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LOP with Fine Wire vs Massive Plugs


FLYFST

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On 4/12/2019 at 9:50 AM, FLYFST said:


Agreed and I do the same. I typically start leaning at 75% HP and 100+ ROP, then as I lean below peak the power has dropped to around 65%, but at that setting I see 9.5 to 9.0 gph, and rarely below 9 gph.

My thinking, of which I am not confident, is that the fine wire plugs MAY allow for a more efficient combustion LOP and therefore smoother operations. For ROP operations I see little added value in the extra cost of the fine wire plugs.


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I think it’s important to point out that you’re running more power than you think. Remember that at rich efficiency ratios power is a function of mass air flow and RPM. At lean effiency ratios power is simply a function of FF. An angle valve IO360 (8.7CR) will produce 15.13hp for 1GPH of burn. Using round numbers, 9gph LOP is 68% horsepower 9.5gph is 72% horsepower. The 65% you mentioned occurs @ 8.6gph.

Edited by Shadrach
math typo and calculation correction
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2 hours ago, mike_elliott said:

The Bravo's LOP ops are highly dependent on a "good" ignition system. Any weakness in the spark really affects them, even with well balanced flows to each cylinder.

I'd say that's true for ANY motor--I had a weak left mag, and getting it retimed made much more difference than the fine-wires for LOP and starting.

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On 4/12/2019 at 10:15 AM, mike_elliott said:

The Bravo's LOP ops are highly dependent on a "good" ignition system. Any weakness in the spark really affects them, even with well balanced flows to each cylinder.

Point taken, but both the Bravo and its engine predate fine wire plugs but quite a bit. Given the first M20M rolled off the factory floor in 1989, it’s amazing that they’ve managed to operate for 3 decades when fine wire have only been available for about the last half. Now that we have fine wires, are people actually suggesting that massives should be considered a “weakness in spark”?

 

Edit: @Bob_Belville has set straight as to when fine wires came on the scene. @mike_elliott my apologies for my lack of knowledge on the history of FW plugs. I thought they were relatively new to aviation. Did/does the Mooney factory deliver new aircraft with fine wires?

Edited by Shadrach
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I have about 300 hours on my Tempest massives and typically fly 20-30 LOP in my J with no problem. They are rotated every annual or 100 hours - whichever comes first. I previously had a mixture of massives on top and fine wires on bottom when I bought the plane, but it made rotating them problematic based on the theory the fine wires were to be used on the bottom to overcome oil in the cylinders. No problems with starting as my engine typically starts on 1-2 blades if I prime correctly. LOP speeds are in the ~150+ kph range.

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Just now, ArtVandelay said:

Ditto.
BTW, have you ever cleaned your JPI?

Tom

Right before I weighed it to insure an increase in UL. :D

Truthfully, those pictures were taken right after the Aspen was installed, and we had not yet cleaned everything up from the final work. I had to run down to Lakeland to check on the house, so there was still a significant amount of cleaning to do. I had Nigel Williams from CC Bright Cleaning come through and do a 12 man-hour cleaning job on the plane about a month later. Looks more like this now:

image.thumb.png.c31790c1f6682866cdd3abcbbe06be02.png

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Better...maybe I am just anal.....
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Tom


I can handle the fingerprints. What gets to me is the dust bunnies on the ledges.

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And don’t get me started about these things!

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That’s how a “can you do anything about this?” Turns into a brand new panel!


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14 minutes ago, ArtVandelay said:

Better...maybe I am just anal.....

 

5 minutes ago, Marauder said:

And don’t get me started about these things!

 

11 minutes ago, Marauder said:

That’s how a “can you do anything about this?” Turns into a brand new panel!

You guys are killing me! :D

Okay, I am going out to the airport TOMORROW and taking out the q-tips to clean so I can pass inspection. I just have to keep the kids out of it since they want to point at everything - from 0" away.

And Marauder is right - a new panel is forthcoming, but probably not for another year. You cannot believe how many ATI holes a panel can have cut into it and then have round instruments put into them. And holes cut for switches that are moved to the other side of the cockpit!

But I hear your concerns, and will endeavor to clean up my act. And my panel.

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You guys are killing me! 
Okay, I am going out to the airport TOMORROW and taking out the q-tips to clean so I can pass inspection. I just have to keep the kids out of it since they want to point at everything - from 0" away.
And Marauder is right - a new panel is forthcoming, but probably not for another year. You cannot believe how many ATI holes a panel can have cut into it and then have round instruments put into them. And holes cut for switches that are moved to the other side of the cockpit!
But I hear your concerns, and will endeavor to clean up my act. And my panel.


I’ve been where you are. Fortunately during the last install the shop who quoted my replacement left panel said to me that he couldn’t let me leave his shop with a Frankenstein look for the center and right panels. He cut me new panels at no charge just because he wanted people to see a quality job from his shop.

Between the naugahyde covering and the extra holes, he was right.


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I think it’s important to point out that you’re running more power than you think. Remember that at rich efficiency ratios power is a function of mass air flow and RPM. At lean effiency ratios power is simply a function of FF. An angle valve IO360 (8.7CR) will produce 15.3hp for 1GPH of burn. Using round numbers, 9gph LOP is 69% horsepower 9.5gph is 73% horsepower. The 65% you mentioned occurs @ 8.5gph.

Yes I am familiar with the formula, but does it account for OAT? I based my numbers on the EDM-830 in my panel, which I have been careful to tune, and its internal algorithm for calculating Hp. At such settings, my CHTs are always lower than at peak EGT and usually 340 or lower at cruise power.


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1 hour ago, FLYFST said:


Yes I am familiar with the formula, but does it account for OAT? I based my numbers on the EDM-830 in my panel, which I have been careful to tune, and its internal algorithm for calculating Hp. At such settings, my CHTs are always lower than at peak EGT and usually 340 or lower at cruise power.


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OAT is irrelevant to calculating LOP hp. What you’re burning is what you’re burning. Colder air does not allow for the extraction of additional BTUs from a unit of fuel.  Colder air does allow for the production of more power (because it allows for addition fuel burn) regardless of which side of the mixture spectrum you’re running. As an example: WIth the throttle and Ram air open on a 10 degree day, I can achieve higher LOP fuel flows then I can on a 90 degree day.  While there is more MP available at lower temps, making that additional power requires more fuel.  Using round numbers, 10gph on the lean side of peak is always 150hp (75%) whether it’s 20 degrees or 95 degrees. 

Edited by Shadrach
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15 minutes ago, Shadrach said:

OAT is irrelevant to calculating LOP hp. What you’re burning is what you’re burning. Colder air does not allow for the extraction of additional BTUs from a unit of fuel.  Colder air does allow for the production of more power (because it allows for addition fuel burn) regardless of which side of the mixture spectrum you’re running. As an example: WIth the throttle and Ram air open on a 10 degree day, I can achieve higher LOP fuel flows then I can on a 90 degree day.  While there is more MP available at lower temps, making that additional power requires more fuel.  Using round numbers, 10gph on the lean side of peak is always 150hp (75%) whether it’s 20 degrees or 95 degrees. 

I can't remember who it is here that often points out that BSFC actually worsens below 20-30 LOP ( @PT20J?).  That suggests that you can't just calculate the power from the fuel flow as you lean further.  I assume that the fuel flow formula works for one point on the curve, like 20 LOP.  So as long as you're 20 LOP and happen to be 10 gph, you're at 75%.

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2 hours ago, jaylw314 said:

I can't remember who it is here that often points out that BSFC actually worsens below 20-30 LOP ( @PT20J?).  That suggests that you can't just calculate the power from the fuel flow as you lean further.  I assume that the fuel flow formula works for one point on the curve, like 20 LOP.  So as long as you're 20 LOP and happen to be 10 gph, you're at 75%.

The APS power formulas and the JPI calculations are approximations, but seem reasonably accurate. Really, the only way to know for certain the power being developed is to have a torquemeter. Many of the large radial engines had one built in (calibrated as BMEP) and Roy LoPresti installed one in the airplane when developing the 201. That's why the M20J AFM power tables are very accurate. If you take Lycoming's published sea level and altitude curves for the IO-360 and create a power table similar to the Mooney table, you'll find that the Mooney  requires 1 to 1.5" more MAP to generate the same power. This is the difference between running in a test cell and running on an airframe with it's less perfect induction and exhaust system.

Here's the ubiquitous chart from Lycoming  (also reproduced in some Continental publications) that gives idealized engine parameters as a function of mixture strength. Note that the BSFC is approximately constant during the "best economy" range from about 10F LOP to 75F LOP. It is higher, and therefore less efficient, anywhere outside  this range. The curve most likely isn't quite this flat, and Continental in the second  chart below calls the best economy range 25-50F LOP which seems reasonable.

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Despite what the APS guys say, power is related to fuel flow both ROP and LOP. I do not believe they are trying to be misleading - they are just oversimplifying. If you operate within the "best economy" range, power is easily calculated from fuel flow because BSFC is essentially a constant. If you are ROP it's more complicated. I chose the chart below from Continental to show this.

FF.thumb.jpg.3316a79a86d6c827e92490400a51ec94.jpg

Note that the best economy (LOP) lines are essentially linear, whereas the best power and full rich lines (ROP) curve up slightly. But, they don't curve a lot. So a first order approximation for ROP power as a linear function of fuel flow wouldn't be far off. The problem with coming up with a single formula is the vertical offset between ROP and LOP mixtures - not the linearity.

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21 hours ago, jaylw314 said:

I can't remember who it is here that often points out that BSFC actually worsens below 20-30 LOP ( @PT20J?).  That suggests that you can't just calculate the power from the fuel flow as you lean further.  I assume that the fuel flow formula works for one point on the curve, like 20 LOP.  So as long as you're 20 LOP and happen to be 10 gph, you're at 75%.

I would be one of those people. In fact it was the reason for my 3rd comment in this thread that fine wires allowing you to run more “deeply” into the lean spectrum isn’t very useful for most operations. BSFC drops off at very lean levels because the combustion event gets so slow that it is not producing enough pressure at a rapid enough pace to transfer much energy to the piston/crank. This is to say that the combustion event is still in process after BDC which is the exhaust stroke. In practice at 100LOP I start to see the EGT on number 3 go up again because the combustion event is now releasing much of its energy in the exhaust stack. The other EGTs follow suite and the engine gets rough. That being said, 20LOP is not the magic number that BSFC falls in all applications. The Lyc chart in PTJ20’s post is conceptual, not a representation of engine data. Manifold pressure and compression ratio play a roll. I’ve been told that some turbo aeroengines can run 90% power running high manifold pressure and as lean as 80LOP. For a normaly aspirated aeroengine that would be the worst of both worlds. The FF multiple numbers we use are the best we have to estimate power. They work reasonably well for folks who don’t lean beyond what is practical. Explaining what is practical is another matter.

Edited by Shadrach
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3 hours ago, Shadrach said:

BSFC drops off at very lean levels because the combustion event gets so slow that it is not producing enough pressure at a rapid enough pace to transfer much of the energy to the piston/crank.

I play with mixture/MP/RPM when I'm bored on longer trips.  Anecdotally, using the Miles per Gallon readout, I find that reducing RPM compensates somewhat for the slow combustion event at more extreme LOP operations.  EGT also drops which sort of confirms more energy going to piston push and less out the exhaust.  I assume that lower RPM brings the peak pressure back closer to the ideal 15 degrees (or so) ATDC.

I'll sometimes go 80-100 LOP at 2100-2150 at Carson speed.  (BY plugs)

I'd be curious to see an instrumented test of how RPM affects BSFC.

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I agree with all that above...

But...

we are talking mostly about the structure of the tip of the spark plug....

The big difference is what we can find related to fuel vapor and air flowing around the (more) closed structure of the Massive plug vs. the fine wire plug...

There are going to be certain cases where that small flow difference matters...

In most cases... we need the spark to ignite the first molecules of gas and O2 that arrive... after that... it is all thermodynamics...

 

If we can run deeper LOP with a fine wire plug... that would indicate that we are able to ignite a fuel mixture that is not getting into the massive plug.  Interesting flow dynamics...

Our engines have pretty well blended fuel and air when they are warmed up...  but cold starting is another issue... it isn’t very surprising when somebody says the engine starts better with the fine wires... getting mixed fuel vapor/air to where the spark is, is key!

Selecting the proper company to build your spark plug is important...  there is a chance that one company can better deliver on the quality promise... the other company has made bad plugs for years without ever admitting the problem...   ever measure the resistance of your spark plugs before?

having the tip fall off your spark plug can be disappointing.... but when you talk to the company, they want to understand the problem better, and exchange the old part with a new part....

I found an interesting plug failure the other day... brought to me by the same company that makes sells BK radios...

Two plugs...  actually, one plug in two different configurations....

See what changes?

52B1ABE3-0D98-4049-8A46-24DE0AF381C1.thumb.jpeg.34e6f4457fc5ff75ae6afb705074a59a.jpeg5C23FF7E-6E9B-48E0-9A91-970DB512DF2E.thumb.jpeg.cb40a3aef0700b61bc1d298cc62a77ee.jpeg

It’s hard to see...

That little ceramic piece is free to move around... every now and then, it causes a skip...  fortunately the Expedition has something like a JPI, just not as good...

The seat of the pants can tell something is wrong... but the check engine light won’t come on for days... (bouncing rpm about 10 times per minute, at idle) when it comes on, it does tell what cylinder number is being affected...

Brand new $11 Allied Signal plug.... it is only designed to go 100kmi.  This one didn’t go two mi.

I’m glad the hoop design retained and prevented the ceramic shards that would have been circulating...

 

Do we have room in the head for a fine wire hoop?  Keep the fine wire core from escaping...

I’m not going Champion for some time....

And.... My allegiance to Allied Signal has been faaaaaading.... :)

 

The best part of this conundrum... I was able to speak intelligently with my car mechanic... because I have MS experience...   I was unwilling to pull the old steal plugs out, that are deeply entrenched in the aluminum heads...

He swapped in a good plug for the broken one in minutes, no charge, even though I supplied the nine plugs...  it’s like having a good Mooney mechanic... don’t let go of a good mechanic!

Best regards,

-a-

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Point taken, but both the Bravo and its engine predate fine wire plugs but quite a bit. Given the first M20M rolled off the factory floor in 1989, it’s amazing that they’ve managed to operate for 3 decades when fine wire have only been available for about the last half. Now that we have fine wires, are people actually suggesting that massives should be considered a “weakness in spark”?

 

??? I ran fine wire plugs in my first M20E. That was early ‘80s. And iridium or platinum plugs were not new then.

 

 

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1 hour ago, Bob_Belville said:

 

??? I ran fine wire plugs in my first M20E. That was early ‘80s. And iridium or platinum plugs were not new then.

 

 

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You were a trend setter!...and I was apparently a mushroom. I’d never heard of fine wire plugs or seen an advertisement for them until maybe 5-7 years ago. Never saw them mentioned here or on the red board. 

From what I can find, RAM is the only one who has compiled any data (and it’s with one engine and no methodology given). In their case pertaining to turbo applications they claim they saw a 2.2% fuel savings but that everyone else should expect 1%. I have no doubts that fine wires are superior under certain conditions. I don’t seem to operate under conditions that warrant them. To each their own. I would love to see real data. 

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You were a trend setter!...and I was apparently a mushroom. I’d never heard of fine wire plugs or seen an advertisement for them until maybe 5-7 years ago. Never saw them mentioned here or on the red board. 

From what I can find, RAM is the only one who has compiled any data (and it’s with one engine and no methodology given). In their case pertaining to turbo applications they claim they saw a 2.2% fuel savings but that everyone else should expect 1%. I have no doubts that fine wires are superior under certain conditions. I don’t seem to operate under conditions that warrant them. To each their own. I would love to see real data. 

 

I don’t remember why I went to fine wire- long before MS, Savvy, or the internet- I did have an IA who flew a 400 Comanche which was notorious for vapor locking, maybe he put me on them. I was flying 250 hours per year so probably going through plugs. I had Norm Bender transfer my fine wire plugs to a factory new engine. I suppose I put 1000 hours on those plugs

 

 

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Ross,

Try this on for size...

From theory....

A delay of the ignition because a plug design is mechanically clumsy...

Can probably be equated to a delay of ignition timing, with a more able plug design...

So...

Somebody claiming better efficiency of one plug over the other... must be having the fuel mixture exiting the cylinder still burning, more for one than the other...

If this was a true statement... setting timing of the mags could be adjusted parts of a degree specifically based on the plugs that are installed....

our timing isn’t that exact....

 

On another topic of one plug vs. the other.... People don’t like the football shaped wear patterns of the massive plugs...

 

I wonder if the electronic ignitions will avoid the second spark that occurs 180° out of phase with the engine... this would cut some wear in half...

In line with that question... some sparks are going from core to the outside of the plug, the others the electricity is running the opposite direction...  wonder if the electronic ignitions have a more organized flow of electrons...

Preferred wear of one part vs. the other part of the plug could be a choice in this case... avoiding the football shaped core...

 

PP logic only, based on magneto ops explained on the internet...  know what i’m Seeing?

Best regards,

-a-

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Busch, and Tempest(?), recommends rotating plugs to even out the anode/cathode effect. For my 4 cylinder IO360 I exchange 1 & 4 top and bottom and 2 & 3 top and bottom when the plugs are serviced at the annual. (My fine wires are supposed to suffer less than massives from ion transfer but the recommendation remains.)

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