TIT - Turbo Saratoga

N

N8381V

Filing Flight Plan
Joined
Jul 1, 2014
Messages
1
Display Name
Display name:
Toga81V
I've recently purchase a 1981 Turbo Saratoga and I need some assistance regarding temperatures. First off - I can't find a maximum TIT temperature anywhere in the manual? The plane is equipped with a EDM800 and the previous owner programmed max TIT at 1520. All my leaning is based on keeping the TIT at or below 1520. That puts my CHT's at 350ish, and EGT's are 1475ish.

It seems that everyone else is leaning based on EGT and CHT. I have to lean based on my TIT or I'll redline the 1520 TIT. I'm burning 19 gph+ at 75% and nearly 17 gph at 65%. The

What is a healthy TIT temp for a Turbo Saratoga?

Thanks.
 
Because at 1800 parts start melting usually.


We run our columbia at 1600 max.
 
I was a wrench bender back in the '60sfor an airline that flew L-188 turboprop aircraft. The largest instrument on the panel was the TIT gauge, and was so labeled.

We also had a stew school (long before they were "flight attendants") and they all had to come one by one into the flight deck during their initial training.

We had a breakout box to test the instrument gauge itself and had no end of fun with young gullible females and how we could detect their ... appendage size ... by simply putting this box near their frontal anatomy and adjusting the controls appropriately.

Great fun. Until the Old Man caught us one night playing this game with his niece.

Jim
 
Other than the Malibu, Lycoming sets 1650F as redline for turbo engines, at least all the ones I'm aware of.

In SI1094D, Lycoming recommends TIT be at least 100F on the rich side of maximum allowable, i.e. 1550F or cooler. They say rich side, but what really matters for that is 1550F or cooler. Most people I see flying turbo Lycomings will do more or less what you do, lean to a given TIT and that does the job fine.
 
Ted DuPuis said:
Other than the Malibu, Lycoming sets 1650F as redline for turbo engines, at least all the ones I'm aware of.

In SI1094D, Lycoming recommends TIT be at least 100F on the rich side of maximum allowable, i.e. 1550F or cooler. They say rich side, but what really matters for that is 1550F or cooler. Most people I see flying turbo Lycomings will do more or less what you do, lean to a given TIT and that does the job fine.
Click to expand...

Ted-

If I lean to 1520 I'd be burning a ton of gas also (relative term). I use 1600 and that seems to give a more reasonable fuel flow. Are you saying we need to be that rich?
 
Alexb2000 said:
Ted-

If I lean to 1520 I'd be burning a ton of gas also (relative term). I use 1600 and that seems to give a more reasonable fuel flow. Are you saying we need to be that rich?
Click to expand...

I'm not saying that it "needs" to be that rich per se, but it is the recommendation from Lycoming and I have seen good results from it.

These turbo singles seem to often have a higher cruise power than many twins do to get reasonable cruise speeds, and that tends to elevate TIT some. As a result, I do see more engine issues on some of these turbo singles. Saratogas and your T206 aren't known for great longevity in the Lycoming world. Compare that to Navajo engines that are typically run richer (ie cooler) with a good reputation for longevity.

Send me an eMail with some details on your MP/RPM/FF combos and we can discuss. I seem to recall LOP didn't work great on your engine when you tried it.
 
Ted DuPuis said:
I'm not saying that it "needs" to be that rich per se, but it is the recommendation from Lycoming and I have seen good results from it.

These turbo singles seem to often have a higher cruise power than many twins do to get reasonable cruise speeds, and that tends to elevate TIT some. As a result, I do see more engine issues on some of these turbo singles. Saratogas and your T206 aren't known for great longevity in the Lycoming world. Compare that to Navajo engines that are typically run richer (ie cooler) with a good reputation for longevity.

Send me an eMail with some details on your MP/RPM/FF combos and we can discuss. I seem to recall LOP didn't work great on your engine when you tried it.
Click to expand...

I'll just post it here to keep this thread alive, it's one of the best on POA IMO. (edit: I meant any of Ted's engine advice threads).

I used to run much harder, but I've slowed down. Now I cruise at 27", 1600 TIT, 390-400 CHT, 2400 RPM, and 16.2 GPH. This yields about 150 KTS at 10K. My bird will run LOP, but to get that same 150 KTS I have to run 31". It does cool the CHT's a little better though and fuel flows are only about .5 less.

My plan is to hit TBO before anyone figures out I've been abusing it.:)
 
Last edited:
Alexb2000 said:
Ted-

If I lean to 1520 I'd be burning a ton of gas also (relative term). I use 1600 and that seems to give a more reasonable fuel flow. Are you saying we need to be that rich?
Click to expand...

Pull to 1520-1550 lean of peak, it won't hurt to go through a few moments of higher. Try this, find your 70% power speed for 2500rpm or whatever your max continuous rating using book operating procedure and note your fuel flow,TIT, and CHT. Now grab the red handle and pull it back through peak, note what it is, and back to 1550 TIT or 15° lean of peak, whichever is less. Note fuel flow, TIT, CHT, and Airspeed. Now start progressing the throttle forward adding manifold pressure until you get your lost airspeed back. Note all your FF, TIT, CHT, and EGTs paying attention to the spread to make sure you don't have a hot cylinder.

You are now making 70% power LOP. From this point I would look at what my numbers were and see where I was against my limits. Next change I would make is to reduce my RPM to the bottom of the green arc and start adding MP up towards max continuous and see if I can get my speed back (speed is your primary power % reference when operating LOP), if I can't, I bring in RPM until I get there. All the while of course watching CHT and TIT for limits and EGT for individual aberrations as well. If I haven't hit any limits yet, I have a good mid cruise power setting. If I want to find my most efficient cruise power setting, calculate 1.3 L/D max and start pulling the prop back to the bottom of the green arc to slow down to it. When the prop is all the way back, start pulling mixture to slow down. Only when the TIT & EGT start a big drop do you quit leaning and reduce manifold pressure, if required, to get slowed to your target speed.

If I want to find my high power cruise setting I set for max cont RPM(safest against detonation) and keep adding throttle until I limit out on something.
 
Last edited:
1725 on the Lyc engine in my Commander. I run it max around 1575 (EI primary gauge) and 1650 (JPI non-primary gauge).
 
Alexb2000 said:
I used to run much harder, but I've slowed down. Now I cruise at 27", 1600 TIT, 390-400 CHT, 2400 RPM, and 16.2 GPH. This yields about 150 KTS at 10K. My bird will run LOP, but to get that same 150 KTS I have to run 31". It does cool the CHT's a little better though and fuel flows are only about .5 less.
Click to expand...

I make a point of aiming for CHTs below 380F (Lycoming says below 400F, but cooler is better). Also, 2300 RPM is peak torque on these engines (little more efficient) and lower RPM will tend to lower EGT/TIT a bit since there's more time for combustion.

The 31" LOP is no problem at all, and I would rather run there if it lowered CHTs and kept TIT equal or lower. Ultimately you're reducing your peak ICPs and even 0.5 GPH is worth something If you're only saving 0.5 GPH, then I'd imagine that you're running probably not very far ROP which means peak ICPs. My suggestion would be to start by seeing what power setting at 2300 RPM LOP would produce you the same speed and fuel burn. I'd bet that you'd save a bit of fuel and lower CHTs for equal or lower TIT.

Basically, lower temps are going to be better. And a lower RPM will also be a hair quieter, what's not to like?

My plan is to hit TBO before anyone figures out I've been abusing it.:)
Click to expand...

Good plan. :)
 
Ted DuPuis said:
I make a point of aiming for CHTs below 380F (Lycoming says below 400F, but cooler is better). Also, 2300 RPM is peak torque on these engines (little more efficient) and lower RPM will tend to lower EGT/TIT a bit since there's more time for combustion.

The 31" LOP is no problem at all, and I would rather run there if it lowered CHTs and kept TIT equal or lower. Ultimately you're reducing your peak ICPs and even 0.5 GPH is worth something If you're only saving 0.5 GPH, then I'd imagine that you're running probably not very far ROP which means peak ICPs. My suggestion would be to start by seeing what power setting at 2300 RPM LOP would produce you the same speed and fuel burn. I'd bet that you'd save a bit of fuel and lower CHTs for equal or lower TIT.

Basically, lower temps are going to be better. And a lower RPM will also be a hair quieter, what's not to like?



Good plan. :)
Click to expand...

OK so 2300, 31-32 inches, and LOP enough to get the CHT's about 380. Then see how it runs?
 
Alexb2000 said:
OK so 2300, 31-32 inches, and LOP enough to get the CHT's about 380. Then see how it runs?
Click to expand...

That sounds like a good place to start. :)
 
Ted DuPuis said:
That sounds like a good place to start. :)
Click to expand...

I had about three hours today to just play around with various settings. I ended up just about where you thought we would, and the fuel flows are pretty good for a big girl like mine. Getting lower temps than this really slowed me down a lot so I kept coming back here. Ted, you are the freakin man. Maybe this will help out some other Lycoming turbo drivers like the OP. Thanks again.
 

Attachments

  • IMG_1335.jpg
    IMG_1335.jpg
    3 MB · Views: 65
  • IMG_1336.jpg
    IMG_1336.jpg
    3.3 MB · Views: 53
That looks pretty excellent. More than 10% reduction in fuel flow with lower temps and pretty much the same speed, not to mention quieter. Glad it worked out! :)
 
Ted DuPuis said:
That looks pretty excellent. More than 10% reduction in fuel flow with lower temps and pretty much the same speed, not to mention quieter. Glad it worked out! :)
Click to expand...

I'm REALLY happy with that too, 16.2 to 14.2, I could never get that much fuel reduction with reasonable speed/temps until I tried your settings. It's no 550 Bo going 165 on 11GPH, but it is what it is. Anything else you would try given all your time in a test cell?
 
Alexb2000 said:
I'm REALLY happy with that too, 16.2 to 14.2, I could never get that much fuel reduction with reasonable speed/temps until I tried your settings. It's no 550 Bo going 165 on 11GPH, but it is what it is. Anything else you would try given all your time in a test cell?
Click to expand...

Buy a 310. ;)

You also are flying a much larger plane than a Bo, not to mention hanging the gear out all the time. On a low compression turbocharged engine, the sort of speed and economy you're seeing I think is pretty good.

For your airplane, I think you've hit on what's probably about the best compromise you'll find. If Lycoming did the -AJ1A as a high-compression, turbo-normalized type setup rather than a low-compression boosted setup, you'd see a bit better economy and run a bit lower manifold pressure. But, as you say, it is what it is.
 
Ted DuPuis said:
Buy a 310. ;)

You also are flying a much larger plane than a Bo, not to mention hanging the gear out all the time. On a low compression turbocharged engine, the sort of speed and economy you're seeing I think is pretty good.

For your airplane, I think you've hit on what's probably about the best compromise you'll find. If Lycoming did the -AJ1A as a high-compression, turbo-normalized type setup rather than a low-compression boosted setup, you'd see a bit better economy and run a bit lower manifold pressure. But, as you say, it is what it is.
Click to expand...

OK last question: Do you think running that much MP will cause any issues long term?
 
Alexb2000 said:
OK last question: Do you think running that much MP will cause any issues long term?
Click to expand...


Nope......temp is the limiting factor. Keeping it at 380 by leaning more, to keep it cool if needed is smart flying.

All MP is is air.....when your LOP power is controlled by fuel, not air.
 
Aaronk25 said:
Nope......temp is the limiting factor. Keeping it at 380 by leaning more, to keep it cool if needed is smart flying.

All MP is is air.....when your LOP power is controlled by fuel, not air.
Click to expand...

I was concerned about detonation. While the attached chart isn't directly applicable to my engine, it is the basis of my concern. Not having one to reference I thought it would be a good idea to ask since I'm sure Ted has the information. What are your thoughts?

http://www.avweb.com/media/newspics/pp43_detonation_scale_lg.gif
 
Running at 31" instead of 28" will work your turbo a bit harder, but overall the lower temps balance out to make it easier on the turbo in my opinion.

With respect to detonation, I'd guess you're probably in the range of about 50 LOP there? Just a rough guess. I wouldn't be worried about detonation at that power setting, but I would keep an eye on CHTs. If they start to rise, you may need to go back to a richer setting to cool things off for a bit. If they go above 380, keep an eye on things and try leaning a hair more. Above 400, probably need to reset to rich and try again. What really matters is if you see temps start to rise radically, which your G1000 will alert you to.
 
Last edited:
Ted DuPuis said:
Running at 31" instead of 28" will work your turbo a bit harder, but overall the lower temps balance out to make it easier on the turbo in my opinion.

With respect to detonation, I'd guess you're probably in the range of about 50 LOP there? Just a rough guess. I wouldn't be worried about detonation at that power setting, but I would keep an eye on CHTs. If they start to rise, you may need to go back to a richer setting to cool things off for a bit. If they go above 380, keep an eye on things and try leaning a hair more. Above 400, probably need to reset to rich and try again. What really matters is if you see temps start to rise radically, which your G1000 will alert you to.
Click to expand...

First picture above shows delta peak at -68 degrees, so you're very close. I'll definitely keep an eye on it. Thanks again.
 
You must log in or register to reply here.
Back
Top