Is my Mooney slow?

[Will.iam]

4 hours ago, Shadrach said:

Those numbers look optimistic me. Without seeing gps flight data of a three-way speed run, I am skeptical.

I am currently in the process of adjusting JPI K-Factor with the goal of achieving FF accuracy of <.3GPH. That process has left me skeptical that any monitor is sufficiently accurate to determine LOP power until tested.

I have my FF down to .1 accuracy but it takes running a tank dry to calibrate it with a fuel pump that is calibrated which i put into a 5 gallon gas can to keep the pump meter honest. Fly one tank dry in straight level flight no turbulence (think early morning time) once engine quits, switch to other tank and land. Fill up empty tank with 5 gal gas can. takeoff on the fuller tank and reset the totalizer when you switch to the 5 gallon side tank. When engine quits note totalizer reading as you switch back to other tank. Repeat until totalizer turns from 4.9 to 5.0 right as the engine dies. Your done. 
i only had to do it 2 times with the 3rd time as verification. I forget where i found it but jpi published how much k-factor needs to increase or decrease to change .1 per/hour difference. That really helped the math zero in on being more precise. 

[Hank]

19 minutes ago, Will.iam said:

I have my FF down to .1 accuracy but it takes running a tank dry to calibrate it with a fuel pump that is calibrated which i put into a 5 gallon gas can to keep the pump meter honest. . 

The can I use for my lawn mower will easily accept 5.6 gallons, and still.not be up to the opening. 

[MikeOH]

4 hours ago, Shadrach said:

Those numbers look optimistic me. Without seeing gps flight data of a three-way speed run, I am skeptical.

I am currently in the process of adjusting JPI K-Factor with the goal of achieving FF accuracy of <.3GPH. That process has left me skeptical that any monitor is sufficiently accurate to determine LOP power until tested.

I think an .3 gph error is about as good as you're going to get. When I first got my Mooney I spent a bunch of time setting the K-factor.  I did it based on roughly 40-45 gallon fills (64 gallon tanks) and came to the conclusion that 2-3% is about the best accuracy I could achieve on a repeatable basis (1 gallon fill error)

[Will.iam]

1 minute ago, Hank said:

The can I use for my lawn mower will easily accept 5.6 gallons, and still.not be up to the opening. 

My can has a 5 gallon line molded into the plastic near the filler hole. Been right on the line from multiple auto gas stations as well as aviation pumps. Pretty consistent i would say. 

[Mooneymite]

5 hours ago, Schllc said:

Beware of the magic Mooney owners, they are always  opining on the performance that defies the rest of the fleet.   Just like all the O3 owners who see 190tas at 8,000 on 11gph. 
trust but verify…..

I'm pretty sure the MOONEYSPACE terms of service forbid contesting unbelievable speed claims since all Mooneys are unbelievably fast.

Don't verify.  You'll damage the brand.  

Edited August 17 by Mooneymite

[Will.iam]

For the people that think owning a turbo is really only for high terrain here is where the turbo is also beneficial in that at 7,500ft on up i can fly LOP and maintain the 65% power where the NA engines can not. Thus i do not see the 5-7 knot slow down because I’m adding enough extra air to stay LOP at that 65% FF is 9.96 but just setting 10 gets me close enough at 65.2% but since running LOP is cooler because of the slower flame front effectively retarding my timing i can push my FF up to 11.2 which LOP gets me 73% with the same CHT as running ROP at 65% 

if you are flying at say 4000ft you can test the ROP vs LOP in a NA for yourself in that now you have enough air from mother nature. Setup ROP per the POH then once stabilized note speed. Then calculate the FF you would need to produce the same HP as the charted ROP in the POH then just WOT the throttle and big mixture pull to the calculated fuel flow for the same HP and if your injectors are balanced enough to run smooth at that setting watch the airspeed settle down at the same speed as the ROP setting but with cooler CHT’s. 

[Echo]

5 hours ago, Shadrach said:

Are you the YouTube guy to which I was referring? Those are the number that looked a bit flakey.  Seems highly unlikely that an additional 1000ft and .01gph of fuel netted nearly 4kts of additional TAS.

He had ram air open and was pulling more MP.  An E CAN do better than what he posted at 7500'.  I relooked at my video.  I was level and actually climbed a bit while I shot it.  My VSI is actually a bit above level in the photo I shot of the video.  Not sure why anyone would lie in this situation.  What does that gain you?  My groundspeed WAS sub 130 as I had a massive headwind.  Should of bumped it to 11.5gph  

[Shadrach]

2 hours ago, Echo said:

He had ram air open and was pulling more MP.  An E CAN do better than what he posted at 7500'.  I relooked at my video.  I was level and actually climbed a bit while I shot it.  My VSI is actually a bit above level in the photo I shot of the video.  Not sure why anyone would lie in this situation.  What does that gain you?  My groundspeed WAS sub 130 as I had a massive headwind.  Should of bumped it to 11.5gph  

Collecting accurate data is not easy. Not suggesting that any one is lying. I’m suggesting that their numbers are imprecise.

[Shadrach]

8 hours ago, Will.iam said:

For the people that think owning a turbo is really only for high terrain here is where the turbo is also beneficial in that at 7,500ft on up i can fly LOP and maintain the 65% power where the NA engines can not. Thus i do not see the 5-7 knot slow down because I’m adding enough extra air to stay LOP at that 65% FF is 9.96 but just setting 10 gets me close enough at 65.2% but since running LOP is cooler because of the slower flame front effectively retarding my timing i can push my FF up to 11.2 which LOP gets me 73% with the same CHT as running ROP at 65% 

if you are flying at say 4000ft you can test the ROP vs LOP in a NA for yourself in that now you have enough air from mother nature. Setup ROP per the POH then once stabilized note speed. Then calculate the FF you would need to produce the same HP as the charted ROP in the POH then just WOT the throttle and big mixture pull to the calculated fuel flow for the same HP and if your injectors are balanced enough to run smooth at that setting watch the airspeed settle down at the same speed as the ROP setting but with cooler CHT’s. 
 

I am pretty sure my engine will make 65% hp LOP at 7500’. 

 

 

 

 

[aviatoreb]

On 8/16/2024 at 2:51 PM, A64Pilot said:

LOP really hurts speed, but of course does increase MPG, a significant amount of that better MPG comes from lower speed, but whatever, LOP does increase MPG.

 

You are the first person I have ever seen say that and it has occurred to me for a long time.  That if I loose say 5kts do to lean of peak its only fair to compare the fuel mileage not to a same percentage of engine power but to a same speed on the rop side.

[dkkim73]

On 8/16/2024 at 12:51 PM, A64Pilot said:

LOP really hurts speed, but of course does increase MPG, a significant amount of that better MPG comes from lower speed, but whatever, LOP does increase MPG.

Are you saying the dominant change in efficiency is due to (internal) frictional losses and aero drag?

The intrinsic thermodynamic efficiency (expressed as BSFC) should be higher LOP. But some (I) may have been over-weighting that. The lower CHTs and cleaner burn, presumed better longevity, are the probably the reason I've been flying LOP most of the time. 

Have been experimenting with prop speed. It would stand to reason that a coarser pitch would better "fit" the higher airpeed, in the sense of selecting an appropriate gear. But friction is another argument, with slower being better. Another argument: I suppose the faster the prop tips go, the more non-linear losses you get... (that's a conjecture). 

Apples-to-apples would probably require working out a large matrix of power settings for a specific plane, ROP and LOP. 

 

[Echo]

Most Mooney's CAN be fast, but you have to burn some gas.  To turn a "Is my Mooney slow" thread into a discussion about flying LOP does not make sense to me.  There are so many variations regarding what creates True Airspeed.  It comes down to how much gas do you want to burn to achieve speed?  There are areas in configuration that deliver speed at a minimal loss of fuel burn.  If you want to fly slow, Fly slow.  If you want to fly faster, fly faster.  That is why there are performance charts for different settings at the same altitude.

Experiment with YOUR plane to see where you are compared to charts knowing that weight, temperature and HOW you configure make a difference in True Air Speed.

People are willing to spend on "speed mods" like crazy.  The BEST speed mod is the red knob.

So in answer to your question Andre "Is my Mooney slow".  My answer is: Compared to what?

[Shadrach]

4 hours ago, dkkim73 said:

Apples-to-apples would probably require working out a large matrix of power settings for a specific plane, ROP and LOP. 

One can conduct an apples to apples almost every time they fly, especially with a turbo. Set you engine for a book 100ROP power setting, let stabilize and note the IAS and CHT. Then adjust MP and mixture for the same speed on the lean side.

In my experience an IO360  will see a fuel savings of ~10% and a notable decrease in CHTs running same power LOP VS 100ROP.  If I make the comparison at low altitudes and power settings above 70% where the appropriate ROP mixture setting is near full rich, the fuel savings is substantial. 

eg: let’s say I’m bucking a headwind at 4K in the winter. I can set the book number 25’x2500 at 80% power full rich (no leaning below 70%) burning ~14.8hph or I can run 80% at the same speed while saving >3gph. 

[Fly Boomer]

4 hours ago, dkkim73 said:

Apples-to-apples would probably require working out a large matrix of power settings for a specific plane, ROP and LOP. 

This is quite likely not relevant, but I was inspired by this topic to seek out some of Walter Atkinson's writings, and this one kind of jogged my brain in a new way:

"For example, when LOP all of the below settings produce the same HP:

25/2500/14 gph
25/2400/14 gph
23/2400/14 gph
25/2700/14 gph
28/2700/14 gph
and so on...

When ROP, all of the below settings are the same HP:

23/2300/18 gph
23/2300/17 gph
23/2300/16 gph
23/2300/15 gph
23/2300/14 gph
and so on."

 

[Shadrach]

11 hours ago, Fly Boomer said:

This is quite likely not relevant, but I was inspired by this topic to seek out some of Walter Atkinson's writings, and this one kind of jogged my brain in a new way:

"For example, when LOP all of the below settings produce the same HP:

25/2500/14 gph
25/2400/14 gph
23/2400/14 gph
25/2700/14 gph
28/2700/14 gph
and so on...

When ROP, all of the below settings are the same HP:

23/2300/18 gph
23/2300/17 gph
23/2300/16 gph
23/2300/15 gph
23/2300/14 gph
and so on."

 

More or less. There are marginal differences with RPM changes. Friction losses affect power output. Is it a lot? No. I asked our favorite “Attorney/Salesman” about it back in 2010 and he had this to say:

 

[Fly Boomer]

24 minutes ago, Shadrach said:

More or less. There are marginal differences with RPM changes. Friction losses affect power output. Is it a lot? No. I asked our favorite “Attorney/Salesman” about it back in 2010 and he had this to say.

Like some others, I just need a few go-to settings that are kind to my engine.  I don't feel like I'm getting any closer to a "complete" understanding.

[AndreiC]

Since I was asked “compared to what?” — my question was meant to be “compared to similar planes to mine, but well-configured.” In other words — am I getting the most bang for my airplane, or should I try to improve rigging, add speed mods, etc. 

The reason for asking this is that I have heard it said many times that book numbers are a bit of a marketing gimmick, as in they are what a test pilot managed to get on a perfectly calm day, with a plane that had no antennas, freshly waxed new paint, brand new prop, etc. I certainly can’t seem to be able to reproduce these numbers. The question was, for my airplane as described (55 years old, 3 blade prop, non-flush rivets, etc.) how much of the performance penalty comes from these, which are things I can’t change easily, and how much is a problem of rigging, or other small things that I can hope to correct.

By asking people to guess, and then comparing to what I will see in a real world situation, I hope to answer the question above. The specific power setting, and especially the LOP/ROP debate was not what I meant to ask — it was just so we have a specific setting to talk about. 

[AndreiC]

@Shadrach, two further questions:

1) Would you feel comfortable running 80% power at 4000 feet, leaned to peak or slightly LOP? (That would be about 10.6 gph according to my calculations, so indeed a saving of > 4 gph.) Assume that CHTs stay below 375. I was told that’s a no-no, but you seemed to suggest in your previous message that it could be fine.

2) Do frictional losses only decrease by about 2% going 2500->2300 because the RPM reduction is modest? In my car, going the same speed on the highway (so engine putting out the same amount of power) the MPG change is quite big going from running the engine at 3500 RPM to 1800 RPM by shifting. (I drive a stick.)

[Shadrach]

37 minutes ago, AndreiC said:

Since I was asked “compared to what?” — my question was meant to be “compared to similar planes to mine, but well-configured.” In other words — am I getting the most bang for my airplane, or should I try to improve rigging, add speed mods, etc. 

The reason for asking this is that I have heard it said many times that book numbers are a bit of a marketing gimmick, as in they are what a test pilot managed to get on a perfectly calm day, with a plane that had no antennas, freshly waxed new paint, brand new prop, etc. I certainly can’t seem to be able to reproduce these numbers. The question was, for my airplane as described (55 years old, 3 blade prop, non-flush rivets, etc.) how much of the performance penalty comes from these, which are things I can’t change easily, and how much is a problem of rigging, or other small things that I can hope to correct.

By asking people to guess, and then comparing to what I will see in a real world situation, I hope to answer the question above. The specific power setting, and especially the LOP/ROP debate was not what I meant to ask — it was just so we have a specific setting to talk about. 

Well, next time just say 65% so it does not trigger the crowd that thinks “you loose a lot of speed cruising at 65% LOP compared to 65% ROP”…

[M20F]

I always love these threads.  
 
My F will do on a perfect day 175kts at 11.3GPH.  

[AndreiC]

7 minutes ago, M20F said:

I always love these threads.  
 
My F will do on a perfect day 175kts at 11.3GPH.  

Whaaat? I thought the J model was called 201 because it could reach 201 mph (174.8 knots) all out. Is your F faster than the ideal J that came out of the factory?

[M20F]

3 minutes ago, AndreiC said:

Whaaat? I thought the J model was called 201 because it could reach 201 mph (174.8 knots) all out. Is your F faster than the ideal J that came out of the factory?

Yes it is. 

[Shadrach]

17 minutes ago, AndreiC said:

@Shadrach, two further questions:

1) Would you feel comfortable running 80% power at 4000 feet, leaned to peak or slightly LOP? (That would be about 10.6 gph according to my calculations, so indeed a saving of > 4 gph.) Assume that CHTs stay below 375. I was told that’s a no-no, but you seemed to suggest in your previous message that it could be fine.

2) Do frictional losses only decrease by about 2% going 2500->2300 because the RPM reduction is modest? In my car, going the same speed on the highway (so engine putting out the same amount of power) the MPG change is quite big going from running the engine at 3500 RPM to 1800 RPM by shifting. (I drive a stick.)

Frictional loss questions are above my pay grade which is why I asked George about it.

I am comfortable running my IO360 LOP at at max achievable manifold pressure any altitude. I frequently fly at sub sea level DAs in winter time @2500rpm WOT RAO. I simply not WOT, full rich CHTs and shoot for slightly more conservative numbers on the lean side.

[AndreiC]

5 minutes ago, Shadrach said:

@2500rpm WOT RAO.

What does RAO mean?

[AndreiC]

9 minutes ago, M20F said:

Yes it is. 

Wow! Impressive. Many speed mods, I assume?