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MT 3 blade vs Hartz. 2 blade performance

Bob, Today I got the following
DA 8500', WOT, 2700RPM, 50ROP, 206ITAS, 16.0GPH

If you have the "D" blade hartzell, try 2600RPM. Should give you about 2 knots more and reduce the fuel flow about one gph.

However, with a "J" blade Harzell, it should reduce the speed by about 2 knots with the reduced fuel flow.

This would be for a stock Lyc. IO-540. A pumped up Lyc. IO-540 would act differently.

Jim Ayers
 
Just curious. Is 7,200' Station pressure altitude, Pressure altitude or Density altitude?

It's good to see you used WOT. Using WOT and density altitude is key to obtaining repeatable flight test cruise data.

Just a side note, Lycoming identifies three "standard" EGT leaning temperatures.

Peak EGT - Best economy

50 degrees F ROP - Maximum longevity

100 degrees F ROP - Maximum power

I have seen about 2 knots difference in airspeed at the same power setting, depending on the leaning method. Leaning to Peak EGT was the slowest.

Jim Ayers

Thanks Jim. This is good information to know. I have always been mistaken about where the maximum power point is. I thought from the engine graphs, the peak of the power graph was at lean, but I was incorrect. Sometimes it's hard to keep everything straight in this old head of mine.
 
Makes me wonder why Hartzell doesn't start producing more of these props and getting the price down. How much better is this prop at say 200-250 knots where a Rocket might operate? 20 knots is huge. Was this prop any faster at race speeds?

That burst of speed by Mike in the last lap was my fault. Sorry. When he saw the white flag, he turned up the wick a bit.

Ah, ha, now I know where *not* to share my secrets :).... so, let me see if I can put a name with a face... Were you the turbo expert on Mikes Egg :).... You know you guys are gonna "affectionately" be known as "the Egg"... Just as well get used to it...

Anyway, it was a fun race, the results had a bunch of pylon cuts listed until yesterday, that didn't make any sense as we knew we didn't cut one... On board telemetry actually showed it as well as video. The database on RARA looked a little messed up, so before we said anything, we figured they'd find it and fix and sure enough they did.

Toughest part for us, we knew we had more engine, and we thot we had a "spotter channel" open to Lynn, but as it turns out, he hadn't put the radio in monitor mode so never got any of our spotter banter... Didn't know where Mike was as a result and by the time he did see him, didn't have enough race left to chase him down.... Good play on your part waiting, bad on ours as the ground crew let the pilot down.... But as they say, there is always next year. :)

Those 20kts of additional speed were at "cruise" power settings and not race power settings, so if Hartzell will let you run that prop on a Lyc (that's what Kevin and Jon were running btw), then it should work just fine on an F1... It shocked us all at how much more efficient it was than the 3 blade counter weighted that Lynn ran last year.
 
Ah, ha, now I know where *not* to share my secrets :).... so, let me see if I can put a name with a face... Were you the turbo expert on Mikes Egg :).... You know you guys are gonna "affectionately" be known as "the Egg"... Just as well get used to it...

Anyway, it was a fun race, the results had a bunch of pylon cuts listed until yesterday, that didn't make any sense as we knew we didn't cut one... On board telemetry actually showed it as well as video. The database on RARA looked a little messed up, so before we said anything, we figured they'd find it and fix and sure enough they did.

Mike wasn't really waiting, he just suddenly noticed the white flag and thought, man I better get this party started...

Mike was pretty sure he did not cut either but what can you do? Yeah, I'm the turbo/ injection guy. It was a great race and like you say, there is always next year. We have a list of mods to do and test for '08 and hope for some big speed increases- hope to worry the NXTs- if they don't find another 10-15 mph next year of course. Likely to find out how strong the 550 is- hopefully not the bad way.

Hope Lynn, DG and Parker plus the NXTs and a few others will be there next year. Gotta love this class.:)
 
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I'll Throw Some More Avgas on the Fire

I know Darwin was pretty convinced that his Whirlwind was fast so here is another data point that some other props MAY be faster than the mighty Hartzell: http://www.attawayair.com/ Pretty impressive speed
 
Gentlemen, take a knee.

I have my red pen in my right hand. Let's make like a bunch of Fonzi's and 'be cool'. Seriously. Respect my rules or leave.



Doug Reeves
Bad Cop / Owner
 
He went faster because.....?

I know Darwin was pretty convinced that his Whirlwind was fast so here is another data point that some other props MAY be faster than the mighty Hartzell: http://www.attawayair.com/ Pretty impressive speed
He went faster on a cross country race? Could it be he flew better or the winds where more favorable? :rolleyes: (Say another plane w/ the same Hartzell prop flew the same race two years in a row and also gained 11 mph, with the same prop. What does that mean? Too many variables to draw a conclusion. Van says the WW200RV is 2 mph slower than the Hartzell BA. But when you talk 1 or 2 mph you are talking within the margin of error, at least for this data.)

Van's Aircraft found (2,500rpm/8,000ft DA/WOT) the WW200RV (206.9 mph) was a tad faster as the old Hartzell HCC2YK/F7666-4 (205.4 mph), but the WW200RV was 3 mph slower than the new Hartzell BA (72") (208.9 mph). See thumbnail data below.

Prop data is hard to get, record and compare, no doubt. So its ripe for claims. I wish Cafe Foundation ORG would do real flight test on props, fixed and constants speed (but the EAA does not support them any more). Unfortunately some manufactures might not be happy or willing to support it with a donated prop for many reasons, so it would require a lot of volunteers to donate their prop for short term for testing.


Attn: all RV'ers, IF YOU DO PROP/PLANE PERF TEST, Please lets agree on standard condition to test:

-8,000 ft DA (not indicated Alt., fly @ corrected pressure & temp density alt.)
-2,500 RPM (the most common, useful, typical RPM, if other RPM used note)
-WOT (trying for about 75% power, some planes may vary, so note MAP)
-Lean* for best / max power about 130F ROP. 100F-150F range)

Notes: Record TAS by observed IAS, corrected for inst error, temp and pressure. Record GPS runs, preferred method three legs on constant "TRACK". National Test Pilot School, NTPS, has the info and spread sheet to calculate TAS here LINK. The two-way or box 4-sided-90deg method's with simple averages have more error, especially w/ unfavorable winds. Here's a 3-leg constant heading method but requires 90deg cardinal Hdg's (if you like that better) LINK. The NTPS method is more general and versatile. For fun do both and the simple 4-leg N, S, E, W average method if you want to burn the fuel. PS LOOK for traffic. Also don't forget to note gross weight, engine or any special info with data, like flt conditions, smooth/turbulent. Part of good flight test is documentation of methodology, what ever or how ever you do it.

(* Caution: Its not recommended to lean above 75% power. Its possible some RV's may be a little over 75% power (2-4%) at 8,000ft DA & 2,500RPM & WOT. With EGT 150F ROP w/ 100LL avgas, you're still safe even if a little over 75% a few points. I'm not cavalier or promoting exceeding limits or Lycs recommendations, but flight test does some times require envelope pushing for knowledge, but do it at your own risk. You have the option to retard the throttle or climb higher to get 75% power at 2500rpm, just note the conditions you recorded the data at. However its better to stay WOT and just record your higher power (RPM/MAP/Temp/DA). Please understand your tach-gauge, airspeed-indicator and even GPS are not 100% accurate. Even if you're perfect, recording bad instruments is like measuring with a microscope and cutting with an Ax. There's always some error, but check & calibrate your instruments. The better the instruments you use, the better the data. That's what I was explaining to Jim, errors are part of flt testing, but it's a matter of knowing where the errors are & mitigating. Doing side by side testing is often a good way to weed out gross error, say indicated airspeed. Two planes flying side-by should indicate the same airspeed, right? Quick and dirty.)

BY USING A STANDARD TEST CONDITIONS WE CAN COMPARE DATA MUCH EAISER
(Kevin Hortons's RV site is fantastic (LINK) with flight test info and links. With all that info you would think he did flight testing for a living? :D:rolleyes:)



The WW200RV and BA Hartzell are close, 3 mph, nod going to the BA, which basically makes them top two. The WW 200RV is only $1,500 more than the BA & 17 lbs lighter. The only thing which worries me about smaller sized Prop companies is getting service & parts (worry/concern not fact). WW makes good products and seems to have good customer service. The WW is a very close second choice for me, but overall more than speed, the Hartzell is a better value with better support in my opinion. Also I have a small concern of repair cost and difficulty of repairs on composite props (which is a fact). A small nick/dent on a metal Hartzell may just mean a short file session with the prop still mounted on plane. A composite repair may mean removal, dis-assembly, shipping and higher cost. Small damage easily repaired on a solid metal prop may require replacement with a composite prop. This is not a trivial thing. :D

(click me & watch me grow)


PS Hartzell where is my free prop? ha-ha
 
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Hi,

I agree completely a 'standard' (even if it is just a VAF standard) for comparative testing would be great, and provide a bit more value to some of the claims. It makes sense to also add some other parameters to any records, eg:
Pilot
Date
RV model
Engine details - including size / type / induction / ignition
Fuel type AvGas / MoGas
Any additional mods - Plenums / custom cooling drag reduction
Optional recorded data log of the flight - GPS records and/or Engine/EFIS records

And although 8K DA is the aim, I'd also like to see Pressure ALT and Temp recorded.

A final thought on parameters - some of us won't be able to actually control where the mixture leaning is (or the spark advance) but we can record the values - can this be 'calculated' out later?

Can Kevin H / Bob A / AJ / other chip into this idea and get a single agreed reference for any tests? 3 way, 4 way, box / example tracks. What about wind aloft max / mins?

Hopefully Doug might be able to arrange some form of 'documentation/common' page, if not I'm sure between us we can host the information (I'll volunteer if it is wanted).

Regards,

Carl
 
The other standard - in the weeds hair on fire

The other standard I would offer is WOT, 2,700 RPM, Full rich at Sea Level. However this is hard to test unless you live near water or flat land. Sea Level is pretty low to fly. :D Even if its not the way we fly, it's an excellent condition to compare, just not practical to repeat.

May be a 1000ft or 2,500ft DA - WOT - 2,700 RPM - Full Rich would be a good standard for HIGH speed test to compare. I say high speed because its not sea level top speed.

What altitude do you think would be good to make "Standard"? Most of the USA is below 1000 feet MSL, so 2,500 ft DA might be good. Folks in Dnever, out of luck.

Great posts above, and Yes, you're right, your last post would not last. :D:D
 
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Sea level isn't practical for many (most?) people.... and using 2700 RPM restricts what engine configurations / prop are possible for testing - some are 2650, some 2650 limits..... Lets make this inclusive - we aren't neccarially worried about absolute maximum speeds - just comparative speeds at a known condition....

Carl
 
Great points

Sea level isn't practical for many (most?) people.... and using 2700 RPM restricts what engine configurations / prop are possible for testing - some are 2650, some 2650 limits..... Lets make this inclusive - we aren't necessarily worried about absolute maximum speeds - just comparative speeds at a known condition....Carl
Great points Carl.

Yes, 2,650 rpm sounds better than 2,700 rpm. A common Hartzell restriction for popular prop/engine combos is "Ops above 2,600 rpm are limited for takeoff only".

At first I thought 2,600 rpm may be better still, being most inclusive, but 2,650 rpm splits the difference. Even props with the reduce to 2,600 rpm ASAP after T/O **limit, can fly at 2,650 rpm for a few minutes to collect data.

**Talking to Hartzell its a long term fatigue issue, especially with electronic ignition, but fatigue done for two minutes at 2,650 rpm (for props with the 2,600 rpm limit) is equivalent to a few full 2,700 rpm take-offs. With the high end limits, the greater the RPM above the limit the worse, so the 2,650 is not the full 2,700 rpm and a nice compramise, inclusive of all Hartzell's. Also its not a HARD limit. It does not say do not exceed 2,600 rpm ever, just don't fly above 2,600 rpm all day. Again flight test tend to push the limits some times (as long as the PIC deems it safe).

The max continious RPM limit is not structural. Hartzells are certified to 2,900 rpm max structurally, not withstanding the fatigue limit Hartzell added for some engine/prop combos, espcially EI fired engines.


HIGH SPEED comparison Bench-mark: WOT, full rich, 2,500 ft DA @ 2,650 rpm (or max allowed for continuous Ops, CYA)


2650 rpm also gets the prop Gov more on-line and some prop/gov set-ups can't quite get a full 2,700 rpm. The good news is the new "7497" BA blade does not have a limit and can run at 2,700 rpm all day (see chart below).

I've done sea level runs (cool temps, 500 msl), but there's a lot or risk going fast low. It's just not practical as you say. Bird strikes are a big danger & worry to me; those bird-brains just don't expect you going so fast low; the lower you are, the more feathered friends there are. ++200 mph can make a mess of the sheet metal and plexi.

This illustrates the beauty of the 8,000 ft DA/2,500 rpm "Bench Mark"; its practical, meaningful, realistic and useful for comparison.

 
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TAS

I'm thinking Robbie's TAS was impressive with the Whirlwind, race speeds as George says could be due to winds. How many other RV6s can true 196.5 knots? Just saying the WW can't be half bad.
 
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The cruise performance testing I have been doing has been focused on getting repeatable data, so it is a little different than the testing being discussed so far. Perhaps some of the items I took into consideration might be of benefit.

Aircraft CG - a change in CG location will affect performance.
I identified a location and maitained it for each test. However, knowing the CG location initially will allow you to move the CG and determine the change.

Aircraft weight - Needs to be consistant for repeatable results.
I install propellers with a 12 pound weight difference. I used ballast in the baggage compartment for the heavier propellers to maintain the aircraft CG and flew off fuel weight to maintain the same aircraft wieght as with the lighter propellers.

Aircraft configuration - For my cruise performance tests, there were no changes made to the airframe. For my drag reduction testing, I make one airframe change at a time.

For my testing, smooth air is a most. No bumps allowed. Also, no standing waves allowed.

Holding altitude - I have fould that I need to fly in a 10 foot altitude window to get consistant data. This altitude control needs to be maintained until the airspeed has stabilized.

Stabilization - For my RV-3, I found it takes about 20 minutes to stabilize the airspeed.
For the testing in the RV-6A, I shorten the stabilization time by starting all of my tests 100' high. I make all of the power setting adjustments and mixture adjustments at this 100' high position. I found if I exceed peak EGT during when making the fuel mixture adjustment for the next power setting, I loose the stabilized airspeed.

Altitude - Density Altitude
I am using 8,000' and 12,000'. I try to include 4,000' and 16,000'. 4,000' doesn't usually happen because the air isn't smooth enough. (Even though I go up to 60 miles past the coastline, the mountains are still too close.)

Power Settings - WOT and engine RPM from 2000 to 2700 RPM in 100 RPM increments.

Mixture Setting - I use the maximum longevity mixture setting of 50 degrees ROP. Maximum longevity is a term provided by Jon Delamarter, manager of the Thunderbolt engines division of Lycoming.
Peak EGT is based on the first cylinder to peak, NOT peak EGT on the hottest cylinder. You'll need to know your EGT gage for this one.
As a side note: on my O-360 engine, the first cylinder to peak means that all other cylinders are ROP. For a fuel injected engine, the EGT off of peak should be far less. For the "beyond GAMI" fuel injectors becoming available, all the cylinders peak together.

Data run - I stay 100' high until the fuel flow and EGT readings have stabilized. Then I start down at 100 fpm until I am 20' above test altitude. I used this last 20 feet to level out at the test altitude and maintain zero on the VSI until the airspeed stabilizes. This takes about 3 or 4 minutes, and I usually see a 1 knot decrease. This is when the 10 foot altitude window has to be held.

A RV-10 used the Van's Aircraft test point of 8,000' density altitude, WOT and 2500 RPM to obtain the basic airspeed and fuel flow for his RV-10. He leaned to peak EGT.

At 2500 RPM, he was burning 20 gph.
At 2300 RPM, he was 1 knot faster burning 15 gph.
At 2100 RPM, he was 6 knots slower burning 12 gph.

So there is some useful information that can be obtained by using the full RPM range available. Although this probably only needs to be done once, unless there are some big changes made in drag reduction.

As seen in the RV-10 data above, there is a characteristic airspeed vs RPM curve for each propeller. From my data analysis, I found the curve changes with altitude. Specifically, the peak airspeed can occur at a different RPM with a change in altitude.
I have heard at least one Reno race pilot refer to this peak in the curve as a "sweet spot".

Regards,
Jim Ayers
 
Fuel flow

From my experience with the IO-540 the fuel flow reported at 8000' DA, WOT and leaned to peak is quite high (20 gph). 16 gph or just a bit under sounds more like what we saw in the Commanche 260. The book figurers for 75% power (more than at 8000' DA and 2500 rpm) were 18 gph @ 100 degrees ROP and 16 gph @ peak. Bill
 
Fuel Flow

From my experience with the IO-540 the fuel flow reported at 8000' DA, WOT and leaned to peak is quite high (20 gph). 16 gph or just a bit under sounds more like what we saw in the Commanche 260. The book figurers for 75% power (more than at 8000' DA and 2500 rpm) were 18 gph @ 100 degrees ROP and 16 gph @ peak. Bill

Hi Bill,

You brought up a very good point about having the "same" engine for your fuel flow comparision.

I believe the Commanche 260 uses the "same" engine like the IO-540-C4B5 or D4B5 that is commonly used for the RV-10 and Rockets.

I beleive the Commanche 260 engine also has a muffler system and a filtered airbox.
It is very common for the RV-10 and Rocket engines to not only have ram air inlets and no mufflers.
So there will be some power and fuel flow differences related to these items.

Add high compression pistions, and a fuel flow comparision quickly becomes an apples to oranges comparison.

John Harmon's stock IO-540-C4B5 in his HR2 burns a maximum of 26.5 gph. He has flown with other HR2's that were burning bwteen 33 to 36 gph in the same flight conditions.

Perhaps a better use for the three performance numbers I provided is made by looking at the different in fuel flow with the difference in airspeed.

The baseline of 8,000' DA, WOT and 2500 RPM is one used by Van's Aircraft.
2300 RPM increased the airspeed by 1 knot and decreased the fuel flow by 5 gph.
2100 RPM decreased the airspeed by 6 knots and decreased the fuel flow by another 3 gph.
The change in airspeed is very small compared to the change in fuel flow.

Jim Ayers
 
peak egt

can you safely run a io-540 at peak egt for long cross counrty flights? if so is there anything to watch for like pinging? also what is the maxum cly. head temp you guys are running in cruise?
 
can you safely run a io-540 at peak egt for long cross counrty flights? if so is there anything to watch for like pinging? also what is the maxum cly. head temp you guys are running in cruise?

Short answer NO, you should not run at peak egt.
Many articles on this subject and in the archives in this forum.
One here.
http://www.avweb.com/news/pelican/182583-1.html

Wisdom says for engine long life, cht's should be kept below 400. Above for short periods is fine. I see highest cyl 380 in cruise 50rop. About 340 highest 50lop on my io-540 std compression RV-8

Best,
 
Short answer NO, you should not run at peak egt.
Many articles on this subject and in the archives in this forum.
One here.
http://www.avweb.com/news/pelican/182583-1.html

Wisdom says for engine long life, cht's should be kept below 400. Above for short periods is fine. I see highest cyl 380 in cruise 50rop. About 340 highest 50lop on my io-540 std compression RV-8

Best,

And I continue to be confused by this. Below 70% or 75% power, I was under the assumption you can run at any EGT. I typically run at 55% to 65% power at altitude at peak EGT and see cylinder temps in the 350 dF range. Now I'm wondering if I'm damaging my cylinders?
 
peak EGT?

BELOW 75% power, Lycoming provides the following definitions for leaning:

Best Economy - At peak EGT.
Best Longevity - 50 degrees F ROP
Best Power - 100 degrees F ROP

My additional thoughts.
Lean to the first cylinder to reach peak EGT.
All of the other cylindes will be ROP. More so on carburated engines, less on fuel injected engines. All cylinders very close to peak EGT with Gami injectors. And identical peak EGT's with custom injector modification.

Leaning to peak EGT on the hottest cylinder will leave the other cylinders at unknown conditions both ROP and LOP.
Lycoming disapproves operating LOP.

Cylinder head temperature control is actually a function of engine cooling. There is a wide scatter of engine/oil cooler temperature issues already discussed in other threads from too hot to too cold.
Running the engine mixture richer will help with an engine that is running too hot.

For the lower cylinder position temperature probe, 300 to 400 degrees F is the usually operating range with a max. temp of 500 degree F.

For the spark plug position temperature probe, the maximum cylinder head temperature is usually 425 degrees F.

Check the Lycoming book for your specific engine.

Regards,
Jim Ayers
 
Jim: Thanks for additional info. My IO360 has 10:1 pistons and I have no idea how this will affect fuel flows or safe leaning. From what you've heard is 50 degrees ROP a safe target for the high comp engines? Bill
 
Jim: Thanks for additional info. My IO360 has 10:1 pistons and I have no idea how this will affect fuel flows or safe leaning. From what you've heard is 50 degrees ROP a safe target for the high comp engines? Bill

Has something changed from the latest info. The posts and articles from Walter Adkins (hope I got the last name right - I am horrible with names:)), say the danger zone is 40deg rich of peak, so the best place to run is 50deg Lean Of Peak.
 
Wade: I thiink Lycoming doesn't recommend LOP operation. They say peak for best economy, 50 ROP for best longevity, 100 ROP for best power. We ran three 540 Lycs to overhaul (over 2000 hours) using peak for cruise and 100 ROP for climb. All three did fine but these were stock engines with no high compression pistons. Maybe GAMI injectors would allow LOP ops - will ask them someday. Bill
 
I don't care for 50F ROP

Wade: I think Lycoming doesn't recommend LOP operation. They say peak for best economy, 50 ROP for best longevity, 100 ROP for best power. We ran three 540 Lycs to overhaul (over 2000 hours) using peak for cruise and 100 ROP for climb. All three did fine but these were stock engines with no high compression pistons. Maybe GAMI injectors would allow LOP ops - will ask them someday. Bill
Bill, I agree but where did you read 50 ROP is best longevity according to Lycoming? That's the worst place or peak CHT happens around near 50F EGT. From the chart you can see at about 60F ROP EGT gives max CHT.

From chart below: Max Econ (min FF) about 20F LOP*; Max power about 140F ROP; .

Best econ range between 75F (LOP) to 20F (ROP)

Best power (not max power) between 100F (ROP) to 175F (ROP)​

*LOP limited by smooth operations or lack there of.

The LOP thing has been beat to death in these forums, but Lycoming does not actually condemn it, just does not promote/recommend it (except for some of their high perf TIO540's). Look at the Lyc chart below, it shows LOP operations in the Econ range. It's more an issue of practicality for the average pilots, average fuel delivery system (injector balancing) with typical instrumentation (multi channel EGT/CHT scanners). RV'ers and Rocket guys are not average and have the motivation, skill, knowledge and engine monitors to tune their plane for LOP operations. Carb installations may still have fuel balance issues keeping them from smooth LOP operations. Still its not harmful if you are below 75% power. Also you have to remember is thinking for small engines gas savings is small for smaller engines, which was not a big deal when Avgas was in the buck something range. With it at $5.00/gal a 0.50 gal an hour savings is something. Of course a 540 is going to save more than a 360 by using LOP mixtures.

However 60F ROP is not great EGT to live at; I'd try to go either leaner or richer at least 40F from that. I personally stay in the +100F ROP range when at higher power, say above 60%-65% power. Once you get into the sub 60% range not even 50F ROP is going to be a temp issue. The caveat to all this is you should have normal oil temps and CHT temps at all time. Normal being 165F-220F for oil and CHT (well) under 400F.

(click)
 
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GMCJP = Thanks for the info and insights; I've read so many different ideas and interpretations of this and am not sure what to do for my Lycon engine. Ken Tunnell hasn't been forthcoming with recommendations on how to handle his 10:1 pistons so am a bit in the dark. Have read the 50 degrees ROP best longevity mantra several places; is it apocryphal? I do appreciate your thoughts and facts. Bill
 
peak EGT

Has something changed from the latest info. The posts and articles from Walter Adkins (hope I got the last name right - I am horrible with names:)), say the danger zone is 40deg rich of peak, so the best place to run is 50deg Lean Of Peak.

I believe his article was based on leaning to peak EGT for the hottest cylinder.

Leaning to peak EGT on the hottest cylinder doesn't provide any information for the other cylinders in relationship to their peak EGT. Some of the other cylinders could be ROP and some of the other cylinders could be LOP.

Leaning to peak EGT for the first cylinder to reach peak EGT means that all of the other cylinders are ROP.

I believe it is much easier to program a digital EGT gauge to peak to the hottest cylinder, than to program the gauge to show the first cylinder to reach peak EGT. Both types of EGT gauges are available.

Regards,
Jim Ayers
 
Lycoming LOP position document

Wade: I thiink Lycoming doesn't recommend LOP operation. They say peak for best economy, 50 ROP for best longevity, 100 ROP for best power. We ran three 540 Lycs to overhaul (over 2000 hours) using peak for cruise and 100 ROP for climb. All three did fine but these were stock engines with no high compression pistons. Maybe GAMI injectors would allow LOP ops - will ask them someday. Bill

Hi Bill,

Lycoming has an interesting document entitled "Experts are Everywhere to Help You", Lycoming Part Number SSP700. This appears to be addressing GAMI's LOP leaning technique. Will worth reading through.

Basically, this document discusses basic issues with leaning practices and proceedures. It also discusses leaning LOP and power recovery. And particularly the increased risk of detonation. Two sentences summarize Lycomings experience with LOP operation.
"The fact is that the technique of operating lean of peak and power recovery was discontinued due to the resulting increase in service issues. Burned pistons, valves, ruined rod and main bearings were traced to the inability of pilots to utilize this technique with the instrumentation and distractions found in typical general aviation aircraft."

In the second paragrath of this document is an interesting sentence.
"For optimum service life, Lycoming suggests operating 50 degree rich of peak EGT or TIT."

Also, the last sentence of the second to last paragraph seems to be related to the GAMI injector leaning procedures.
"If you have a problem resulting from operating according to the expert's recommendations he does not intend to cover your repair or replacement costs."

A good resource for leaning is section 3 of the Lycoming Operator's Manual, O-540 & IO-540 series.

One paragragh caught my attention on page 3-6 under "general rules".

"For maximum service life, cylinder head temperatures should be maintained below 435 degrees F (224 degrees C) during high performance cruise operation and below 400 degrees F (206 degrees C) for economy cruise power."

Regards,
Jim Ayers
 
Jim: Thanks for your thoughts. I have read the Lyc documents and am still confused. Still, their comments re damage and maintenance issues warrent our thoughtful attention. In years past Joe Diblin @ Lycoming spoke to us about these ussues and recommended the peak EGT in cruise and 100 degrees ROP in climb. This served us well for our stock engines. Joe felt temps were OK and plugs ran cleaner as did oil running this way; less varnish etc. Still doesn't help with how to operate 10:1 pistons. Wish I knew. Maybe Gami injectors and peak or 50 ROP? Don't wish to risk detonation! Bill
 
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