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08-09-2011, 09:18 AM
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Join Date: Feb 2005
Location: Chesterfield, Missouri
Posts: 4,514
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Quote:
Originally Posted by Moura
Since Don from AFP was mentioned, I did replace my restrictors and they were perfect. Only replaced 3 for 25 dollars (I think that is what I paid) each.
But you know what puzzles me, Don mentioned he would never run not even an inch above 24MAP!! Should I be confused?
Moura
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Yep, and for me the number is 23. That's the thresh hold into the dreaded red box or 75% power.
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08-09-2011, 09:58 AM
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Join Date: Jul 2009
Location: Mojave
Posts: 4,652
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Quote:
Originally Posted by David-aviator
Yep, and for me the number is 23. That's the thresh hold into the dreaded red box or 75% power.
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For those that believe a "red box" even exists for our engines, remember that "power" is MP and RPM... You can still run big MP, but use low RPM to drag the % power out of the red box if you choose... Look at the picture in post #17. Thats nearly 26 inches of MAP; happily LOP at low RPM.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.
Michael Robinson
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Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
Last edited by Toobuilder : 08-09-2011 at 10:02 AM.
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08-09-2011, 10:08 AM
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Join Date: Oct 2009
Location: Uberaba, MG, Brazil
Posts: 122
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Quote:
Originally Posted by Toobuilder
For those that believe a "red box" even exists for our engines, remember that "power" is MP and RPM... You can still run big MP, but use low RPM to drag the % power out of the red box if you choose... Look at the picture in post #17. Thats nearly 26 inches of MAP; happily LOP at low RPM.
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What is best in that case (flying low), high MAP and low RPM, low MAP and high RPM or somewhere in between such as 24/24?
Last edited by Moura : 08-09-2011 at 10:31 AM.
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08-09-2011, 11:18 AM
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Join Date: Jul 2009
Location: Mojave
Posts: 4,652
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"Best" is a tough subject...
WOT (high MP) produces the best VE from an engine...
High RPM without MP makes lots of friction and noise...
While I'm no expert, it sure seems like MP is king... After all, the main proponents of this LOP thing are the turbonormalized guys. Those engines will pull 30 inches of MP from the ground up to the flight levels, so if high MP was bad, they would certainly not spend to money to make it. Mooney (and others) have offered "ram air" systems; many of the aftermarket cowls offer the same - all with the stated benefit of increased MP. Nobody would install/use this equipment, then negate the benefits by partly closing the throttle, would they?
If I'm not in an extreme hurry, I'll crank the RPM way down and run it WOT even down low. In fact, the only time my engine is not WOT is in the pattern, or really just loafing around sighteeing. If I'm going from A to B - it's on the stop, wide open. I use RPM and mixture for power output.
While there are some MP/RPM combinations that may cause resonance issues with certain prop/engine combinations, I doubt you can actually "lug" an aircraft engine enough to cause damage. The power output would be so low as to be impractical for flight.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.
Michael Robinson
______________
Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
Last edited by Toobuilder : 08-09-2011 at 11:22 AM.
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08-09-2011, 11:59 AM
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Join Date: Sep 2010
Location: Charlotte NC
Posts: 1,167
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Not sure if I can get this to format correctly but I did a test flight today in my RV6 and recorded some data points. Those who have high compression engines may be interested. The engine is a ECI IO360 with their fuel injection and dual lightspeeds. The Pistons are 10 to 1.
All data points are at 8500 feet, 68F OAT, WOT and 2500 RPM with a RV200 prop. All speeds are knots.
FF 10.7 CHT/EGT 332/1260 358/1299 354/1245 363/1287
120 ROP 154 IAS 183 TAS
FF 8.9 330/1380 360/1423 353/1363 365/1410
peak 149 IAS 177 TAS
FF 8.0 309/1337 338/1379 332/1328 346/1379
50 LOP 147 IAS 175 TAS
FF 7.5 288/1317 317/1344 312/1312 323/1343
80 LOP 143 IAS 170 TAS
Glancing at the numbers a couple of things surprised me. The first was that my CHT's were not really different from 120 ROP to peak. It may be that I did not allow enough time for the temps to stabilize at the 120ROP setting. The peak numbers I see all the time and are right on. I am going to repeat that part another day and see what happens. CHT's dropped rapidly LOP. The other thing was that IAS loss was only 11 knots from 120 ROP to 80 LOP however fuel flow was down 2.2 gallons. I was actually trying to run 100 ROP so did not hit the numbers quite on but 154 is pretty much best power IAS at 8500.
I would appreciate it if anyone is seeing anything in these numbers that would suggest any issues with LOP ops on my aircraft. Getting ready for the first couple long cross countries and plan on LOP ops unless of course I chicken out. As mentioned in past threads I have very little piston engine experience and still trying to get a grasp on how to best operate my engine.
George
Last edited by sailvi767 : 08-09-2011 at 12:04 PM.
Reason: TYPO
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08-09-2011, 01:19 PM
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Join Date: May 2005
Location: Tuttle, Oklahoma
Posts: 2,563
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Quote:
Originally Posted by sailvi767
Not sure if I can get this to format correctly but I did a test flight today in my RV6 and recorded some data points. Those who have high compression engines may be interested. The engine is a ECI IO360 with their fuel injection and dual lightspeeds. The Pistons are 10 to 1.
All data points are at 8500 feet, 68F OAT, WOT and 2500 RPM with a RV200 prop. All speeds are knots.
FF 10.7 CHT/EGT 332/1260 358/1299 354/1245 363/1287
120 ROP 154 IAS 183 TAS
FF 8.9 330/1380 360/1423 353/1363 365/1410
peak 149 IAS 177 TAS
FF 8.0 309/1337 338/1379 332/1328 346/1379
50 LOP 147 IAS 175 TAS
FF 7.5 288/1317 317/1344 312/1312 323/1343
80 LOP 143 IAS 170 TAS
Glancing at the numbers a couple of things surprised me. The first was that my CHT's were not really different from 120 ROP to peak. It may be that I did not allow enough time for the temps to stabilize at the 120ROP setting. The peak numbers I see all the time and are right on. I am going to repeat that part another day and see what happens. CHT's dropped rapidly LOP. The other thing was that IAS loss was only 11 knots from 120 ROP to 80 LOP however fuel flow was down 2.2 gallons. I was actually trying to run 100 ROP so did not hit the numbers quite on but 154 is pretty much best power IAS at 8500.
I would appreciate it if anyone is seeing anything in these numbers that would suggest any issues with LOP ops on my aircraft. Getting ready for the first couple long cross countries and plan on LOP ops unless of course I chicken out. As mentioned in past threads I have very little piston engine experience and still trying to get a grasp on how to best operate my engine.
George
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I would be suspect of your temperature data. At least in comparison to what I have seen with my engine ( ECI IO-340 with 9.0:1 CR). I typically see: - CHT's in the 375-400 and EGT's in the 1250-1350 range when running around 100 ROP.
- CHT's in the 290-320 and EGT's in the 1350-1400 range when running around 50 LOP.
When analyzing your performance runs, your data shows that when you compare the differences between the 120 ROP run and the 80 LOP RUN: - your 2.2 gal/hr decrease in fuel flow is yielding a change of 29.91%
- your 13 KNOT speed decrease is yielding a change of 7.10%.
So these numbers are the basis of the decision you have to make. Is it worth a 7% decrease in speed in order to see a 30% decrease in fuel burn?
My last comment pertains to your statement about ". . .unless of course I chicken out." This I don't understand. What are you afraid of? - When reading this thread or other threads dealing with LOP operations are you still disbelieving those who are posting that they are successfully running LOP?
- Are the expert opinions, stating the likelihood of damaging our small engines is really very small, not convincing enough?
- Is your own data not convincing you that running LOP is a realistic goal you can achieve?
If your temperature readings are accurate then you surely do not need to worry. As has been posted here and elsewhere, the key is to keep the CHT temps down. If you are successfully doing this there should be little, if anything to worry about.
Live Long and Prosper!
Last edited by RVbySDI : 08-09-2011 at 03:18 PM.
Reason: Forgot to mention I am running a 9.0:1 ECI IO-340 engine
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08-09-2011, 02:24 PM
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Join Date: Sep 2010
Location: Charlotte NC
Posts: 1,167
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My big concern is with the compression. I have yet to find someone running 10 to 1 who also runs LOP. I agree the data is compelling however the engine manufacturers still all seem against LOP ops in high compression engines. Most however seem against it because they don't have any real data.
I don't know about the temps. I did not build the aircraft however the builder was from Arizona and spent a lot of time working on the engine cooling with a custom cowl and plenum. Below is a quote from his website that leads me to believe the indications are correct. Your aircraft seems to have a bigger drop when LOP. What may be a factor is perhaps I did not give the temps enough time to stabilize. I will look at that when I take a long trip. The plenum could also be a factor in the lower drop I am seeing. The top numbers I do like however.
"The plenum took almost 35 hours to complete but the benefits were; CHT down to 430 degrees on the first flight of my new ECI engine in Phoenix OAT 95 degrees. When the rings seated, about 2 hours later, the CHT went down to 360 degrees."
360 seems to be around the max I am seeing. The other day with the takeoff temp at 99 degrees I saw closer to 380 however I was climbing at 100 knots for the first 3000 feet. I am very pleased with the CHT temps. It was not the builders first RV and he really understands cooling and engines. Even though I did not buy the aircraft from him directly he spent a great deal of effort discussing the aircraft and its construction with me. Seems to be the norm with the people in this community. Everyone is beyond helpful.
Edit. I just realized you might be talking about the difference in EGT's more then CHT's. Not sure why we would see such different data points as far as drop ROP to LOP.
George
Last edited by sailvi767 : 08-09-2011 at 02:48 PM.
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08-09-2011, 02:47 PM
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Join Date: Aug 2006
Location: santa barbara, CA
Posts: 1,682
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George's data seem comparable to what I see on my Aerosport Power (ECI parts) IO-360B1B. I dont see how you can argue against LOP with reduced CHTs and reduced fuel flow. As long as you are monitoring all cylinders, dont be afraid to play with the mixture knob and see how it changes things. If its running rough, the temps are elevated, or your speed has dropped below an acceptable level, adjust the mixture! Roughness and temps will tell you if your engine is happy or not
erich
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08-09-2011, 03:34 PM
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Join Date: May 2005
Location: Tuttle, Oklahoma
Posts: 2,563
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Quote:
Originally Posted by sailvi767
My big concern is with the compression. I have yet to find someone running 10 to 1 who also runs LOP. I agree the data is compelling however the engine manufacturers still all seem against LOP ops in high compression engines. Most however seem against it because they don't have any real data.
I don't know about the temps. I did not build the aircraft however the builder was from Arizona and spent a lot of time working on the engine cooling with a custom cowl and plenum. Below is a quote from his website that leads me to believe the indications are correct. Your aircraft seems to have a bigger drop when LOP. What may be a factor is perhaps I did not give the temps enough time to stabilize. I will look at that when I take a long trip. The plenum could also be a factor in the lower drop I am seeing. The top numbers I do like however.
"The plenum took almost 35 hours to complete but the benefits were; CHT down to 430 degrees on the first flight of my new ECI engine in Phoenix OAT 95 degrees. When the rings seated, about 2 hours later, the CHT went down to 360 degrees."
360 seems to be around the max I am seeing. The other day with the takeoff temp at 99 degrees I saw closer to 380 however I was climbing at 100 knots for the first 3000 feet. I am very pleased with the CHT temps. It was not the builders first RV and he really understands cooling and engines. Even though I did not buy the aircraft from him directly he spent a great deal of effort discussing the aircraft and its construction with me. Seems to be the norm with the people in this community. Everyone is beyond helpful.
Edit. I just realized you might be talking about the difference in EGT's more then CHT's. Not sure why we would see such different data points as far as drop ROP to LOP.
George
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It sounds to me that your engine is happy running LOP.
I think most engine manufacturers are not willing to accept LOP operations because of the lawyers. They are afraid there is too small of a margin for all of the variables associated with installation and operation when running LOP. Without a pilot understanding what he is doing and without proper instrumentation to monitor there could potentially be problems. However, in our experimental world most everyone I know flying LOP has a great wealth of information readily at their disposal. Of course, we are fortunate in the experimental world to have this detailed instrumentation. The certificated GA world is not so blessed. I am sure these manufacturers are thinking in terms of all of those GA aircraft that may be woefully inadequate when it comes to engine monitor instruments. So they are going to err on the side of conservative views on this issue.
I forgot to mention what engine I am running in my previous post ( I have edited the previous post to reflect my engine information). I am running an ECI IO-340 with 9.0:1 CR pistons. As far as the temps on my engine, I am definitely seeing a decrease in CHT temps when I run LOP. I usually will not see CHT temps above 325 and usually they are closer to 310 during cruise. When I run ROP the CHT are closer to 375-380 with the hottest pushing toward 400 in some instances. There is a drastic difference in CHT temps LOP vs. ROP with my engine. Not sure why.
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08-09-2011, 03:47 PM
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Join Date: Jul 2009
Location: Mojave
Posts: 4,652
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Another point that seems to be missed with those in "fear" of LOP is that detonation is a chemical thing that can be eliminated both with too rich and too lean a mixture. If Deakin's chart is right, then 50 or more LOP will NOT support detonation, regardless of MP, RPM, CR or any other reasonable variable we are likely to find in our engines.
If I'm reading this stuff right, too lean kills a bit of power, but it also seems to kill ALL detonation. The only part that really requires skill is jumping across the evil red box quickly enough to not do any damage. And even with the big turbo engines, you still have plenty of time, apparently.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.
Michael Robinson
______________
Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
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