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stanrv4

Well Known Member
Can someone please tell me what my max RPM should be? I'm turning a Catto 68X70 Prop. Thanks
 
The "red line" on a Lycoming engine is really a "rating" RPM. You have to go quite a ways over rated RPM to hurt a Lycoming.
Even though the rated RPM on most Lycomings is 2700 many people run them on up toward 3000 when racing. It will probably shorten TBO, but shouldn't hurt it other than that.
Mine Catto will turn about 2750 flat out at 8k feet. I typically run 24-2500 rpm cruise for cross country.
 
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Jon is totally correct. Perhaps my post was "over simplistic".
Obviously any operation beyond the manufacturer's recommendation puts you "on your own".
Also consider, if the engine is under any kind of warranty, this type of operation will probably void that warranty.
 
I have it from a very in-the-know source that the crankshaft torsionals go "through the roof" as an O-360 approaches 2970 rpm. Why that number? It's the 10%-over figure required for certification runs, and the source was intimately involved in the testing. He also said that the mags were resolutely unhappy at those speeds, and that mag failures kept interrupting the certification runs.

How long will an O/IO-360 last at 3000 rpm? Obviously long enough to race?and the engine in question did survive the 150-hour Part 33 test, as well as some number of hours after that in follow-up testing?but I sure wouldn't treat the engine that way if I intended to use the airplane for transportation.
 
THE REAL WORLD

I was involved with competetition aerobatics for 22 years. Much of this was in a Pitts S1S which I built from scratch. 0 360A4A with pressure carb. The first prop was a 76 x 56 Sensenich metal which was the standard factory prop in those days. This prop would turn 3500 plus in a dive at 180 plus ias. I ran this prop for about 300 hours. I then changed to a modified Sensenich 76 x 60 which would only turn 3300 in a dive. I ran this prop for about 700 hours. Every aerobatic flight in this airplane was at max r/m for much of the flight. I had a loose intake tube where the tube is swedged into the sump, a minor problem with the carb, and one mag failure. The cause of the mag failure was a fiber gear installed when the mag was factory remanufactured. No problems with the other mag which had the proper nylon gear.
It is likely that 90% of the Pitts with fixed pitch props have been flown this way for most of their life. I have never seen a major failure on a 180 lyc on an aerobatic airplane. I have heard of several prop flange failures on angle valve engines. Most were with the heavy hartzell prop.
 
RPM=HP?

The 0-290GPU was designed in the 1940's to provide remote power on the flight line. It's continuous RPM rating was 2850-3000.
My airboat friend JR has rebuilt over 5000 Lycomings in the past 40 years. In that time he has developed aftermarket rods, forged pistons and racing rings to increase performance. His quote is "heat is the enemy, not RPM." His highly balanced engines (primarily IO-540's) endure continous 3000+ RPM running with no cowlings or baffles and CHT's near 500F. He has never had an engine catastrophically fail that had oil in the case. When I asked him about the 2700 rpm rating by Lycoming he stated that it revolved around the original design numbers for the 0-290. The increase in HP from 2700-3000 is 8-10%. Does operating above 2700 hurt the engine? It depends on how you operate it .:)

Smokey
HR2
 
rated rpm engine vs design rpm of prop

The "Rated RPM" according to the Lycoming manual supplied with my Aerosport 0-320-D2A is 2700 rpm. The "Design RPM" of my Catto 70x70 prop is 2750 rpm (with a "Red line Max RPM" of 3200).

The Lycoming SB noted above seems pretty resolute. Does this mean I should not be trying to achieve the 2750 rpm for which Craig Catto designed the prop? I'm trying to figure out where to set the redline for my Dynon tachometer. Basically, it seems to come down to setting it at 2700 to make the engine manufacturer happy or 2750 to take full advantage of the prop.

Thoughts?
 
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alpinelakespilot2000 said:
The "Rated RPM" according to the Lycoming manual supplied with my Aerosport 0-320-D2A is 2700 rpm. The "Design RPM" of my Catto 70x70 prop is 2750 rpm (with a "Red line Max RPM" of 3200).

The Lycoming SB noted above seems pretty resolute. Does this mean I should not be trying to achieve the 2750 rpm for which Craig Catto designed the prop? I'm trying to figure out where to set the redline for my Dynon tachometer. Basically, it seems to come down to setting it at 2700 to make the engine manufacturer happy or 2750 to take full advantage of the prop.

Thoughts?
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I would set it @ 2970, 10% max above the "Rated RPM". You won't be flying @ 2750 very often I would think anyway, but these little Lycomings like the higher RPM's. :)
 
We're talking two different engines here.

The original post asked about the O-320 engine. Most of the "warnings" noted relate to the O-360. Even though these engines are very similar, the O-320 has always been touted to be somewhat more "bullet proof" than the O-360.
Again as stated earlier, anything over the manufacturer's recommendation puts you "on your on".
 
0 320

The parallel valve 360 has a higher piston speed than the 360. Same pistons, rings etc in both. In theory this translates into a longer life for the 320. The reality is the 360 will run 12-1400 hours turning 33-3500 r/m.
 
alpinelakespilot2000 said:
The "Rated RPM" according to the Lycoming manual supplied with my Aerosport 0-320-D2A is 2700 rpm. The "Design RPM" of my Catto 70x70 prop is 2750 rpm (with a "Red line Max RPM" of 3200).
Click to expand...

LifeofReiley said:
I would set it @ 2970, 10% max above the "Rated RPM". You won't be flying @ 2750 very often I would think anyway, but these little Lycomings like the higher RPM's. :)
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Not sure I need to set it that high (2970), since the Lycoming SB linked early in this thread doesn't seem to like it above rated rpm at all. It seems to suggest that anything more than three seconds at 0-10% above rated RPM is not good, but maybe I'm not reading it clearly.

I'm just wondering if setting red line closer to somewhere between 2750-2775 or so would be a good, reasonable compromise, allowing me to use the full 2750 that Craig Catto seemed to design the prop for. It sounds like Mel can get up to 2750, but his post doesn't really indicate whether he's comfortable operating continuously at that power setting (assuming he was OK with burning the fuel that rpm required). What are other people who have 0-320's using for red line? And, assuming your prop doesn't have a prohibited range, are you using a yellow band on the tachometer at all?

Also wondering how setting a higher red line might impact the accuracy of the Dynon's % of power indication. I seem to remember reading somewhere that the two were linked.

As you can probably tell, understanding this stuff is definitely not one of my strengths!
 
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alpinelakespilot2000 said:
Not sure I need to set it that high (2970), since the Lycoming SB linked early in this thread doesn't seem to like it above rated rpm at all. It seems to suggest that anything more than three seconds at UP to 10% above rated RPM is not good, but maybe I'm not reading it clearly. I'm just wondering if setting red line closer to 2750-2775 or so would be a good, reasonable compromise to allow me to use the full 2750 that Craig Catto seemed to design the prop for. Perhaps that area between 2700 and 2750 could be a yellow band on the tachometer? It sounds like Mel can get up to 2750, but his post doesn't really indicate whether he's comfortable operating continuously at that power setting, so I'm not sure what color 2750 should fall in.

Also wondering how setting a higher red line might impact the accuracy of the Dynon's % of power indication. I seem to remember reading somewhere that the two were linked.
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You can use 2750 RPM... that will work fine. We are looking at an Aerosport
O-360 right now that a good friend of mine owns, he got about 480 hrs and his engine is trash from a rod bearing issue. Looks like we have THREE professionals on the engine disassembly, the overall outlook is all of the rod caps were not torqued correctly and we now have a pile of metal. :mad:
 
LifeofReiley said:
You can use 2750 RPM... that will work fine. We are looking at an Aerosport
O-360 right now that a good friend of mine owns, he got about 480 hrs and his engine is trash from a rod bearing issue. Looks like we have THREE professionals on the engine disassembly, the overall outlook is all of the rod caps were not torqued correctly and we now have a pile of metal. :mad:
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That sounds painful, especially if it came from Aerosport that way!
 
I like Mel's prop...

I have used several props over the years, and like my antique Bryan Cook Pacesetter 200 the best. It statics 2250 and runs 2750 at 8K throttled by altitude...hmmm...maybe my O-320 (pre A off a 55 Apache) has seen 2850 downhill....but never any trouble at those numbers in 25 years....It seems to me that turning a 12 pound toothpick generates a lot less load than a 35 pound plus metal prop...who wants to fly very long behind something turning more, anyway...?
 
LifeofReiley said:
You can use 2750 RPM... that will work fine. We are looking at an Aerosport
O-360 right now that a good friend of mine owns, he got about 480 hrs and his engine is trash from a rod bearing issue. Looks like we have THREE professionals on the engine disassembly, the overall outlook is all of the rod caps were not torqued correctly and we now have a pile of metal. :mad:
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What did Bart have to say?
 
Rev me up...

Two of my RV's (RV4/RV6X) have 0-320's built by an Airboat racing engine builder, my friend JR. Racing airboats run between 3000-3200 RPM (some with NO2 injection) with no baffling. They use temperature lasers to determine CHT which normally run around 500F. JR told me he has never had a Lycoming engine returned for self destruction that had oil in it or wasn't sunk.
He told me high RPM isn't as big a problem as oil starvation/cleanliness or bad timing, both of which do serious damage. He installs aftermarket shot peened rods and forged pistons and TRW rings. His biggest gotcha is actually the accessory case gears which he ALWAYS replaces new(aftermarket gears) every overhaul.

Both of my Catto props would Rev to [email protected]. producing some pretty amazing numbers for an 0-320. When I asked JR about it he smiled and said "not even working hard" :)

FYI...
Smokey

The original 0-290G power carts ran the engine continuously at 2900 RPM.
 
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Let's not forget that Lycoming runs their helicopter engines pretty hard. Many run 2900 to 3200 RPM with little more than a data plate change from the airplane model.

It's the propeller that is generally the LIMFAC.
 
I doubt that you will be running at even 2700 RPM often. My "limit" is set at 2700 and I usually run at 2600 RPM max.

O-360, Catto three blade prop
 
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Good thread. Nice timing too as i'm setting the limits on my new EMS as well. For my O-320 i'll be using 2700 caution and 2900 limit. My reasoning is that I don't want to operate the engine continuously above the rated rpm limit (yellow line), but I want my EMS to scream at me if I get near the 10% over over the rpm limit (red line).

Thanks!
 
alpinelakespilot2000 said:
With a Catto prop? If so, what is the design rpm that Craig pitched your prop for?
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I do not recall exactly but it is above 2700 RPM. Maybe over 3000 but do not take that as fact.

Most of the time I can't get above 2700 RPM anyway at Ron Lee cruising altitudes and even if I could the noise increase is a negative.
 
Stan,

We have a Catto 68x72 on our Lycoming O-320-D2J (160 HP) equipped RV-4. Craig has the prop dialed in to produce 190 MPH TAS at rated (2700) RPM at cruise. It produces 2200 static RPM on the ground. The engine is red lined at 2700 RPM, and the prop itself is rated for 3200 RPM.

As Ron said, we seldom run at maximum RPM. As a rule of thumb, 55% produces a nominal 165 MPH TAS, 65% 175 MPH TAS and 75% 185 MPH TAS with our prop/engine combination.

Due to the low inertia and fixed-pitch of the composite prop, I've found it's necessary to let the prop wind up and then adjust power down to desired cruise setting.

One other point to ponder is the accuracy of your tach--best to check it to make sure apples = apples.

Cheers,

Vac
 
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