Temps for the O-320 160hp

[Drew]

In the CPs there is a discussion by either Burt, Dick, or Mike Mellville on running at "high" rpm---like 2700 to 2900 rpm.  I encourage you to read through that----you can get the text online.  In your "tin can" airplane, you are swinging a much heavier mass (aluminum propeller).  Additionally, some engine/aluminum propeller combinations have a resonant frequency (certain rpm to avoid) that is destructive.

As I said before, full throttle (non turbo/non supercharger/non altitude compensating engine) is approx 75% at 8000 ft---and drops off from there.  Ideally when you are trying to match your fixed pitch prop to your aircraft, here is what you are trying to do (and of course each one of these things is fighting with you---so you have to compromize):
--generate enough static rpm on the ground to be safe (can't remember what this number is----but probably around 2200 to 2300 rpm).  If you can't generate the rpm, then you need a prop with less bite (assuming a properly running engine).
--generate the rpm you would like to cruise at---at your "normal" cruising altitude--at full throttle (assuming your normal cruise altitude is above 8000ft).  If you have too much rpm up here---then you need more bite.

As you can see, if you need more bite at altitude, but can't generate the required rpm on deck, you are going to have to compromize---you may need longer runways with the bigger bite-----or accept a little more higher rpm at altitude.

I typically run between 2500 and 2700 rpm---depending on noise, how fast I am trying to get somewhere, how hot the engine is running, etc

An interesting note on LOP----engine has a different sound to it in this regime.

[Bruce Hughes]

AGGGGH.     :shock:

NEVER, NEVER, NEVER consider wrapping an exhaust pipe!

You need a metal (SS?)  shield to protect the cowling.

I am NOT an expert; I'll just tell you what happened to me.

I read the info in Aircraft Spruce and Specialty's catalog.
Bought that lie hook, line, and sinker.   Bought the wrap
(now another type is in the catalog but the idea is the same)
and installed it.

After some time (I was just doing taxis at the time) I noticed
that the exhaust nuts were rusting severely.     :shock:
 
Those were the exhaust manifold nuts (STD1410 or 1411, I
forgot which size) specified for Lycoming engines.

I tried to take the nuts off.   Got 6 off with some difficulty.
The last 2 were hopeless.   Rust crumbling off the outside.
Of course, the high temperature of the exhaust gas was
held in the pipe and reflected back to the flange and nuts.

I filed the nuts down on 2 sides until I could get a 5/16" wrench
on the nut.   Turned it 60 degrees.   Filed again.   Turned it
60 degrees.   Turned it and filed the 3rd set.   This filing took hours.
 

I took the wrap off and bought more nuts.   Never believe
what a manufacturer's label says; ask someone who has been
there.

Bruce Hughes    

[Bruce Hughes]

You might try calling Lycoming.    :idea:

I think the tech rep will tell you that a major cause of
engine failure is overheating of the exhaust valves.    

Bruce Hughes

[allen]

Went up last night to get some numbers and here they are. This is with an O-320 swinging a Great American 62x72 and with 25 gallons of fuel on board at 8.5k.

Outside air temp on the ground was reported as 74F, winds calm. Static RPM run-up was up to 2500 with no problems. On takeoff I noticed that at rotation speed I was showing 2650rpm.

Ground taxi was with aggressive leaning and running at 800-1000 rpm and brake down. Temps stayed nice and low.

Once at altitude I made a few long (60-80nm) flights to allow the motor to settle in and determine the winds up there. My 396 was reporting winds at altitude as 5kts. With that in mind I made 2 circuits with the winds abeam, and two with winds head on and dead astern.

Once settled:

RPM: 2660 firewalled and leaned
Grnd Spd: 173kts average, (as reported by my Garmin-396 post flight)
Oil: 197
CHT 1: 315
CHT 2: 303
CHT 3: 370
CHT 4: 347

EGT 1: 1238
EGT 2: 1374


Bruce,

   Thanks for the information. I have sent an email to Lycoming for clarification. Once I hear back I’ll post it here.

Allen

[Drew]

What did you use for leaning technique?

Do you have a fuel flow gauge?

Your engine is running just fine as it is---actually it is fairly cool.  The oil temp is about 17 degrees higher than ideal---but is ok.

If you want, you can work at balancing the airflow around the cylinders.  From what I see (brainfart here---#1 is the one closest to the prop?), your cylinders by the firewall are the hottest---which is normal---but you can fix.  But before you do anything---make sure that the TCs are correct.

There is a lot of documentation in both the CPs and CSA newsletters that talks about balancing.  One has to do with the baffles that go around the cylinders.  Basically, the air will enter into the opening of the baffles on the bottom of the cylinders.  You can remake/rebend the baffles accordingly to make the entry area smaller for the cooler cylinders and larger for the hotter cylinders.  Obviously, this will be an iterative approach.  The other thing to do is to build fiberglass ramps to divert air to the front cylinders.  In the Cozy, you build a rather large ramp to make sure the air gets to the front cylinders---and if you do it right (ramp big enough), you will hopefully overcool the front cylinders.  Then you start cutting down pieces of the left and right side of the ramp until the cylinders are even.  Don't cut too much at a time---much easier to cut ramp than to add ramp!

By the way, your engine rpm on the roll is always higher than static.  The windmill effect relieves some of the load on the prop.  I would say that you have a good prop engine match.

[allen]

Drew,

   No fuel flow gauge on board. I have been looking at swapping in one of the multiple function gauges that has fuel flow as one if its functions. One plane that I looked at had a gizmo that showed engine power in a percentile of max output. I found it to be helpful when trimming out at cruise.

    In regards to leaning out the motor at altitude I have been doing some trial and error. Since LOP is not an option for a carbureted motor I have been trying to find the sweet spot.

    Today I went for a scenic flight. It was a bit cool today. ATIS reported 70F and calm winds. On the ground I leaned until the motor ran rough, then increased the mixture until it ran smooth again and stopped. Up at 4.5k I trimmed out and followed your recommendation and cruised at a higher RPM than I usually do. This flight I kept it under 2700 and tried to keep it about 2650-ish. The GPS showed calm winds at altitude and a ground speed of 165kts.

   After I was established and the temps looked good I started to play with leaning out. I leaned the motor while watching the CHT’s and EGT’s. One thing I noticed was that RPM would increase by about 10-15 while the temps climbed about 25 degrees. The motor also ran smoother. I guessed this to be the sweet spot. The temps all behaved.

    After a while I landed at Martinsville to gas up and watch the locals. On my walk around I noticed that I had a considerable amount of black soot on the prop. Interestingly enough, the soot buildup was almost entirely on one blade. Not too sure how that happened. More to the point, I’d like to know why I had all this soot in the first place!

      Before I took off for Roanoke I cleaned off the soot to see if I could recreate the event. Once in Roanoke I looked at the prop again and although I had some soot again, it was not anywhere near the amount I noticed in Martinsville.

   Since I had been fairly low today I made a real effort to not lean to aggressively; only to the point that the EGT/CHT increased, then increased the mixture until I notices the EGT/CHT start to decline again. Once the temperatures began to cool down again I stopped enriching the mixture.

   On a side note I have installed my onboard camera. It worked great! Initially I was worried that the vibration would be a problem, but to my surprise the video was perfectly clear. The setup is very similar to the one Jason Redman is running in his Berkut.

   Where can I find the CP’s and CSA letters? Who do I contact about joining the CSA? I have joined the EAA and will be joining the local EAA chapter as soon as I can make a meeting. (They majority of the local chapter are retired so their meetings tend to be at time when I am at work.)

Stay safe. See you when you get back.

Allen

[Bruce Hughes]

Hi Allen

The CSA information that you need is in this website.   On
the Homepage, click at the 5th item on the left margin.

Terry has old issues; I believe that the price is the same
as a current subscription ($30 for 1 year including the
directory).   I think you can buy individual issues.

A little further down is the Canard Pusher info.   It is no
longer published so that is all the info we will get.

Bruce Hughes  

[Drew]

Without knowing what your %power is---I would stay below 2500 rpm in cruise unless you are above 8K ft.  Once you figure out what 75% is, then go ahead and throttle up.

What do your pipes look like?  Ideally, you want them to look sort of tan looking on the inside.  If they are black, you are either running too rich or you could have a problem with one of the cylinders on that side----most likely too rich.

Go search the web on leaning technique--many people do many things---and everyone's setup varies.  I monitor all four cylinder EGTs.  I lean to peak (Dynon Engine monitor makes this real easy----but your conditions need to be real steady---steady speed and altitude).  I then enrich about 75 to 100 deg EGT on the first cylinder to peak (there are discusions on running at peak, 25, 50, 100, 200 ROP).  I also look at the value of the hottest EGT---if too hot, I enrich some more.  Download the instructions from several of the engine manufacturers such as JPI or EI----great discussions on things to look for).

Another technique is to lean until rough, then push it back in until smooth.

The way to tell good performance of your airplane is to record TAS---either with a TAS gauge----or calculate when you get back on the ground (grab the OAT at altitude---or look it up the nearest weather balloon on line).

How are you getting winds at altitude?  Does your GPS have a feed from your pitot-static system?  I get winds from my BM Lite---do you have something similar?

[allen]

Drew,

   Sorry for the delay. To answer yor question though the pipes were rather black and not the tan you described. This was something new so I attribute it to my failed leaning temps. The method I used was to lean until rough, then increase until smooth again. Guess I need some practice.  Still, what would make the soot build up so significantly on only one blade? A harmonic anomaly maybe.

   This plane does not have an OAT gauge so I would have to best guess after the fact. One thing I have learned so far is that these planes love to be up high so I suspect I will spend most of my time above 8k. I’ll do some more reading on leaning methods. I’m at a conference in San Antonio until the 23rd, but when I get back I may be making a flight to Montgomery Alabama the following weekend. I’ll plan that flight at p around 10k or so depending on the weather.

   I went to XM radio to see if I could find where they get their winds aloft data. They are mum as to the source. From what I could gather from previous flights it seemed to be more accurate than I could get. This 396 is very handy. It even puts up TFR’s as they change. According to the website they quarry that data right from the FAA website. Initially I was really hesitant to buy this thing but I have to say, it has got to be one of the best tools I have in my VFR arsenal so far. Great gadget.

[Jack]

    In regards to leaning out the motor at altitude I have been doing some trial and error. Since LOP is not an option for a carbureted motor n

On a really big recip like a R-2800 with a carb we leaned to LOP as SOP. Tis an old wives tale about running LOP. If you have the gauges and touch use it.

Lycoming long ago highly recommended using LOP on their motors. It kinda of fell by the wayside.

Iraqijack

[Drew]

My guess is that Lycoming lost the secret sauce somewhere---and now their carb motors won't run LOP.

With fuel injection, you can get the cylinders to peak near enough to one another to run LOP.

But---you can always try to run LOP with a carb motor.  The motor will tell you if it does not like it there.

Jack---when you coming up to Speicher next?!

[Bill James]

Allen-
You mentioned leaning in your thread. For the last couple of years I have flown what could be called extreme LOP. My VariEze can be flown with the throttle full open and the RPM reduced with mixture, down to around 2000 RPM. Am still developing the efficiency potential. With the previous stock oil sump induction the lowest comfortable RPM with wide open throttle was about 2350, about normal I hear. I am not at all suggesting anyone needs to cruise at 2000 RPM, but rather per your comment, am offering some elemental thoughts on leaning during this experience. You proabably have more info than you can use. The simple intent is to mention some personal experience and sources. Satisfying curiosity and resolving the unknowns and concerns, they can be shelved and we can go fly.

Because of length, it is posted at http://www.ezchronicles.com/blogger.html

Good flying

[Jack]

My guess is that Lycoming lost the secret sauce somewhere---and now their carb motors won't run LOP.

?!

It's in my database at home on leaning LOP with the Lycs. Have to go back to the 70s or so for their actual procedures. Article I read the pilot used some serious gauges and finally resorted to leaning back to a slight rise in RPM and then drop it a tad. Which was basically what we used in R-2800s with the BMEP or power gauge being utilized.

Lately only been running to Biap and to the West. Right through freaking Fallujah and hauling ass in that pissant city.  If you hit the big city or the snake drop me an email. I could be running either one of them.  Been pushing us hard lately.

Next month I head back for my R&R for a couple of weeks.

Cheers;

Jack

[Drew]

Jack,
I had heard of running LOP with carb'd Lycomings but did not think they would run there anymore due to the cylinder "not flying very close in formation."  However, you do have Bill James and others doing it---but not with stock Lycomings---they have screwed around with induction tube lengths and whatnot to solve the problem.

All of my wandering around Iraq will be limited to the North (MND-N) since that is where all my trucks are based.  Don't drive too fast----if you can see, you can avoid.  After R&R are you going to be doing any runs up north?

[LongEZDaveA]

Lean of peak will only work if you are fuel injected---carb engines don't really like it on the "other side" due to the vastly different conditions between the cylinders.  Even if you are fuel injected, it may not like it "over there" unless the fuel flow between the cylinders is balanced real well (all cylinders peaking on EGT at the same time---or near the same time).

Drew - I agree with your post except this part.  My Long EZ has a O-235 with a carb and does well very lean of peak.  I only go LOP when full throttle and less than 65% power.  If I try to throttle back it starts running rough.  A big point is that I also have a Light Speed EI.  I think the multi spark is important LOP.