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12 minutes ago, Hank said:

It's a WAAS GPS navigator, it knows both heading and track, and declination is not an issue. I do have to enter OAT and altimeter setting and check / correct IAS --> CAS. It makes a great whiz wheel and calculates TAS, headwind direction and strength (just not the headwind component).

Please explain how a NON AHRS equipped GPS knows heading.  E.g. a Garmin 430W.

How is declination not an issue as the GPS is programmed with declination correction factors; if they don't match actual declination it would seem that would introduce an additional error.

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Just now, Hank said:

You missed the biggest challenge of all--having a carbureted Lycoming engine!

I got you covered in the Gami spread... no FIs required... you still get a Gami spread.  :)

Unfortunately, it may require an engineering degree or two to go with that...

Best regards,

-a-

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21 hours ago, Ragsf15e said:

I’ve done a bunch of 3 and 4 way speed runs using ground speed to solve for TAS. I was curious about my asi as well because I would also use my 430 from time to time just like the OP if I wanted a quick check and it seemed high.

So I took careful data at a couple of altitudes and solved back for IAS and found the asi was indicating about 4kts fast at about 130kts indicated. Not terrible, but that’s why I dont trust anyone just showing their TAS on an Aspen or G5 when we all debate who’s is faster.  It’s a garbage in/garbage out or “close enough for government work” type of thing.  If you want exact, you gotta do the 3 way speed tests.

Not being contentious, but I did not start this thread to claim that my plane is faster than anyone else’s.  That was not my intent and I apologize to anyone who has taken it that way.  I don’t believe I have made or implied any such claims.  If I am bragging on anyone, it would be Al Mooney.  It is the Mooney breed that I’m bragging on.  Even if the the tolerance build up in this calculation was way off, I believe it says a lot about the efficiency of our planes.

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52 minutes ago, MBDiagMan said:

Not being contentious, but I did not start this thread to claim that my plane is faster than anyone else’s.  That was not my intent and I apologize to anyone who has taken it that way.  I don’t believe I have made or implied any such claims.  If I am bragging on anyone, it would be Al Mooney.  It is the Mooney breed that I’m bragging on.  Even if the the tolerance build up in this calculation was way off, I believe it says a lot about the efficiency of our planes.

It's not that you're contentious. It's that you continue to claim that your Mooney will get almost 21NMPG (24MPG) at 152KTAS (175MIAS).  There is a lot of experience on this board.  We know Mooneys are efficient.  There are many normally aspirated Mooneys that will go 152KTAS.  There are some normally aspirated Mooneys that will approach 21NMPG.  There are no normally aspirated Mooneys that will do 152kts and 21NMPG at the same time save for perhaps the very highly modified and experimental Cafe Foundation E model.  I mean no disrespect when I tell you that I see no physical way for a  normally aspirated J or an F or an F with certified mods to turn 7.3gph into 152ktas in level flight.  I have near 100% confidence in this assertion. 

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18 hours ago, MBDiagMan said:

I have never doubted that is good for the engine.  I have only said that it must be done correctly.  I have fought a hot cylinder since I go the plane and couldn’t try it.  My only contention is that it nmustbe done correctly by someone that knows what they’re doing.

All leaning must be done correctly.  LOP operations are no more difficult than ROP.  LOP is more forgiving in many ways.

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17 hours ago, KLRDMD said:

It shouldn't make any difference when LOP. LOP, % power is determined exclusively by fuel flow, nothing else.

I mean no offence, but that's not how combustion works.  Advancing the timing will indeed affect where peak pressure occurs (also affecting mean pressure) during the power stroke. This will in turn affect how much mechanical energy is transferred to the crank.   Would you believe that retarding the timing to 10°BTDC would have no effect on power when LOP?  It most certainly would.

Edited by Shadrach
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49 minutes ago, Shadrach said:

It's not that you're contentious. It's that you continue to claim that your Mooney will get almost 21NMPG (24MPG) at 152KTAS (175MIAS).  There is a lot of experience on this board.  We know Mooneys are efficient.  There are many normally aspirated Mooneys that will go 152KTAS.  There are some normally aspirated Mooneys that will approach 21NMPG.  There are no normally aspirated Mooneys that will do 152kts and 21NMPG at the same time save for perhaps the very highly modified and experimental Cafe Foundation E model.  I mean no disrespect when I tell you that I see no physical way for a  normally aspirated J or an F or an F with certified mods to turn 7.3gph into 152ktas in level flight.  I have near 100% confidence in this assertion. 

I never made such a claim.  I simply reported what I saw with no guarantee it was correct.  I even commented along the way that I am anxious to hear from a savvy J pilot.  In the meantime I was doing my best to find information to compare to.

Talk to the people who have met me in person.  I don’t make claims like that.  If it came across that way I apologize.

I am STILL waiting for a knowledgeable J pilot to tell me how far off it is.  In the interim please don’t be characterizing me as a type of person who I am not!

Thank you!

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17 hours ago, J0nathan225 said:

Thoughts on how a surefly changes this data and fuel flow? I have seen the .5 GPH decrease as advertised, but am I running less power now?   Typical cruise is as you described it.  

Given you don't have a Dyno for your lycoming, your best bet would be to collect as much data as possible before the Surefly install and then use airspeed as a proxy for power to get derive post installation power increases. If can cruise at the same avg speed on .5gph then you can derive a new LOP power multiplier using the new numbers.

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17 hours ago, KLRDMD said:

It shouldn't make any difference when LOP. LOP, % power is determined exclusively by fuel flow, nothing else.

I agree with Ross. This is a statement often made by the APS folks and it is an over simplification. It arises from the observation that the brake specific fuel consumption curve is very nearly linear for the first 50 deg. F or so LOP. So, you can approximate the percent power if you know the fuel flow which is easily set by the mixture control. The APS formulas that everyone uses for this calculation are also approximations and the compression ratio that enters into the formula is only a proxy for thermal efficiency of different engines. 

Skip

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1 hour ago, Shadrach said:

I mean no offence, but that's not how combustion works.  Advancing the timing will indeed affect where peak pressure occurs (also affecting mean pressure) during the power stroke. This will in turn affect how much mechanical energy is transferred to the crank.   Would you believe that retarding the timing to 10°BTDC would have no effect on power when LOP?  It most certainly would.

So what's the answer?

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2 hours ago, MBDiagMan said:

Not being contentious, but I did not start this thread to claim that my plane is faster than anyone else’s.  That was not my intent and I apologize to anyone who has taken it that way.  I don’t believe I have made or implied any such claims.  If I am bragging on anyone, it would be Al Mooney.  It is the Mooney breed that I’m bragging on.  Even if the the tolerance build up in this calculation was way off, I believe it says a lot about the efficiency of our planes.

I didn’t say you did.  Collectively, “we” as in MS always debate our cruise speeds. 

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23 minutes ago, PT20J said:

I agree with Ross. This is a statement often made by the APS folks and it is an over simplification. It arises from the observation that the brake specific fuel consumption curve is very nearly linear for the first 50 deg. F or so LOP. So, you can approximate the percent power if you know the fuel flow which is easily set by the mixture control. The APS formulas that everyone uses for this calculation are also approximations and the compression ratio that enters into the formula is only a proxy for thermal efficiency of different engines. 

For those of us flying around in the real world, what do you suggest we use that's better than what APS has provided us?

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Just now, KLRDMD said:

So what's the answer?

As I said in my reply to Jonathan, without a dynometer, it’s impossible to know but using airspeed as a proxy for power might provide a useable means of deriving a new multiplier. The short answer is that all other things being equal one cannot change when the flame front is initiated without affecting internal cylinder pressure. Internal cylinder pressure and the  crank angle in which that pressure occurs is what drives engine efficiency 

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26 minutes ago, PT20J said:

I agree with Ross. This is a statement often made by the APS folks and it is an over simplification. It arises from the observation that the brake specific fuel consumption curve is very nearly linear for the first 50 deg. F or so LOP. So, you can approximate the percent power if you know the fuel flow which is easily set by the mixture control. The APS formulas that everyone uses for this calculation are also approximations and the compression ratio that enters into the formula is only a proxy for thermal efficiency of different engines. 

The APS guys are correct, when taken in the correct context. There are certainly a number of things that can affect horsepower in all situations. But I believe the context is the comparison of the two levers I have control of in the cockpit. The throttle regulates air and the mixture regulates fuel. Given those are my two options when LOP, my only control over HP is fuel. When ROP my only control over HP is air. Is it simple? Of course? But I don't control spark advance, humidity, OAT, etc. Given those two options, this "over simplification" works.

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1 hour ago, Shadrach said:

I mean no offence, but that's not how combustion works.  Advancing the timing will indeed affect where peak pressure occurs (also affecting mean pressure) during the power stroke. This will in turn affect how much mechanical energy is transferred to the crank.   Would you believe that retarding the timing to 10°BTDC would have no effect on power when LOP?  It most certainly would.

I do not understand the intracacies of LOP combustion as well as you guys, but I found myself laying awake at 3am thinking about it.  Even though the fuel flow is the same with a SF, the advance has to do something... just like Ross’s example with 10 btdc... what if You get all set up 15 LOP and then shut off one mag?  Fuel flow is still the same.  Anyone think the engine will still be making the same power?  Even if it’s still running smoothly, you’ll be slowing down.

 I know skip nailed it with FF = power being a simplification, but the examples where that doesn’t work make me understand it better.

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4 minutes ago, KLRDMD said:

For those of us flying around in the real world, what do you suggest we use that's better than what APS has provided us?

As I said before - If you are considering a surefly, I would suggest you collect as much data as possible before installation of the new mag. Then compare post installation data with preinstsllation data. Any efficiency games will manifest as a reduction in FF for a given airspeed. It’s imprecise but it’s the best that can be done by an owner. 

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1 minute ago, gsxrpilot said:

The APS guys are correct, when taken in the correct context. There are certainly a number of things that can affect horsepower in all situations. But I believe the context is the comparison of the two levers I have control of in the cockpit. The throttle regulates air and the mixture regulates fuel. Given those are my two options when LOP, my only control over HP is fuel. When ROP my only control over HP is air. Is it simple? Of course? But I don't control spark advance, humidity, OAT, etc. Given those two options, this "over simplification" works.

 

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5 minutes ago, gsxrpilot said:

The APS guys are correct, when taken in the correct context. There are certainly a number of things that can affect horsepower in all situations. But I believe the context is the comparison of the two levers I have control of in the cockpit. The throttle regulates air and the mixture regulates fuel. Given those are my two options when LOP, my only control over HP is fuel. When ROP my only control over HP is air. Is it simple? Of course? But I don't control spark advance, humidity, OAT, etc. Given those two options, this "over simplification" works.

The APS guys would likely tell you that having variable timing ignition that’s capable of advancing 13° beyond stock fixed timing for Lycomings and 18° beyond stock fixed timing for a Continental does indeed change output.. Whether  it changes enough To be worth coming up with a new calculation is a question that I can’t answer because I don’t have a Dyno.  Why don’t you email Walter or George and see if they agree with your assessment that more than 10° ignition advance has no meaningful effect on power output? My guess is that they’ll tell you that LOP becomes more efficient with more advance and actually widen the BSFC curve.

 

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59 minutes ago, Ragsf15e said:

I do not understand the intracacies of LOP combustion as well as you guys, but I found myself laying awake at 3am thinking about it.  Even though the fuel flow is the same with a SF, the advance has to do something... just like Ross’s example with 10 btdc... what if You get all set up 15 LOP and then shut off one mag?  Fuel flow is still the same.  Anyone think the engine will still be making the same power?  Even if it’s still running smoothly, you’ll be slowing down.

 I know skip nailed it with FF = power being a simplification, but the examples where that doesn’t work make me understand it better.

Imagine a fixie bike is traveling along at some speed. The peddles are turning with the rear wheel. The only way you can add power is to push on the pedal from one vector. You have a very narrow window by which you can actually affect pressure on the crank from that one vector. The speed of the pedal will determine how much and how fast you apply pressure on each successive rotation . Now think of that pedal as your piston and your crank arm as a connecting rod. In an engine, the pedal represents a piston. With a fixed timing engine the only way we can control the pressure and speed at which that pressure is applied to the piston is with mixture.  The timing is fixed at 25° or 20° BTDC depending on application. The mixture setting affects how much energy is put into the cylinder and how fast that energy is released. That energy is released in the highest quantity and most abruptly at about 40° ROP.  As you get richer or leaner the combustion event slows.  You can take this as the difference between a hammer blow and a slow even push. It is optimal to have the most pressure on the crank occur at an angle with the most mechanical advantage. When you turn a wrench, you apply force at the most optimal angle possible. You’re doing the same thing with a mixture control. Variable ignition throws a new “variable“ into the mix. Allowing the combustion event to start earlier gives a wider range of possible mixture settings and also changes how the combustion event interacts with the crank which means that the power produced will be different. 
 

This is an oversimplification, but I’m running a power saw on two large maples at the moment. It’s about as far down the rabbit hole as I can go.

Edited by Shadrach
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16 minutes ago, Shadrach said:

The APS guys would likely tell you that having variable timing ignition that’s capable of advancing 13° beyond stock fixed timing for Lycomings and 18° beyond stock fixed timing for a Continental does indeed change output.. Whether  it changes enough To be worth coming up with a new calculation is a question that I can’t answer because I don’t have a Dyno.  Why don’t you email Walter or George and see if they agree with your assessment that more than 10° ignition advance has no meaningful effect on power output? My guess is that they’ll tell you that LOP becomes more efficient with more advance and actually widen the BSFC curve.

If I ever install such an ignition system on my engine, I'll ask them.

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Just now, gsxrpilot said:

If I ever install such an ignition system on my engine, I'll ask them.

The sub discussion was about surefly and it’s effect on the FF multiplier used derive power LOP. I appreciate you reinforcing what the guys at APS have said but no one was suggesting they were wrong. The genesis of the discussion came from Ken’s assertion that an extra 13-18° Of advance made no difference on power when LOP peak. I do not think that’s correct and I think the guys at APS would agree with me.

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3 minutes ago, Shadrach said:

The sub discussion was about surefly and it’s effect on the FF multiplier used derive power LOP. I appreciate you reinforcing what the guys at APS have said but no one was suggesting they were wrong. The genesis of the discussion came from Ken’s assertion that an extra 13-18° Of advance made no difference on power when LOP peak. I do not think that’s correct and I think the guys at APS would agree with me.

Sorry, I missed that part. I suspected I was missing it somewhere. 

I'll just confirm that I don't know anything about the effect of variable timing on HP, LOP ops or anything really :unsure:

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