LOP operation

On Thu, 15 Apr 2004 20:53:48 -0700, "kage"
wrote:

*****Once again, not necessarily. Once the GAMI injectors are installed,
Deakin has been able to lean right to the point of having the engine
quit due to a mixture too lean to fire, without any roughness at all.
If there's roughness then the injectors are not matched properly.*****

That is just simply incorrect. There is roughness that anyone, including
Deakin and Braly notice. It has nothing to do with the injectors being
mismatched. It has everything to do with the need for the engine's timing to
be adjustable. LOP REQUIRES the timing to be further advanced. GAMI knows
this, and is the reason they are developing their Prism system of engine
management.

Best,

According to Deakin's article "Mixture Magic", the speed at which the
fuel air mixture burns varies depending on the stochiometric ratio.
At the ideal mixture ratio of about 15 to 1 by volume, the mixture
burns fastest. On either side of that ratio, the burning slows down.

Because the timing is fixed, adjusting the mixture is the only way to
vary where the Peak Pressure Point (the point at which the combustion
process produces the highest pressure within the cylinder. It's
important that this occur when the crankshaft throw is about 16
degrees past TDC so that maximum leverage is applied to the piston.
If PPP occurs when the piston is closer to TDC, there is little
mechanical advantage and the pressure of the combustion pushes against
a piston that just pushes back instead of accelerating away and adding
thrust to the rotation of the crankshaft). The timing of the engines
and the mixture setup (full rich) is specifically adjusted such that
during full power operation, the PPP occurs at about 16 degrees past
top dead center. This is the source of the common knowledge that a
rich mixture cools the engine. The rich mixture doesn't hose down the
inside of the combustion chamber, it merely slows down the rate of
burning such that PPP occurs at 16 degrees past top dead center. When
the mixture is leaned out so that it approaches the ideal burning
ratio, the mixture burns faster and the PPP begins to occur while the
piston is much closer to TDC. This increases the pressure inside the
combustion chamber and heat goes up. This is the "peak" part of the
LOP or ROP operation. Either side of "peak" the mixture burns slower
which allows the engine to run cooler.

But lean the mixture further, beyond the ideal, and the rate of burn,
as mentioned above, slows down. This allows the piston to be at 16
degrees past TDC again which greatly reduces heat. It also reduces
the amount of gas you use.

As Deakin points out, at about 8,000 feet and full throttle, the
engine is only producing about 60% power and at that power setting you
cannot hurt the engine no matter where you put the mixture, so you
might as well lean to best power setting (which is rich of peak) and
leave it there, if you want to fly at your fastest cruise speed and
range is not an issue.

If the timing ***COULD*** be varied, there would be no need for a
mixture control knob, it could be set for best ratio by the mechanic
and the variable timing would take care of keeping the PPP at the
proper location. Variable timing would also simplify starting.
Engines start much easier when the timing can be retarded to fire the
plugs when the piston is at about TDC, or perhaps even a little after
TDC.

So in answer to your last statement above, LOP operation does not
require that the timing be further advanced. LOP operation actually
has the affect of retarding the timing because it slows down the
combustion process just as an over-rich mixture likewise slows down
the combustion process, allowing the PPP to occur in the desired
place.

Corky Scott

Howdy!

In article ,
kage demonstrated an amazing lack of reading
comprehension when he/she wrote:


For a given power setting, in general (module altitude effects), there
are two mixture settings to give that power. One ROP, the other LOP.
If you run at, say, 70% power, your airspeed is going to be fixed at
a particular level, assuming stable, level flight. If you run LOP,
you run less fuel through the engine, and you burn all of it up. If
you turn ROP, you use some of it to cool the engine -- using more
fuel than LOP operation. All this for the same speed.

Only at very low altitudes. Get YOUR facts straight. LOP is worthless at
altitude because you simply cannot push enough gas through the engine to
develop any meaningful horsepower, unless, like I said, you are
turbocharged.

You didn't read a thing I wrote, apparently.

If you are running at, say, 70% power, you are spinning your fixed-pitch
prop at a particular RPM. At sufficient altitude, you may not be able to get
70% power, but that is irrelevant to the discussion.

It doesn't matter whether you are LOP or ROP. If you are getting X RPM,
you are getting Y% power. For a constant speed prop, the indicator is
different, but the concept is the same.

Of course, at high power levels, LOP is bad, but usually 75% power and under
is safe (from a detonation perspective).

To effectively operate LOP, you also need better control over the fuel
distribution from cylinder to cylinder -- particularly problematic with
carburetted engines. However, that doesn't change the essential fact that
operating LOP uses less fuel for a given power level than operating ROP.


What CHT level do you think is "just fine"? How does this argue
in favor of ROP?

For decades we were running ROP and there were no casualties from high CHTs.
I ran several IO520s to overhaul in the 70's without any premature cylinder
pulls.

You didn't answer my question, and you left out your assertion that I
responded to. If your engine is capable of running LOP, you can manage
CHTs just fine.

Engines run clean enough ROP.

Your data is unsupported, not mine. There are, and never were prolems with
Cont/Lyc running "dirty." Where is YOUR data to assert this. You are pulling
this out of thin air. Lack of experience and GAMI propaganda here.

Ummm...now you leave out my response and continue with the bald assertions.
You made the claim -- now back it up, unless you are just making stuff up.

Engine stresses have been doing just fine now for 100 years ROP.

Oh? Have you ever examined the operations of round engines,
especially the bigger things like R-3350s? IIRC, LOP operations
were mandatory to get satisfactory performance and engine life.

So what? We are talking Walter here, GAMI----remember. They don't make
injectors for R-3350s

You didn't make that distinction. You simply asserted a century of ROP
operation without distinguishing particular engine types. I, once again,
note that LOP operations were essential to satisfactory operation of
round engines, especially the large ones, and may have been part of
stardard operating practices for other engine types as well. I don't
know all the answers, but I'm not claiming universal use of ROP as the
normal operating regime for all (aircraft) engines for the last century.

CO is not a problem in maintained exhaust systems.

What does that have to do with the decision? LOP makes less CO;
isn't that a positive?

No. Not necessarily. Where is your data, as you like to say, that this is
positive? You aren't some tree hugger are you?

CO is formed when there is more carbon (fuel) than oxygen -- the definition
of a "rich" mixture.

You didn't answer the part about how CO production has any real relation
to deciding whether to operate LOP or ROP. I guess that means you don't
have a reason for including that point in your list -- it was just padding.

Your ad hominem ("tree hugger") further reinforces that conclusion. You
resort to name calling when you can't make a substantive response.

Busted!

Airplanes fly faster ROP.

That claim is especially brown and smelly, given the orifice it
was pulled from. See discussion above. Speed is all about power
levels.

Impossible to pull sufficient power at any reasonable higher altitude
without a turbo. Try running LOP at 10,000 ft. Look at your charts(worthless
LOP) at 10,000 and show me how much power/speed you are making.

Non sequitur. As in, that does not follow. Reread the response to your first
non-point.

Oh, I don't have charts available to me, but somehow I don't think they
really reference the mixture setting when telling you how much power you
can get at a given altitude, or how to get it. If you'd care to provide
a citation that we can all see to the contrary, I'll concede the points
where I am actually mistaken.

Even the LOP diehards admit engines run smoother ROP.

As opposed to the ROP blowhards who can't abide admitting they might
be wrong? See! I can use cheap rhetorical devices, too! Would you
care to try a logical approach, or are you just interested in being
fanatical?

Again you don't even make a point. Smoother is smoother, period.

I made as much of a point as you did, and I even admitted that I was using
cheap rhetorical devices. You just say "did too".

Gamis have more value in a turbocharged engine.

What does this have to do with deciding to operate LOP? Or are you
just trying to obfuscate with more irrelevancies?

Turbo engines benefit from LOP because they can still pull the necessary
power to run at altitude. You really should get some facts straight about
available power at altitude LOP.

What do you mean by "at altitude"? 10,000 feet? 20,000 feet?

I'm pretty sure you can get your normally aspirated light single up to 10k,
for many values of "light single".

And, I have plenty of dirt under my nails, thank you for asking.

Do you have real qualifications to back up your amazing assertions?
How about real data? Sound logical reasoning?

This is Usenet. You have shown me NO logical reasoning. Only GAMI claims.
Cooler, cleaner, less stress----irrelevant!

....and just because it's Usenet doesn't mean you get a free ride when you
make ridiculous claims and don't back them up. You still have not offered
any checkable facts, or any credentials that would tell us why we should
take your word on this.

I have shown (though you clearly ignored it) how more than one mixture
setting can produce the same power level, but you continue to assert
something else. You gave us a laundry list of "reasons" why LOP was a
bad thing but offered no reason for us to take your word for it. When
called on that, you simply continue to repeat, deny, and change the
subject.

Get some experience and check back in.

You first.

yours,
Michael

--
Michael and MJ Houghton | Herveus d'Ormonde and Megan O'Donnelly
| White Wolf and the Phoenix
Bowie, MD, USA | Tablet and Inkle bands, and other stuff
| http://www.radix.net/~herveus/

Howdy!

In article ,
kage wrote:
Hey Charles,

If your reading is better than your Cessna model number knowledge, be aware
that I've always maintained GAMIs and Turbo engines are a good deal. A
Cessna 410(sic) is turbocharged. For normally aspirated engines, however,
their benefit is greatly diminished by the FACT that LOP reduces power,
especially where you need it most---at cruise at altitude.

*****Once again, not necessarily. Once the GAMI injectors are installed,
Deakin has been able to lean right to the point of having the engine
quit due to a mixture too lean to fire, without any roughness at all.
If there's roughness then the injectors are not matched properly.*****

That is just simply incorrect. There is roughness that anyone, including
Deakin and Braly notice. It has nothing to do with the injectors being
mismatched. It has everything to do with the need for the engine's timing to
be adjustable. LOP REQUIRES the timing to be further advanced. GAMI knows
this, and is the reason they are developing their Prism system of engine
management.

Are you calling John Deakin a liar? It sure looks that way.

Listen, howzabout you provide us with some way to verify your claims besides
taking your word for it. Links to verifiable accounts, etc.

yours,
Michael


--
Michael and MJ Houghton | Herveus d'Ormonde and Megan O'Donnelly
| White Wolf and the Phoenix
Bowie, MD, USA | Tablet and Inkle bands, and other stuff
| http://www.radix.net/~herveus/

*****So in answer to your last statement above, LOP operation does not
require that the timing be further advanced. LOP operation actually
has the affect of retarding the timing because it slows down the
combustion process just as an over-rich mixture likewise slows down
the combustion process, allowing the PPP to occur in the desired
place.*******


Oh GREAT. Tell that ot GAMI. They can stop their work on PRISM right away.


wrote in message
...
On Thu, 15 Apr 2004 20:53:48 -0700, "kage"
wrote:

*****Once again, not necessarily. Once the GAMI injectors are installed,
Deakin has been able to lean right to the point of having the engine
quit due to a mixture too lean to fire, without any roughness at all.
If there's roughness then the injectors are not matched properly.*****

That is just simply incorrect. There is roughness that anyone, including
Deakin and Braly notice. It has nothing to do with the injectors being
mismatched. It has everything to do with the need for the engine's timing
to
be adjustable. LOP REQUIRES the timing to be further advanced. GAMI knows
this, and is the reason they are developing their Prism system of engine
management.

Best,

According to Deakin's article "Mixture Magic", the speed at which the
fuel air mixture burns varies depending on the stochiometric ratio.
At the ideal mixture ratio of about 15 to 1 by volume, the mixture
burns fastest. On either side of that ratio, the burning slows down.

Because the timing is fixed, adjusting the mixture is the only way to
vary where the Peak Pressure Point (the point at which the combustion
process produces the highest pressure within the cylinder. It's
important that this occur when the crankshaft throw is about 16
degrees past TDC so that maximum leverage is applied to the piston.
If PPP occurs when the piston is closer to TDC, there is little
mechanical advantage and the pressure of the combustion pushes against
a piston that just pushes back instead of accelerating away and adding
thrust to the rotation of the crankshaft). The timing of the engines
and the mixture setup (full rich) is specifically adjusted such that
during full power operation, the PPP occurs at about 16 degrees past
top dead center. This is the source of the common knowledge that a
rich mixture cools the engine. The rich mixture doesn't hose down the
inside of the combustion chamber, it merely slows down the rate of
burning such that PPP occurs at 16 degrees past top dead center. When
the mixture is leaned out so that it approaches the ideal burning
ratio, the mixture burns faster and the PPP begins to occur while the
piston is much closer to TDC. This increases the pressure inside the
combustion chamber and heat goes up. This is the "peak" part of the
LOP or ROP operation. Either side of "peak" the mixture burns slower
which allows the engine to run cooler.

But lean the mixture further, beyond the ideal, and the rate of burn,
as mentioned above, slows down. This allows the piston to be at 16
degrees past TDC again which greatly reduces heat. It also reduces
the amount of gas you use.

As Deakin points out, at about 8,000 feet and full throttle, the
engine is only producing about 60% power and at that power setting you
cannot hurt the engine no matter where you put the mixture, so you
might as well lean to best power setting (which is rich of peak) and
leave it there, if you want to fly at your fastest cruise speed and
range is not an issue.

If the timing ***COULD*** be varied, there would be no need for a
mixture control knob, it could be set for best ratio by the mechanic
and the variable timing would take care of keeping the PPP at the
proper location. Variable timing would also simplify starting.
Engines start much easier when the timing can be retarded to fire the
plugs when the piston is at about TDC, or perhaps even a little after
TDC.

So in answer to your last statement above, LOP operation does not
require that the timing be further advanced. LOP operation actually
has the affect of retarding the timing because it slows down the
combustion process just as an over-rich mixture likewise slows down
the combustion process, allowing the PPP to occur in the desired
place.

Corky Scott

On Fri, 16 Apr 2004 06:54:49 -0700, "kage"
wrote:

*****So in answer to your last statement above, LOP operation does not
require that the timing be further advanced. LOP operation actually
has the affect of retarding the timing because it slows down the
combustion process just as an over-rich mixture likewise slows down
the combustion process, allowing the PPP to occur in the desired
place.*******


Oh GREAT. Tell that ot GAMI. They can stop their work on PRISM right away.

I guess I don't understand your remark. What I've been explaining is
that GAMI has been saying. The fact that a lean or rich mixture burns
more slowly than the ideal mixture isn't made up, it's what happens
inside air cooled certified aircraft engines with fixed timing.

Why would GAMI want to stop work on their variable timing electronic
ignition?

Corky Scott

Thomas,

How are you, Sir? Hope things are going well.

I so enjoy the nay-sayers to LOP operation and get a lot of laughs out
of their remarks and repeated recitation of OWTs. It's funny how many
people are content to rely on myth rather than data. Ah, well.

Just finished 10 days of flying a Cessna 206 in Belize for LightHawk
in support of environmental research and data collection. Fuel there
is about $4.25 U.S. per gallon, so on top of 90 degree F temps,
keeping the fuel burns minimized is one of those very high priority
items in one's operating plan. Plus, one may only purchase fuel at
one airport in a country the size of the U.S. state of Mass.
Therefore, GAMIs and LOP ops are essential. I very much appreciate
the fact that when I've got the rear doors off the 206, with
photographers hanging outside, I'm able to maintain the requested 85
knots indicated with the cowl flaps closed and CHTs in the 350 degree
F range. If I go ROP, the CHTs hit 400 degrees F immediately and even
opening the cowl flaps, which adds a bunch to drag at those speeds,
and requires a power increase, doesn't cool things off much. When I
can burn 11 gph in that IO-520 at 24 inches and 2200 rpm LOP while
keeping the engine very happily cool in the tropical heat, I just
shake my head in wonder at those who still don't get it. Plus, even
with the questional quality control on the cylinders, that engine is
running clean and doing a very nice job of hanging in there in terms
of an absence of gunk in the various areas where you get the products
of incomplete combustion in ROP operated engeines.

Warmest regards,
Rick

Thomas Borchert wrote in message ...
Roger,

I'm especially interested in the experience of anyone doing it
with a fixed pitch carb engine with single EGT and CHT probes.


How would you know you're LOP on all cylinders with that kind of
set-up? Our Tobago (O-360) will not run smoothly LOP. I haven't tried
to enhance smoothness by adding carb heat, which some say helps even
out fuel distribution.