. I simply don't hear much about crank failure or anything related to crank frequency.so why care about the force or frequency applied to the crank. The difference between 2400 and 2700 Is insignificant in an engine with a range of 600 - 5000 rpm. The fact that it is de-rated to a max of 2700 doesn't mean that is the end of it's range.

Research the common failures and then assess the likely causes. I suspect incorrect break in procedures account for far more cylinder issues than the take off rpm used.

[jj_jetmech]

Originally Posted by lr172

Why do you believe that crankshaft failure is the chief enemy of the lycoming. I hear much more about glazed cylinders, valve failures head cracking, bearing failure, etc. I simply don't hear much about crank failure or anything related to crank frequency.so why care about the force or frequency applied to the crank. The difference between 2400 and 2700 Is insignificant in an engine with a range of 600 - 5000 rpm. The fact that it is de-rated to a max of 2700 doesn't mean that is the end of it's range.

Research the common failures and then assess the likely causes. I suspect incorrect break in procedures account for far more cylinder issues than the take off rpm used.

FYI I never indicated I had a concerne for crankshaft failure specific to Lycoming. All elements in Gravity have a resonance frequency. Would you like me to explain Gravity. I maintained a fleet of Lycoming's for years my hugest concerns with a Lycoming is dropping a valve... Incorrect beak in usually results in high oil consumption...the bottom end could care less....

Do a little research about RPM, Frequencies and torsional vibration etc... I have an O 360 in my hangar off a mooney with a hole in the top and the bottom of the case... I never spun a wrench on this engine.... 700 TTSOH by Lycoming it came apart, a connecting rod broke and the crank fractured at the aft main journal..

Just because you haven't seen it doesn't meen it doesn't happen..

[DanH]

This is an interesting chart taken from a Superior Vantage engine document (linked by Kurt in post #9). Every intersection inside the envelope is 144hp, at three different mixture settings. The red lines indicate a detonation limit for oversquare operation, in terms of CHT...i.e, 2400 RPM at high MP is prohibited at high CHT.

Originally Posted by jj_jetmech

FYI I never indicated I had a concern for crankshaft failure specific to Lycoming.

I wouldn't either. My vibratory concern would focus on exceeding the fatigue limits of the propeller, in particular given a crank without pendulum absorbers.

Hartzell and MT do full vibration surveys, so an approval or warning is probably available from either, again the question being 2400 at high MP. Back in late summer, Whirlwind's Jim Rust was shopping for an appropriate telemetry system, so we may see approved combinations or prohibited RPM ranges for Whirlwinds in due course.

[SHIPCHIEF]

Just a data point:
My RV-8 is equipped with a converted IVO-360A1A from a Brantley B2B helicopter.
It's rated to run @ 2900 PRM, 180 HP @ 1500' MSL. The Lycoming operating manual has the usual power RPM fuel consumption graphs which rate this engine @ 188 HP @ 2900 RPM when compared to the same graph for an aircraft variant.
This engine was overhauled twice @ 1000 hours each time. Probably the recommended TBO. The unique oil cooling lines from the oil gallery to the exhaust valve guides is a pretty clear indication that Lycoming considers the exhaust valves to be a point of concern at high load, high temperature operation.
Nice Graph, Dan. My take would be that these engines are more 'at risk' for high cylinder head temp induced detonation on Mogas if equipped with a fixed pitch prop. This combination runs in 'over square' often, without a manifold pressure gauge, the operator would never know it.