Fuel tank crosstalk

[Ragsf15e]

50 minutes ago, FlyingDude said:

@Ragsf15e

"if you’re really 10-20f lean of peak (just barely past peak), you should see cylinders cooler than 100 rop."

Why?  If I'm dwindling around peak with EGT 100F warmer than 100ROP, why should the cylinders be cooler?  Isn't all that extra gas in the rich setting supposed to further cool the cylinders?  I'll measure that specifically next time.  Now I don't recall the comparison.  But I'm curious about your reasoning...

I have JPI700.  CHT and EGT on all cylinders are pretty much balanced, except for Cyl4 running a bit warmer, because the oil cooler is stuck on its back.

I read the Lycoming IO360-A1A manual and I recall full rich for take-offs and all climb situations.  Same in '67E POH.  It mentions leaning for run-up, take off and climb in hot temps or high elevations.  In those cases, yeah, I've done that.  But, it's not my general rule.  

So, the egt is not the cht.  Just because egt is higher, that doesn’t mean the cht will be.  For example, when you do your mag check, egt goes up, right?  Cht actually drops because more combustion is happening later and not all inside the cylinder.  Lean of peak egt will be higher than rop egt, no doubt, but the combustion is taking longer at the lean mixture and carrying more heat down into the exhaust.  The cht ends cooler.   The place you don’t want to be is just rich of peak which is why I asked if you’re sure all your cylinders were past peak.  That’s not good for your engine but probably won’t hurt it at lower power settings.  Read about it on MS, not just my reasoning, there’s a whole APS course about engine management and theory.

The target egt isn’t in the poh because we’ve got better in the last 50 years and because we now have egts/cht on all our cylinders instead of just 1.  Basically, you just need to know your sea level takeoff full rich egt, then you lean as you climb to maintain that number.  Every couple thousand feet is fine.  Most airplanes in the 70s started to say lean above 5000’ in the climb.  Target egt takes that a little further and smoother.  Monitor your chts, enrichen if required, but your Engine will remain happy.

Edit- To answer your question about ROP being higher cht, lower egt... the extra fuel allows the burn (flame front I think APS calls it) to happen faster.  This allows more heat contained in the cylinder vs the exhaust.  Thus cht is warmer.  Yes, some of the extra is cooling, but at 100 rop, you end up with warmer cht than you do at 10-20 LOP.  Maybe at 200 ROP the cht would be cooler than Lop but that’s just a waste of fuel.

Edited February 18, 2021 by Ragsf15e

[Hank]

4 hours ago, N201MKTurbo said:

I keep it simpler than that.

If the minute hand is on the right side of the clock, I'm on the right tank, if the minute hand is on the left side, I'm on the left tank.

But then I have an A13A1 clock where I can start the minute hand at the start of the flight.

Too many changes! Every half hour or so . . .

[N201MKTurbo]

3 minutes ago, Hank said:

Too many changes! Every half hour or so . . .

I've been changing tanks every 1/2 hour for over 5000 hours of Mooney flying. Never seen any detrimental effects on the fuel selector. It gets kind of boring up there some times, I need something to keep me occupied.

[Hank]

Just now, N201MKTurbo said:

I've been changing tanks every 1/2 hour for over 5000 hours of Mooney flying. Never seen any detrimental effects on the fuel selector. It gets kind of boring up there some times, I need something to keep me occupied.

Just too much busy work. I switch every hour, except the second time on a tank I can run 1½ hours. makes it easier figuring out burn on each tank, not nearly as much to remember and it all fits on the fingers of whichever hands isn't holding the yoke.

But whatever work for you! This is just what works for me.

[SSimpson77]

Every time I see the term “I’m an engineer” I laugh and think of this:

https://www.latimes.com/archives/la-xpm-1999-oct-01-mn-17288-story.html
 

I can say that joke because I was once an engineer, but in my line of work an engineer just drives. I bet that drives some of you crazy...

[Hank]

8 minutes ago, SSimpson77 said:

Every time I see the term “I’m an engineer” I laugh and think of this:

https://www.latimes.com/archives/la-xpm-1999-oct-01-mn-17288-story.html
 

I can say that joke because I was once an engineer, but in my line of work an engineer just drives. I bet that drives some of you crazy...

When people asked my why I was studying engineering, my normal answer was "because I want to drive trains!" I can't help bu think that would be more exciting than helping to make little plastic parts for someone else to put together [what I've been doing since 1989].

As for the Mars shot, you have to pay attention to detail. In my jobs, thousandths of an inch matter [being off by 0.001" may be acceptable, but being off by 0.003" rarely is], sometimes ten-thousandths of an inch matter [one part I was responsible for had a feature that was 75μ tall [0.0075 mm = 0.00295"], so we really couldn't be off much at all. Attention to detail!

[Hank]

11 minutes ago, FlyingDude said:

That's not a simple math error. That's wake up call with London Big Ben hammering into your ears that it's past time to ditch the imperial system... 

I'm from Europe, so to me it's as exotic as garden bucket size pop corn. I'm fine with it when you're only stating your height or room size or your weight but it's clumsy math. Not only for me, also for the automakers of the 1930s, such that they tried to implement the mils, a decimal inch-based system, but it failed too... Today they use metric. 

NASA in the 50s, 60s was using metric and converting to imperial to accommodate the astronauts. Just wanted to point out before anyone said "there are countries that use the metric and others that went to the moon"...

My current Fortune 500 employer uses Imperial units everywhere except at my plant, which was purchased after being started by a European company. 

My previous Fortune 500 company designed products in metric and in-house tooling to make them in inches.

A previous smaller employer did everything in inches, and was still using plastic injection molds built in the 60s and designed with pencil and paper.

[M20S Driver]

Don Maxwell advises against running the tank dry.  He stated that a marginal "O"ring in the fuel selector will allow air to leak into the line and disrupt the fuel flow from the tank with fuel.  A couple of gallons in the tank will prevent the leak. 

Did anyone experience this?  Does running the low boost pump solve this potential issue?

[slowflyin]

5 hours ago, FlyingDude said:

To be pedantic, the first reflex should be "mixture full rich, boost pump on, switch tanks, carb heat".  No need to separate them or dwell on the sequence, if you accomplish all four in 100milliseconds.  You could have descended from 9000' for landing without cutting throttle and with your mixture setting left at the 100F LOP @9000', your mechanical pump might have failed, your tank might have dried up, and carb heat is a b**ch...  

Anyway, I love the "minutes hand of the clock matching the tank to be used" idea, but I don't have a mechanical clock.  I use the counter/timer on G 345 for IFR things. I might get a 1cm diameter clock and Velcro that next to the placard

 

I wear a watch .   I realize I’m in part of an ever shrinking minority!

[Hank]

21 minutes ago, slowflyin said:

I wear a watch .   I realize I’m in part of an ever shrinking minority!

Me, too, but the yoke clock is front and center and in my face. Plus it's never covered by sleeves or coats . . . .

[carusoam]

When concerned about leaky seals in the fuel line.... get them fixed...

If your method of finding the leaky seal is changing tanks after they run dry... get them fixed then...

With all due respect for Mr. Maxwell...  

 

It isn’t normal to expect the seal to leak...

So... if you have a leak... and air is drawn in... it really depends on how much air is being drawn in...

in the hangar... while executing the baby food jar test.... and you see bubbles flowing with the fuel....

Time to get a new seal...

The way to know you have an air leak....   your FF appears to be higher than normal...

The fuel system separates out a fair amount of air... while the FF sensor thinks it’s all fuel...

 

If you don’t have a FF sensor... consider getting one...

Pp thoughts only, not a mechanic...

Best regards,

-a-

[FlyingDude]

27 minutes ago, slowflyin said:

I wear a watch .   I realize I’m in part of an ever shrinking minority!

OMG, I wear a watch, too.   

How could I not think of that!!!  I think I'm getting too obsessed with modifying the aircraft that I could only focus on what gets installed on her...

[slowflyin]

1 minute ago, FlyingDude said:

OMG, I wear a watch, too.   

How could I not think of that!!!  I think I'm getting too obsessed with modifying the aircraft that I could only focus on what gets installed on her...

Now that’s funny! .....and common!

[TTaylor]

Actually many of the tablet flight Software packages have a fuel switching reminder built in.  Turn the function on and set how long for the reminder after take-off. 

 

 

 

[FlyingDude]

7 minutes ago, TTaylor said:

Actually many of the tablet flight Software packages have a fuel switching reminder built in.  Turn the function on and set how long for the reminder after take-off. 

 

 

 

The previous owner set up a switch tanks reminder on 430W with the scheduler function. I'll be frank: it was annoying...it used to blink the MSG icon yellow in the middle of knob twisting for other purposes, and you'd have to switch pages to read and snooze it. I also use Garmin pilot, maybe they have a less intrusive way of displaying it on a tablet.

Edited February 18, 2021 by FlyingDude

[carusoam]

I use the totalizer to switch tanks...

The only real accuracy... is the notes that you take... 

So if you miss by a gallon, record the actual and the time you make the switch...

With 100 gallons, and no requirement to switch... every 20 gallons, is about every hour...

Flight timer is used at the beginning of the flight...

Long body fuel methodology...

Best regards,

-a-

[Ragsf15e]

6 hours ago, FlyingDude said:

Exhaust temperature is not governed by that in a thermal machine during the adiabatic expansion phase. Variations in combustion affect the heat in. Exhaust is heat out. Anyway we don't have to discuss Carnot cycles here. More pragmatically: I just looked at the io360-a1a manual and it does confirm your statement. Egt drops faster at ROP vs LOP. CHT is slightly lower at 100F ROP than at peak, but 200F ROP CHT is 200F hotter than 100F LOP CHT. Please remember that LOP is for 75% and under, whereas ROP is at any setting, including 100%. So there's more chemical energy being released in ROP cases than in LOP. That's why at the same rpm and throttle, you go 8% faster in ROP than peak or LOP. Apparently the evaporation of the excess fuel is not providing enough cooling to the cylinders (unlike advertised).

Next time I fly, I'll try to compare CHT at peak, 100F LOP and at 100F and 200F ROP at constant RPM and same speed (130kts) by varying throttle and mixture only. This should force the same power demand from the engine, requiring same amount of chemical energy release into the cylinder. Egt vs CHT variations will hint at whether the excess fuel really cools the cylinders. At constant speed, ram air will be the same.

This should be fun...

one thing I just noticed... you posted the O360 manual.  I didn’t realize you’re not injected.  Carb engines are definitely tougher to operate LOP because the fuel distribution is not as even between cylinders.  It’s possible, but people struggle to get it to work well because your GAMI spread is likely to be rather big.

So there’s how it works in theory and books, then there’s how it works in practice.  I have no doubt that you understand the engineering theory of this, no doubt, but you should do a little reading on how we apply it in our IO360s.  The way you’re operating your engine is likely ok, and I’m glad you’ve read the manual, but the APS folks have done the “graduate” work on engine operation.  If you google “Mooney Gami spread” or “Mooney lean of peak” or “red box” you’ll get all kinds of MS threads on this from folks much smarter than me.

You have to realize that you don’t have 4 identical cylinders either. They are each getting slightly different air and fuel mixtures.  Rich of peak is based off the first cylinder to peak.  LOP is based on the last cylinder to peak.  In no case should a cylinder be say 20 ROP or “around peak”.  It should be definitely on the lean side or 100 ROP.

100 degrees LOP isn’t a practical power setting to use and/or compare with anything.  LOP is measured off the last cylinder to peak, so if you’re 100 lop, 3 cylinders are even more lean than that.  Power falls very quickly on the lean side.  Much faster than rich.  Somewhere around 20-40 lop is about the best you’ll do for efficiency.  You’ll notice a big speed drop off more than that.  
 

On the rich side of peak, power is governed by MP and RPM.  But on the lean side, just FF.  So for our engine, about 9 gph LOP is 65% power. This is a safe place to operate your engine with whatever mixture you like, so a good place to experiment.

Edited February 19, 2021 by Ragsf15e

[FlyingDude]

On 2/18/2021 at 6:38 PM, Ragsf15e said:

one thing I just noticed... you posted the O360 manual.  I didn’t realize you’re not injected

No, I have io360-a1a. It's injected. There's only one manual for all variations.

https://www.manualslib.com/manual/1044332/Lycoming-O-360-Series.html

The graph I shared (p44) is for ALL engines covered by this manual. P57 and p73 are specific for io360-a1a.

Ok, I'll look at the threads you mentioned. Thanks for sharing.

Though nowhere have I seen a satisfactory explanation as to why the first 100F of ROP are bad. .. Do you know why?

[carusoam]

The reason to go ROP... is to avoid heat and detonation...

50°F is often recommended in old POHs for best cruise...

It is a good power setting if you have a budget for spare cylinders...

There isn’t a strong line of where to avoid running your engine...

Some MSers enjoy flying in flaming dragon mode...

Others prefer saving the hardware when possible...

Some, it depends on the day...

Best regards,

-a-

[J0nathan225]

https://www.advancedpilot.com/articles.php?action=article&articleid=1838

"Remember, 50°F ROP is the worst possible mixture setting from a detonation standpoint, from an overall heat standpoint, and from a stress standpoint, because the peak pressures are occurring very soon after TDC, beating on that poor piston like the hammer of Thor."

good read I think

Disclaimer I was supposed to paste the whole article apparently, but I think linking it keeps the spirit of the Author's intent. 

Edited February 20, 2021 by J0nathan225

[FlyingDude]

11 hours ago, carusoam said:

50°F is often recommended in old POHs for best cruise

The previous owner recommended that go 50F ROP but the way he did it was +50F+ 20F margin on the temperature displayed when JPI announces "peak found" , which is -20/30F under peak (computer looks for a plateau and decrease after the period of increase. So there will be an overshoot) . So he was ending up with 100F ROP. I add +100F to the peak temp I read by pressing the right button on the JPI after the announcement, which is the recorded peak. I don't use the EGT temp displayed at the moment of announcement. Long story short, the final setting is at 1400/1430F by either method. 

So my point is, maybe in the past people were advocating +50F ROP but it was leading to +100F ROP due to their skew built into their method of measurement.

Edited February 20, 2021 by FlyingDude

[Ragsf15e]

11 hours ago, FlyingDude said:

No, I have io360-a1a. It's injected. There's only one manual for all variations.

https://www.manualslib.com/manual/1044332/Lycoming-O-360-Series.html

The graph I shared (p44) is for ALL engines covered by this manual. P57 and p73 are specific for io360-a1a.

Ok, I'll look at the threads you mentioned. Thanks for sharing.

Though nowhere have I seen a satisfactory explanation as to why the first 100F of ROP are bad. .. Do you know why?

Ok, with the IO360, your fuel distribution should be more balanced and allow you to be a little more precise setting all 4 cylinders to a particular egt setting reference to peak.

@J0nathan225 and @carusoam nailed the reason not to be less than ~100 on the ROP side.  It can be tough on the engine.  If you do it low enough at a high power setting, you can cause detonation and destroy the cylinders pretty quickly.  In practice, it’s pretty hard to cause actual detonation on an io360.  Bigger, especially turbos, it’s much easier.  Anyway, it’s not a fixed line - ie 90 deg ROP isn’t necessarily going to hurt anything.  At 12,000’, you probably only get 55% in cruise, so maybe 20 ROP might not hurt anything, however it’s not doing much for you.  It’s hotter than 100 ROP and basically the same power.  Commonly accepted, ~100 is a good place to be for engine longevity on the ROP side.  
 

LOP is totally different and you can run closer to peak.  The higher you are, the less power on the engine, the closer to peak you can run safely.  You can safely run at peak at 65% power and some people use that as a good efficient power setting.  Remember, all 4 cylinders need to peak, so 3 will be LOP and the richest will be at peak.  Read about “red fin” or “red box”.  
 

Step 1 for you next time you fly is to check your gami spread.  You can Google it, but basically, set up for cruise at maybe 7,000’ or so, 2500rpm and wide open throttle (just an example, other altitude s and power settings will work).  Then lean very slowly and note the fuel flow when the first cylinder peaks, keep leaning and note the ff when the last peaks.  The difference is your gami spread.  Less than 0.5gph is decent and you can probably run LOP ok.  There’s a lot of other writing on this but it tells you about the the fuel and air distribution to your cylinders.

Edited February 20, 2021 by Ragsf15e

[FlyingDude]

5 minutes ago, Ragsf15e said:

check your gami spread.

I'll do that. Sounds fun. 

I'll do it along with figuring out what map and ff give same IAS at same rpm. By the conservation of energy, each piston stroke will generate the same power, and require the same amount of chemical energy=fuel. Any difference in FF will hint at differences in combustion efficiency and fuel dumped. The difference in CHT will show the effectiveness of whether that dumped fuel in cooling cylinders. 

Now I'll be frank with you: I am curious about what all this Google "folklore" has to say, but it's not official literature. I worked as design engineer, then lead engineer, then manager, so I interacted with and later managed technicians who were very keen on showing engineers that they don't know anything, things are very hard to maintain. All the while I did use to ask them what they would do differently and even took the time to explain how 3/4 of their ideas would invalidate other design aspects. Other 1/4 would get taken into consideration.

So I do appreciate your input, I'll read about the red fin and red box and all the gami spreads, but I won't do anything that contradicts what's published on the graphs in the manual...

 

[carusoam]

Dude,

Measurement is everything...

Find the discussion regarding the scientist with the cat in the trunk...  classic tech discussion point.  Do you remember schroedinger?

Whatever method you use... 50°F means 50°F...

If you are leaning quickly... you will find out everything comes to equilibrium over a minute or two...

The POHs are not complete crap... they just are written for different objectives...  and some have missing data, or incomplete data...

The best way to get to the bottom of this for your plane, and your objectives... find the APS presentation on leaning and LOP...

It helps to build the context that surrounds all of the rules that are used...

Otherwise, you may be following a rule that sounds right, but misses something...

Finding peak... is easy to miss... a pilot can easily be off by many degrees...

This could be caused by the thickness of the jacket of the EGT sensor...

peak occurs in one place....

Being slow and methodical...  you will find it...

wether you get there from the ROP side or the LOP side... it will be in the same place...

If you miss the peak... go back and find it...

 

Some engine controls make this extra challenging... if you have a vernier mixture control dial out the mixture... if you go too far... dial it back in...

While sweeping through the mixture quickly... you can easily miss the peak...   start creeping when you get within range...

 

There are delays in the physical process... the mixture is changing, so the EGTs are changing, so the sensor is changing.... your observation is changing...

One way to simplify this process... find Rob, get the auto-lean system... let Otto lean your engine...  

Practice until the magic wears off...

Since, the red box is detrimental to engines... avoid the red box by having the %bhp less than 65%... so use 20” of MP while you get a feel for what you have...

Then we can discuss setting power for DAs above 3k’ for best T/O power...

 

Use your engineering expertise to get to the next level... don’t waste too much time on who could have done what better...

You will run out of time to go flying...   

PP thoughts only, not a combustion scientist...

Best regards,

-a-

[FlyingDude]

41 minutes ago, carusoam said:

You will run out of time to go flying...   

Oh in MI right now that's not a problem Snow snow and more snow...

I'll look into the material you guys suggested. Then I'll discuss that with my dyno calibration friends at the OEM in SE Germany and one who used to work at one in Detroit. I'm feeling there's going to be a lot of beer consumption in the upcoming days