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IO-360 at reducted RPM for 160 hp

WVM

Well Known Member
Hi,

I got a request from my local aviation authorities to provide the necessary documentation for the engine and propeller setup I would like to use in my RV-9.

Originally I got approval to install the IO-320 with 160 hp from Superior: XP-IO-320-B1AD2. But my engine shop advised to install the IO-360 at reduced RPM instead: XP-IO-360-B1AD2.

XP = Superior
IO = Fuel Injection
360 = 360 Cylinders
B = Constant Speed Thin Wall
1 = 1 Dynafocal Rear Governor
A = Unison PA FI
D = Horizontal Front, Roller Lifter (FI Only)
2 = Power Group 8.5 / 180

Primary reasons for this suggestion are noise reduction, less engine vibrations + stabilization and reduced wear. By limiting the maximum RPM to 2400 we never exceed the 160hp. Important note: We are not allowed to exceed the maximum as defined by VANS. For my RV-9 this is 160 hp.

The aviation authorities now want to know which propeller I would like to use. I did not yet decided but I would like to go for a WW200 RV of a Harztell two bladed metal propeller. I prefer to use a constant speed setup.

This idea to reduce the RPM on an O-360 is not invented by the engine shop. It has already been done on a Cessna 172 with an IO-360-L2A:

FAA Type Certificate 1E10
Rated horspower: 160
Rated speed, RPM: 2400
Bore, inches: 5.125
Stoke, inches: 4.375
Displacement, cubic inches: 361.0
Compression ratio: 8.5:1
Firing order: 1-3-2-4
Spark occurs, degrees BTC: 25
Valve rocker clearance (hydraulic tappets collapsed): .028-.080
Propeller drive ratio: 1:1
Propeller driven rotation (viewed from rear): Clockwise

The authorities responded that this is correct, but that the setup was with a Mac Cauley 1C 235/LFA 7570, fixed pitch propeller. Not a constant speed.

They do not deny my request, but I should provide them the necessary paperwork for a setup with a constant speed Hartzell/WhirlWind.

Is anyone using this or a similar setup or able to help me to provide these details? I have already contacted both Hartzell and WW, but they appear not to be the fastest to answer. I am bit on time pressure because I ordered my wing/fuselage/firewall forward/finishing kit and they will be shipped end of January. Major issue is that my exhaust was ordered at Vetterman because VANS can not deliver a standard exhaust for a Superior engine with cold sump. These orders were made for an IO-360. If I don't provide the paperwork to the AA, I will never get my airworthiness certificate.

Any help is more then welcome.
 
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Your engine shop is simply wrong on a few engineering principles. As for hard on the engine, the 360 at 2400 is being punished harder than the 320 at 2700 RPM.

For fear of starting a crazy debate, lets just simply move to the best outcome.

The IO320 and the appropriate propellor make this a delightful aircraft. It is efficient and does everything it should and nothing it should not.
 
I can not provide the necessary documentation but it has been done - the Carbon Cub is certified LSA with a 0360 using the same paper methodology. I've seen the placard on the instrument panel restricting HP to meet the certification requirements.

You may have to hire an expert to provide such documentation. Perhaps your certifying authority could recommend such a source of engineering data.

From a practical point of view, they may accept from you informal HP determination . HP to a certain extent is determined by fuel flow. My spread sheet shows 158.8 HP at a fuel flow of 13.5 gph for any Lycoming engine. (assuming a BSFC of .51 which was determined during a dyno run - you may have to do such a test to legitimize the data)

Tell the certifying authority the airplane will be equipped with an accurate fuel flow system and its flow will be limited to 13.5 gph. After all, it is an experimental airplane, why not? :)
 
Good luck with your certification.

I have an RV-9 taildragger with an O-360 and fixed pitch composite prop (Catto).

I would not want a metal CS prop due to weight and balance issues.

Since you are going to use a CS prop, you need both manifold pressure and RPM settings that will limit you to 160 hp.

For example, on takeoff, your RPM should be 2700 but at a reduced MP. Otherwise, you should just use a fixed pitch prop.

There are two RV's based at my airpark; mine and a -7 with an O-360 and CS prop. Our neighbors keep commenting on how quiet my RV is compared to the other one. It all has to do with prop speed.
 
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Your engine shop is simply wrong on a few engineering principles. As for hard on the engine, the 360 at 2400 is being punished harder than the 320 at 2700 RPM.

For fear of starting a crazy debate, lets just simply move to the best outcome.

The IO320 and the appropriate propellor make this a delightful aircraft. It is efficient and does everything it should and nothing it should not.

I beg to differ with you, David.

Years ago I bought a 0360A4M with 1950 TTSN. It was removed for time in service from a Cherokee, the owner wanted a new engine rather than over haul what he had. He was conservative to say the least. Most of the 1950 hours was flown at 2100 rpm according to the shop owner who had maintained the engine since new.

I installed the engine in a Cozy MKIV and flew it for about a year before having it overhauled. What a waste of money. The crank was in new limits and the cylinders/valves could have been cleaned up and it would have continued to run just fine, according to the people who did the tear down.

Running a 0360 at 2400 or 2100 is NOT harmful to the engine. It will last longer than a life of 75% or more power, no question of it. The most important aspect of life expectancy is clean oil - and conservative HP with an appropriate fuel/air mixture.
 
Can you not get approval for the 180 HP engine? Or are you "locked in" once you get the original approval?
 
I beg to differ with you, David. <snip>
Running a 0360 at 2400 or 2100 is NOT harmful to the engine. It will last longer than a life of 75% or more power, no question of it. <snip> .

I would agree at the 2400 rpm level. However, there are some details. At 2400, you would more likely get 166 hp assuming constant BMEP, and with better breathing it will be a little more. If they accept 2400, better for you.

Thermal loading and speed related stresses are lower no question. Cylinder pressure is likely a slight increase due to better breathing - thus Davids comment. Also you will be slightly closer to the detonation limit, so running here at wot, low altitudes, hot day would not be advised. Probably not something you would do anyway.

Last, using the CS prop governor to limit speed would be an (probably the most) appropriate way to limit the RPM at all altitudes. You would have to discuss this with the manufacturer to ensure you still have full range control, springs might have to be exchanged. This way, you can not adjust higher rpm from the cockpit and violate the agreement.

Kind of silly to limit ground speed with a fixed pitch to 2400, because at altitude you can just go faster!

Actually, what you propose will barely limit your performance and with the 360 at altitude, it will be very good.

You could use the IO360 performance curves to show the officials what performance would be at 2400, that is an official document.

Good luck, this is an interesting challenge.
 
Can you use the data on Page 8 of your Superior manual (linked below) to placard maximum MP at various RPM?

For instance:
DO NOT EXCEED
26.5" MAP @ 2700 RPM
27.5" MAP @ 2600 RPM
28.5" MAP @ 2500 RPM
NO RESTRICTION 2400 RPM AND BELOW

http://www.superior-air-parts.com/PDF/FlliersDocuments/VantageEngine/Vantage_Model Spec.pdf

Granted, it's not "certified" data, but depending on what your CAA requires perhaps nothing would count as "certified" data with an experimental engine.
 
Your engine shop is simply wrong on a few engineering principles. As for hard on the engine, the 360 at 2400 is being punished harder than the 320 at 2700 RPM.

SRSLY-G3AR.jpg

So there are no cases where your statement isn't true i.e. turning a 320 at 2700 RPM is always easier on the engine than turning a 360 at 2400RPM? Or perhaps there are certain conditions where that is true and you neglected to mention them?
 
It would seem to me that a fixed pitch prop, RPM limited by redline on the Tach would provide the HP limitation and simplest solution. With a 360 you will be able to get plenty of power for takeoff even with a cruise prop and then will be RPM red line limited for cruise or descent. Like many certified airplanes with climb props, the engine power limit is the red line and the pilot manages RPM.

Since you want a CS prop, why limit RPM's when all that you need to limit is MP? Since your engine is a superior engine and experimental, I would think you would need power charts from Superior, similar to the Lycoming charts to make a MP limit chart (RPM vs MP) and placard to keep you under 160hp. The Lycoming data is part of the engine TC but since this is a Superior engine they could perhaps argue that the data needs to come from Superior.
 
What your engine shop is wrong about is that the 360 is "smoother" than the 320. Why make your licensing efforts difficult & complicated by installing the 360?

Install an IO-320 with a constant speed prop and never look back! You'll love it! I promise!
 
Hi,

Many thanks for the replies so far. I would like you to give a little bit of background information.

I am actually not looking for certification. In my country the aviation authorities follow the build very closely. First of all you need to submit a case for which they need to give approval. Every major milestone (empennage, wing, fuselage, engine) is followed with a VERY detailed inspection and at the end a 2 days airworthiness check. It doesn't has to be a bad thing to have someone locking over your shoulder. Only down side is that it costs a lot of time and money. We are allowed to build an experimental aircraft, but the regulations here are very strict before you are allowed to fly it.

Beginning of the year I submitted my case for the IO-320 with an MT 3 bladed propeller. No problem with that. I got approval based on a case from the Light Aircraft Association (UK). The key factor here is, to my opinion, responsibility. The inspector just needs something to refer to. I agree with you that experimental is not really what it suppose to be in that way. But this is another debate.

He is not against me doing this, but he needs his paperwork based on reliable data.

The reason for changing to the IO-360 is coming from an friend and engineer that worked on piston engines longer that I am on earth. I asked his opinion on the 3 versus 2 bladed propellers. All RV builders near me tend to use a 3 bladed MT propeller. The reasons are simply because they copy each other, the factory from MT is nearby and a 3 blade propeller looks cool on tail dragger.
I was in Oshkosh and tried to get information on the efficiency of 3 versus 2 bladed propeller. It became clear to me that a 2 bladed is more efficient (another debate!). But the 3 blade propeller is more stable. He told me that an IO-320 has no counterweights on the crankshaft while an IO-360 does. This will lead to vibration with on IO-320. He agreed that this will be minor vibration and probably negligible. In Europe we have a lot of difficulties with environmental regulations, so noise reduction is a key element for our airplanes. These where the reasons that he suggested me to change to an IO-360 instead. This idea was based on a Skyhawk R which was introduced in 1996 and was powered with a derated Lycoming IO-360-L2A. At 2400 RPM it produces 160 horsepower (120 kW). It was also the first Cessna 172 that had a factory fitted fuel injected engine. Only problem is that this setup used a fixed pitch propeller Mac Cauley 1C 235/LFA 7570. I want to use a constant speed propeller. And this is the question that I got from the inspector: How will you derate the engine to 160 hp? We should not exceed the maximum horsepower of 160 hp as designed by VANS according to local regulations.

I just got a reply from Hartzell. They don't have specific data for me. The propeller can be used up to 2700 RPM at 180 RPM, so any lowed configuration is allowed. This is true, but not really what I am looking for. I need to know if they have a factory setting for this propeller to limit it to 160 hp. No answer from WhirlWind aviation yet.
 
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You should have the discussion with the GOVERNOR manufacturer not the prop. Ask Hartzell governor guys. The governor may be simply adjusted, but might need flyweight and/or spring changes. The governor WILL address your control to 2400 rpm

You may need to set the propellor pitch stops to limit to 2400 for governor overrun purposes, but the governor will control the engine speed on TO (and above) using the propellor pitch to control the engine.

You may have missed this in post #7.
 
You should have the discussion with the GOVERNOR manufacturer not the prop. Ask Hartzell governor guys. The governor may be simply adjusted, but might need flyweight and/or spring changes. The governor WILL address your control to 2400 rpm

You may need to set the propellor pitch stops to limit to 2400 for governor overrun purposes, but the governor will control the engine speed on TO (and above) using the propellor pitch to control the engine.

You may have missed this in post #7.

I indeed overlooked it. And you may be correct indeed. If expected that Hartzell propeller was also Hartzell governor, but this appears not to be the case. Thanks for the tip!
 
Bigger Issue with IO-360-L2A

The IO-360-L2A used on the C-172 does not come with the front fitting for the prop oil line nor the gear and governor mount on the accessory case.

I used one and had to change cases. Sent a private message.
 
Hi,

...... He told me that an IO-320 has no counterweights on the crankshaft while an IO-360 does. This will lead to vibration with on IO-320. He agreed that this will be minor vibration and probably negligible. In Europe we have a lot of difficulties with environmental regulations, so noise reduction is a key element for our airplanes. These where the reasons that he suggested me to change to an IO-360 instead. This idea was based on a Skyhawk R which was introduced in 1996 and was powered with a derated Lycoming IO-360-L2A. At 2400 RPM it produces 160 horsepower (120 kW). It was also the first Cessna 172 that had a factory fitted fuel injected engine. Only problem is that this setup used a fixed pitch propeller Mac Cauley 1C 235/LFA 7570. I want to use a constant speed propeller. And this is the question that I got from the inspector: How will you derate the engine to 160 hp? We should not exceed the maximum horsepower of 160 hp as designed by VANS according to local regulations.

Whoa...hold up here a second. Your trustworthy engine source is mixing apples, oranges and tomatoes all at once! Indeed SOME 360's have counterweights, but most of those are angle valve engines which are quite a bit heavier than the parallel valve 360's (which is the most commonly used engine on RV's)...and most (not all) of the Clones are non counterweighted engine. In fact, I've personally only ever seen 1 or 2 parallel valve series Lycoming 360s'w WITH counterweights (that is a bit of an oddball engine in fact).

Having put a lightweight Barret modified parallel valve 360 on an RV9 with a 3 bladed prop, I can attest to the fact it's a wonderful combination but I'm not sure I'd ever put an angle valve or counterweighted anything on the front of a 9...derated or not - just because of the weight and size factor(s).

Anyway, I can't take sides here because there has been some good points made, but I would caution you to "trust but verify" the info you've been given on "IO" 360's and "which" of them you're being told about. There is a pretty huge difference between the parallel valve and angle valve engines (weight, size, etc..).

Just my 2 cents as usual.

Cheers,
Stein
 
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Whoa...hold up here a second. Your trustworthy engine source is mixing apples, oranges and tomatoes all at once! Indeed SOME 360's have counterweights, but most of those are angle valve engines which are quite a bit heavier than the parallel valve 360's (which is the most commonly used engine on RV's)...and most (not all) of them are non counterweighted engine. In fact, I've personally only ever seen 1 or 2 parallel valve series 360s'w WITH counterweights (that is a bit of an oddball engine in fact).

Having put a lightweight Barret modified parallel valve 360 on an RV9 with a 3 bladed prop, I can attest to the fact it's a wonderful combination but I'm not sure I'd ever put an angle valve or counterweighted anything on the front of a 9...derated or not - just because of the weight and size factor(s).

Anyway, I can't take sides here because there has been some good points made, but I would caution you to "trust but verify" the info you've been given on "IO" 360's and "which" of them you're being told about. There is a pretty huge difference between the parallel valve and angle valve engines (weight, size, etc..).

Just my 2 cents as usual.

Cheers,
Stein

I got confirmation that the Superior IO-360 has those counterweights, but I also have to trust on what I am told. The sad thing is that Hartzell just told me that it is indeed the governor but it is a user adjustable governor. Getting nowhere with that info.
 
Stein started to touch on a point I was hinting at.

We both built RV-9's with 180 +/- hp engines with fixed pitch Catto props. If you are worried about the noise issue, go with a three bladed fixed pitch Catto. (I'm not sure my two bladed Catto is any louder.)

Most of the noise you hear on takeoff is from the propand CS props are louder on takeoff because they spin faster than a FP prop.

With an O-360 up front, you will not want for climb performance, even with a FP prop.
 
If you want to limit HP I would consider lower compression Pistons. Pistons are not expensive to change and going with a lower compression makes the use of alternative fuels easier. I know I have heard of 7 to 1 Pistons. I think someone mentioned 6.5 to 1 as being available. Then you don't have to limit RPM.

George
 
Titan based 0-340

the Carbon Cub is certified LSA with a 0360

David, your point is valid but CubCrafters is using an 0-340. I do not understand all the paperwork technicalities but the engine is, per the manufacturer, 180 HP peak, 80 HP continuous.
 
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I got confirmation that the Superior IO-360 has those counterweights, but I also have to trust on what I am told. The sad thing is that Hartzell just told me that it is indeed the governor but it is a user adjustable governor. Getting nowhere with that info.

Prior to electronically controlled fuel injection on diesels, there was a couple of screws that set the full fueling and thus horsepower. There was a seal on there, so, you might use that argument and offer a seal. After all - why would you change it after all is matched and tested for 2400 RPM? You can change the prop if it was fixed too. You are going to build a compliant airplane not one that is frozen that way. I know, logic does not (usually) fly with regulators. You will need to set the low pitch limit to keep the rpm from surging too high as will on TO.

If you want to limit HP I would consider lower compression Pistons. Pistons are not expensive to change and going with a lower compression makes the use of alternative fuels easier. I know I have heard of 7 to 1 Pistons. I think someone mentioned 6.5 to 1 as being available. Then you don't have to limit RPM.

George
George, this would work, but the lower Cr would mean less efficiency, and combined with the increased friction at 2700 vs 2400 rpm, it would be pretty bad. It would be much better to limit via RPM.

Good Luck!
 
I wouldn't worry about de-rating the 360. The lycoming family is already de-rated. Think about how much HP you got from a 350 CI Chevy with no emission constraints! Heck, I have a 383 CI Ford that puts out over 500HP. The aviation engine philosophy is to use large, de-rated engines to improve reliability. My BMW 5 series rarely has cruise RPM's above 2300 and it has 120K miles and doesn't burn a drop of oil.

The only issues is heat. You don't want to run it so low that that CHT's fall out of the normal range. I don't think that would be the case. Lots of the RV's out there with 360's are cruising at 2400 RPM with no issue. The fact that they take off with 2700 is doing nothing to enhance their longevity.

Larry
 
I beg to differ with you, David.

Years ago I bought a 0360A4M with 1950 TTSN. It was removed for time in service from a Cherokee, the owner wanted a new engine rather than over haul what he had. He was conservative to say the least. Most of the 1950 hours was flown at 2100 rpm according to the shop owner who had maintained the engine since new.

I installed the engine in a Cozy MKIV and flew it for about a year before having it overhauled. What a waste of money. The crank was in new limits and the cylinders/valves could have been cleaned up and it would have continued to run just fine, according to the people who did the tear down.

Running a 0360 at 2400 or 2100 is NOT harmful to the engine. It will last longer than a life of 75% or more power, no question of it. The most important aspect of life expectancy is clean oil - and conservative HP with an appropriate fuel/air mixture.

David, are you sure we disagree?

The engine wear of a 2700RPPM engine operated at that RPM is no more than 2400 RPM provided the oil is OK.

The forces on the crank of a 360/2400 are greater than those at 2700 in a 320 at the same HP. Do the physics/maths.

The majority of its life it will be at a cruise RPM anyway so much the same number. If there was any wear difference, it would be negated by the above.

I think you actually agree. ;)
 
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.
 
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Take note that Cessna did the same thing. Why would they do that if it was worst then using a IO-320 instead? The only difference in my setup is that I want to do it on a RV-9 and with a constant speed propeller. The Cessna used a Mac Cauley 1C 235/LFA 7570 instead. The IO-320 and IO-360 are nearly the same engine. They share a lot of parts. The IO-360 has a slightly wider body. Weight is nearly the same.

I am happy to hear your advise and suggestions, but am a bit surprised that it would be that different then with an IO-320.
 
David, are you sure we disagree?

The engine wear of a 2700RPPM engine operated at that RPM is no more than 2400 RPM provided the oil is OK.

The forces on the crank of a 360/2400 are greater than those at 2700 in a 320 at the same HP. Do the physics/maths.

The majority of its life it will be at a cruise RPM anyway so much the same number. If there was any wear difference, it would be negated by the above.

I think you actually agree. ;)

I wouldn't worry about de-rating the 360. The lycoming family is already de-rated. Think about how much HP you got from a 350 CI Chevy with no emission constraints! Heck, I have a 383 CI Ford that puts out over 500HP. The aviation engine philosophy is to use large, de-rated engines to improve reliability. My BMW 5 series rarely has cruise RPM's above 2300 and it has 120K miles and doesn't burn a drop of oil.

The only issues is heat. You don't want to run it so low that that CHT's fall out of the normal range. I don't think that would be the case. Lots of the RV's out there with 360's are cruising at 2400 RPM with no issue. The fact that they take off with 2700 is doing nothing to enhance their longevity.

Larry

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.

This discussion is off topic for the OP. I will open a new thread under traditional engines for this discussion. Short answer, 2700 ->2400 will indeed be a lower physical load on the engine, and it will live longer. How much is not easily quantified, but it will be longer. It will certainly limit the range of operation, but since this is an aircraft, not a ground vehicle, it should not adversely affect the usability of the plane. Torsionals would not change, and as long as there is no limitation for the prop/engine combination, then the range of operation might actually improve. Low CHT should be no issue, but if a lot of cold metal won't allow the oil temperatures to attain 170-180F then that becomes the issue - besides, if you want higher CHT's that is so easy, throttle the inlet, and if you are DanH, the exit for lower cooling airflow. Again, lower CHT, would yield a longer fatigue life of the head material.

Again, I will expand on the physics/math if that is what you want in the new thread.

The discussion should return to the OP's issue.
 
The easiest way may be going with a g Lund adjustable pitch prop. The you could look at the power charts and pick a static RPM and manifold pressure to "limit" you to the 160 HP goal. By limiting the manifold pressure as well as the RPM you could ensure that the detonation margins and cylinder pressures remain in the safe zone even if the engine is heavily loaded such as during a steep climb. This method may also be the easiest method to gain approval from the inspector by referencing the method used by the C-172R as was previously stated.
 
This discussion is off topic for the OP. I will open a new thread under traditional engines for this discussion. Short answer, 2700 ->2400 will indeed be a lower physical load on the engine, and it will live longer.
This is not off topic and applies right here.

I would agree in some not all cases the power pulses are greater at a specific rpm increasing torsional vibration. Stating that all engines will live longer if run at 2400 is false... You may have a configuration where the crankshaft resonant frequencies are worse at 2400 rpm than at 2550 or even 2700... Depending on propeller selection, compression ratio, ignition and many other factors.

There are a number of accounts of high performance engines and airplanes being fairy'd home from a race and having an engine failure at a reduced or cruise power setting...

Again, I will expand on the physics/math if that is what you want in the new thread.

Most of us have seen the physics and read the documents we don't need it explained or an attempt to explain it again a new thread.

The point I'm trying to make is that if you don't have real testing data or surveys for a specific configuration you simple don't know.

Ok great Bobs prop stayed on his plane for 2500 hours and the engine looked good at tear down. So you can do just what Bob did its probably going to work great but be aware you are assuming risk, this after all an experiment.

Some people seem to be under the misconception that all this shiny stuff has been tested in a test cell or a lab in all configurations and combinations ... Nope its being tested on the front of your airplane.


I challenge anyone using math or physics not opinion to tell me with absolute certainty what my operational limitations should be.

I have the following to be installed on my RV-7... IO-360-A1A 9.0:1 Compression WO/Counterweights, One mag at 25 degrees and one LSE Plasma III, Likely a WW200RV or a 74..


In this case this gentleman is calling the manufacturers trying to get data for a proposed engine and propeller combination and guess what they don't have it. They have some testing for certified engine and propeller combinations seems he will have to choose one of those.
 
No correlation, just a comment

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? Nothing other than that same engine would last longer at lower rpm.

Whats the difference between 2700 rpm and 2400 rpm? Statistically, it may fall in the tail of the distribution where it really could go either way as far as "failing to reject null hypothesis" and so forth. However, if based on feelings rather than data, I like 2400 rather then 2700. 2400 also sounds nicer. :)
 
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!
 
Rpm

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? :eek:
 
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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? :eek:

I think you must have read something wrong!:confused:
 
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.
 
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..
 
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.



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.
 
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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.
 
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