LOP GUY POURS ON THE COAL SURPRIED BY RESULT

[MyNameIsNobody]

23 hours ago, Bartman said:

I've been running LOP for 9 years and at the altitude I fly in my J there has never been a time that I have been more than about 15 LOP, except for GAMI testing and LOP mag testing.  She is still smooth at 50 LOP but its not very efficient and the speed drops off quickly that deep LOP.  The higher I go the less LOP and above about 10,000 in my experience it best to just run as close to peak as possible.  That was before I discovered an intake gasket last week, but had seen effects over last 3 flights.  I am anxious to see how she runs on Monday.

What I have noticed is that if I do not go rich enough and let EGT stabilize, then you can get misleading results and look like you are LOP when you are reallly ROP.

Thanks.  Makes sense.

[MyNameIsNobody]

On 9/30/2017 at 2:07 PM, Ah-1 Cobra Pilot said:

No, Mooneys are efficient because they have so much less drag than other aircraft.  The very similar airframes all do well with very different sized engines and beat most other aircraft with the same engines.

What everyone needs to understand is that an engine, any engine, is at its highest power when the fuel-air mixture is at the stoichiometric ratio.  This means that the fuel and oxygen in the air both burn completely with no residual of either in the exhaust.  That should be your 'Peak', and LOP will be less fuel, leaving no fuel, but some oxygen, left over in the exhaust.  The worry is that Peak is too hot for long-term engine life.  Could your instruments indicate that Peak is not overheating your engine?  Sure.  Do you want to bet an overhaul on it?...  That is the important question.

The stoichiometric ratio will vary by the fuel you use.  It can even vary slightly between loads of 100LL, but you will probably not notice the difference...maybe from summer blends to winter blends.  Regardless, you correct for it via the mixture knob, and unless you mark it, you will never know any difference.

I hear ya.  I clearly stated that I am a die-hard LOP (10-15) for entire ownership of my plane.  THAT is why I was very surprised at the HUGE boost in ground speed indicated with increase in fuel flow.  This was to beat some weather.  An hour in an over 700 hour relationship with the engine.  No regrets.  I don't "need" to get there, nearly ever, where 10-20 minutes matters.  It did here and cylinder temps were just over 300 across the board.  I agree that I was ROP.  I did a quick push and 12.5 came up and so did the speed.  The wonky indications on the G3 showing white vs. magenta (ROP) were weird to me.  I am a big pull guy when I lean.  Lean quickly to rough and enriched/fine tune.

[Tommy]

I thought you increased RPM?

And you changed altitude?

The most important thing is did you re-do the lean find after you change power / altitude?

[Bob_Belville]

So, flew up north with my wife and two dogs Thursday. No weather in forecast, and then when launching saw Weather painted over Twin Cities.   Looked like we were OK, at 7500 feet, but we're only doing about 130 knots.  The usual cloud build up around lacrosse caused me to drop down to 5500. I generally run about 9.5 to 10 gallons an hour. This is  lean of peak. The weather was closing in so I decided to increase fuel flow. Ran 2500 RPM but increased  fuel flow to 12 1/2 gallons per hour. Speed jumped up to 150 knots.  The fuel flow/G3 was showing I was still lean of peak. Just, but still lean of peak. It surprised me.  I never fly at fuel flow  that  High. Drop down to 3500 and reduce fuel flow to 11 1/2 still lean of peak indicated?    Happy ending as we fueled, tied down,  and got back to the cottages  as the weather closed In and winds  really picked up.  Nice to know the old girl can get up and go when needed for an extra gallon an hour. 

If you're flying a J or older (200 hp) I doubt that you were LOP at those FFs. LOP for a 200hp engine should be under 8.5 gph.


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[Bob - S50]

For  the IO-360, LOP will depend on the power setting.  75% will be <10 GPH, 65% will be < 8.7 GPH, to be LOP at 11.3 GPH would require >85% power.

[ArtVandelay]

For  the IO-360, LOP will depend on the power setting.  75% will be 85% power.

He gave his altitude, so that limits the % of power.

[Bob_Belville]

For  the IO-360, LOP will depend on the power setting.  75% will be 85% power.

???

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[jaylw314]

From others' reactions, I assume you have an IO-360?

You said you were LOP at 9.5-10 gal/hour?  Am I to assume that means that at your typical cruising altitude of 7500 ft at 2500 RPM?  According to my M20J POH, at about 7500 ft, at 2500 RPM, your "Best Economy" or 25 ROP fuel flow is 9.2 gal/hour (settings for 65% power). 

Also according to my POH, you can get to 75% power at 4000 ft/2500 RPM, and that fuel flow is 12.2 gal/hr for best power.  So at least according to your settings, it sounds like you were at full throttle, best power (100 ROP).  On the POH speed chart, 75% at 5500 ft at max gross gives you something like 164 kts on a standard day.  You didn't mention if 150 knots was groundspeed or TAS, but if you gained 15-20 knots, that would be consistent with going from 60% power (best economy at 65% settings) to 75% power

I'm making a lot of assumptions here, but unless there's something horribly wrong with those numbers or your instruments, you COULD NOT be flying LOP either before or afterwards?

When I cruise at 6000 ft, if I lean to peak at 2500 RPM at full throttle, I can barely get 9.2 gph for comparison. 

Could there be something wrong with your fuel-flow meter?  When did you last calibrate it?  It would have to be WAY off for that to be the explanation, but having cylinder temps around 300 F is not consistent with running at 75% power.

Edited October 2, 2017 by jaylw314

[Cruiser]

I see the difference as BSFC being the most EFFICIENT operation of the mixture (LOP) control.

While the best MPG result as being the most ECONOMICAL operation.

Simply looking at the FF and not the MPG may not give the best result. We can be LOP with a lot of different power, rpm, mixture settings.

Some can be better than others. 

[AH-1 Cobra Pilot]

9 minutes ago, Cruiser said:

I see the difference as BSFC being the most EFFICIENT operation of the mixture (LOP) control.

BSFC is a measurement of efficiency in pounds of fuel used/horsepower/hour, so it may vary by the output of the engine.  Power is the Torque x the rpm, (essentially).  The shape of the Torque curve will determine where the very best BFSC occurs.

[jaylw314]

3 hours ago, Bob_Belville said:

???

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I think @teejayevans was saying that with mixture lean of peak, the power is determined by and directly proportional to fuel flow only.  MP and RPM do not determine power, so the throttle and RPM settings in your cruise chart won't correspond to your actual performance if you are LOP.

I think for an IO-360, while LOP the number is about 15 hp/gph, so 10 gph produces 150 hp or 75%.

Of course, MP and RPM do affect power output somewhat (through friction and volumetric efficiency), but they are no longer the PRIMARY determinants of power.  While ROP, of course, the reverse is true--MP and RPM are the primary determinant of power, and fuel flow becomes less important.

[MyNameIsNobody]

22 hours ago, Tommy said:

I thought you increased RPM?

And you changed altitude?

The most important thing is did you re-do the lean find after you change power / altitude?

No RPM increase.  I descended from 7500 LOP to 5500'.  Ground speed increased with fuel flow by 20 knots.  When I dropped down to 3500 feet I reduced fuel flow and throttle.  My indications were regarding my increase in Fuel flow and indicated LOP on all cylinders on my G3.  No, I did not re establish peak and LOP at 10-15 PRIOR to increasing fuel flow at 5500'.  So, unless I reestablish Peak the outputs are entirely erroneous on the G3?  I have two fuel flows.  One on G3 and also an EI fuel flow.  They are VERY close on their reading so don't think fuel flow is "off" on transducer.

Yes, everybody I completely understand I was NOT LOP with the increase in fuel flow.  Just wondering about indications on the G3.  Learning here.  Yes, I normally fly at 7500.

[MyNameIsNobody]

IO360A1A in front of a 66 M20E.  Ram Air OPEN.  My Owners manual gives following at 2500RPM: At 25.0MP BHP is 163 and 82%BHP with a flow of 11.5GPH.

I have a responder saying "you were not LOP" at 9.5GPH...

Anybody have charts with altitudes that show numbers at Peak and 100ROP?  I would be interested in seeing that.  

[Tommy]

27 minutes ago, MyNameIsNobody said:

No RPM increase.  I descended from 7500 LOP to 5500'.  Ground speed increased with fuel flow by 20 knots.  When I dropped down to 3500 feet I reduced fuel flow and throttle.  My indications were regarding my increase in Fuel flow and indicated LOP on all cylinders on my G3.  No, I did not re establish peak and LOP at 10-15 PRIOR to increasing fuel flow at 5500'.  So, unless I reestablish Peak the outputs are entirely erroneous on the G3?  I have two fuel flows.  One on G3 and also an EI fuel flow.  They are VERY close on their reading so don't think fuel flow is "off" on transducer.

Yes, everybody I completely understand I was NOT LOP with the increase in fuel flow.  Just wondering about indications on the G3.  Learning here.  Yes, I normally fly at 7500.

Indeed, the only logical explanation I have with your G3's mistake is that you actually moved the peak EGT by changing altitude / power setting, so without re-do the lean-find on your G3 again, it was still using your old peak EGT as the reference. There are, of course, potentially other reasons. 

[MyNameIsNobody]

15 minutes ago, Tommy said:

Indeed, the only logical explanation I have with your G3's mistake is that you actually moved the peak EGT by changing altitude / power setting, so without re-do the lean-find on your G3 again, it was still using your old peak EGT as the reference. There are, of course, potentially other reasons. 

Yup, that makes sense.  The wonky readings were based on having initially set at 7500 prior to decent.  I will look for the data at altitudes.  Definitely did NOT redo lean-find prior to fuel flow increase.  Thanks Tommy.

[MyNameIsNobody]

My Pilot Manual shows at 7500 feet and 9.9GPH is 68%BHP and 135BHP.

[kmyfm20s]

My MVP-50 has a LOP and ROP find mode. The monitor assumes you know you starting on the rich side. If I'm on LOP find mode and I start leaning from the rich side the monitor will put tags on each cylinder as it hits peak. Once i lean past peak it assign a negative number indicating how far past peak I'm going. If I'm on the lean side and start enriching the mixture it will reestablish a new peak with a tag and then show again a negative number on the rich side even though I'm in the LOP find mode. The point is the monitor doesn't really know the difference it simply measures a peak and degrees below the peak. I'm sure you where established LOP and when you enrichened the mixture which went to peak then past peak on the rich side and the monitor measured it a degrees below peak. Since you where in the LOP mode it assumed you knew which direction you where going. This is the same principle people use when doing the big mixture pull then using the ROP find from the lean side to find peak and degree below peak.

[MyNameIsNobody]

My guess on the chart is that I was somewhere between 80-85% manual shows at 5000 (vs my 5500) and 2600rpm a MP of 25"  85% at 12.0GPH.  True airspeed in table is191@2575#

Edited October 2, 2017 by MyNameIsNobody

[MyNameIsNobody]

Found a great AP called IO-360 Power Calculator.  Looks like a great AP. It shows my power at more like 75%.  Check it out.

[Bob - S50]

8 hours ago, Bob_Belville said:

???

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He cut out most of the quote.  Go up a couple places and you can see what I actually wrote.

[Bob - S50]

3 hours ago, MyNameIsNobody said:

No RPM increase.  I descended from 7500 LOP to 5500'.  Ground speed increased with fuel flow by 20 knots.  When I dropped down to 3500 feet I reduced fuel flow and throttle.  My indications were regarding my increase in Fuel flow and indicated LOP on all cylinders on my G3.  No, I did not re establish peak and LOP at 10-15 PRIOR to increasing fuel flow at 5500'.  So, unless I reestablish Peak the outputs are entirely erroneous on the G3?  I have two fuel flows.  One on G3 and also an EI fuel flow.  They are VERY close on their reading so don't think fuel flow is "off" on transducer.

Yes, everybody I completely understand I was NOT LOP with the increase in fuel flow.  Just wondering about indications on the G3.  Learning here.  Yes, I normally fly at 7500.

Alrighty then.  Since we have beat that dead horse over nothing, I guess the confusion is really with the G3.  Without reading the manual, is it possible that the G3 just looks at the peak EGT and compares it with the current EGT without actually checking the fuel flow?  That is, could it be you went ROP during the descent and it was saying degrees LOP when you were actually that many degrees ROP?

[MyNameIsNobody]

10 minutes ago, Bob - S50 said:

Alrighty then.  Since we have beat that dead horse over nothing, I guess the confusion is really with the G3.  Without reading the manual, is it possible that the G3 just looks at the peak EGT and compares it with the current EGT without actually checking the fuel flow?  That is, could it be you went ROP during the descent and it was saying degrees LOP when you were actually that many degrees ROP?

Wow.  Never mind.  Don't beat the dead horse on my account Bob.

[MyNameIsNobody]

So what have I learned?

1) From Economy to Power fuel setting (LOP to ROP) in my plane at 5500' I realized a 20 knot gain.  

2) The G3, when set to monior 15 LOP and set up for one altitude will give erroneous readings.

3) Cylinder Temps were not significant + or - 320 with power cruise setting.

4) There are times when burning $10 an hour more in fuel is worth it.

5) Going fast can be addictive...in addition to burning < fuel.

6) Owning a plane that can do both is awesome.

 

Edited October 3, 2017 by MyNameIsNobody

[AH-1 Cobra Pilot]

On 9/30/2017 at 2:17 PM, teejayevans said:

Not quite, actually best power is about 50 ROP, the reason I think is that all the avgas molecules can't react with all the air molecules, so in order to use up all the air you have to have a little excess of fuel.

A couple of things...Best Power may be something different from maximum power..  Note too, that the POH lists Best Power and Best Economy, and that both are ROP.  We know even better economy exists LOP.  So what is "Best"?  That depends.  What are you trying to accomplish without busting other limits?

Perhaps I should have included the word "possible".  Stoichiometric combustion may not be available at all engine settings.  It is affected by rpm, timing, etc.  The rpm is  influential, as the flame speed and piston speed not not coincide.  Proper mixing of the fuel and air is also essential for stoichiometric combustion, and again, it depends on many factors, such as injector/carburetor effectiveness, intake geometry,...

BTW, my J-model POH shows Best Power at 100 ROP. (?)  Is that an engine-model-dependent number?

[ArtVandelay]

A couple of things...Best Power may be something different from maximum power..  Note too, that the POH lists Best Power and Best Economy, and that both are ROP.  We know even better economy exists LOP. 

Best economy is ROP? Where did you get that from?

Never mind, I found it, I read this as pull mixture to 25° less than peak:

No wonder my numbers never match the POH...