What RPM do you cruise at?

[Mr_Boondoggle]

My PA20 has a Lycoming O-320/150 hp engine. Up to now, I always set my engine power at 2400 rpm and I burn almost exactly 9 gallons per hour without leaning. I'm thinking that I could go further (longer range) if I ran my engine at 2200 rpm. I'm assuming my fuel burn would drop to 7 gallons per hour and my range would go from increase from 420 sm to 488 sm. If my calculations are correct, I could actually fly to Lock Haven PA faster by flying slower because I wouldn't have to stop for fuel. I realise, I wouldn't have much of a fuel reserve if I made it non-stop.

What do you think? What do you normally set engine power at?

[Bultaco Jim]

I have a PA 22/20 150 and also burn close to 9 gph, if flying low and not leaning. When flying high (over 8500), I burn around 7.7 gph. Anything over a thirty minute trip, and it's crazy to not fly high. It starts to be a no-win situation, when, you fly over 12000 with a Pacer as the engine performance drops below 75%.
Really, anything over 7000 really rewards you with many benefits,( safety, speed, mileage). Also, after talking to some people who have run flight schools, (and ran up thousands of hours on Lycomings), I cruise at 2500 to 2550 rpms,(redline 2700). They told me that Lycomings (O-235 and O-320) don't last as long at 2300 rpms. They consistantly got 3000 to 4000 hrs out of their engines, and should know. 2200 rpms sounds like a bad idea to me. Jim

[Steve Pierce]

I lean all the time except tale-off and climb. I burn a little over 9 gallons when running 2350-2400. She seems to feel better at 2400.

[andya]

I also lean all the time except for takeoff and go around/touch and go, I typically am always above 6000 and if going somewhere am at 8500-10500. With a 150, 58" prop and almost full throttle, leaned to about 80 rich of peak I'm turning 2600 +- ( have to pull off power in any descent otherwise it will do over the 2700) and average fuel burn for a 2-3 hour trip at those altitudes is something around 8.6-8.7 per hour. Lycomings seem to run better and hold up longer when run hard. I fly a constant speed on another Lyc powered bird and run it at 2500 all day long when most guys would pull it back to 22-2400.

[Mr_Boondoggle]

Very interesting responses to my initial post. I have always ran my engine at 2400 rpm to get better lead scavaging. And a local owner of a flight school told me the same thing...run it hard...don't baby it. Thanks for all the advice.

When I go cross country, I usually prefer to remain around 1000 agl. As for leaning, Lycoming told me three things cause cylinders to crack: fatigue, bad timing and aggressive leaning. I really need my new Titans to last my life time.

What do you think about Titan cylinders? I thought Classic Cast cylinders were great until the AD note. Although, ECI stood behind them. The warrentee on my Classic Cast cylinders expired yet ECI took them back and sent me four new Titans for $1100.00 including shipping....pretty good deal.

[Steve Pierce]

I built an engine with them and am about to build another. They broke in immediately and no oil consumption issues. I am using the nickle cylinders. The first engine is in south Texas and doesn't fly regularly and the one I am about to build will be based in south Louisiana. I really don't think you are going to hurt your cylinders by leaning till you lose rpm and then enrichen a little. All of the cracking issues I have seen have been due to fatigue. I am not a fan of rebuilt cylinders because of the number of cylinders I have had to remove with 300-400 hours since rebuild. I think it is due to the number of cycles. When you look at the work order numbers scribed on the cylinder flange it is sometimes scary seeing the cylinder has been overhauled 6 or 7 times.The only new cylinders I have ever had to remove prior to TBO were on big bore Continentals.

[andya]

A note on leaning, if you are less than 75% power, leaning is ok at any altitude. When I lived back in the mid west, I would typically be at 2-3000 for short jaunts and after level off would set manifold pressure to 22" ( which is some less than 75% ) and lean to about 75 rich of peak. That engine has 700 hours since top.

I also topped an engine on a twin comanche with Titans. For the initial flight it would appear we did everything wrong, ie flew in 105 degree temp at 3000 msl, 25-26 inches MP, at 145 mph indicated (other engine pulled back because gear would not go up), almost to redline on ships CHT, oil temp was obviously above 200 +, for two hours before landing. Flew another two hours on delivery flight not going over 6000 but still using 25 inches. No oil on plugs after 5 hours and used a qt every 17-18 hours.

Have been very happy with Titan cylinders, but they need to be broke in hard that first run. Know of one other case of new Titans on a vendor ovhl that was run on a test stand with no more than 23-24 inches mp, approx 2400-2500 rpm, CHT kept below 400 entire 1+20 test run and then it burns qt every 7 or so hours. According to all the documentation, the test cell run was the correct way and our top was not.

go figure

[DroopTip]

They consistantly got 3000 to 4000 hrs out of their engines, and should know. 2200 rpms sounds like a bad idea to me. Jim

Man i love lycomings. I have heard this exact statment from my mechanic. I only hope mine holds out this long as i am getting up there over 1700 hours now.

Josh

[Bultaco Jim]

I actually took 500 hrs off of what they told me, just in case they were exaggerating! Of course, you have to take into consideration- none of their planes sat for more than 48 hrs, and that is a big factor.
One more thing on leaning; have you all noticed that on some mornings the plane just seems to have more power than you remembered? It's not your imagination. I have an air-density gauge that I take to the race tracks, and you wouldn't believe the difference in oxygen from one weekend to the next. I have always felt that both of the planes were overly rich, (in other words, ran better when the mixture was pulled a few clicks out, and my field is at sea level). I believe that the carbs are set up very conservatively (which is good) and are only going to run perfectly on "Big Air" days, unless leaned out some.
I can't imagine what "proper leaning" would hurt, in any engine - even at 1000 ft.

[mjlossner]

Great question! The Piper PA-22-150 Owners Hand book is a little vague on cruise settings or i just can't figure out the Chart properly. I have a Manifold Pressure Gauge in our Trike and have been trying to use 24" at cruise at all altitudes. RPM runs 2350 to 2450 down low, depending on the day to 2500 RPM+ at altitude. Fuel burn is 9 GPH. Indicated Airspeed at 2500-3500 MSL 123 MPH all as advertised by Piper. Don't know If thats the way to do or not? Works for me. I ran the R.H.Tank dry after transferring the Belly Aux. Fuel to it using these numbers and missed tank dry by two minutes. Really pissed off my wife when it quit but now I know.(I warned Her it was gonna quit too!) I Dip Stick my Tanks with the Tube available in SWPC Magazine. I look forward to reading more Performance/Operational Stuff in the future.

[Stephen]

I generally run between 2450 and 2500rpm, (I go for higher speed over water)) and lean anytime I'm cruising. I agree with Steve's recommendation of installing new cylinders when needed, instead of rebuiling the old ones. I usually think of reparing clylinders as only a short term fix.

I recently installed an analog dual EGT mainly for the purpose of leaning, but I have found that it is worthless and not near as responsive as the tach or doing it my sound.

The last time I checked my fuel comsumption was over a year ago on a trip with some SC's and as I was running at 2300 rpm I got under 7gph.

[N4567A]

Looking for some comments...
I'm in the CG Auxiliary, and here's a method some of the other O-320 drivers use.
When in the patrol area, they will throttle down to 1750rpm or so, depending on the airframe.
Then carb heat on, and lean the blazes out of it. I tried this with the Tripacer and ended up loafing along at
about 80mph. I'm told fuel burn will be around 4 gph, so lots of loiter time.
Is this going to be hard on the engine...I mean I don't mind contibuting time and effort,
but holy smokes I have no intention of contributing an engine!
TIA
Rodg

[Bultaco Jim]

According to the experts, you'll get more lead and carbon deposits, and less engine life. I'd run it at the high rpms, since the C.G. Aux. picks up the fuel tab.

[azevedoflyer]

My overiding limitation is the depth of my $ pocket!
Whatever I fly and how I fly has to fit within my shoestring budget.
I rarely fly much above 3000' AGL as the Zephyr God seems always to know were I am going and perversely command winds to blow at my nose. And stronger if I go higher. I lean aggressively all the time (lean to roughness / enrich a little method) except for TO/LDG or climbing. In cruise, I run 2100 rpm, achieve 106 mph indicated (112/115 mph TAS) at 1700/1750 Lb AUW, Cylinder head temp a shade less than 300 F, oil at Summer peak rarely higher than 180F, burn 1 qt. every 20h (use Castrol Aviator 100 during the Summer and Aeroshell 20-50 during winter), for a fuel consumption of a little less than 7 gph. I do plan 8 gph. Never had (4 years now) problems with lead fouling . Do use MMO in the fuel every other tank. My prop is a Sensenich cruise prop. Even firewalled, I never get more than 2550 rpm, 2450 rpm being norm. Recently I plotted all cylinder leakage ratios since engine was overhauled. As expected, cyl.3 is the worse one and shows an expected life of 2300h. to a 60/80 limit. All the others should go way beyond 2500 h. I am happy with the numbers and state that I am a weekend flyer, flying less than desired but achieving 50h/year average.
Cheers,
Miguel Azevedo
PA22/20-150

[spenav8]

I'm coming late to this discussion but I'll jump in. No one mentioned the Pacer Owners Manual. O-320-160, for 75% power, 2400 RPM @ sea level then add 25 RPM for each 1000 feet above sea level. O-290-D2,for 75% power, 2375 RPM @ sea level add 25 RPM Per 1000'. I've been using the O-290 setting for decades and I'm now using the O-320-B numbers. I lean in cruise (lean till rough then in till smooth) when density altitude is above 5000' OR I'm sure that I'm below 75% power. I've always gotten book TAS and fuel burns and the O-290 is past TBO and doing well with both compression and oil consumption. According to the Textron Lycoming Engine Operator's Manual the O-320 (normally aspirated) produces 75% power to a pressure altitude of 8500' and 65% power to approx 12500'. My O-320 B with a 61 inch prop appears to match book speeds and burns and with a tuned exhaust it appears to exceed book climb rates but I haven't flown it at gross yet. The nice thing about the 61 pitch prop is that the 160 hp Tri-Pacer performance charts and fuel burn data are based on that prop appear to be useful.
Hope this is constructive. This is a great site.
Ron

[sbjmobil]

A old IA freind said (he's 85 ) best way to lean her is to come up on left mag, pull mixture out tell she spudders , then push mixture in tell it smooths out then go bach to both mag's.Should be were you ought to be. Been doing this for years and it seems to work for me. To simple for some I guess.

N615A

[Tripod]

2200 RPM if I'm just putting around the local area. 2350 if I'm heading to nearby airports for a hamburger. 2450 (or best RPM available) if I'm really going cross country. In other words, throttle to the firewall above 5000 feet (I have a cruise prop).

-dave

[cudavll]

I run a A290D2 in my PA-22 and I cruise at 105 GPS at 2100 rpm and burn 5.3 GPH