Need tech help with power settings O-360

I am a new member in need of some info. I recently purchased a beautiful RV-6 with an Aerosport O-360 w/ 9.2 pistons and C/S prop. The engine has one EI and one mag. I just finished installing a new EI graphic engine monitor and a EI fuel flow/totalizer. I am beginning to get used to the aircraft and trying to get a handle on appropriate power settings, leaning techniques, and fuel flow readings.

Even with the EI analyzer, leaning by CHT seems a bit inaccurate. Not sure if I am getting the false peaks the manual talks about. If I had some fuel flow numbers to shoot for it would be a big help. I thought this airplane burned about 9.0 gal at 75% at 8000. My numbers seem about 20% higher.

I have been cruising at about 23 inches and 2350 RPM and have found the egt's to be in the 1150 range and the fuel flow to be about 11.5 at 6500 feet. This is about 100 ROP on the leanest cylinder. These numbers seem cool on the EGT and high o the fuel flow to me!

If anyone has the same engine I would be interested to know your power settings and EGT/fuel flow numbers. Here are some of my related questions?

My 0-360 manual does not take the higher compression pistons into account on the power charts. What would 65% and 75% power settings be? Is it considered appropriate to operate at cruise using 75% power with the higher compressiion pistons? What cruise power settings are recomended with these pistons?

How many degrees ROP is recomended with this engine? 100 degrees seems to produce very cool EGT's and high fuel flows.

What kind of EGT's and fuel flows show I be showing at the recomended cruise power settings at 3, 6, and 9K.

I would really appreciate some help or a good reference for these questions

I live in the Washington DC area and would love to go for a ride who is an expert on this stuff.

Most of my flying experience is with jet fuel and I am feeling a bit rusty on the recip engine particulars.
Thanks for the help!

John C

You should be leaning by EGT, not CHT. Try leaning by pulling back on your mixture control till you experience a slight engine missfire or drop in RPM. Then go rich till it smooths out. Check your EGT. I generally run my EGT around 1310-1325. My CHT is usually around 325 deg F. After a while, you will sense what is right for your conditions.

What does the previous owner/builder offer for guidance?

I have a Lycoming 0-360 A1A with a Hartzell prop.

Roberta

Mix setting

Never get in a habit of setting at a given EGT temp, the higher you fly the colder you peak temp will be, also affected by atmospheric conditions. Always lean very slowly and watch your EGT on hottest CYL when it wont get any hotter go just a bit further tell it starts to fall a degree or two, now you know what your peak is, now advance you mix to 50 degrees rich off peak. If you lean to fast you will starve the engine before your EGT can keep up and you won?t ever see the peak temp. I have a digital EGT that makes this very easy. I have an angle valve IO-360 with 10 to 1, at low altitudes I run about 1220 EGT this gives 9.8 GPH, I was told not to lean to peak below 3000? or above 65 or 75% power I think, to avoid possible detonation with the high compression. At 6, 8, 12k? it burns less using 50 degrees ROP then down low. I run 23? manifold pressure and 2450rpm with an MT 2 blade prop on an RV-4. Some people run 25 degrees ROP witch will save even more fuel, I like 50 degrees ROP just seems good for my particular engine. There is a very good explanation of how why to set your mixture on the Lycoming web sight, worth the read.

EGT menas nothing Kind of & Be nice to your engine

Russ McCutcheon said:

Some people run 25 degrees ROP witch will save even more fuel, I like 50 degrees ROP just seems good for my particular engine. There is a very good explanation of how why to set your mixture on the Lycoming web sight, worth the read.

Click to expand...

First 10.6 gph is the FF of a O-360 at 75%. With the HC pistons you are making a little more power.

Yes at 4000 feet 23/2350 is about 75% power, but because of the HC piston you are (guess) about 5.5% higher hp. So you are like a stock O360 running at 79%. You are still at 75% power, but your total power is higher. The throttle is key to fuel burn, right. You don't like 11 gph, pull it back to 65% or even better 55% power. You can use the same RPM/MAP settings for % power but you will be at a higher HP.

Yes the absolute temp sounds low, but the absolute EGT is not critical. The only temps that are assigned a number is oil temp and CHT as long as OT=180Fmin (190F ideal) and CHT=200F min (300-350F typ/ 400F max for long engine life) you are OK. EGT is affected by the probe type and location. You can put the probe 1" from the cylinder or 6" from the cylinder. This will effect the temp you read. Close is accurate but the probe will not last. Too far down the pipe it is too slow to react and not accurate. What you want are the EGT probes to all be in the same spot, relative to each cylinder's pipe. I like 3.25 inch as a good location for the EGT. The difference is all that matters not the value itself. Once you know "Normal" changes or differences tell you a story of what is going on. You are clearly burning fuel. You did not mention how fast you are going. I an sure you are moving. If you want to save fuel throttle back and consider lower RPM, provide it is out of any limitation of the prop, like the Hartzell yellow band range, Approx 2000-2250 RPM.

Two good post above but I would not run anything as lean as 25 ROP or even 50 ROP, I would consider 100 ROP the best compromise and considered the "gold standard" to aim at. I would consider 75 ROP a min. Yes you can run leaner but it may cost you down the road.

By running leaner than 100 ROP you will save fuel, but in my opinion not enough to justify that your engine is at a higher temp. I do think Lycoming recommends 100ROP to 150ROP. DO I think there is any damage at 25 or 50 ROP, probably not but possible. There is more margin with the lower temp (Richer operation). Pilot choice and I think cooler is more conservative. Valves are expensive and since you have HC pistons and electronic ignition you can get into a LEAN detonation situation, where you are so close to lean mixture you get spontaneous or fast burn of the mixture which can multiply pressure and temp in the combustion chamber. I am stretching a little. However this is not out of the question or unlikely or even rare. By running HC piston and advanced timing (EI) you are already closer to detonation. As long as you are sure you are below 75% power you should not have a problem leaning.

Most stock Lycomings use 8.5 to 1 or less, and except for a few none above 9 to 1. One O235 model had 9.7 to 1 and was taken off the market, due to problems. I am not trying to scare you just be aware that you sould not lean above 75% power. There is a reason for this. However with an engine monitor and proper operation you will avoid problems. Lycoming has to consider the average pilot abusing the engine without benefit of engine monitors, so they are more conservative. But that O235 was fine on the test stand but had problems in the field.

Read the monitor manual again, you should have a FIRST to peak function and yes you are are looking at EGT not CHT. Be paitent if you probes are down the pipes, go slow. You can do as was suggested and lean till rough, back up (richen up a little) and than start to find FIRST TO PEAK.

George

Thanks for the info guys. Sorry for the typo, I meant to write EGT for leaning not CHT.

Still have some questions though.

You say 10.6 gal/hr is 75%. Is that a leaned engine and if so how many degrees lean of peak?

How are the fuel flow numbers vs. % HP affected by the higher compression pistons.

What I would really like to know is: Using the 0-360 with the 9.2 pistons what are the cruise power manifold/rpm/fuel flow numbers for various altitudes which will prevent detonation and help the engine to make a 2000 hr TBO?

Many thanks of all the help! I will check out the lycoming web site as well. I am wondering if the folks that make the 9.2 pistons have any info on this stuff.

You got an experimental hot rod engine

"QUOTE=hiddenhearth" "You say 10.6 gal/hr is 75%. Is that a leaned engine and if so how many degrees lean of peak?"

That is from Lycoming and I think leaned for best economy.

"How are the fuel flow numbers vs. % HP affected by the higher compression pistons."

I would talk to the shop or manufacture (Superior/Aerosport) and ask them. I am sure there is some predicted estimate for higher compression. You would think some one ran a dyno test and came up with power vs. FF charts. Even with out that you can count a fix increase in FF over a stock engine. My GUESS was 5% higher HP.


"What I would really like to know is: Using the 0-360 with the 9.2 pistons what are the cruise power manifold/rpm/fuel flow numbers for various altitudes which will prevent detonation and help the engine to make a 2000 hr TBO?"

I am sorry I don't have a chart off the shelf. Remember you are running an experimental aircraft engine with HC pistons and electronic ignition. My first answer is you need to flight test and figure it out for your self. Next you can use the STOCK Lycoming O-360A1A performance charts as a starting point. Flight test, calibrate your FF gauge, record performance of aircraft, from that you will have a fairly fixed relation ship with RPM/MAP/FF between your FF and that of a stock engine.

From your original email you are burning 0.9 GPH more. You can expect to burn about 0.90g/h +/- 0.20g/h more at the same rpm/map settings. With that FF you say you had you are about 11 HP more than stock (not 9 HP like I thought). You should be going about 1.9% faster. If you throttle back about 6-7% you will match the FF and airspeed of stock; you will be making the same HP at a lower %pwr than the stock at a 6-7% higher power (map/rpm). Remember the MAP/RPM combos will give you about the same %power for a given value of RPM/MAP. However your % is based on 191 HP not 180HP. Therefore % power for you is (Power% = X / 191). I am guessing your total power is 9 HP to 11 HP more. Did they Dyno the engine?


"Many thanks of all the help! I will check out the lycoming web site as well. I am wondering if the folks that make the 9.2 pistons have any info on this stuff?"

Call folks who build Hi-Peft custom aircraft engines like: Ly-con , Berrett, Aerosport, Mattituck and Superior and tell them what you have. They may have some RULE of thumbs or set correction factor you can apply to the stock power charts. They may have some experimental aircraft charts. For now you can use the standard power settings you would use on a stock setting. As far as making TBO, that is a whole subject on to itself. The biggest killer is disuse and corrosion. As far as operation maintain temps with in limits and do not lean over 75% power. You may want to not lean say above %72 power. Look you have a higher HP engine and you got it with compression, which is fine and very efficient method of boosting power, but it was not an economy modification. It was a performance mod and you will burn more gas. The only way to get it down in run at low power settings below 72% to 55%. Also you are making more HP and the pressures and forces in the engine are higher. Again HC pistons are not an economy endurance mod. You may make TBO but chances are you will wear the engine out a little faster just from fact you are working it a little harder, but you are in control of that. You say you fly jet. I do to. We often do an assumed temp take off and derate the engine power to improve the life of the engine. A jet and piston are two different things but my point is you can operate it wide open like a race car or baby it. Than the issue comes up, why have HC pistons and make more power unless you are going to use it, but that is up to you and your throttle hand.

Many members (RV builders) have posted spread sheets for stock O-360s. You can change the total HP and it will guess at a %power and FF. You can down load them and modify them for your own use. Bottom line you relax, it sounds all OK to me and you just need to get use to the airplane and engine. My guess is you are making more total HP than you realize. You need to compare your airspeed to what Van's specs say for a given % power. This will give you a sanity check. Lets say Van says you should go 190mph at a certain % power and you are going 195, you can verify you are making more power and justify the extra fuel burn. BTW are you breaking in the engine? FF will be higher until you break it in. G

Thanks for the info

G- Thanks for your insight. It seems inline with what I was thinking. I was planning on doing the inflight testing but was hoping to get some base line numbers from someone with the same engine/prop/airframe configuration so I have something to compare with. The engine was not dynoed and as you say even if it was that would have been pre breakin numbers. I understand the estimated HP of the engine to be approx 194. As to why the additional HP when you might "derate" for cruise the answer is takeoff performance when the engine is somewhat protected by a very rich mixture. Some of the literature seems to indicate that those who operate engines with EI and higher compression pistons need to be extra careful in preventing detonation. Since this is true perhaps 75% power does not provide enough detonation margin for leaning. An earlier post suggests leaning 150 ROP. My preliminary test whould indciate that the mixture control is almost "full in" to get a 150 ROP at 6500 MSL. I am wondering if my initial "peak" was actually a false peak and therfore all the numbers are suspect. Again, part of my reason for trying to get some baseline numbers from somewhere. Thanks very much for the input. BTW I fly the Bus for JB and am furloughed Usairways. You?