Best RPM for a 150 lycoming

Would like some coments on what RPM the lycoming 150 cruises at. Mostly interested in the highest RPM that won't damage engine, in your opinion. Thanks.

Larry:
Seems like nobody wants to stick there neck out this so I will.
I'm not comfortable running mine over 2450 for long periods of time although, I'm sure it would be perfectly ok to do so. I prefer running 2350-2400RPM.

Well if we are going to start sticking our necks out for criticism, I like to cruise at 2250, and to climb out at 2400. THat is just my $.02USD

Bill

Tips and tricks

Thanks for your input . I felt like I opened a taboo question . Larry

Naw you asked a good question Larry, People just get battered around here if they answer out of the norm. Actually I like to putt around at 1900 to 2000 rpm light and cool, but thats not what you asked.

Idelelte

The following is from a 1976 Cessna 172M Skyhawk with a O-320-E2D 150hp @ 2700 RPM.

Pressure Alt RPM %BHP GPH
2000 2550 75 8.2
2500 71 7.8
2400 64 7.2
2300 58 6.7
2200 52 6.2

4000 2600 75 8.3
2500 68 7.5
2400 61 6.9
2300 55 6.5
2200 49 6.1

6000 2650 75 8.2
2600 71 7.9
2500 65 7.2
2400 59 6.7
2300 53 6.3
2200 47 5.9

8000 2700 75 8.3
2600 68 7.5
2500 62 7.0
2400 56 6.6
2300 51 6.2
2200 45 5.8

10,000 2700 72 7.9
2600 65 7.3
2500 59 6.8
2400 54 6.4
2300 48 6.0
2200 43 5.7

12,000 2650 65 7.3
2600 62 7.0
2500 57 6.6
2400 51 6.2
2300 46 5.9
2200 41 5.5

Mixture Leaned above 3000

The above figures may vary some due to prop configuration.

AHHHHHHHHHhhhhhhhhhhhhhh I just spent several minutes typing and nicely spacing the above so it would be easy to read. When I posted the information, it was all squeezed together. Hopefully you'll still be able to decipher it. AHHHHHHHHHhhhhhhhhhhhhhhhhhhh

Why do you want to run your engine at max RPM? It will gain you very little speed, but will cost you a good deal more for fuel. The O-320 operator's handbook shows a graph of fuel consumption vs RPM. The graph is "S"-shaped: [from memory] at the steep part of the curve an 8% increase in RPM can cause a 27% increase in fuel consumption. You can be sure you won't be seeing a 27% increase in speed! In most cases you will be best served by using the range at the bottom part of the "S," just at the point of the curve where it starts to climb steeply.

delete

TJ:
Never heard that one but use of the cubs was starting to slow down when I got started. Only time I ran mine 3000 rpm was when I shot 4" off the tip and had to file same off the other end to get home.

I never heard of that either. Perhaps someone has heard 30" and has confused that somehow with Lycoming. We used to run 30" on the Pratts quite a bit. You can pretty much run the 320 any old way, it's one of the most indestructable engines ever made. 320, 360, 470, 985, there's just some engines that seem to take a lot more than others and those are a few.

On that rpm/leaning question: there's a powerpoint presentation that's pretty good floating around on the Husky list, just hit the right links to get to the list, hit May's subjects and ask Don Lawton to send you one. It pertains to the smaller Lyc also.
Matt
http://husky.taildragger.info/

Heck you guys know I don't mind getting kicked! Diggler hit the mark with his answer, most guys that fly the 032 a lot will tell you that they know the "sweet" spot. That is right! it depends a lot on the Prop combination, If you run a 74/56 cruise prop you probably run lower RPM cause the darn things run so stinking rough you can't drink a cup of coffee above 2300! My current plane runs best at 2450-2500, and I lean using my fuel flow and Single EGT, keeping an eye on the oil temp and Cylinder temp. Mind you I am running an 82/41 borer prop! Much also has to do with the balance of the internal parts of the engine, the flow matching of the heads etc. My neighbor has a "blue printed 0-320 that runs as smooth as a turbine, mine is more like a dump truck, but it don't burn oil, is a strong puller and you could eat out of the combustions chambers, I expect mine to go past TBO like all the other engines I have run,

My Theory is that you should run them as hot as practical not to exceed 220 degrees clyd head for extended time, DON'T IDLE AROUND, AND DON'T SHOCK COOL THE CYLINDERS, I don't chop the trottle, unless I am going over on the nose!

Hope this helps,

Tim

Tim and Diggler have got it right I reckon.

The technical explanation goes something along the lines of low manifold pressures means low combution camber pressures. These pressures need to be high to ensure the piston rings are pressed hard against the bores. If they are not pushed out hard they flog around and chatter and glaze up the bores. A simplified explanation, but that's about it. The long and short of it is don't baby your engine.

It all depends on the prop you run, but if you install a manifold pressure gauge you'll get a better idea. You don't really want to run at below 23" MP routinely.

And yeah that story about 3000 rpm is probably true. A lot of the aerobatic boys with the S1 pitts' have their unoffical read line at 3000 rpm. Don't forget the HIO-360 in the Hughes 300 is red lined at about 3200 from memory and the 360 has a greater stroke (can't cope with the revs so much as the shorter stroked O-320).

There is a now vintage race car here in New Zealand called the Lycoming Special. That's right it runs an O-320. I spoke to the guy who built it once. If he ran it over 3600 rpm the pistons cracked. His "red line" was 3300 rpm. Reckoned he had no trouble at that.

My Dad when he was looking after a fleet of Pawnee topdressers (dusters) used to tick the pilots off for coming out of the hills at 2900 rpm in the 2450 or 2550 red-lined O-540. So, yes it happens.

Again about $.02 worth.....

Tips and Tricks

I've only had a super cub for one year ,my licence for eight months. I Know if you want to learn something , you better ask someone with some time and experience,the book just gives you a general idea . It would be great if I buy a few thousand hours of flying time.but I have to earn them. I can take all these replys and do what I think will be best for me . Thanks.

if you are going over 2700rpm redline you´ll probabely crack your valvesprings(on a normal O-320 or O-360). If you want to go higher you have to make some mods in the valvetrain.

I have a friend who flies a 160 hp O-320 powered SC for the USDA hunting coyotes. He tells me he runs it on the redline most of the time and always gets TBO or better. He doesn't have to pay for the fuel.

TJ, as for the 3000 rpms, I never sprayed with a Cub. Harold Harbour, who you met the other day, tells me that back in the "good old days of cropdusting" they cut a few inches off the SC props to get them to spool up more and get them off shorter with a load. He thought I was crazy when I put on the long Borer. That doesn't exactly jive with the Borer theory, does it?

murph

I run my O320 between 2400 and 2450, where it runs the smoothest. I had this engine overhauled a couple of years ago, and the engine shop said 2400 was about right. They felt that Lycomings worked best if worked a bit hard, and that running them slow was not good. So far the engine seems to like running at these speeds.

A friend of mine has an O-320 and he runs it full throttle all day long does proper leaning and is now just taking the engine off for overhaul It has around 2500 hours on it and virtually never a problem of any significance He is only doing the overhaul for piece of mind it still runs great, I dont personally totally agree with the full throttle idea and it burns gas but it seems to work for him...Once he has the engine apart I´ll update on how it looks inside...

I do think the Lycomings can be run hard with few major problems, I used to tow Gliders with a Supercubs, Full throttle climb with slowly reduced throttle decents so the engines were not shock cooled and the club where I flew had 4 SC with varing between 1500 and 3500 hours on the engines with little major problems.

David.

About the only comment I can add is beware of prop changes on high-time engines. If the engine ran at low RPM all its life, then sticking a high RPM prop on it could cause you grief. No problem the other way around.

S.F.
Nick