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 Post subject: Re: Aerostars
PostPosted: 16 May 2017, 19:49 
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Location: KGNF, Grenada, MS
Aircraft: Baron, 180,195,J-3
Forrest,

I noticed that your fuel pumps were on.

Why?

What were your TIT's?

Jgreen

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 Post subject: Re: Aerostars
PostPosted: 16 May 2017, 20:07 
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Username Protected wrote:
Forrest,

I noticed that your fuel pumps were on.

Why?

What were your TIT's?

Jgreen


I always ran the fuel pumps over 10K. It was on the checklist I received from the previous owner. The primary reason given to me was before the fuel cools, you can get vaporization bubbles in the fuel lines.
After an hour or two, I would shut the fuel pumps off.

Tim


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 Post subject: Re: Aerostars
PostPosted: 17 May 2017, 00:57 
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Joined: 01/14/12
Posts: 2070
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Location: Hampton, VA
Aircraft: AEST
I leave pumps on until 2-3 minute/1000' after top of climb, otherwise I see fuel pressure wiggles.

Highest TIT was 1640-1650.

Other three were low 1600s -high 1500s.

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Forrest

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 Post subject: Re: Aerostars
PostPosted: 17 May 2017, 06:16 
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Joined: 01/14/12
Posts: 2070
Post Likes: +1492
Location: Hampton, VA
Aircraft: AEST
I'm planned to fly back at FL230 this AM, I'll write down some cruise numbers.

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Forrest

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 Post subject: Re: Aerostars
PostPosted: 17 May 2017, 14:42 
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Joined: 01/14/12
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Location: Hampton, VA
Aircraft: AEST
John, Here are some numbers:

TOC: 0925


FL230 Time: 0929
-15C
LOP Fuel Pumps "on"
26" x 2200
TAS 210

1
1443 1413
330 311

2
1366 1457
344 325

3
1541 1489
336 322

4
1515 1523
334 310

5
1549 1539
347 320

6
1518 1508
331 306

TIT1
1602 1626

TIT2
1639 1601

FF
12.8 12.6


FL230 Time: 0948
-17C
LOP Fuel Pumps "on"
26.5" x 2200
TAS 215

1
1454 1441
328 315

2
1368 1476
329 327

3
1549 1506
334 325

4
1518 1540
330 311

5
1555 1551
347 324

6
1527 1523
327 310

TIT1
1601 1637

TIT2
1645 1610

FF
13.2-13.3 12.8-13.1

Attachment:
IMG_3906.JPG


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Forrest

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 Post subject: Re: Aerostars
PostPosted: 17 May 2017, 16:22 
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Joined: 11/08/13
Posts: 1914
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Location: KCRQ
Aircraft: Breeezy, 182,601P
Forrest,
I thought TIT redline was 1650... I'd always tried to give 100 deg or so margin on that number. So I'm running tit of 1550 to 1575.

You are runnign signficantly hotter... thoughts or comments..?

(601P with Machen intercoolers and short props.)

What TIT do you climb at I've been climbing at 2500 29.5 and TIT 1450
As I get more used to the airplane I plan to run LOP, not yet doing so...

Paul


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 Post subject: Re: Aerostars
PostPosted: 17 May 2017, 17:22 
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Posts: 2070
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Location: Hampton, VA
Aircraft: AEST
I'm under the 1650 TIT limit. (Highest is 1645)

I have the Iconal exhausts and tail pipes which (in theory) should give me an additional margin from 1650 (I believe PA-46s have a 1750TIT limit).
Engines are well LOP, which puts them clear of the red box.

If you look you'll find that running 1550-1575 puts an intercooled 601P in the middle of the Red Box.

What kind of CHTs are you seeing? I bet they are higher then the ones I reported.

Find peak EGT and then see where those %#$@ put you relevant to peak EGT, I'm betting 30-50 deg cool of Peak EGT.

My thinking is that TIT has an impact on turbo life, and operating in the red box will have an impact on engine life. I get 600-800 hours out of a set of turbos before they need to be sent off to ATC for overhaul, that is a real cost, however, I assume the fuel I save and the ability to operate at lighter weights (due to needing to carry less fuel) has more benefit then any additional turbo life.
Any improvement in engine life is just a bonus.

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Forrest

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 Post subject: Re: Aerostars
PostPosted: 17 May 2017, 20:51 
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Aircraft: Aerostar, SR22,RV8,
Username Protected wrote:
I'm under the 1650 TIT limit. (Highest is 1645)

I have the Iconal exhausts and tail pipes which (in theory) should give me an additional margin from 1650 (I believe PA-46s have a 1750TIT limit).
Engines are well LOP, which puts them clear of the red box.

If you look you'll find that running 1550-1575 puts an intercooled 601P in the middle of the Red Box.

What kind of CHTs are you seeing? I bet they are higher then the ones I reported.

Find peak EGT and then see where those %#$@ put you relevant to peak EGT, I'm betting 30-50 deg cool of Peak EGT.

My thinking is that TIT has an impact on turbo life, and operating in the red box will have an impact on engine life. I get 600-800 hours out of a set of turbos before they need to be sent off to ATC for overhaul, that is a real cost, however, I assume the fuel I save and the ability to operate at lighter weights (due to needing to carry less fuel) has more benefit then any additional turbo life.
Any improvement in engine life is just a bonus.


Ok, I was with you until you said that running TIT 1550-1575 puts you in the middle of the red box. How?

Assuming TIT reflects and is roughly proportional to EGT, wouldn't 75-100 rich ( or lean) of the max continuous limit be well outside the red box? And in any case is there even a red box at 2200/26"? My cruise power tables suggest that's around 70% power or less, depending on temps.

Not picking, just trying to understand.


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 Post subject: Re: Aerostars
PostPosted: 17 May 2017, 21:21 
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Aircraft: AEST
Keep in mind peak cylinder pressures occur 30-50 ROP.

Unless you have done a GAMI Test and estiblished your spread (you don't need GAMIs to do the test) you don't know how ROP each cylinder is.

I run 50 to 70 LOP (I don't know an exact number because I just do a BMP, and roll most of the time), let's say my richest cylinder is 50 LOP, then if peak cylinder pressure is at 30 ROP that cylinder is 80 degrees away from the center of the red box.

(Side Note: the "Red Box" I refer to is the APS red box not the non-intercooled 601P red box)

If you are operating 100 ROP (TIT) and you have one (or more) cylinders that are a bit leaner than average (believe me - you do), for example, 50 deg leaner, that cylinder is going to be running 50 ROP with the TIT 100 ROP. (That is significantly close(r) to the center of the red box)

Bottom line:

Until you know the fuel flow that gives peak EGT for each cylinder, you don't know whether you are in the red box or not because you don't know how far each cylinder is from its (FF) point for peak cylinder pressure.

Some folks (not me) believe that CHT is a surrogate for peak cylinder pressure, RELATIVE (not absolute) CHTs do give an indication, I listed CHTs as well as EGTs, next time you are in cruise, write down your CHTs and compare them with each other and the other engine. Big variations are an indicator that conditions in one cylinder are different from its fellows.

If all this is leaving you scratching your head, please sign up for and attend the next APS course, it's fun, and when you get back you'll be prepared to make better decisions about operating your motors.

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 Post subject: Re: Aerostars
PostPosted: 18 May 2017, 04:45 
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Location: KGNF, Grenada, MS
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Forrest,

I've taken the APS course and have a mediocre understanding of it all.

Your TIT's are a concern to me.

Jgreen

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 Post subject: Re: Aerostars
PostPosted: 18 May 2017, 07:11 
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Maybe one of the APS guys will be along to shed some additional light on the subject of TIT limits and the relationship between TIT and EGT and CHT and Peak Cylinder Pressure.

I'm approaching the limit of my theoretical knowledge.

But, here's what I have:

1. The original 1650 limit was for one probe per engine on the right side exhaust before the turbo (I can't remember whether the probe is ahead of the WG or not). That limit was established back when the only option was the old style steel exhaust. There are no time limitations for operating at 1650.

2. TIT is positively correlated with power and altitude, my experience has been that, leaning from full rich causes TIT to rise and then fall, and then rise again as cylinders go over lean (causing incomplete combustion, with fuel burning in the exhaust).

3. I may be getting less life out of my turbos and waste gates due to my decision to operate at TIT temps close to the 1650 limit (JBI alarm is set for 1650), but in 1500+ hours I have not seen any sign of traumatic degradation of any turbo components.

4. I have seen less oil consumption and less blow-by since I started running LOP.
LOP ops (up high -21-25K) is more demanding of turbos than ROP Ops. As turbos start to wear I find that I need to run higher RPMs to maintain MAP at altitude, I don't notice any issues ROP (in climb and before I go LOP), someone who only ran ROP (especially below 20K') would never notice the loss of turbo capability.

5. I have not seen any significant degradation of my exhaust components.

6. Based on my experience, I do not believe that I experience significantly more turbo issues than I would if I ran using a lower TIT as my operating maximum.

7. I have talked with 700 owners who chose to operate LOP at %#$@ above 1650, they reported good LOP performance and no turbo issues. I'm not recommending exceeding temp limits but their experience reenforces my theory that the Ioconal exhaust components effectively raise the temperature where bad stuff starts to happen (maybe above 1750?)

8. How we operate or engines is our choice. We could choose to limit cruise power to 65%, or even 50%, and if we did our engines would (might) last longer, (more hours).

But we'd lose performance, and if the design limits were correctly set in the certification process we won't get much additional life because power/heat related wear only goes up sharply once limits are exceeded, there isn't much to be gained by reducing power/heat below to point where the wear increase starts.

9. I beleve that on a 601P, running LOP and limiting max continuous TIT to 1649 gives the best performance/economy/reliability result.

10. I'm happy to read contradictory opinions (backed up by evidence), and if it was convincing I'd consider changing my ways.

:cheers:

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Forrest

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Last edited on 18 May 2017, 07:30, edited 1 time in total.

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 Post subject: Re: Aerostars
PostPosted: 18 May 2017, 07:11 
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For the normally aspirated guys and gals. If you like to run rich of peak and you begin your leaning procedure, the first cylinder to peak is your leanest cylinder. When your first cylinder peaks, stop the leaning procedure and begin richening the the first cylinder that peaked to 50+ rich of peak, all cylinders will be well rich of peak and all will be fine.


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 Post subject: Re: Aerostars
PostPosted: 18 May 2017, 07:39 
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Username Protected wrote:
For the normally aspirated guys and gals. If you like to run rich of peak and you begin your leaning procedure, the first cylinder to peak is your leanest cylinder. When your first cylinder peaks, stop the leaning procedure and begin richening the the first cylinder that peaked to 50+ rich of peak, all cylinders will be well rich of peak and all will be fine.


Not so fast young Sky Walker:

http://www.vansairforce.com/community/s ... hp?t=75132
(Apologies, this was the first place I found the APS charts, I was too lazy to dig up the original source material---my APS t-shirt)

Excerpted:

Attachment:
IMG_3907.PNG


50 deg ROP will put that cylinder very close to peak ICP.

Run at 75% power and it WILL be in the red box.


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Forrest

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 Post subject: Re: Aerostars
PostPosted: 18 May 2017, 08:32 
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Joined: 11/25/11
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Location: KGNF, Grenada, MS
Aircraft: Baron, 180,195,J-3
Forrest,

I do not disagree with anything you have written. I "baby" my airplane's engines and rarely run over 60% power. It's just me. I do the same with every piece of construction/ranch equipment I have. Maybe I'm just "fat, dumb and happy", but I am happy, and I rarely have engine issues with anything.

As I have told you before, I lean by TIT's and never let 1600 on the dial. From looking at your numbers and mine, I burn about 5 gph more than you at equivalent speeds.

We are both happy. :peace:

Jgreen

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 Post subject: Re: Aerostars
PostPosted: 18 May 2017, 09:17 
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Joined: 10/11/11
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Company: PlaneCareLLC.com
Location: KHGR
Aircraft: C-T210N & C-441
LOP has been discussed with within many forums and on many sites. There will always be the LOPers and ROPers. I am definitely a LOPer myself after much diligence, investigation, and flight time experience. I am content with my decision and aircraft(s) performance.

I have 100s of hours in a turbo 210 utilizing lean of peak with no ramifications. I set high (top of green) manifold pressures and high RPM (also top of green). The mixture is used for managing fuel flow. I use a JPI for monitoring.

I also have 100s of hours in a 702 Aerostar with similar LOP parameters that complement those used by Forrest. I have great confidence and no problems with this engine management technique.

I will note however that Continental engines "feel better while flying" to me as a pilot utilizing LOP over Lycomings. This is 100% anecdotal. I have not found over the years that there has been any unexpected or excessive maintenance or degradation of parts due to my engine management methodology in either aircraft.

3 ¢

OK .. now I am ready to be slapped around.

Ali


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