Question for the PhD chart gurus out there.

[Will.iam]

Pursuing through the continental tsio-360 manufacturer’s charts i came across a couple of issues that i couldn’t  make since of. Our POH says TIT limit is 1650 for TSIO-360MB (and LB) engines yet on this leaning chart from continental they have a note 3 which states a 1550 limit for cruise operation! At first glance i thought it was a typo but both the MB and LB engines charts have this limitation it looks like above 160HP which is 76% power on the MB and 72% power on the SB but i have 78.5% power charts in my mooney POH but it says nothing about staying below 1550 only to be below 1650.  Why does continental have a 1550 limitation on these charts? Or to put. It another way why at power greater than 160hp is the turbo tit now limited to 1550?

 

[N201MKTurbo]

First off, the airplane POH supersedes the engine manual.

It seems reasonable to limit the TIT at higher power settings. you will probably never get to 1550 without exceeding the CHT limit anyway.

[Will.iam]

1 hour ago, N201MKTurbo said:

First off, the airplane POH supersedes the engine manual.

It seems reasonable to limit the TIT at higher power settings. you will probably never get to 1550 without exceeding the CHT limit anyway.

LOP i do as CHT’s are below 380 but my TIT is up around 1580 or so. Guess I can’t operate there anymore since I’m over the limit. 

[T. Peterson]

1 hour ago, Will.iam said:

LOP i do as CHT’s are below 380 but my TIT is up around 1580 or so. Guess I can’t operate there anymore since I’m over the limit. 

Will, I would explore this a little further before abandoning your prior procedure. Something just doesn’t seem right about that. Lots of smart guys have not commented, but two of them have noted that the POH trumps the engine manual. On another thread @hubcap pointed out that Continental says continuous rpm should be limited to 2400. I don’t doubt him for a minute, but that wipes out half the cruise chart in the POH. I’m sure someone will be along to help us out.

[N201MKTurbo]

3 hours ago, Will.iam said:

LOP i do as CHT’s are below 380 but my TIT is up around 1580 or so. Guess I can’t operate there anymore since I’m over the limit. 

But the high power settings are used for takeoff and climb. You don’t want to run LOP, or lean in climb. Once you are set up for cruise, go LOP run your TITs as high as you want, up to 1650 if you like. 

[Will.iam]

16 hours ago, N201MKTurbo said:

But the high power settings are used for takeoff and climb. You don’t want to run LOP, or lean in climb. Once you are set up for cruise, go LOP run your TITs as high as you want, up to 1650 if you like. 

I get that but continental when testing and making that chart did not specify during climb, they specified above 160hp limit the tit to 1550. I would like to understand why that limitation what at >160hp will cause harm if the tit is above 1550 when below 160hp you can go up 100 degrees hotter on the limit. Do we have a continental engine design engineer on the forum? Or someone with turbo design theory as to why the lower limitation at higher HP?

And actually LOP climbs are fantastic in the summer time at keeping the CHT’s lower while climbing through that 100 degree plus texas heat. The fuel used is about the same 5 gallons burned up to 10,000ft it’s just weather you do it in 12 mins or 33 mins.  

[kortopates]

On 11/2/2024 at 12:43 PM, Will.iam said:

I get that but continental when testing and making that chart did not specify during climb, they specified above 160hp limit the tit to 1550. I would like to understand why that limitation what at >160hp will cause harm if the tit is above 1550 when below 160hp you can go up 100 degrees hotter on the limit. Do we have a continental engine design engineer on the forum? Or someone with turbo design theory as to why the lower limitation at higher HP?

And actually LOP climbs are fantastic in the summer time at keeping the CHT’s lower while climbing through that 100 degree plus texas heat. The fuel used is about the same 5 gallons burned up to 10,000ft it’s just weather you do it in 12 mins or 33 mins.  

Its not nearly as complicated or mysterious as your suggesting - or perhaps over thinking it.

Every engine as a "maximum cruise power" even though you may not find it stated directly as such; both NA and especially Turbo. But it is also seen as the maximum horsepower listed in the cruise tables. The definition refers to upper limit in HP for leaning to be allowed. That is only full rich or very limited leaning should be done above that max cruise power. And this is exactly what the chart is saying.

Furthermore 1550F TIT is too high! as I'll try to explain.  I counsel that it shouldn't go above 1450F which is a limit used on the bigger bore TCM Turbo's, as I have seen many partial power losses hitting 1550 and detonation events getting that lean above max cruise power. More so in the TSIO-360's than the bigger turbo's. (If you really know what you're doing you can safely get away with running LOP above max cruise e.g. 80% and some here do, but if you're not expert at doing it, you can get into trouble very quickly.) 

So now that's we've established this isn't a power setting for cruising (unless you want to cruise full rich at max FF) its really only for climb power. And I counsel all my savvy clients that if your TIT is exceeding 1450F at full power full rich, your fuel flow is to low. I prefer to see it no higher than 1350F In the bigger Turbo's such as the TSIO-550's in the Acclaims, Cirrus and Corvalis the POH says to specifically turn on the aux boost pump when your TIT exceeds 1450F in climb! (1450F not 1550F), Cirrus even has you climb from seal level with the aux boost pump on to help ensure FF stays high. Rocket Engineering actually has a limitation in the POH that full power engine TIT limitation is 1450F.

So think of 1550F as a real redline not to exceed when you aren't at or below max cruise power where you can lean to higher TIT's. But just like we don't run at redline CHT temps, the more practical conservative advice is to use 1450F since 1550F is aggressive. Add with a worn TIT probe which may be under indicating as much as 100-150F its a setup for impending disaster with partial power loss and detonation damage very quickly.

Edited November 3, 2024 by kortopates