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Are GAMI Useful for M20J IO-360 Engines?


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On 9/16/2022 at 5:22 AM, Philip France 13 said:

Good help : I will definitively try LOP at my next cross coutry trip when 80k or above. If i got it right  : full throttle, 2500rpm, and mixture LOP just passing the peak. Philip

Yes, but just past peak for the last cylinder to peak, not the first.  There’s probably a “lean find” on your engine monitor that would help.

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1 hour ago, A64Pilot said:

You know when I think about a coal plant being 33% efficient, maybe by the time you subtract transmission and distribution losses and charger losses and your charging what I strongly suspect are relatively inefficient EV’s, it’s not a big stretch that you could get just as good an efficiency from an efficient Hybrid.

That is why there are Near Zero and Zero Emissions vehicles.  They pollute near or less than electric, when you take into account the generation, transmission, and distribution efficiencies.

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30 minutes ago, Ragsf15e said:

Ha!  Mine is.  Good guess.  Why do you think it’s usually #2?

I have no insight as to why. Maybe because it’s closest to the divider.  My experience with multiple angle valve IO360s has shown #2 is typically richest and #3 is normally leanest.

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On 9/14/2022 at 3:12 PM, A64Pilot said:

If your 70% or lower, although I’ve read 75% I accept 70, heck I use 65% to be safe, you can’t hurt the motor doing anything you want to with mixture. I think we accept that.

So set up cruise at 65% power ROP, then using your single probe EGT find peak, then keep leaning until one mark lower than peak, enjoy your day. You will be close enough to best BSFC, a little over lean, but close enough for most.

I don’t have it handy but back in WWII the P-38’s economy cruise was to set up normal long range cruise settings, flip the switch that disabled the prop governor, lean until there was a 50 RPM drop, turn the governor back on, repeat for the other engine. That put them LOP and at about the best BSFC, they didn’t know they were LOP, didn’t care, just knew they were extending their range. There were problems with new pilots forgetting to go back to auto rich when the enemy was spotted.

Now if you choose to do the LOP thing above I’ll accept 70% then you do need at least an engine monitor, preferably one with settable alarms.

Personally I fly LOP to save $$, and I understand that to really save fuel you both slow down AND run LOP, so I use 65% ROP power settings, of course LOP power will be less than best power if MP and RPM are the same.

Is the accepted number of power production per fuel flow 14? Meaning when LOP you get 14 HP per gl of fuel flow per hour?

If so then 65% of 200 is 130, 130 div by 14 = 9.25, so if your LOP and fuel flow is less than 9.25, your below 65% and safe

70% works out to a nice even 10 GPH.

Check my math, I’ve been wrong before, and I may be wrong about the 14 thing too.

Another way to ensure your in the safe zone, personally I’m never close to 9 GPH when LOP, much less 10.

At higher altitudes you’ll experience that even wide open that LOP may not give you enough power, if so start running richer, gradually increasing until your at best power, when you get there at 2700, well that’s all there is :)

Whats the average labor for an engine monitor install?

Then Lycoming has published for max engine longevity, operate the engine at 65% or less power, so there’s another reason to stay below 65% power.

LOP isn’t for those who desire speed above other considerations, but it’s another tool.

 

FWIW, I suspect if the P-38's were only dropping 50 RPM, they were probably still ROP, since that's about a, what 3% power drop from 2000 RPM?  LOP would probably be more than a 5% drop.

I've flown LOP enough I can tell when I'm in the right ballpark by the change in the engine sound while pulling the mixture, although that's obviously not terribly accurate...

IIRC, the ff to power ratio LOP in IO-360's is about 15.1, so 65% amounts to 8.6 gph, and 70% is 9.2 gph.  I just shoot for a FF of 9.0 gph in cruise call it a day.  If I'm below about 9,000' MSL, I'm LOP, if I'm above, I'm ROP.

Also FWIW, I hadn't realized the WRC has changed to a hybrid-gas standard platform this season, AFAIK they're the first top-tier racing circuit that has.

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3 minutes ago, EricJ said:

F1 has had hybrid powertrains since 2014.

 

Yeeeeesss, that's sort of true, although AFAIK the goal of KERS is performance, with a button for the driver to use the extra power for a brief boost.  That doesn't strike me as significant in terms of curbing emissions.  In my book a hybrid system has to be on by default.

Of course, WRC is unique in that each special stage is only 15-20 minutes of hard driving, so the teams have to develop an energy management strategy by adjusting how much is used on accelerations, so that you start with a full battery, and end the stage just as the battery is running out.  It's not clear to me if they can change this mapping once per race, on any repair stop, or before every special stage.  There are also the long stages between SS's driving on normal roads where the battery can be recharged while driving.

From an interview:

“So the driver is not allowed to have, for example, a separate switch to add boost or some indication of how the boost might come, it has to be integrated into the torque path so that you have a combination of internal combustion engine and electric motor combined into one torque which is linearized through the pedal map.

“And that’s the way it has to be deployed, so effectively if you have the boost available then you have a combination of engine and motor together and if you don’t then you have only the engine.”

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2 minutes ago, jaylw314 said:

Yeeeeesss, that's sort of true, although AFAIK the goal of KERS is performance, with a button for the driver to use the extra power for a brief boost.  That doesn't strike me as significant in terms of curbing emissions.  In my book a hybrid system has to be on by default.

That's pretty much what any typical hybrid system does, whether it is the driver pushing a button or the computer engaging it.   I bought a Fusion hybrid several years ago, basically to commute to A&P school because my then 13-year-old CTS-V was just not the right tool for that job.   It does the same, the gas motor may be the only thing providing propulsion, or maybe just the electric, they just augment each other using spare kinetic energy the electric system harvests.   That's not really that dissimilar to what F1 does with KERS, although the F1 systems also have the cool MGU-H ERS interconnect with the turbo shaft that most hybrid cars don't have.

Also, FWIW, ALMS/ELMS cars started using hybrid propulsion at LeMans before F1, in 2012.    Well, Audi did, anyway.  ;)

WRC is catching up, which is cool to see.   The hybrid systems for aircraft seem to be making steps as well, although airplanes don't accelerate/decelerate enough to have the same sort of harvesting opportunities.   Recovering energy on descent is pretty much it, which just means you probably just start descent later.   I'm not sure the same rewards exist to be had.

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1 hour ago, jaylw314 said:

FWIW, I suspect if the P-38's were only dropping 50 RPM, they were probably still ROP, since that's about a, what 3% power drop from 2000 RPM?  LOP would probably be more than a 5% drop.

I've flown LOP enough I can tell when I'm in the right ballpark by the change in the engine sound while pulling the mixture, although that's obviously not terribly accurate...

IIRC, the ff to power ratio LOP in IO-360's is about 15.1, so 65% amounts to 8.6 gph, and 70% is 9.2 gph.  I just shoot for a FF of 9.0 gph in cruise call it a day.  If I'm below about 9,000' MSL, I'm LOP, if I'm above, I'm ROP.

Also FWIW, I hadn't realized the WRC has changed to a hybrid-gas standard platform this season, AFAIK they're the first top-tier racing circuit that has.

I don’t think there’s much utility comparing an Allison V-1710 to an air cooled, NA IO360 timed 20° BTDC.  Those big Allisons and Merlins ran more advance (usually staggered with first mag firing > 30°BTDC). They also apparently ran quite smooth because the blower facilitated uniform atomization of the intake charge.

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4 minutes ago, Shadrach said:

I don’t think there’s much utility comparing an Allison V-1710 to an air cooled, NA IO360 timed 20° BTDC.  Those big Allisons and Merlins ran more advance (usually staggered with first mag firing > 30°BTDC). They also apparently ran quite smooth because the blower facilitated uniform atomization of the intake charge.

True that.  I'm just guessing that the RPM stuff is based more in the laws of physics than engineering, but that's not always accurate :) 

My thinking is that if they turned off the governor, the power output is directly proportional to RPM

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1 hour ago, EricJ said:

That's pretty much what any typical hybrid system does, whether it is the driver pushing a button or the computer engaging it.   I bought a Fusion hybrid several years ago, basically to commute to A&P school because my then 13-year-old CTS-V was just not the right tool for that job.   It does the same, the gas motor may be the only thing providing propulsion, or maybe just the electric, they just augment each other using spare kinetic energy the electric system harvests.   That's not really that dissimilar to what F1 does with KERS, although the F1 systems also have the cool MGU-H ERS interconnect with the turbo shaft that most hybrid cars don't have.

Also, FWIW, ALMS/ELMS cars started using hybrid propulsion at LeMans before F1, in 2012.    Well, Audi did, anyway.  ;)

WRC is catching up, which is cool to see.   The hybrid systems for aircraft seem to be making steps as well, although airplanes don't accelerate/decelerate enough to have the same sort of harvesting opportunities.   Recovering energy on descent is pretty much it, which just means you probably just start descent later.   I'm not sure the same rewards exist to be had.

I guess my nitpick with KERS is that if the default is to allow the driver to control it, it's NOT for curbing emissions, because that's the last thing on a racing driver's mind :) 

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KERS does curb emissions, as it provides power without burning fuel.  It recovers most of the energy from regenerative braking.  Another source of power is from the rotation of the turbo.

KERS is not only a push to pass.  It is used all the time, but at a lower discharge rate.  The driver can override that for a short period of time, but doing so depletes the battery, so the next lap is at a lower total power.

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1 hour ago, jaylw314 said:

True that.  I'm just guessing that the RPM stuff is based more in the laws of physics than engineering, but that's not always accurate :) 

My thinking is that if they turned off the governor, the power output is directly proportional to RPM

You may be right about the power setting but I don't think power is directly proportional to RPM in the same way that it is not proportional to airspeed. Drag is not linear and a prop blade is just a wing.

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3 minutes ago, Shadrach said:

You may be right about the power setting but I don't think power is directly proportional to RPM in the same way that it is not proportional to airspeed. Drag is not linear and a prop blade is just a wing.

I just remember my days in a Cherokee 140, where the power with a fixed pitch prop is directly to RPM, but that's an even worse comparison to a P-38! :D

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19 minutes ago, Pinecone said:

KERS does curb emissions, as it provides power without burning fuel.  It recovers most of the energy from regenerative braking.  Another source of power is from the rotation of the turbo.

KERS is not only a push to pass.  It is used all the time, but at a lower discharge rate.  The driver can override that for a short period of time, but doing so depletes the battery, so the next lap is at a lower total power.

Thanks, I hadn't realized that nuance about KERS.  I guess the only fundamental differences with the WRC Rally1 car is that the driver has no override AFAIK, and the electric motor peak power almost doubles the total peak power of the car!

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22 minutes ago, jaylw314 said:

I just remember my days in a Cherokee 140, where the power with a fixed pitch prop is directly to RPM, but that's an even worse comparison to a P-38! :D

I just looked at the Cherokee 140 AFM and it does shows both power, RPM and airspeed as linear and proportional.  My Mooney POH shows airspeed and power as proportional as well. every additional 20hp yields 10mph.  If I could just get an IO720 STC, it appears she'd do well over 200kts at 75% at 7500'.

 

 

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13 minutes ago, Shadrach said:

I just looked at the Cherokee 140 AFM and it does shows both power, RPM and airspeed as linear and proportional.  My Mooney POH shows airspeed and power as proportional as well. every additional 20hp yields 10mph.  If I could just get an IO720 STC, it appears she'd do well over 200kts at 75% at 7500'.

 

 

That was kind of a point of the Carson's speed discussion, that if Carson's speed is the minimum of specific power vs speed, then around Carson's speed the power per speed will be pretty linear.

Up around 200 knots, maybe not so much :D

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17 hours ago, jaylw314 said:

Thanks, I hadn't realized that nuance about KERS.  I guess the only fundamental differences with the WRC Rally1 car is that the driver has no override AFAIK, and the electric motor peak power almost doubles the total peak power of the car!

BMW looked a hybrid M3 a number of years ago.  Not a Prius like one, but a KERS like one.  Controlled by the drivers foot, and supplying an additional 70 HP for hard acceleration only.

I would have bought that, and be happy telling everyone that I drove a Hybrid. :D

One Top Gear, the star they had one was a car guy.  When asked if he had a Prius, he said of course, it is required in Hollywood.  He drove his home from the dealer and then it sat in his garage.  He NEVER drove it, but could honestly answer, "Of course I have a Prius." :D

 

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Speed is proportional the square of the power.  Mainly because of drag.

With a fixed pitch prop, the power is proportional to RPM.

But on a constant speed prop, you need a combination of RPM and Manifold Pressure to determine power.

One thing people are missing about running LOP is, you need to run a higher MP for the same power setting.   On the link below you will see power settings for an Aerostar where both engines are producing the same power, one ROP, one LOP.  We know the power is the same, because there is no yaw from differential power.  And you will see the same RPM, but 3" higher MP on the LOP engine.

https://gami.com/articles/baconsbonus.php

 

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38 minutes ago, Pinecone said:

Speed is proportional the square of the power.  Mainly because of drag.

With a fixed pitch prop, the power is proportional to RPM.

But on a constant speed prop, you need a combination of RPM and Manifold Pressure to determine power.

One thing people are missing about running LOP is, you need to run a higher MP for the same power setting.   On the link below you will see power settings for an Aerostar where both engines are producing the same power, one ROP, one LOP.  We know the power is the same, because there is no yaw from differential power.  And you will see the same RPM, but 3" higher MP on the LOP engine.

https://gami.com/articles/baconsbonus.php

 

I have posted that Aerostar pic at least 5 times. Those that don't get it just ignore it...as they do the Cirrus SR22T LOP cruise power tables that top out at 85%.

So, If speed is proportional to the square of power (I've been taught this is true) and given that a propeller blade is a wing, why is power directly proportional to RPM?  Is the prop not subjected to the same drag properties as the airframe?

Interestingly both the the Mooney M20F POH and the Cherokee 140 show proportional increases in speed across the power range. both POHs suggest that 10% increases in power correlate to 10mph increases in speed.

The PA28 POH says 110mph at 55% (82.5hp) 120mph at 65% (97.5hp) and 130mph at 75% (112.5hp).

The M20F POH says 156mph a 59% (118hp) 166mph at 69% (138hp) and 176mph at 79% (158).

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1 hour ago, Pinecone said:

Speed is proportional the square of the power.  Mainly because of drag.

No.  Power is proportional to velocity cubed.  PFV, and F∝V2.

1 hour ago, Pinecone said:

With a fixed pitch prop, the power is proportional to RPM.

But on a constant speed prop, you need a combination of RPM and Manifold Pressure to determine power.

Since P=Tω, you can use RPM with the torque, but torque can be hard to determine.  Turboprops usually have PROP RPM and Torque gauges, making the calculations easy., but on a recip, since you do not have a torque gauge, you need RPM, MP, altitude, temperature, and Fuel Flow to determine approximate power.

I once had a CWO trying to tell everyone to "set cruise power as soon as reaching altitude, as that gets you to cruise speed fastest."  I pointed out that higher acceleration is produced by higher power, and reducing the RPM from 1900 to 1700 is a greater percentage reduction than the increase in torque it produces.  He kept trying to argue that the props "take a bigger bite of the air" at the lower RPM.  (Of course, I pointed out, that that bigger bite is reflected in more torque?)  He would not believe the Math, and had to test the idea in the aircraft on his next flight before he would believe me.

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