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Van's Air Force
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155kt cruise?
- Thread starter steve91t
- Start date
N941WR
Legacy Member
This is not always true. Many of us fly with custom cut FP prop and Catto and the others can and do cut them to our specifications. Thus a generalization like this is not always true.
Back in the days when a prop maker only had on prop design, it was probably true.
RV10inOz
Well Known Member
Dan
You amaze me, with yet again more cherry picking, this time from a very "promotional" brochure.
The Lycoming data sheet is at least from some serious test data, albeit detonation testing. The funny thing is that the Lycoming data sheet actually supports my posts, not yours. Now you have a brochure that supports your postings.
I sit here with a Lycoming publication that says 100F ROP. Now All the data I have seen from many years ago to todays data off the GAMI engine stand (the best source of data available in the world) shows 75-80F ROP for best power. Lycoming openly declare in the publication I am reading that says "Sometimes too much information can be a problem" So you can understand its easy for them to say 100ROP and that is a bit on the safer side! So whether we argue 75-80 Vs 100, is really neither here nor there. I will trust the Lycoming test data to be more likely a true representation of what actually happens with where Best power begins. The fact it lines up with TCM, Pratt & Whiteny, Wright, and GAMI test data I think says it all.
Bottom Line is, Lycoming continue to produce material that is in contradiction to their other materials. Having said that they are starting to cheange their tune on LOP ops and so on. Slowly slowly the wheel turns full circle
You amaze me, with yet again more cherry picking, this time from a very "promotional" brochure.
The Lycoming data sheet is at least from some serious test data, albeit detonation testing. The funny thing is that the Lycoming data sheet actually supports my posts, not yours. Now you have a brochure that supports your postings.
I sit here with a Lycoming publication that says 100F ROP. Now All the data I have seen from many years ago to todays data off the GAMI engine stand (the best source of data available in the world) shows 75-80F ROP for best power. Lycoming openly declare in the publication I am reading that says "Sometimes too much information can be a problem" So you can understand its easy for them to say 100ROP and that is a bit on the safer side! So whether we argue 75-80 Vs 100, is really neither here nor there. I will trust the Lycoming test data to be more likely a true representation of what actually happens with where Best power begins. The fact it lines up with TCM, Pratt & Whiteny, Wright, and GAMI test data I think says it all.
Bottom Line is, Lycoming continue to produce material that is in contradiction to their other materials. Having said that they are starting to cheange their tune on LOP ops and so on. Slowly slowly the wheel turns full circle
Look again.
But, no matter. As before, please present your choice of hard data for a naturally-aspirated Lycoming or Lycoming clone.
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RV10inOz
Well Known Member
Your best power starts at 80F LOP on that blown up version of the chart, so what, 75 or 80, we are agruing over the accuracy of the print on the chart next
That is along way from your original statement
We all know Best power is almost a flat line from 75...sorry 80F ROP so try telling me how to suck eggs why don't you.
Remember any statement made has to be referenced to something, a datum if you like, so we use PEAK EGT, so Best Power does not begin at 250 or 200 or 150 Rich of Peak, it begins from 75/80 ROP.....referenced from peak not towards peak.
And as for a Lycoming or clone chart, Lycomings graphs are NO BETTER than the Superior one you showed previously. They are illustrations, nothing more. I must commend you on selecting the detonation chart though, it at least is a detailed chart. Unlike the generic illustration the give you here http://www.lycoming.textron.com/support/tips-advice/key-reprints/pdfs/Key Operations.pdf And yet again it contradicts other published info.
I am over arguing the ink dot margins on a graph, you simply want an argument for the sake of one. Lycoming have a very good reliable engine, but their data and educational material sucks, so much so I think you will have a hard time finding a decent chart anywhere from them. Of course I do know where some 6 cylinder Lycomings have been run and data logged, but I also know you will reject them so I am not even bothered to ask for them.
Ciao
That is along way from your original statement
We all know Best power is almost a flat line from 75...sorry 80F ROP so try telling me how to suck eggs why don't you.
Remember any statement made has to be referenced to something, a datum if you like, so we use PEAK EGT, so Best Power does not begin at 250 or 200 or 150 Rich of Peak, it begins from 75/80 ROP.....referenced from peak not towards peak.
And as for a Lycoming or clone chart, Lycomings graphs are NO BETTER than the Superior one you showed previously. They are illustrations, nothing more. I must commend you on selecting the detonation chart though, it at least is a detailed chart. Unlike the generic illustration the give you here http://www.lycoming.textron.com/support/tips-advice/key-reprints/pdfs/Key Operations.pdf And yet again it contradicts other published info.
I am over arguing the ink dot margins on a graph, you simply want an argument for the sake of one. Lycoming have a very good reliable engine, but their data and educational material sucks, so much so I think you will have a hard time finding a decent chart anywhere from them. Of course I do know where some 6 cylinder Lycomings have been run and data logged, but I also know you will reject them so I am not even bothered to ask for them.
Ciao
Finley Atherton
Well Known Member
Concerning the Best Power discussion. It seems that all the graphs presented show the Best Power band starting at about 80 ROP and with the power curve then being fairly flat for some time as the mixture is enriched. So you could say Best Power is anywhere from about 80 ROP to some higher richer value (Lycoming's graphs indicate up to about 170ROP) but even after this power only drops slowly as the mixture is enriched.
I can't find anywhere that Lycoming says that Best Power IS at 150 ROP. Rather I think they suggest 150 ROP as this will give a greater safety margin than 80 ROP as CHTs and ICPs are lower at 150 ROP. Most things are a compromise and I think Lycoming is suggesting 150 ROP for Best Power as it is a safer place (especially for a carb engine) to operate than 80 ROP but at the expense of higher fuel consumption (Specific Fuel consumption is higher at 150 ROP than 80 ROP for virtually the same power output).
Lycoming does contradict itself however when it says for Best Power operate at 150 ROP in one publication and at 100 ROP in another publication. I think the 100 ROP recommendation is in the more recent publication so maybe they now consider 100 ROP a safe place to operate?
Lycoming's Part Throttle Fuel Consumption Chart that I used for Best Power FF in earlier posts is from the same publication that recommends 150 ROP so I presume the Fuel Flows I quoted for Best Power are based on flow rates at 150 ROP rather than 100 ROP.
I have to say that for me this is all a bit academic as I always cruise at Best Economy rather than Best Power mixture settings.
Fin
9A
I can't find anywhere that Lycoming says that Best Power IS at 150 ROP. Rather I think they suggest 150 ROP as this will give a greater safety margin than 80 ROP as CHTs and ICPs are lower at 150 ROP. Most things are a compromise and I think Lycoming is suggesting 150 ROP for Best Power as it is a safer place (especially for a carb engine) to operate than 80 ROP but at the expense of higher fuel consumption (Specific Fuel consumption is higher at 150 ROP than 80 ROP for virtually the same power output).
Lycoming does contradict itself however when it says for Best Power operate at 150 ROP in one publication and at 100 ROP in another publication. I think the 100 ROP recommendation is in the more recent publication so maybe they now consider 100 ROP a safe place to operate?
Lycoming's Part Throttle Fuel Consumption Chart that I used for Best Power FF in earlier posts is from the same publication that recommends 150 ROP so I presume the Fuel Flows I quoted for Best Power are based on flow rates at 150 ROP rather than 100 ROP.
I have to say that for me this is all a bit academic as I always cruise at Best Economy rather than Best Power mixture settings.
Fin
9A
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Starts at 80? Sure. The above dyno record does show a flat line max power from 80 ROP to 220 ROP. I've marked a 100 to 200 range. Same thing....the middle is still 150.
David, lets have some fun; an imaginary race right there in your neighborhood using identical RV-10's, Point Lookout to Point Moreton at 500 MSL. After all, this thread is about speed.
What engine and prop settings will you use?
David, lets have some fun; an imaginary race right there in your neighborhood using identical RV-10's, Point Lookout to Point Moreton at 500 MSL. After all, this thread is about speed.
What engine and prop settings will you use?
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RV10inOz
Well Known Member
Finley,
I see you are onto it. I think the reason Lycoming are guarded with any data, and the reason they talk about 100 or any higher number is not that there is more power to be had, but it is due to the fact out of the factory their engines are not capable of getting all their 6 or 4 little engines playing the same game. TCM's generally do this better.
Having said that, I recently flew an identical factory IO540 powered RV10 and it went LOP with a spread no greater than 0.2GPH at various settings and went beyond 60LOP smotth as. That is the first time I have ever seen that. Ours was a pig out of the box, could not get all of them to peak without the spread being 1.5 or more GPH and it was clearly running on only a few cylinders by the time the last one peaked. We had to do a rough guess on the first two rounds of injector tuning just to get an engine we could work with to tune. Unreal.
So back to your comments yes the detonation margin. But this argument was about where best power is. The richer you go down around 200ROP the effective ignition is retarded and this is all about detonation margin. Get a well set up engine and you get best power from ALL cylinders at the 75-80 mark. However and here is the kicker..............Lycoming don't give you that when you hand over 30-50 AMU's.
So when you read their blurbs, and look at these generic graphs, they are butt covering IMHO.
So Dan, to your mental race..........
Is that at Cape Moreton you mean
So do we care about fuel burn for the trip? Is there a penalty applied for litres used over a certain amount? Or do we want to keep the engine for 2000 hrs? Just asking? Not sure what the Nascar boys get but a V8 Supercar engine is good for about 4000km (25k miles) and they play with mixture because fuel burn is a mission critical thing. Maybe Nascar do not care.
So I would have a well set up IO540, and being a race, it would be at a RPM figure in the 2600's (Pierre will know exactly what I am on about ) and I would run at a position probably just lean of full rich, Target EGT like for a climb, and I would go test all this on the Dyno first to work out where a good detonation margin might be. In the absence of good data it would be leaned just a fraction or most folk would say nahh just leave it full rich, waste some fuel so who cares. And this is why generic and simple statements are made for pilots not capable of understanding things for themselves.
Now, if there were fuel penalty points applied, and it was a real race, it would be over the start line as I had gotten the last one back from the peak side to the 75/80 point. Squeeze every equine unit per hydrocarbon I could.
Now lets take the race to 10,000' where the detonation issue is less a problem, or is not even a consideration. Where would you run now?
I see you are onto it. I think the reason Lycoming are guarded with any data, and the reason they talk about 100 or any higher number is not that there is more power to be had, but it is due to the fact out of the factory their engines are not capable of getting all their 6 or 4 little engines playing the same game. TCM's generally do this better.
Having said that, I recently flew an identical factory IO540 powered RV10 and it went LOP with a spread no greater than 0.2GPH at various settings and went beyond 60LOP smotth as. That is the first time I have ever seen that. Ours was a pig out of the box, could not get all of them to peak without the spread being 1.5 or more GPH and it was clearly running on only a few cylinders by the time the last one peaked. We had to do a rough guess on the first two rounds of injector tuning just to get an engine we could work with to tune. Unreal.
So back to your comments yes the detonation margin. But this argument was about where best power is. The richer you go down around 200ROP the effective ignition is retarded and this is all about detonation margin. Get a well set up engine and you get best power from ALL cylinders at the 75-80 mark. However and here is the kicker..............Lycoming don't give you that when you hand over 30-50 AMU's.
So when you read their blurbs, and look at these generic graphs, they are butt covering IMHO.
So Dan, to your mental race..........
Is that at Cape Moreton you mean
So do we care about fuel burn for the trip? Is there a penalty applied for litres used over a certain amount? Or do we want to keep the engine for 2000 hrs? Just asking? Not sure what the Nascar boys get but a V8 Supercar engine is good for about 4000km (25k miles) and they play with mixture because fuel burn is a mission critical thing. Maybe Nascar do not care.
So I would have a well set up IO540, and being a race, it would be at a RPM figure in the 2600's (Pierre will know exactly what I am on about
) and I would run at a position probably just lean of full rich, Target EGT like for a climb, and I would go test all this on the Dyno first to work out where a good detonation margin might be. In the absence of good data it would be leaned just a fraction or most folk would say nahh just leave it full rich, waste some fuel so who cares. And this is why generic and simple statements are made for pilots not capable of understanding things for themselves.Now, if there were fuel penalty points applied, and it was a real race, it would be over the start line as I had gotten the last one back from the peak side to the 75/80 point. Squeeze every equine unit per hydrocarbon I could.
Now lets take the race to 10,000' where the detonation issue is less a problem, or is not even a consideration. Where would you run now?
SO....
setting aside the academic minutiae, and the political discussion of why Lycoming says or prints what it does, and then getting to the point of what all of this means in practical application - I have heard nothing to dissuade me from the following pilot best practices (assume always WOT, CS prop) :
1) Down low if you want to go as fast as possible - economy/fuel burn be dammed - run at 150 ROP at an RPM that is prudent to you.
2) As altitude increases, you can lean further, eventually to 70 - 80 ROP, to still produce max speed, (economy still not important to mission), with prudent engine management (no undue abuse).
3) When mission requires that range is more important than max speed, the best efficiency is arrived at by RPM reduction (as compared to throttle reduction) until below 65% power, and then lean to 20 - 40 LOP.
4) Finally, when absolute max range is needed, reduce RPM further while remaining 20 - 40 LOP until you get an airspeed that best suits your range needs - Carson's speed for practical max range or Vy for absolute “don't care when I get there as long as I make it” speed.
(sorry fix pitched guys, having to reduce throttle to make these things happen is part of the efficiency compromise that you made)
Assuming the usual consideration for winds and altitudes, does anyone that is still in this thread have a problem with any of this??
Thanks
(PS: For me it would be 125 - 150 ROP)
(PSS: for Steve91t, I still don't think that 8.5 gph is anywhere close to max power for an IO-360 at 8000'. Get max power (WOT, at least 2400 RPM, 80 - 100 ROP, 10 - 10.5 gph) and your KTAS will increase to close to the expected "normal" numbers)
setting aside the academic minutiae, and the political discussion of why Lycoming says or prints what it does, and then getting to the point of what all of this means in practical application - I have heard nothing to dissuade me from the following pilot best practices (assume always WOT, CS prop) :
1) Down low if you want to go as fast as possible - economy/fuel burn be dammed - run at 150 ROP at an RPM that is prudent to you.
2) As altitude increases, you can lean further, eventually to 70 - 80 ROP, to still produce max speed, (economy still not important to mission), with prudent engine management (no undue abuse).
3) When mission requires that range is more important than max speed, the best efficiency is arrived at by RPM reduction (as compared to throttle reduction) until below 65% power, and then lean to 20 - 40 LOP.
4) Finally, when absolute max range is needed, reduce RPM further while remaining 20 - 40 LOP until you get an airspeed that best suits your range needs - Carson's speed for practical max range or Vy for absolute “don't care when I get there as long as I make it” speed.
(sorry fix pitched guys, having to reduce throttle to make these things happen is part of the efficiency compromise that you made)
Assuming the usual consideration for winds and altitudes, does anyone that is still in this thread have a problem with any of this??
Thanks
(PS: For me it would be 125 - 150 ROP)
(PSS: for Steve91t, I still don't think that 8.5 gph is anywhere close to max power for an IO-360 at 8000'. Get max power (WOT, at least 2400 RPM, 80 - 100 ROP, 10 - 10.5 gph) and your KTAS will increase to close to the expected "normal" numbers)
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RV10inOz
Well Known Member
I don't care.......you do what you want
my answer will depend on what the terms of the race are. Which bit of motor sports do you not get? In the category I race in there are very strict rules on everything down to suspension pick up points, yet engines...heck so long as it comes from the same manufacturer!
Enough thread drift from me.........and I suggest you too!
