An We Discuss IO360A1A Fuel Flow?

[PT20J]

1 hour ago, M20Doc said:

14.5 GPH is pretty lean for full power, 9% of rated horsepower is a quick and easy number to remember.  Precision fuel injectors are not field adjustable with regards to full power fuel flow, they have to go to a shop with a proper test bench.

Clarence

 

That sounds reasonable. Most people seem to report about 18 gph for a 200 hp IO-360. I actually tried to find out what it should be. Lycoming doesn't specify it. At rated power, the test cell data shows air flow but not fuel flow. My engine had a rated power airflow of 1118.5 pph. At lower power, Lycoming specs high and low fuel flow limits at several air flows. Extrapolating the curves gives a rated power fuel flow of 15.8 to 17.5 gph. 

Precision Airmotive sets the RSA injectors to Lycoming specs. At 600 pph airflow, the fuel flow is 48 - 52 pph and at 1400 it is 120 - 125.2. Interpolating to an airflow of 1118.5 pph, gives a fuel flow of 15.8 to 16.6 pph. However, that's using calibration fluid on the flow bench which may be different than gasoline.

Skip

[A64Pilot]

Pretty much every engine there is goes into what’s often called power enrichment, which means extra rich at high power, this extra rich isn’t for power production, it’s for cooling. So be careful of extrapolating fuel flows from lower power settings because they don’t have the extra fuel for cooling.

Carburetors often have an extra circuit that comes on line just before full throttle, most engine manufacturers caution against reduced power takeoffs and climbs as the engine can actually run hotter than at full throttle, fuel injection of course is similar

https://www.flight-mechanic.com/float-type-carburetors-economizer-system/

Edited May 13, 2022 by A64Pilot

[PT20J]

The RSA-5 does not have power enrichment.

[Mooney Dog]

18 hours ago, A64Pilot said:

9.6 at what MP/RPM altitude and how far LOP or ROP? For 9.6 to be a valid number you need the rest

I had said before 2400rpm, 23mp. the charts are for best power/rop which i run. 

[A64Pilot]

1 hour ago, PT20J said:

The RSA-5 does not have power enrichment.

I bet it does, it may not have a separate circuit, but I’ll bet lunch money at full throttle mixture is richer than partial, with the mix knob full rich

Apparently in some cases it does. I don’t work on these things I send them off,  but every recip engine I know of including cars, outboard motors and even radials has a way of going extra rich at close to full throttle. It’s one of the things that’s hard to train pilots coming from recips to turbines, on recips they always use full throttle for takeoff and climb to reduce engine temps, turbine get hotter the harder they are run, increasing fuel just makes them hotter, they like a Diesel are always LOP.

https://precisionairmotive.com/wp-content/uploads/2019/06/15-338e.pdf

https://precisionairmotive.com/wp-content/uploads/2019/06/15-812_b.pdf

 

Edited May 13, 2022 by A64Pilot

[PT20J]

No, it does not. There is no description of such in the manuals, and I confirmed with Al Jesmer at Precision Airmotive that it does not have any power enrichment function (sometimes called an economizer) when he recently gave me a tour of the factory. The only connection between throttle and mixture is the idle circuit which is controlled by the external linkage the length of which is adjusted to set idle mixture.

 

[Fly Boomer]

10 minutes ago, PT20J said:

Al Jesmer at Precision Airmotive

Did the diagram come from their web site?  I was just over there, and didn't see any diagrams like yours.

[PT20J]

36 minutes ago, A64Pilot said:

I bet it does, it may not have a separate circuit, but I’ll bet lunch money at full throttle mixture is richer than partial, with the mix knob full rich

Apparently in some cases it does. I don’t work on these things I send them off,  but every recip engine I know of including cars, outboard motors and even radials has a way of going extra rich at close to full throttle. It’s one of the things that’s hard to train pilots coming from recips to turbines, on recips they always use full throttle for takeoff and climb to reduce engine temps, turbine get hotter the harder they are run, increasing fuel just makes them hotter, they like a Diesel are always LOP.

https://precisionairmotive.com/wp-content/uploads/2019/06/15-338e.pdf

https://precisionairmotive.com/wp-content/uploads/2019/06/15-812_b.pdf

 

You are probably confusing the RSA-5 used on the IO-360 with the RSA-10 used on larger engines. The RSA-10 does have a power enrichment feature.

[PT20J]

4 minutes ago, Fly Boomer said:

Did the diagram come from their web site?  I was just over there, and didn't see any diagrams like yours.

It’s under Service Information in Technical Data.

https://precisionairmotive.com/wp-content/uploads/2019/06/WALLCHART_rsa.pdf

[A64Pilot]

Doesn’t matter if it has a separate circuit or not, although I posted a couple of links that seemed to say it may.

The only relevance is does it go to a richer mixture at high power, if it doesn’t then it’s the only engine I have experience with that doesn’t.

I won’t fly on Fri the 13th myself, but this is easily determined, fly at 50% power full rich, then 100%, see if fuel flow is exactly double, if there is no enrichment it will be.

My fuel flow on takeoff is 19 GPH (80’ MSL), I don’t think I burn 9.5 GPH at 50% full rich, If I remember I’ll try and see, should be going to Breakfast on Sun.

 

Edited May 13, 2022 by A64Pilot

[Fly Boomer]

30 minutes ago, PT20J said:

It’s under Service Information in Technical Data.

Thanks!

[jaylw314]

1 hour ago, A64Pilot said:

Doesn’t matter if it has a separate circuit or not, although I posted a couple of links that seemed to say it may.

The only relevance is does it go to a richer mixture at high power, if it doesn’t then it’s the only engine I have experience with that doesn’t.

I won’t fly on Fri the 13th myself, but this is easily determined, fly at 50% power full rich, then 100%, see if fuel flow is exactly double, if there is no enrichment it will be.

My fuel flow on takeoff is 19 GPH (80’ MSL), I don’t think I burn 9.5 GPH at 50% full rich, If I remember I’ll try and see, should be going to Breakfast on Sun.

 

It does correspond linearly to airflow to full open throttle in the IO-360-A3B6, I tried that shortly after getting my M20J because I was reading about economizer circuits and thought there was one.  I asked my mechanic if something was wrong, and he said what @PT20Jsaid.

FWIW, you can't prove it to yourself using 50% power since the RPM's will drop and change volumetric efficiency, which introduces another variable, but you can graph linearly from 30" MP down to about 20" MP at 2700 RPM (at constant altitude)

 

18 hours ago, M20Doc said:

14.5 GPH is pretty lean for full power, 9% of rated horsepower is a quick and easy number to remember.  Precision fuel injectors are not field adjustable with regards to full power fuel flow, they have to go to a shop with a proper test bench.

Clarence

 

It wasn't clear to me if @MBDiagMan was talking about 14.5gph on takeoff, or at altitude during the climb.  That would be certainly reasonable at 3000-5000' MSL, when a lot of people start leaning

Edited May 13, 2022 by jaylw314

[A64Pilot]

I believe I can run 17” at 2600 RPM, that’s 50% power, and 28.5” is 100%. Now I do not think these automated charts take installation losses into account, but ought to be close enough. For that matter none of my instrumentation has probably ever been calibrated either.

Not sure at what MP you come off of the governor, speed will play into it too.

When I fly it I’ll find out, I’ve not really paid attention to MP at low power I’m looking to stay below 1500 or above 2000.

 

Edited May 13, 2022 by A64Pilot

[PT20J]

In case anyone is interested, here is the calibration data for the Bendix RSA-5AD1 part number used on the Lycoming IO-360-A.0997_200302113325_001.pdf0997_200302113325_001.pdf

[A64Pilot]

Just at a glance it seems all the test points are at full throttle (WOT) except one that’s at I assume idle cut off (ICO)

Assuming I can’t make 50% at 1600 which I think is probable there is another way to skin this cat. Note full throttle fuel flow at 2600, then reduce to 50% fuel flow and see what the power output is.

I’m saying 2600 as I can’t quite make 2700, I’ll adjust it after verifying my 41 year old tach

 

Edited May 13, 2022 by A64Pilot

[jaylw314]

2 hours ago, A64Pilot said:

Just at a glance it seems all the test points are at full throttle (WOT) except one that’s at I assume idle cut off (ICO)

Assuming I can’t make 50% at 1600 which I think is probable there is another way to skin this cat. Note full throttle fuel flow at 2600, then reduce to 50% fuel flow and see what the power output is.

I’m saying 2600 as I can’t quite make 2700, I’ll adjust it after verifying my 41 year old tach

 

You don't need to figure out % power or anything, just plot FF vs MP at  constant RPM (at any constant mixture setting).  Fuel flow is metered by volume airflow, which should be pretty much proportional to MP.  If there's an enrichment circuit there will be a jump at the top.  If there isn't, it will be directly proportional.

Edited May 13, 2022 by jaylw314

[A64Pilot]

Just now, jaylw314 said:

You don't need to figure out % power or anything, just plot FF vs MP at  constant RPM.  If there's an enrichment circuit there will be a jump at the top.  If there isn't, it will be directly proportional.

I agree and that’s what I think I’ll do, leave altitude, RPM and hopefully OAT constant, start at full throttle, record MP and FF, then reduce by 2” record MP and FF, repeat to get several data points. If they are valid they should line up either in a straight line or a curve, you’ll laugh but I’ll need graph paper, yes I was taught how to use a spreadsheet, but haven’t in decades, maybe just post the numbers and one of you guys can?

However I’m not saying there is an enrichment circuit, but I do think it will run richer at high MP, not all systems use a separate circuit, motorcycle carbs don’t for instance, but Holley carbs do, they call it a power valve which makes more sense than an economizer, because it decreases economy   

[jaylw314]

1 hour ago, A64Pilot said:

I agree and that’s what I think I’ll do, leave altitude, RPM and hopefully OAT constant, start at full throttle, record MP and FF, then reduce by 2” record MP and FF, repeat to get several data points. If they are valid they should line up either in a straight line or a curve, you’ll laugh but I’ll need graph paper, yes I was taught how to use a spreadsheet, but haven’t in decades, maybe just post the numbers and one of you guys can?

However I’m not saying there is an enrichment circuit, but I do think it will run richer at high MP, not all systems use a separate circuit, motorcycle carbs don’t for instance, but Holley carbs do, they call it a power valve which makes more sense than an economizer, because it decreases economy   

graph paper??  Dang, that's old school, man 

[PT20J]

11 hours ago, A64Pilot said:

I bet it does, it may not have a separate circuit, but I’ll bet lunch money at full throttle mixture is richer than partial, with the mix knob full rich

Now, I think you are just trying to get out of buying me lunch 

Went flying today and took some data:

Data taken at 2000' DA. Mixture rich. 2690 rpm. Rightmost data point is WOT. Other data points obtained by throttle reduction only. Engine IO-360-A3B6. 

Note:

Lycoming cell and Precision flow bench data is based on metered fuel at a particular airflow to yield a constant mixture and plots as a straight line. The FF curve is not a straight line when plotted against manifold pressure because metered fuel varies as the dynamic pressure which is a function of airflow squared. However, the important point is that there is no "break" in the curve indicating that some enrichment feature kicks in.

Skip

[Ragsf15e]

33 minutes ago, PT20J said:

Now, I think you are just trying to get out of buying me lunch 

Went flying today and took some data:

Data taken at 2000' DA. Mixture rich. 2690 rpm. Rightmost data point is WOT. Other data points obtained by throttle reduction only. Engine IO-360-A3B6. 

Note:

Lycoming cell and Precision flow bench data is based on metered fuel at a particular airflow to yield a constant mixture and plots as a straight line. The FF curve is not a straight line when plotted against manifold pressure because metered fuel varies as the dynamic pressure which is a function of airflow squared. However, the important point is that there is no "break" in the curve indicating that some enrichment feature kicks in.

Skip

I’d have never guessed you were an engineer… 

[A64Pilot]

9 hours ago, PT20J said:

Now, I think you are just trying to get out of buying me lunch 

Went flying today and took some data:

Data taken at 2000' DA. Mixture rich. 2690 rpm. Rightmost data point is WOT. Other data points obtained by throttle reduction only. Engine IO-360-A3B6. 

Note:

Lycoming cell and Precision flow bench data is based on metered fuel at a particular airflow to yield a constant mixture and plots as a straight line. The FF curve is not a straight line when plotted against manifold pressure because metered fuel varies as the dynamic pressure which is a function of airflow squared. However, the important point is that there is no "break" in the curve indicating that some enrichment feature kicks in.

Skip

Well if that’s the data then indeed I do owe you lunch. I have never seen a motor not go into power enrichment at high power.

What that means of course is we are way richer than necessary at partial throttle, and many do operate full rich at partial throttle, approaches and pattern work for instance

 

[Fly Boomer]

19 hours ago, A64Pilot said:

When I fly it I’ll find out, I’ve not really paid attention to MP at low power I’m looking to stay below 1500 or above 2000.

 

 

Usually my Google Fu is pretty strong, but I can't find the source for this interactive tool.  Where did you generate these?

 

[PT20J]

I do believe that the IO-360-A runs pretty rich at full rich mixture. From the Lycoming curves in the Owner's Manual, best power mixture at full power occurs at a fuel flow of 94 pph or 15.7 gph.  I can lean it back to perhaps 14 gph at sea level full power before the CHTs start to climb (I am not recommending this, but the Lycoming field service tech rep suggested that it was OK for short periods as a test for another issue).

I think the reason I calculated lower fuel flows from the test cell data is that I assumed that the 1118.5 pph air flow at WOT and 2700 rpm represented full power. But the engine was not broken in yet. The manifold pressure was 27.7" at OAT of 75F which calculates out to 190 bhp. Now that the engine is broken in it probably flows better and if it's running at an airflow of 1250 pph that would come out to around 18 gph.

Skip

[PT20J]

Let's see what a reasonable full power air flow upper limit would be for an IO-360.

There are two intake strokes per revolution at 90 cu in each. At 2700 rpm, that works out to 16875 ft³/hr. Sea level air on a standard day has a density of 0.074887 lbm/ft³. So it works out to a volumetric mass airflow of 1264 pph. The IO-360 has a pretty good induction system and the angle valve head is supposed to be pretty efficient, so if the volumetric efficiency is 95% , that would give us around 1200 pph.

What does that mean in terms of fuel flow? Averaging the RSA min/max fuel flow limits previously posted for the measurement points of 600 pph and 1400 pph airflow and interpolating for 1200 pph yields 17.4 gph fuel flow. So within measurement accuracy, this all seems to make sense.

Skip

[MikeOH]

How do you figure two intake strokes per revolution on a four-cycle engine?? It's ONE intake stroke per TWO revolutions, if I remember correctly

(your numbers are still correct, however: divide by two, multiply by 4 cylinders)

Oh, never mind... you were saying 180 ci Total for the engine per revolution!