Redline on LYC O320-D2A?
 

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.

Here is Lycomings CYA
 

http://www.lycoming.textron.com/supp...dfs/SB369J.pdf

Experts like Mel know that this is just to cover their butts. However, to my knowledge, this is the official SB.

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.

Catto's standard for the 160 hp RV-4 is a 68x74. Yours must wind up pretty good! Read the first two in this thread:

http://www.vansairforce.com/communit...design+dummies

Tony

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?

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. :)