Question regarding TIT

[231LV]

For turbo drivers I have a question. With the EDM 900 now installed and working, I am seeing my TIT sitting at 1620 when running LOP. MP is between 28 and 29 inches and RPM is 2500. Hottest CHT is 340 and hottest EGT is around 1530 with a FF of 10 gph. Altitude doesn’t seem to matter as I see this down below 10,000 ft as well as up closer to 20,000 ft. I’m trying to figure out which parameters affect the TIT. Leaning further doesn’t seem to cool it....maybe I’m not leaning it enough.....opening cowl flaps wider seems to have a marginal affect....of course, reducing power reduces it but that’s not gonna happen in a climb. The red line is 1650 and this is the one parameter I’m struggling to manipulate.....I would appreciate some thoughts from those of you smarter than I about the TIT and how it’s impacted.

Edited April 13, 2019 by 231LV

[smccray]

Turbin drivers or turbo?  Assume turbo-

How far lean of peak are you at 1630?  Check the recording resolution of the JPI (take datapoints more frequently than the default) and post a flight with a lean test.  I assume you have a 231 from your username- do you have an inter cooler?  Are you wide open throttle?

[jackn]

TiT 100 degrees over EGT sounds right. Some engines run further LoP than others even with fine wires & Gamis. If you can go further LoP without losing too much speed, try it. 

[Bryan]

My TiT is elevated when running LOP but never dangerously high.  I only run LOP at 65% or below.  I do run 75% sometimes but only 100F/+ ROP.

[231LV]

Thanks for initial thoughts....I’m running pretty deep LOP at 10 gph.....I can keep leaning but eventually the engine quits. It does have Gamis..... and an inter cooler.....and no, not running WOT due to TIT limitation....wish I could run WOT. This post refers exclusively to LOP ops as this is where I spend 99 % of cruise time.

[smccray]

30 minutes ago, 231LV said:

Thanks for initial thoughts....I’m running pretty deep LOP at 10 gph.....I can keep leaning but eventually the engine quits. It does have Gamis..... and an inter cooler.....and no, not running WOT due to TIT limitation....wish I could run WOT. This post refers exclusively to LOP ops as this is where I spend 99 % of cruise time.

How do you know you’re LOP?  Really- this is where we need to start.  You’ve said it a couple times- your fuel flow setting does not (by itself) determine whether or not you’re LOP.

If you’re closing the throttle, you could be closer to peak TIT, but at a reduced power setting due to closing the throttle.  Depending on the setting, you could be ROP at 10 GPH, but the engine running cool enough (as measured by CHTs) because you reduced the throttle setting.

How strong is your ignition system?  Mags/leads/plugs in good condition?  How do you know?

[gsxrpilot]

WOT is for the NA guys, not turbos. And the 231's only run WOT at high altitude in a climb.

I'm with @Bryan in that I run my 252 at 65% or less when running LOP. My TIT is about 1550 at 30° LOP on the richest cylinder.

One test I did was to set 65% power and then lean very slowly to see where my TIT would peak. Mine won't even get to 1600 at that power setting. I would be curious to know what power setting you're using and what your peak TIT is. 

[Rick Junkin]

2 hours ago, 231LV said:

Leaning further doesn’t seem to cool it....maybe I’m not leaning it enough

This doesn't sound right. Here are some questions that might help:

1. Have you run a GAMI check per the GAMI website, or per Mike Busch's procedure at https://www.savvyaviation.com/home/resources/? 
2. What is your GAMI spread?
3. Are all cylinders going lean of peak at the TIT setting you are using?
4. As already mentioned, are all components of your ignition system in good shape? Using fine wire plugs?
5. What is your peak TIT?

The answers to those could help pinpoint an issue that would drive what you're seeing.

Cheers,
Rick

[carusoam]

Some additional details regarding TIT and JPIs...

1) Good EGT data is expected from all six exhaust streams....

2) It is good form to know where the ship’s gauge is actually located... CHT, EGT, And TIT... it is possible that the installer has moved things without the pilot’s knowledge... piggy back sensors, or second holes...?

3) where is the ship’s EGT mounted, in the confluence of three exhaust streams? Or just a single exhaust stream? Continental’s IO550 has a seventh EGT probe, mounted in the confluence of three streams...

4) if all the EGTs are reading similar, the combined exhaust streams actually are, on average, about 100°F hotter than the individual EGTs...  on average, is important, because six pulses of heat are being delivered in the same amount of time as one pulse of heat... averaging a higher temp to be read... thermodynamically speaking ... there is a lot going on inside that system, not a steady stream of steady temps...

5) the TIT is a combined exhaust stream of six... so it averages higher than the individuals... but, it is further down stream where more expansion has taken place... the turbo’s resistance to flow, keeps the first exhaust pipes pretty hot, and well pressurized overall.... (compared to open pipes)

6) The JPI is a great tool for determining how LOP you have gone...

7) Expect peak to occur at the same time... wether it is a single EGT, combined EGTs or, the TIT....

8) There could be some delay in the display of the peaks based on thermodynamic ‘momentum’ caused by thicker walled thermo-couples... 

9) quick test... are all TCs reading the same while on the ground before start-up?

10) official TIT is only measured from one installed location... there may be other locations to get a secondary reading... make sure your install is using the one that you expect...

11) See if you can post your JPI data.  We will see what you were seeing. This way we can work through what you have...

12) you should be seeing the same TIT after the JPI install as you did before... if not... what else changed?

13) 1650°F is the common ‘avoid exceeding’ number... which is pretty hot. When exceeded, there isn’t a much larger number that is going to show up on the JPI, like the flame temp of gasoline and O2... 3,880°F

14) Bumping into this peak temp indication, while slowly leaning to find peak, makes you want to keep good notes to know the combination of MP, RPM, with back-up data like FF... to later perform the big pull method...

15) let’s use the data you have collected already to see if we have enough detail to know where the engine reached peak, went LOP, and achieved a steady state, TIT below 1650°F...

16) Things that effect TIT...

• It tends to get hotter the more fuel you put to it
• more MP and RPM drives more fuel...

17) Ways to cool TIT...

• Use excess fuel, ROP mixture...
• Use excess air, LOP mixture...

18) TIT is inside the exhaust stream, at its very core... if you are using cowl flaps as part of your experimentation... you may have been il-advised...  CHT and cowl flaps are important, but not for controlling TIT... it is possible to see an effect. But, not enough to be a controlling factor...

19) a good Gami spread is required for running LOP with a turbo...  tsio360s are known for running LOP well... find writings by MSer... @jlunseth and people with Ks....

How does that sound? Or do I need to own a tsio360 to be part of the conversation? 

PP thoughts only, not a mechanic...

Best regards,

-a-

 

[DanM20C]

13 hours ago, 231LV said:

I’m running pretty deep LOP at 10 gph.....I can keep leaning but eventually the engine quits. It does have Gamis..... and an inter cooler.....and no, not running WOT due to TIT limitation....

It my experience with intercooled 231’s, 28-29” at 10gph will be very close to peak, probably just favoring the lean side.  Have you tried increasing MP to the 32-34” range while adjusting the mixture to keep it at 10gph?  I typically fly at 32-33” and 10gph, TIT is less than 1530. 

Accurately finding gami spread in a 231 isn’t easy.  Any movement of the red knob changes FF and MP.  So one has to adjust the throttle  Simultaneously to maintain MP, it’s like drawing a straight 45 degree line on an etch-a-sketch.

 I use the big pull method when setting up for cruise, MP will drop 3-5”. I then I use throttle to bring the MP back up to where I want it and fine tune the mixture to get my desired FF.  I second Anthony’s recommendation for reading @jlunseth‘s posts, lots of great info.  I operate very similar to him with the exception I only operate 65% or less when lop.

Once lop you can think of the mixture and throttle to be swapped.  Lop at 29” -10gph or lop at 34” -10gph, both are about 65% but the first is close to peak and the latter is much further lop.

Cheers,

Dan 

 

[testwest]

For the OP, can you please post some data from the 900? Be sure to set the data rate at the smallest possible number, I think it is 1 sample each 2 seconds, look in the setup menu for the 900.

carusoam 's post to you, above, is solid gold!

Remember 1650 deg TIT is a continuous limit, and as such you can momentarily exceed it (like not longer than a minute or so) while leaning, as long as you get back below 1650 on the lean side. Kind of like this:

The straight yellow lines are markers, the vertical one is the time and the horizontal one is at 1650 deg F on the left hand y-axis.

The TIT lines are the purple and orange, superimposed. Note while leaning the TIT goes above the horizontal yellow line at time 1656:25 or so. (Time on the x-axis). Most people chicken out here, but the richest cylinder is not at peak yet, in this case #4. Stopping at this time would leave this engine (IO-540-S1A5 TN intercooled 290hp) at 1650 TIT, 16 gph, and 360 on the C4 CHT roughly. (Those last two parameters are read from the two right-hand y axes, respectively). So, some cylinders are LOP and other are still ROP.

That is why smccray asked if you know you are LOP. It's way too easy to stop early.

Just beyond the vertical yellow marker, you can see I settled the #4 EGT about 25 deg F LOP (highest yellow line, reads to the left hand y-axis). The power is constant from there, and the C4 CHT (lower yellow line) then starts a dramatic decrease down to just below 340 deg F over the next minute and a half.

Even more dramatic, the lowest blue line is fuel flow. Fully LOP we settle at 13.5 gph.

Your new EDM-900 is a treasure trove of data. And I urge you to extract the operating knowledge that is just sitting there waiting!! There are a few of us on MS that just eat this stuff up, and we like nothing more than helping others here. Hope to hear from you more on this thread.

 

[231LV]

On 4/13/2019 at 10:07 AM, gsxrpilot said:

WOT is for the NA guys, not turbos. And the 231's only run WOT at high altitude in a climb.

I'm with @Bryan in that I run my 252 at 65% or less when running LOP. My TIT is about 1550 at 30° LOP on the richest cylinder.

One test I did was to set 65% power and then lean very slowly to see where my TIT would peak. Mine won't even get to 1600 at that power setting. I would be curious to know what power setting you're using and what your peak TIT is. 

I just had a nice opportunity to do some testing on a 3 hour flight back home. At 17,500 ft, I was burning 10 gph at 2500 rpm. I was running 31 MP with the hottest CHT at 360 and corresponding EGT at 1540. TIT was hovering around 1620. I was able to push the MP up to 33 inches and could lean to about 10.2 gph but TIT climbed to 1630. Any leaner and the engine would quit as It was starting to "cobby" with an occasional stumble. The EDM 900 showed 65% power. I showed a TAS of about 165 but had a nice tailwind so GS was 200. The engine is Gami'd but I have not done a Gami spread since getting the overhauled engine with the LB configuration. It may require a different set of nozzles.

Edited April 15, 2019 by 231LV

[testwest]

That really sounds like you have a big GAMI spread. I bet there is one cylinder that is quite leaner than the rest, and as it goes leaner and leaner, the power in that one cylinder is dropping off significantly. Dude, the data will set you free, please download it and post, or send it to me and I can graph it....it should be a .jpi file.

[231LV]

3 minutes ago, testwest said:

That really sounds like you have a big GAMI spread. I bet there is one cylinder that is quite leaner than the rest, and as it goes leaner and leaner, the power in that one cylinder is dropping off significantly. Dude, the data will set you free, please download it and post, or send it to me and I can graph it....it should be a .jpi file.

will have to retrieve and then post...

[231LV]

unfortunately. it looks like EZTrends is not compatible with Macs......and no, I really am not interested is installing Mirrors or some other program that turns a Mac into a PC...been there and done that....

[smccray]

https://savvyanalysis.com/

 

[carusoam]

LV,

Consider buying your plane a PC... it’s a fancy tool that a plane deserves...

Sure, back in the day... they cost so much, one per household was expensive... and it needed to do everything...

My kids seem to throw off these things like last year’s fashion... each class demands some higher graphics card, processor speed, gobs of memory... portability... some companies replace their employee PCs on a schedule... sending the old PCs home...

My plane owns a PC that got tossed by a high schooler... good for loading up databases into a KLN90B, and downloading data out of a JPI...

PCs are everywhere... and dirt cheap... you can even buy used ones from places like tiger direct.  Who cares if it is Apple or IBM, as long as it works.... it’s just a tool...  

http://www.tigerdirect.com/applications/SearchTools/search.asp?keywords=Used+pc

PP thoughts only, not a mechanic...

Best regards,

-a-

[gsxrpilot]

11 hours ago, 231LV said:

unfortunately. it looks like EZTrends is not compatible with Macs......and no, I really am not interested is installing Mirrors or some other program that turns a Mac into a PC...been there and done that....

I do everything on a Mac. Just download the data to a usb stick and then upload it to SavvyAnalysis. No need for EZTrends.

But only if you want to actually solve the problem...

[johncuyle]

Couple notes:  The HP% on engine monitors is generally not too useful.  I don't know about the 900, but I think on mine it's calculated using MP and RPM. 

I agree with everyone else and suspect your GAMI spread is wide.  It tends to cause that broad, flat TIT over a wide range of FF due to different cylinders peaking at different times and would account for your inability to run much leaner than 10 GPH.  Until you get this sorted, since you're likely running one or two cylinders close to peak, you might want to consider just running a lower power setting to keep TIT lower.  Pulling back to something 55-60% (say, ~9.0 GPH, with MP also pulled back to 26-27") will drop your TIT down to something a little farther from the continuous limit.

[N231BN]

The LB uses different fuel injectors than the GB. If you are using the same injectors as before the engine change you need to call GAMI and get them swapped out.

[231LV]

On 4/16/2019 at 6:47 PM, N231BN said:

The LB uses different fuel injectors than the GB. If you are using the same injectors as before the engine change you need to call GAMI and get them swapped out.

yup....thats the plan

[231LV]

here was a flight I did this morning with EGT, CHT and FF shown. The black line on the upper CHT/EGT chart is TIT. You can see when I went LOP.

[DanM20C]

It might be easier to look at if you remove the CHT from the top graph, add MP to the bottom, and then zoom in a bit to see the transition to lop and some of the cruise.

The Savvy tools awesome!

 Cheers,

Dan

[231LV]

1 hour ago, DanM20C said:

It might be easier to look at if you remove the CHT from the top graph, add MP to the bottom, and then zoom in a bit to see the transition to lop and some of the cruise.

The Savvy tools awesome!

 Cheers,

Dan

Here it is...not sure exactly what I'm looking at but intuitively, everything looks fine except my TIT is sitting above 1600 even at 9.6 FF with hottest EGT at 1530...MP at 26 inches at altitude was only 7500 ft.

[kortopates]

Scott @231LV,

Now we're getting somewhere. But in a sense, you are still getting ahead of yourself, trying to run LOP without collecting the data. I don't mean that critically, but just stating the facts you need 2 things to be able to run LOP and they both need to be verified independently. (perhaps you already did this before since you mentioned an overhaul - but if so that data is stale at this point). But that is what the Savvy test profile is for - to check out your mixture distribution and ignition system. Which is why several folks above that have all been down this road have been giving good advice. Right now I wouldn't even focus on TIT, you need to be looking at EGTs and I see you got some decent data to start. 

Zoom into 10:30 where you leaned out the engine from ROP to LOP and measure your Gami spread.

I get the following:

Time: 00:10:28-00:11:32

EGT5 peaked at 10

EGT6 peaked at 9.9

EGT3 peaked at 9.6

EGT4 peaked at 9.5

EGT1 peaked at 9.4

EGT2 peaked at 9

GAMI spread is 1.0

A gami spread of 1.0 isn't sufficient to run LOP  - your leanest cyl will flame out, actually seriously start missing, while you're trying to get your richest cyl lean enough. Keep in mind 1 gami spread isn't enough data to make any conclusions. We need to see consistent, repeatable spreads. So I only only refer to your data as an example. In the above data, Cyl #2 (almost) appears as a rich outlier, but it looks like you may need more than one swap to get your mixture to <0.5 GPH. But maybe not, when we discard #2 mixture comes in at 0.6 GPH - pretty close to our target 0.5 - we still need a lot more data.

I said almost about #2 being a rich outlier, but it has another issue which tells me we really don't know where Cyl 2 is peaking (especially on only 1 gami spread). You notice how EGT2 keeps rising as you lean? well that is a sign of misfire; which could be due to a weak or dirty plug in #2. But that is what the LOP mag test is for - to independently assess the health of each plug and your ignition system as a whole. Ideally this should be done at 50F LOP, But I expect you'll get roughness before you are able to lean that much so just go as far as you can with a smooth engine and then isolate each mag for a minimum of 10 data points or 30 sec. I expect we'll see some misfire in #2 - which should be easy to address if so. But its looking like to me, that you'll probably have to correct any ignition defects before you can get any accurate gami spread data.

But get several gami sweeps done real slowly in both directions from ROP to LOP and back to ROP, followed by the LOP Mag test after slowly going ROP to LOP so you can tell how LOP the test was done - since it puts the results in context.

Once you get past any ignition defects and can get good repeatable  gami spreads, then you can email your results to John-Paul at Gami and he'll be able to get you what injector swap(s) you may need to get good mixture.

But before you collect any more data I suggest you also re-set your EDM sampling rate from its default 6 sec rate to every 1 sec, it will improve the data resolution and improve the diagnostic value tremendously. (The instructions on how to do this in the Savvy Test profile are really for the 730/830 - its a little different in the 900 but close)

http://content.savvyanalysis.com/static/pdf/SavvyAnalysisFlightTestProfiles.pdf 

 

Edited April 18, 2019 by kortopates