Any LOP/ROP Masters in the MD/DE/PA Area??

[Shadrach]

1 hour ago, jaylw314 said:

I'm just thinking of the proportional difference in air-fuel mixture.  At takeoff, we already run rich, maybe 13:1.  20% more fuel would mean something close to 10:1, which really shouldn't be able to produce power, right?  I imagine that would be a pretty scary takeoff...

It appears you’re only considering one side of the equation. air density is not constant. Your 200hp IO360 produces well over rated horsepower on a cold, high pressure day, In my part of the country, the winter can yield conditions that will generate 15% or more over rated HP on an ISA day. Run your own numbers. 

http://www.csgnetwork.com/relhumhpcalc.html

So on high pressure, winter morning, with enough air to make 115% of rated horsepower how much fuel do you think is needed? Do you think 18gph is adequate for a 230HP IO360?

 

 

[jaylw314]

7 hours ago, Shadrach said:

It appears you’re only considering one side of the equation. air density is not constant. Your 200hp IO360 produces well over rated horsepower on a cold, high pressure day, In my part of the country, the winter can yield conditions that will generate 15% or more over rated HP on an ISA day. Run your own numbers. 

http://www.csgnetwork.com/relhumhpcalc.html

So on high pressure, winter morning, with enough air to make 115% of rated horsepower how much fuel do you think is needed? Do you think 18gph is adequate for a 230HP IO360?

 

 

No, I was thinking of more typical weather and air variables, since the OP seemed to imply this was not just happening in isolated instances.  I think that is a reasonable assumption.

[Shadrach]

6 hours ago, jaylw314 said:

No, I was thinking of more typical weather and air variables, since the OP seemed to imply this was not just happening in isolated instances.  I think that is a reasonable assumption.

I live 100NM from the OP.  It had been unseasonably cold in the preceding week (mid 20s) I believe the OP flies for work. I envisioned that he was dealing with the  same cold mornings that I had experienced, only with his airplane. Different frame of reference from say Texas or Oregon, but my way of thinking could be a red herring. 22 GPH is certainly very high and  if it’s consistent could certainly indicate a problem with his instrument.

[Prior owner]

On 12/5/2018 at 10:28 AM, Shadrach said:

Too bad your down for MX. I just touched down at SFO. In and around the bay through Saturday. My schedule is tight anyway. I’d be happy to fly with you next time I’m here. I landed my F at Gnoss Field back in 05. I’m totally into flying with anyone, but I’m not a credentialed propulsion engineer. I’ll leave the tutorials to those folks.

Thanks. Hopefully I’ll get the plane flying again soon

[mschmuff]

Unbelievable!!!!

All I have to do is threaten my plane and she gets right back in line!!  Called JPI about replacing the fuel flow transducer.......next flight - working perfectly again!!  Glad I waited to order a new one!! 

18GPH on climb out.  10.3GPH ROP 156kts / 9.1GPH LOP 152kts at 5500ft. 

Is it "normal" that the DIF running ROP in 100 and LOP is only 30?!?!?

I never flew LOP before but it seems like the plane likes it better.  and for only a 4kt penalty?!?!  What was I thinking before!!

(Not sure why that one pic is landscape - need tech help! lol)

[hypertech]

I just got my GAMI's ordered and am looking forward to seeing what kind of a difference they make.  If @Shadrach's plane is still in MX, I would gladly ferry him from KHGR to wherever this might happen (or meet up at KHGR). 

[jaylw314]

34 minutes ago, mschmuff said:

Unbelievable!!!!

All I have to do is threaten my plane and she gets right back in line!!  Called JPI about replacing the fuel flow transducer.......next flight - working perfectly again!!  Glad I waited to order a new one!! 

18GPH on climb out.  10.3GPH ROP 156kts / 9.1GPH LOP 152kts at 5500ft. 

Is it "normal" that the DIF running ROP in 100 and LOP is only 30?!?!?

I never flew LOP before but it seems like the plane likes it better.  and for only a 4kt penalty?!?!  What was I thinking before!!

(Not sure why that one pic is landscape - need tech help! lol)

 

 

Nice!  those FF's look much more in line with what people typically report with the IO-360.  No idea why it would suddenly change like that, though.

IIRC, the DIF is the biggest difference in EGT's across your cylinders.  Since the absolute EGT value is (almost) irrelevant, the DIF is also (almost) useless, especially if you change settings (like going ROP to LOP and vice versa).  The only significance would be if you saw a major change, like the DIF increased by 200 with no other setting changes, then you'd be looking at your actual EGT's to see which one is wonky.  They didn't want to put alarms on the EGT's, because there is no useful alarm value, but the alarm on the DIF might be enough to draw your attention if one cylinder went astray.

[Shadrach]

41 minutes ago, hypertech said:

I just got my GAMI's ordered and am looking forward to seeing what kind of a difference they make.  If @Shadrach's plane is still in MX, I would gladly ferry him from KHGR to wherever this might happen (or meet up at KHGR). 

I'm scheduled to complete my annual Friday!  Not yet sure how my weekend looks for time.

[PT20J]

On 11/27/2018 at 5:00 PM, Shadrach said:

He may indeed have an issue with his transducer.  But I've lived in both TX and MD.  It's a little different up and over here.  There will be mornings this winter at my 701ft field when the ASOS will be giving a DA of -2700ft and there will be afternoons next summer when the ASOS will be giving DA  of more than 3000ft.  18GPH is fine but it's not max. The servo delivers full rich fuel flow based on mass airflow and that differs with DA.   

Slight correction: the RSA fuel injection in the IO-360 Mooneys doesn't have automatic mixture control, so the fuel flow is regulated by the volume of the airflow rather than the mass. That's why we have to lean as we climb (airflow volume stays the same, so fuel flow stays the same, but air density decreases, so mass airflow decreases, and the mixture gets rich). A lot of books get this wrong. I didn't understand it until I was studying the Bendix-Stromberg pressure carburetors (the grand daddy of the RSA fuel injectors) used on the museum's DC-3. These carburetors have essentially the same fuel metering system as the RSA injectors but have AMC, so you just select Auto Rich or Auto Lean and forget about adjusting for altitude.

We know, of course, that at high DA we need to lean for max. power before takeoff, but I never thought about the converse (I live on the west coast and have never seen a -2700' DA -- Brrrrr.). So, since we cannot go more rich than "full" rich, the fuel flow at full rich must be really rich (what George Braly calls "gobby rich" - whatever that means - must be an OKey expression :-) to provide detonation margin at really low DA. The Lycoming IO-360 Operator's Manual has a curve for fuel consumption that shows 200 hp/2700 rpm/best power mixture fuel consumption at 94 lb/hr (15.7 gal/hr). I cannot find a specification for full rich fuel flow. I usually see around 18 gph full rich at SL +/- 200 ' DA. I'd be interested in what others see for full rich at takeoff with DA noted.

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[jaylw314]

28 minutes ago, PT20J said:

The Lycoming IO-360 Operator's Manual has a curve for fuel consumption that shows 200 hp/2700 rpm/best power mixture fuel consumption at 94 lb/hr (15.7 gal/hr). I cannot find a specification for full rich fuel flow. I usually see around 18 gph full rich at SL +/- 200 ' DA. I'd be interested in what others see for full rich at takeoff with DA noted.

Skip

I'm guessing there is not a spec since there's nothing that can be adjusted, but most people seem to get between 17 and 18 gph

[Shadrach]

1 hour ago, PT20J said:

Slight correction: the RSA fuel injection in the IO-360 Mooneys doesn't have automatic mixture control, so the fuel flow is regulated by the volume of the airflow rather than the mass. That's why we have to lean as we climb (airflow volume stays the same, so fuel flow stays the same, but air density decreases, so mass airflow decreases, and the mixture gets rich). A lot of books get this wrong. I didn't understand it until I was studying the Bendix-Stromberg pressure carburetors (the grand daddy of the RSA fuel injectors) used on the museum's DC-3. These carburetors have essentially the same fuel metering system as the RSA injectors but have AMC, so you just select Auto Rich or Auto Lean and forget about adjusting for altitude.

We know, of course, that at high DA we need to lean for max. power before takeoff, but I never thought about the converse (I live on the west coast and have never seen a -2700' DA -- Brrrrr.). So, since we cannot go more rich than "full" rich, the fuel flow at full rich must be really rich (what George Braly calls "gobby rich" - whatever that means - must be an OKey expression :-) to provide detonation margin at really low DA. The Lycoming IO-360 Operator's Manual has a curve for fuel consumption that shows 200 hp/2700 rpm/best power mixture fuel consumption at 94 lb/hr (15.7 gal/hr). I cannot find a specification for full rich fuel flow. I usually see around 18 gph full rich at SL +/- 200 ' DA. I'd be interested in what others see for full rich at takeoff with DA noted.

Skip

The Bendix RSA 5 most definitely reduces fuel fuel flow as air density decreases. It also increases fuel flow when air density increases. If you set the mixture the system will (crudely) try to maintain that ratio.  I lean my engine in climb and upon arrival at altitude, but the Bendix RSA servo most definately is an AMC device. If it wasn’t, you’d see 18gph at full rich at all altitudes. Try climbing to 13,500 and leaning to your desired setting/fuel flow. Then descend without touching the mixture knob. The system will enrichen in descent automatically as air density increases. 

 Perhaps we’re in semantic discussion, but the system does not use air volume, it uses differential pressure as a proxy for air volume. Pressure at the impact tubes minus suction at the venturi throat. I have the precision air motive training manual on another machine, but I’m sure you can find it online, if you want to check it out.

There is no fuel flow spec. The servo maintains pressure to the flow divider. The system can accommodate much higher horsepower engines than our Lycomings.

Edited January 10, 2019 by Shadrach

[PT20J]

On 11/27/2018 at 5:00 PM, Shadrach said:

I have the precision air motive training manual on another machine, but I’m sure you can find it online, if you want to check it out.

I happen to have a copy of the training manual handy. The first sentence reads:

"Precision Airmotive Fuel Injection Systems are designed to meter fuel in direct ratio the volume of air being consumed by the engine at any given time."

Some confusion may be that there are several models of RSA 5-series fuel injectors. The RSA-5AD1 is used on the IO-360 and does not include AMC. The RSA-5AB1 is used on the HIO-360 and does include AMC.

 

 

 

RSA Operation and Service 15-338e.pdf

RSA training 15-812_b.pdf

[PT20J]

1 hour ago, jaylw314 said:

I'm guessing there is not a spec since there's nothing that can be adjusted, but most people seem to get between 17 and 18 gph

This makes sense. I looked up the test cell data from my factory rebuilt IO-360-A3B6. Lycoming specified a maximum fuel flow of 95 pph at an airflow of 1000 pph. Full rated power yielded a measured airflow of 1118.5 pph, but the fuel flow at this test point wasn't measured. Assuming a linear increase in fuel flow, rated power max. fuel flow would be 106 pph or 17.7 gph. Voila! (maybe).

[carusoam]

I didn’t pay attention to where the FF setting was when I first got the IO550 other than the performance charts...

The STC is where you look for the changes when going to 310hp.  The FF range is clearly stated there with all the details that go with it... oddly enough is in pph, not temp sensitive gph...

Expect that it is written in the M20 tech document that covers everything... the STCs are an addendum to that....

PP fuzzy memory prevents me from stating the tech document’s name... not a secret doc at all...

Best regards,

-a-

[Shadrach]

13 hours ago, carusoam said:

I didn’t pay attention to where the FF setting was when I first got the IO550 other than the performance charts...

The STC is where you look for the changes when going to 310hp.  The FF range is clearly stated there with all the details that go with it... oddly enough is in pph, not temp sensitive gph...

Expect that it is written in the M20 tech document that covers everything... the STCs are an addendum to that....

PP fuzzy memory prevents me from stating the tech document’s name... not a secret doc at all...

Best regards,

-a-

PPH is the measure that Bendix uses as well. This metric used for both for fuel and air.

[Shadrach]

21 hours ago, PT20J said:

I happen to have a copy of the training manual handy. The first sentence reads:

"Precision Airmotive Fuel Injection Systems are designed to meter fuel in direct ratio the volume of air being consumed by the engine at any given time."

Some confusion may be that there are several models of RSA 5-series fuel injectors. The RSA-5AD1 is used on the IO-360 and does not include AMC. The RSA-5AB1 is used on the HIO-360 and does include AMC.

 

 

 

RSA Operation and Service 15-338e.pdf

RSA training 15-812_b.pdf

I am not confused about the RSA systems used in these birds.  I never stated that the system did not meter fuel in direct ratio to volume of air.  I was merely explaining how the system goes about achieving the goal.  The only way to directly measure volume is with an anemometer style fan.  That would be quite detrimental to a free flowing intake and so we there fore use other means.  To measure air the system uses a two chambered sealed diaphragm. A pressure side and a vacuum side.   The pressure side is ported to impact tubes and the other a port in the venture (vacuum).  The expansion and contraction of the diaphragm is what controls the position of the servo valve and meters the fuel going to the flow divider.   So to recap - velocity and density are the only thing driving the servo.  Diaphragms are affected by pressure they don't measure the volume flowing through the throttle body. However, the engineers who designed the system, knowing the volume characteristics of the throttle body use this pressure differential as a proxy for volume. This is why I refer and will continue to refer to the system as a mass airflow device.

AMC- I freely admit that I am unfamiliar with pressure carbs and the AMC circuits therein.  Maybe someday I will have a need for that information but not at the current time.  I am familiar with the RSA 5 as installed in our airplanes. It indeed does compensate for altitude, what it does not do is auto lean. At full rich, it will the same F/A ratio at a DA of -500ft as it will at a DA of 8,500ft. However, that F/A ratio is sub optimal at altitude for a number of reasons I won't bother with here.  More over if you set the mixture in climb, it will seek to maintain the same F/A ratio throughout the climb.  The FA ratio that is ideal at WOT climbing though 2500 is not optimal climbing through 6,500 and is even less so 11,500. Therefor, we lean at altitude.

I was going to reply last night but I begged off because truth be told, I felt as though you were being deliberately pedantic and needlessly nit picky.  I had a chance to sleep on it and decided to consider that the internet offers little in the way of context.  It's my hope that my first impressions were wrong.

Edited January 11, 2019 by Shadrach

[PT20J]

1 hour ago, Shadrach said:

I was going to reply last night but I begged off because truth be told, I felt as though you were being deliberately pedantic and needlessly nit picky.  I had a chance to sleep on it and decided to consider that the internet offers little in the way of context.  It's my hope that my first impressions were wrong

I'm truly sorry that you appear to have taken some of my comments personally; they were not intended that way at all. I merely thought we had a difference in understanding of how RSA fuel injectors work and were discussing it in an open forum so that everyone could benefit. I enjoy hashing out technical subjects with knowledgeable peers -- I learn a lot that way. I won't risk further offending you by commenting on your post other than to say that some of your arguments run counter to my understanding of fluid dynamics. 

There is a great book that those on the forum with an interest in the subject may wish to track down:  Thorner, Robert H., Aircraft Carburetion, John Wiley & Sons, 1946. It explains basic carburetion principles in a very clear manner, as well as going into depth in discussing the fuel metering system used in Bendix-Stromberg pressure injection carburetors, which is exactly the same system used in the later Bendix (now Precision Airmotive) RSA fuel injectors.

Peace.

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