Today's Message Index:
----------------------
1. 11:21 AM - ROP versus LOP...might be off-topic for some (Lynn Matteson)
2. 01:22 PM - Re: ROP versus LOP...might be off-topic for some (BobsV35B@aol.com)
3. 03:28 PM - Re: ROP versus LOP...might be off-topic for some (Lynn Matteson)
4. 03:45 PM - Re: ROP versus LOP...might be off-topic for some (BobsV35B@aol.com)
5. 05:57 PM - Re: ROP versus LOP...might be off-topic for some (Lynn Matteson)
6. 06:10 PM - Re: ROP versus LOP...might be off-topic for some (BobsV35B@aol.com)
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| Subject: | ROP versus LOP...might be off-topic for some |
Over the last week, I've had some fun making some tests with my newly-
installed Rotec TBI-40 mixture-adjustable, carburetor-replacement
device on my Jabiru engine. I don't know whether two of these units
will work on a Rotax, so many of you might want to hit the delete key
right now.
For the most part, I was flying it LOP (lean-of-peak), but yesterday
I made a flight and decided that I would try ROP (rich-of-peak). In
flying LOP, the articles I've read say to keep the power requirements
low, and LOP will work and you won't burn the engine down. I was
amazed that this LOP thing even works at all, let alone work as well
as I've found that it seems too....I guess I'm still a bit of a
skeptic. After all, if going lean is a bad thing, how can going even
leaner be a good thing? I won't argue whether or not it's a good or
bad thing, and there are those of you that may not be able to do any
leaning at all, as I was until I got this unit.
Three days ago, I made two trips totaling 475 miles, using LOP
settings, and yesterday I made a 310-mile trip, using ROP settings. I
had flown the 475 miles leaning out the engine until peak EGT, then
leaning more until the engine was obviously low on power, and I
contentedly flew at this setting, watching the scenery crawl by.
Yesterday I decided to actually GO somewhere, and never mind the fuel
saving, I just wanted to get there, so I decided to try ROP.
Here are the average numbers from those trips:
LOP: 27.77 miles per gallon; 3.3 gallons per hour; 93.14
miles per hour
ROP: 23.66 miles per gallon; 4.37 gallons per hour; 103.3 miles per
hour
Altitudes on all of these flight were anywhere from 3000' MSL (with a
base of 1000') to 10,000 MSL, with throttle settings from 2600 rpm to
3050. Fuel flow as seen on the gauge, ranged from 2.5 gallons per
hour to 5.0 not including takeoffs, but including climbs.
So you can see from these figures (admittedly a low number of
samples) that it does pay to tweak the mixture, and even if flown
LOP, the speed is not too bad.
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 737.3 hrs
Sensenich 62"x46" Wood prop
Electroair direct-fire ignition system
Rotec TBI-40 injection
Status: flying
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| Subject: | Re: ROP versus LOP...might be off-topic for some |
Good Afternoon Lynn,
Just as a quick recap of LOP versus ROP, may we specify what it is that we
are lean of or rich of?
Generally speaking, most folks like to think of rich or lean in relation to
EGT temperature, but the thing we really want to know is whether we are on
the rich side or the lean side of best power. At best power, almost all of
the air that is available will be used. By checking the temperature with
an EGT gauge, we will find that when we are running at "best" power, the EGT
gauge will generally read about 60 degrees F cooler than it will at peak
EGT. We therefore now know that peak EGT occurs on the lean side of best
power. Another way to say that is that best power can be found about sixty to
eighty degrees richer than Peak EGT
The hottest internal combustion temperature will occur when just a bit lean
of best power. Most of our automobile engines are designed to run right at
best power most of the time. Our aircraft engines tend to be designed to
run at full takeoff power for a relatively short time and the cooling
capabilities are designed to be able to handle full power by adding extra fuel
to
the mixture which will slow down the rate of burn, move the point of peak
cylinder pressure later in the combustion process and allow us to keep the
engine temps below the redline while developing high power.
So --- If we are at full or high power running rich and we make the
mixture less rich, we are taking away some of the fuel that has been used to
move the flame front later in the cycle and the cylinder temperatures will
rise. However, if we continue to reduce the fuel flow, the internal temperature
will peak at some rather high number. That will be very close to the best
power mixture. The problem is that our engines are not designed to cool
properly at that high a cylinder pressure. If we continue to make the mixture
less rich, it will eventually get to the peak EGT. That will occur with an
EGT that is between fifty and eighty degrees Fahrenheit hotter than it was
at the peak combustion temperature point. If we now continue to lean the
mixture, the EGT will drop. Less fuel means less fire and the cylinder
temperatures and pressures will continue to drop. At a cruise power of sixty to
seventy percent for most light aircraft engines, the best BSFC (Brake
Specific Fuel Consumption) will be found with an EGT about twenty degrees F
leaner than Peak EGT. (Or about seventy-five to one hundred degrees away from
best power.) It makes sense that when you are burning less fuel the
temperatures will be lower, but when we are running at very high power settings,
we
need the extra fuel to keep the peak combustion pressure and temperatures
down.
Thus, it can truthfully be said that there are times when leaning the
engine will make the heads run hotter, but there are also times when leaning the
mixture will make the heads run cooler.
As Always, It All depends!
Make any sense at all?
Happy Skies,
Old Bob
Stearman N3977A
LL22
In a message dated 8/15/2009 1:21:33 P.M. Central Daylight Time,
lynnmatt@jps.net writes:
--> JabiruEngine-List message posted by: Lynn Matteson <lynnmatt@jps.net>
Over the last week, I've had some fun making some tests with my newly-
installed Rotec TBI-40 mixture-adjustable, carburetor-replacement
device on my Jabiru engine. I don't know whether two of these units
will work on a Rotax, so many of you might want to hit the delete key
right now.
For the most part, I was flying it LOP (lean-of-peak), but yesterday
I made a flight and decided that I would try ROP (rich-of-peak). In
flying LOP, the articles I've read say to keep the power requirements
low, and LOP will work and you won't burn the engine down. I was
amazed that this LOP thing even works at all, let alone work as well
as I've found that it seems too....I guess I'm still a bit of a
skeptic. After all, if going lean is a bad thing, how can going even
leaner be a good thing? I won't argue whether or not it's a good or
bad thing, and there are those of you that may not be able to do any
leaning at all, as I was until I got this unit.
Three days ago, I made two trips totaling 475 miles, using LOP
settings, and yesterday I made a 310-mile trip, using ROP settings. I
had flown the 475 miles leaning out the engine until peak EGT, then
leaning more until the engine was obviously low on power, and I
contentedly flew at this setting, watching the scenery crawl by.
Yesterday I decided to actually GO somewhere, and never mind the fuel
saving, I just wanted to get there, so I decided to try ROP.
Here are the average numbers from those trips:
LOP: 27.77 miles per gallon; 3.3 gallons per hour; 93.14
miles per hour
ROP: 23.66 miles per gallon; 4.37 gallons per hour; 103.3 miles per
hour
Altitudes on all of these flight were anywhere from 3000' MSL (with a
base of 1000') to 10,000 MSL, with throttle settings from 2600 rpm to
3050. Fuel flow as seen on the gauge, ranged from 2.5 gallons per
hour to 5.0 not including takeoffs, but including climbs.
So you can see from these figures (admittedly a low number of
samples) that it does pay to tweak the mixture, and even if flown
LOP, the speed is not too bad.
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 737.3 hrs
Sensenich 62"x46" Wood prop
Electroair direct-fire ignition system
Rotec TBI-40 injection
Status: flying
Message 3
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| Subject: | Re: ROP versus LOP...might be off-topic for some |
Yeah, it makes sense, and I hope I'm doing it right. I lean until the
peak EGT is found, then either richen about 50 degrees (that's what
I've read) for ROP, or continue leaning until the EGT's (all four of
them in my case) also drop about 50 degrees. The CHT's also come down
in my engine, as well as the power....the engine feels like my car
does when I turn on the air conditioner...kinda sagging in power. But
I NEVER do this LOP setting when I am over about 2850 rpm (red line
3300) or when I am stressing the engine. If I'm doing something that
would hurt the engine, I'd certainly like to be alerted to it. But I
only go lean-of-peak EGT when in a slow cruise mode. (When I
mentioned going to 3050 rpm, I was referring to going to ROP in a low
power-requirement mode.)
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 737.3 hrs
Sensenich 62"x46" Wood prop
Electroair direct-fire ignition system
Rotec TBI-40 injection
Status: flying
On Aug 15, 2009, at 4:16 PM, BobsV35B@aol.com wrote:
> Good Afternoon Lynn,
>
> Just as a quick recap of LOP versus ROP, may we specify what it is
> that we are lean of or rich of?
>
> Generally speaking, most folks like to think of rich or lean in
> relation to EGT temperature, but the thing we really want to know
> is whether we are on the rich side or the lean side of best power.
> At best power, almost all of the air that is available will be
> used. By checking the temperature with an EGT gauge, we will find
> that when we are running at "best" power, the EGT gauge will
> generally read about 60 degrees F cooler than it will at peak EGT.
> We therefore now know that peak EGT occurs on the lean side of best
> power. Another way to say that is that best power can be found
> about sixty to eighty degrees richer than Peak EGT
>
> The hottest internal combustion temperature will occur when just a
> bit lean of best power. Most of our automobile engines are designed
> to run right at best power most of the time. Our aircraft engines
> tend to be designed to run at full takeoff power for a relatively
> short time and the cooling capabilities are designed to be able to
> handle full power by adding extra fuel to the mixture which will
> slow down the rate of burn, move the point of peak cylinder
> pressure later in the combustion process and allow us to keep the
> engine temps below the redline while developing high power.
>
> So --- If we are at full or high power running rich and we make
> the mixture less rich, we are taking away some of the fuel that has
> been used to move the flame front later in the cycle and the
> cylinder temperatures will rise. However, if we continue to reduce
> the fuel flow, the internal temperature will peak at some rather
> high number. That will be very close to the best power mixture. The
> problem is that our engines are not designed to cool properly at
> that high a cylinder pressure. If we continue to make the mixture
> less rich, it will eventually get to the peak EGT. That will occur
> with an EGT that is between fifty and eighty degrees Fahrenheit
> hotter than it was at the peak combustion temperature point. If we
> now continue to lean the mixture, the EGT will drop. Less fuel
> means less fire and the cylinder temperatures and pressures will
> continue to drop. At a cruise power of sixty to seventy percent for
> most light aircraft engines, the best BSFC (Brake Specific Fuel
> Consumption) will be found with an EGT about twenty degrees F
> leaner than Peak EGT. (Or about seventy-five to one hundred degrees
> away from best power.) It makes sense that when you are burning
> less fuel the temperatures will be lower, but when we are running
> at very high power settings, we need the extra fuel to keep the
> peak combustion pressure and temperatures down.
>
> Thus, it can truthfully be said that there are times when leaning
> the engine will make the heads run hotter, but there are also times
> when leaning the mixture will make the heads run cooler.
>
> As Always, It All depends!
>
> Make any sense at all?
>
> Happy Skies,
>
> Old Bob
> Stearman N3977A
> LL22
>
> In a message dated 8/15/2009 1:21:33 P.M. Central Daylight Time,
> lynnmatt@jps.net writes:
> <lynnmatt@jps.net>
>
> Over the last week, I've had some fun making some tests with my newly-
> installed Rotec TBI-40 mixture-adjustable, carburetor-replacement
> device on my Jabiru engine. I don't know whether two of these units
> will work on a Rotax, so many of you might want to hit the delete key
> right now.
>
> For the most part, I was flying it LOP (lean-of-peak), but yesterday
> I made a flight and decided that I would try ROP (rich-of-peak). In
> flying LOP, the articles I've read say to keep the power requirements
> low, and LOP will work and you won't burn the engine down. I was
> amazed that this LOP thing even works at all, let alone work as well
> as I've found that it seems too....I guess I'm still a bit of a
> skeptic. After all, if going lean is a bad thing, how can going even
> leaner be a good thing? I won't argue whether or not it's a good or
> bad thing, and there are those of you that may not be able to do any
> leaning at all, as I was until I got this unit.
> Three days ago, I made two trips totaling 475 miles, using LOP
> settings, and yesterday I made a 310-mile trip, using ROP settings. I
> had flown the 475 miles leaning out the engine until peak EGT, then
> leaning more until the engine was obviously low on power, and I
> contentedly flew at this setting, watching the scenery crawl by.
> Yesterday I decided to actually GO somewhere, and never mind the fuel
> saving, I just wanted to get there, so I decided to try ROP.
> Here are the average numbers from those trips:
>
> LOP: 27.77 miles per gallon; 3.3 gallons per hour; 93.14
> miles per hour
> ROP: 23.66 miles per gallon; 4.37 gallons per hour; 103.3
> miles per
> hour
>
> Altitudes on all of these flight were anywhere from 3000' MSL (with a
> base of 1000') to 10,000 MSL, with throttle settings from 2600 rpm to
> 3050. Fuel flow as seen on the gauge, ranged from 2.5 gallons per
> hour to 5.0 not including takeoffs, but including climbs.
>
> So you can see from these figures (admittedly a low number of
> samples) that it does pay to tweak the mixture, and even if flown
> LOP, the speed is not too bad.
>
> Lynn Matteson
> Kitfox IV Speedster, taildragger
> Jabiru 2200, #2062, 737.3 hrs
> Sensenich 62"x46" Wood prop
> Electroair direct-fire ignition system
> Rotec TBI-40 injection
> Status: flying
>
>
> www.matronics.com/contribution _-
> ===========================================================
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| Subject: | Re: ROP versus LOP...might be off-topic for some |
Good Afternoon Lynn,
The only comment I would make is to be certain that you only use the fifty
rich mode when you are pulling seventy percent power or less. Fifty rich of
peak will give you the hottest cylinder temperature that you can get. It
is a mixture to be avoided at any high power settings. I restrict a fifty
rich setting to no higher than sixty-five percent power, but I tend to be on
the cautious side. Fifty lean of peak is leaner than you need for optimum
economy. Twenty lean is just about perfect at sixty-five percent power.
Fifty lean won't hurt a thing, but you lose a little efficiency.
Sounds like fun though.
Happy Skies,
Old Bob
In a message dated 8/15/2009 5:28:52 P.M. Central Daylight Time,
lynnmatt@jps.net writes:
--> JabiruEngine-List message posted by: Lynn Matteson <lynnmatt@jps.net>
Yeah, it makes sense, and I hope I'm doing it right. I lean until the
peak EGT is found, then either richen about 50 degrees (that's what
I've read) for ROP, or continue leaning until the EGT's (all four of
them in my case) also drop about 50 degrees. The CHT's also come down
in my engine, as well as the power....the engine feels like my car
does when I turn on the air conditioner...kinda sagging in power. But
I NEVER do this LOP setting when I am over about 2850 rpm (red line
3300) or when I am stressing the engine. If I'm doing something that
would hurt the engine, I'd certainly like to be alerted to it. But I
only go lean-of-peak EGT when in a slow cruise mode. (When I
mentioned going to 3050 rpm, I was referring to going to ROP in a low
power-requirement mode.)
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 737.3 hrs
Sensenich 62"x46" Wood prop
Electroair direct-fire ignition system
Rotec TBI-40 injection
Status: flying
On Aug 15, 2009, at 4:16 PM, BobsV35B@aol.com wrote:
> Good Afternoon Lynn,
>
> Just as a quick recap of LOP versus ROP, may we specify what it is
> that we are lean of or rich of?
>
> Generally speaking, most folks like to think of rich or lean in
> relation to EGT temperature, but the thing we really want to know
> is whether we are on the rich side or the lean side of best power.
> At best power, almost all of the air that is available will be
> used. By checking the temperature with an EGT gauge, we will find
> that when we are running at "best" power, the EGT gauge will
> generally read about 60 degrees F cooler than it will at peak EGT.
> We therefore now know that peak EGT occurs on the lean side of best
> power. Another way to say that is that best power can be found
> about sixty to eighty degrees richer than Peak EGT
>
> The hottest internal combustion temperature will occur when just a
> bit lean of best power. Most of our automobile engines are designed
> to run right at best power most of the time. Our aircraft engines
> tend to be designed to run at full takeoff power for a relatively
> short time and the cooling capabilities are designed to be able to
> handle full power by adding extra fuel to the mixture which will
> slow down the rate of burn, move the point of peak cylinder
> pressure later in the combustion process and allow us to keep the
> engine temps below the redline while developing high power.
>
> So --- If we are at full or high power running rich and we make
> the mixture less rich, we are taking away some of the fuel that has
> been used to move the flame front later in the cycle and the
> cylinder temperatures will rise. However, if we continue to reduce
> the fuel flow, the internal temperature will peak at some rather
> high number. That will be very close to the best power mixture. The
> problem is that our engines are not designed to cool properly at
> that high a cylinder pressure. If we continue to make the mixture
> less rich, it will eventually get to the peak EGT. That will occur
> with an EGT that is between fifty and eighty degrees Fahrenheit
> hotter than it was at the peak combustion temperature point. If we
> now continue to lean the mixture, the EGT will drop. Less fuel
> means less fire and the cylinder temperatures and pressures will
> continue to drop. At a cruise power of sixty to seventy percent for
> most light aircraft engines, the best BSFC (Brake Specific Fuel
> Consumption) will be found with an EGT about twenty degrees F
> leaner than Peak EGT. (Or about seventy-five to one hundred degrees
> away from best power.) It makes sense that when you are burning
> less fuel the temperatures will be lower, but when we are running
> at very high power settings, we need the extra fuel to keep the
> peak combustion pressure and temperatures down.
>
> Thus, it can truthfully be said that there are times when leaning
> the engine will make the heads run hotter, but there are also times
> when leaning the mixture will make the heads run cooler.
>
> As Always, It All depends!
>
> Make any sense at all?
>
> Happy Skies,
>
> Old Bob
> Stearman N3977A
> LL22
>
> In a message dated 8/15/2009 1:21:33 P.M. Central Daylight Time,
> lynnmatt@jps.net writes:
> <lynnmatt@jps.net>
>
> Over the last week, I've had some fun making some tests with my newly-
> installed Rotec TBI-40 mixture-adjustable, carburetor-replacement
> device on my Jabiru engine. I don't know whether two of these units
> will work on a Rotax, so many of you might want to hit the delete key
> right now.
>
> For the most part, I was flying it LOP (lean-of-peak), but yesterday
> I made a flight and decided that I would try ROP (rich-of-peak). In
> flying LOP, the articles I've read say to keep the power requirements
> low, and LOP will work and you won't burn the engine down. I was
> amazed that this LOP thing even works at all, let alone work as well
> as I've found that it seems too....I guess I'm still a bit of a
> skeptic. After all, if going lean is a bad thing, how can going even
> leaner be a good thing? I won't argue whether or not it's a good or
> bad thing, and there are those of you that may not be able to do any
> leaning at all, as I was until I got this unit.
> Three days ago, I made two trips totaling 475 miles, using LOP
> settings, and yesterday I made a 310-mile trip, using ROP settings. I
> had flown the 475 miles leaning out the engine until peak EGT, then
> leaning more until the engine was obviously low on power, and I
> contentedly flew at this setting, watching the scenery crawl by.
> Yesterday I decided to actually GO somewhere, and never mind the fuel
> saving, I just wanted to get there, so I decided to try ROP.
> Here are the average numbers from those trips:
>
> LOP: 27.77 miles per gallon; 3.3 gallons per hour; 93.14
> miles per hour
> ROP: 23.66 miles per gallon; 4.37 gallons per hour; 103.3
> miles per
> hour
>
> Altitudes on all of these flight were anywhere from 3000' MSL (with a
> base of 1000') to 10,000 MSL, with throttle settings from 2600 rpm to
> 3050. Fuel flow as seen on the gauge, ranged from 2.5 gallons per
> hour to 5.0 not including takeoffs, but including climbs.
>
> So you can see from these figures (admittedly a low number of
> samples) that it does pay to tweak the mixture, and even if flown
> LOP, the speed is not too bad.
>
> Lynn Matteson
> Kitfox IV Speedster, taildragger
> Jabiru 2200, #2062, 737.3 hrs
> Sensenich 62"x46" Wood prop
> Electroair direct-fire ignition system
> Rotec TBI-40 injection
> Status: flying
>
>
> www.matronics.com/contribution _-
> ===========================================================
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| Subject: | Re: ROP versus LOP...might be off-topic for some |
Thanks for those numbers, Bob....I'll give them a try the next time I
fly...probably tomorrow. I tend to fly just to enjoy the ride, and am
rarely in a hurry to get somewhere. I'm always in a hurry to leave
for some place, but not necessarily in a hurry to get there. Know
what I mean? : )
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 737.3 hrs
Sensenich 62"x46" Wood prop
Electroair direct-fire ignition system
Rotec TBI-40 injection
Status: flying
On Aug 15, 2009, at 6:41 PM, BobsV35B@aol.com wrote:
> Good Afternoon Lynn,
>
> The only comment I would make is to be certain that you only use
> the fifty rich mode when you are pulling seventy percent power or
> less. Fifty rich of peak will give you the hottest cylinder
> temperature that you can get. It is a mixture to be avoided at any
> high power settings. I restrict a fifty rich setting to no higher
> than sixty-five percent power, but I tend to be on the cautious
> side. Fifty lean of peak is leaner than you need for optimum
> economy. Twenty lean is just about perfect at sixty-five percent
> power. Fifty lean won't hurt a thing, but you lose a little
> efficiency.
>
> Sounds like fun though.
>
> Happy Skies,
>
> Old Bob
>
> In a message dated 8/15/2009 5:28:52 P.M. Central Daylight Time,
> lynnmatt@jps.net writes:
> <lynnmatt@jps.net>
>
> Yeah, it makes sense, and I hope I'm doing it right. I lean until the
> peak EGT is found, then either richen about 50 degrees (that's what
> I've read) for ROP, or continue leaning until the EGT's (all four of
> them in my case) also drop about 50 degrees. The CHT's also come down
> in my engine, as well as the power....the engine feels like my car
> does when I turn on the air conditioner...kinda sagging in power. But
> I NEVER do this LOP setting when I am over about 2850 rpm (red line
> 3300) or when I am stressing the engine. If I'm doing something that
> would hurt the engine, I'd certainly like to be alerted to it. But I
> only go lean-of-peak EGT when in a slow cruise mode. (When I
> mentioned going to 3050 rpm, I was referring to going to ROP in a low
> power-requirement mode.)
>
> Lynn Matteson
> Kitfox IV Speedster, taildragger
> Jabiru 2200, #2062, 737.3 hrs
> Sensenich 62"x46" Wood prop
> Electroair direct-fire ignition system
> Rotec TBI-40 injection
> Status: flying
>
>
> On Aug 15, 2009, at 4:16 PM, BobsV35B@aol.com wrote:
>
> > Good Afternoon Lynn,
> >
> > Just as a quick recap of LOP versus ROP, may we specify what it is
> > that we are lean of or rich of?
> >
> > Generally speaking, most folks like to think of rich or lean in
> > relation to EGT temperature, but the thing we really want to know
> > is whether we are on the rich side or the lean side of best power.
> > At best power, almost all of the air that is available will be
> > used. By checking the temperature with an EGT gauge, we will find
> > that when we are running at "best" power, the EGT gauge will
> > generally read about 60 degrees F cooler than it will at peak EGT.
> > We therefore now know that peak EGT occurs on the lean side of best
> > power. Another way to say that is that best power can be found
> > about sixty to eighty degrees richer than Peak EGT
> >
> > The hottest internal combustion temperature will occur when just a
> > bit lean of best power. Most of our automobile engines are designed
> > to run right at best power most of the time. Our aircraft engines
> > tend to be designed to run at full takeoff power for a relatively
> > short time and the cooling capabilities are designed to be able to
> > handle full power by adding extra fuel to the mixture which will
> > slow down the rate of burn, move the point of peak cylinder
> > pressure later in the combustion process and allow us to keep the
> > engine temps below the redline while developing high power.
> >
> > So --- If we are at full or high power running rich and we make
> > the mixture less rich, we are taking away some of the fuel that has
> > been used to move the flame front later in the cycle and the
> > cylinder temperatures will rise. However, if we continue to reduce
> > the fuel flow, the internal temperature will peak at some rather
> > high number. That will be very close to the best power mixture. The
> > problem is that our engines are not designed to cool properly at
> > that high a cylinder pressure. If we continue to make the mixture
> > less rich, it will eventually get to the peak EGT. That will occur
> > with an EGT that is between fifty and eighty degrees Fahrenheit
> > hotter than it was at the peak combustion temperature point. If we
> > now continue to lean the mixture, the EGT will drop. Less fuel
> > means less fire and the cylinder temperatures and pressures will
> > continue to drop. At a cruise power of sixty to seventy percent for
> > most light aircraft engines, the best BSFC (Brake Specific Fuel
> > Consumption) will be found with an EGT about twenty degrees F
> > leaner than Peak EGT. (Or about seventy-five to one hundred degrees
> > away from best power.) It makes sense that when you are burning
> > less fuel the temperatures will be lower, but when we are running
> > at very high power settings, we need the extra fuel to keep the
> > peak combustion pressure and temperatures down.
> >
> > Thus, it can truthfully be said that there are times when leaning
> > the engine will make the heads run hotter, but there are also times
> > when leaning the mixture will make the heads run cooler.
> >
> > As Always, It All depends!
> >
> > Make any sense at all?
> >
> > Happy Skies,
> >
> > Old Bob
> > Stearman N3977A
> > LL22
> >
> > In a message dated 8/15/2009 1:21:33 P.M. Central Daylight Time,
> > lynnmatt@jps.net writes:
> > <lynnmatt@jps.net>
> >
> > Over the last week, I've had some fun making some tests with my
> newly-
> > installed Rotec TBI-40 mixture-adjustable, carburetor-replacement
> > device on my Jabiru engine. I don't know whether two of these units
> > will work on a Rotax, so many of you might want to hit the delete
> key
> > right now.
> >
> > For the most part, I was flying it LOP (lean-of-peak), but yesterday
> > I made a flight and decided that I would try ROP (rich-of-peak). In
> > flying LOP, the articles I've read say to keep the power
> requirements
> > low, and LOP will work and you won't burn the engine down. I was
> > amazed that this LOP thing even works at all, let alone work as well
> > as I've found that it seems too....I guess I'm still a bit of a
> > skeptic. After all, if going lean is a bad thing, how can going even
> > leaner be a good thing? I won't argue whether or not it's a good or
> > bad thing, and there are those of you that may not be able to do any
> > leaning at all, as I was until I got this unit.
> > Three days ago, I made two trips totaling 475 miles, using LOP
> > settings, and yesterday I made a 310-mile trip, using ROP
> settings. I
> > had flown the 475 miles leaning out the engine until peak EGT, then
> > leaning more until the engine was obviously low on power, and I
> > contentedly flew at this setting, watching the scenery crawl by.
> > Yesterday I decided to actually GO somewhere, and never mind the
> fuel
> > saving, I just wanted to get there, so I decided to try ROP.
> > Here are the average numbers from those trips:
> >
> > LOP: 27.77 miles per gallon; 3.3 gallons per hour; 93.14
> > miles per hour
> > ROP: 23.66 miles per gallon; 4.37 gallons per hour; 103.3
> > miles per
> > hour
> >
> > Altitudes on all of these flight were anywhere from 3000' MSL
> (with a
> > base of 1000') to 10,000 MSL, with throttle settings from 2600
> rpm to
> > 3050. Fuel flow as seen on the gauge, ranged from 2.5 gallons per
> > hour to 5.0 not including takeoffs, but including climbs.
> >
> > So you can see from these figures (admittedly a low number of
> > samples) that it does pay to tweak the mixture, and even if flown
> > LOP, the speed is not too bad.
> >
> > Lynn Matteson
> > Kitfox IV Speedster, taildragger
> > Jabiru 2200, #2062, 737.3 hrs
> > Sensenich 62"x46" Wood prop
> > Electroair direct-fire ignition system
> > Rotec TBI-40 injection
> > Status: flying
> >
> >
> >
> >
> >
> > www.matronics.com/contribution _-
> >
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| Subject: | Re: ROP versus LOP...might be off-topic for some |
Good Evening Lynn,
I certainly do!
To steal from a lister on another list:
"The flight IS the reason. The destination is just an excuse!"
And I really must brag. Our granddaughter received her private pilot
airplane certificate today flying her Jabiru powered Legend Cub which she built
from a kit.
We will have a few younger aviators after all.
Happy Skies,
Old Bob
In a message dated 8/15/2009 7:57:58 P.M. Central Daylight Time,
lynnmatt@jps.net writes:
Thanks for those numbers, Bob....I'll give them a try the next time I
fly...probably tomorrow. I tend to fly just to enjoy the ride, and am
rarely in a hurry to get somewhere. I'm always in a hurry to leave
for some place, but not necessarily in a hurry to get there. Know
what I mean? : )
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