Continental TSIO-360 power rating

[Lumps]

Can anyone explain why the Cont TSIO-360 engine (say EB model as fitted to many Seneca IIs) is rated at 215hp at 12,000ft, and 200hp at S.L?

In the POH there is a reference to an 'orifice' in the turbocharging / induction system being 'set' at 12,000ft. This is an engine with a fixed waste gate from what I can tell, so what is this orifice? I'm guessing that with the throttles fully forward at 12,000ft you'd get 40" MP, descend and the MP would increase (if throttles remain in position).

Illuminate me someone....

[gassed budgie]

Less back pressure re the exhaust system at 12,500' as opposed to SL.

[Lumps]

simplest answer is often the best....

So why the reference to 12,000ft and an orifice?

[seneca208]

my guess would be that the wastegate is set to provide 215HP at 12000' (ISA) or something along those lines.

[Lumps]

Got it - fixed bleed system. No waste gate, size of the orifice establishes the critical altitude of the engine (fixed amount of exhaust gas bypassing the turbine)

[aditya104]

Seems you have already figured out how this works. In case, you haven't....

http://s16.postimage.org/k5rk5orw5/Fixed_Orifice_Turbocharger.png

Fixed Orifice Turbocharger Control
The simplest form of turbocharger control is to have a fixed orifice exhaust bypass.
A proportion of the exhaust gases always drive the turbo, from the ground upto the maximum operating altitude. This orifice is preset by maintainence guys. This preset orifice setting results in a critical altitude of 12,000ft density altitude (full throttle, 2600 RPM & MAP 40" Hg). Any higher than that, the aircraft will not be able to maintain this MAP.

Critical Altitude
The height above which maximum manifold pressure can no longer be maintained.

[jas24zzk]

ok.......................

That makes sense, in that it will maintain 40 in/hg upto 12k DH. What has me scratching, is why its rated at 200hp at SL and 215 at 12k DH.

To my mind it'd be generating 40 inches from S/L all the way to 12k, making it 215 hp all the way up.

Pondering what I am missing (apart from the req'd knowledge)

[aditya104]

X-post from Tech-Log (http://www.pprune.org/tech-log/486946-continental-tsio-360-rated-power.html#post7223228)

One of the main limitations of turbocharged engines is manifold pressure, which is limited to let's say 40 inHg. For example, the aircraft is stationairy at sea level, ISA conditions. The air is entering turbocharger with temperature 15°C and it has a pressure of 40 inHg, so we calculate density of the air:

T = 15°C = 273.15 + 15 = 288.15 K
p = 40" = 1.3544 bar = 135440 Pa
R = 287 J/(kg*K)

RhoMSL = p/(R*T) = 135440/(287*288.15) = 1.6378 kg/m^3

The TCDS for TSIO-360-EB shows that it has a critical altitude altitude of 12.000 ft (maximum altitude at which turbocharger can provide maximum manifold pressure), which means that the air is colder than at sea level and the density of the air is a bit higher:

T = 288.15 - 12 * 2 = 264.15
p = 135440 Pa

Rho12000 = p/(R*T) = 135440/(287*264.15) = 1.7865 kg/m^3

Since piston engine power is (very, very simplified) more or less a function of the density of the intake air (assuming constant air to fuel ratio, etc.), since if we have constant air to fuel ratio, increasing of density of the air will also increase the mass flow of the fuel, more fuel will burn and the power output will be higher.

So we can calculate difference between densities of the air at MSL and 12.000ft:

1.7865 / 1.6378 = 1.09 = 109%

So if the engine is producing 200hp at sea level, it will produce 200 x 1,09 = 218 hp at 12.000 ft, which is close to 215 hp which is stated in TCDS. Do note that this is over simplified just to show basic principles of increasing power with increasing altitude (up to critical altitude) in turbocharged engines.

So basically, the maximum manifold pressure (40") and maximum RPM (2575) remains the same and the power output is higher at critical altitude than at MSL.


Also, at altitude, the back-pressure on the exhaust is less, thus better exhaust scavenging.

Does anyone have a soft copy of the POH?

Cheers

[Lumps]

I posted this on the tech website also, I may be misreading something in FlyingStones's answer but he was assuming because the air is cooler at 12,000ft it is denser, but doesn't take into account increase in induction air temp due to max impeller speed. Therefor I'll have to go with the simple answer - backpressure. Reduction of this improves cylinder fill with fresh charge of air/fuel, 40" pushing against 18" rather the 30". More air/fuel more power.

[baron_beeza]

The engine is a Continental. It has it's own type certificate and publication suite.

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/025cc4fb35e2e9a6862579530051a486/$FILE/E9CE%20rev%2021.pdf

The POH for a Piper aircraft may only be of limited use. They are generally very basic, perhaps not as much as the rudimentary schematic above.

These are only rated figures, not necessarily related to developed power.

I am sure the Continental books will have more info, the engineers will have swags of them.

The LAME would never refer to a Piper publication for a engine issue, and the POH not much at all. Perhaps for the tyre pressures on a strange aircraft....

[Lumps]

Thanks BB, so some versions produce same rated power at SL or at critical altitude with same RPM and MP. As far as I can tell only one version has a waste gate.

Back into the dark for me.

[Old Akro]

All turbochargered engines must have some sort of waste gate (includes fixed orifice).

The Contenental Engine Operators Manual is the reference you need, not the POH.

[aditya104]

The action of compressing the air rapidly increases its temperature, and reduces some of the increase in density which results from the increased pressure, this loss of density may be partially recovered either by passing the air through a Inter-Cooler or by spraying the fuel into the eye of the impeller so that vaporization will reduce its temperature. Will need the manual for the engine or the turbocharger for more details.

Lumps, you are right though, that FlyingStone didn't take into account the temperature action of the impeller.

Thanks BB, so some versions produce same rated power at SL or at critical altitude with same RPM and MP. As far as I can tell only one version has a waste gate.

Back into the dark for me.


In the PDF (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/025cc4fb35e2e9a6862579530051a486/$FILE/E9CE%20rev%2021.pdf) posted by BB, some versions produce the same rated power at SL and at critical altitude with same RPM and MP. In fact they are also fitted with wastegate.

I will soon be flying the Seneca III which has a TSIO 360KB. The Seneca III has a limitation that Take off Power and 2800RPM can only be used for take-off and for 5 mins max, this power setting will produce 220BHP. But it is not available above critical altitude(14,500') unless you conduct a take-off above that altitude. For all other operations, maximum continuous power at 2600RPM will produce 200BHP, which that PDF doesn't mention.

The Contenental Engine Operators Manual is the reference you need, not the POH.
You are correct, but I need the POH(Seneca III) to read some other stuff.

[baron_beeza]

The link I gave is to the engine Type Certificate Data Sheet. It is one of the prime documents in the maintenance publication hierarchy. The Pilot's Operating Handbook would be at the other end of the scale.

The Continental publications should be used, the POH often has limited info.
I was just corresponding with Piper a couple of weeks ago about the POH for another aircraft model. In that case the first amendment in over 20 years had just been issued, I was a little concerned that an AD from 25 years ago had still not been taken into consideration.

I think the figures being bandied about here are just 'rated' power, it has little to do with the actual power that could be developed.

The Continental Operators' Manual will have a variety of graphs and charts which may answer the question better.

The POH is just a handbook, - literally.

I am sure I have seen links to these various books available for free download.
They will not be current but will do the job for you.

Red Sky Ventures Free Aviation Downloads (http://www.redskyventures.org/free_stuff.php)

[Old Akro]

I've never found free links for the Engine Operators Manual. I bought mine from Essco. If I had some time I'd scan a couple of the graphs. The Engine companies actually know what they are doing. Some (specifically Continental) don't seem to understand quality control or supplier quality assurance. But that's a seperate issue from the engineering.

[Lumps]

So anyone know why some of the TSIO-360 engines have a higher power rating at altitude and others have the same rating regardless of altitude?

Thanks for the interesting literature but still wondering why...

[Old Akro]

Its late and I'm a bit pressured for time, so I'm not guaranteeing that I've haven't made a mistake.

But my reading of the performance chart in the Engine Operators Manual is that 40 in Hg manifold pressure at SL yields 100% rated power (200 Hp). But 40 inches at 12,000ft yields 215 Hp. So, for a given manifold pressure the engine delivers more power at altitude. So, its got to be about inlet temperature and / or water vapour content (humidity). Humidity has a significant detrimental effect on power.

The performance graph also suggests that the engine can only maintain 40 inches to 12,000ft and after that it drops off, crossing 200 Hp at 14,000 ft where it makes about 37.5 inches.

From experience, this is a bit academic, because you're likely to tun into TIT and CHT issues at those altitudes and high power levels. As the air gets thinner, it also becomes a less effective cooling fluid.

The engine operators manuals are relatively cheap and worth having. On long flights it can be interested to pull them out and see where the engine / airframe performance plots. I'd recommend buying the books.

[Lumps]

Akro - or reduced backpressure? Only thing is neither of these answers explain why some models of the engine are rated to same power regardless of alt at same power settings.

[Old Akro]

I'm with some smart engine people next week. I'll ask. But I don't like the back pressure argument. I think if it was reduced backpressure the effect would not drop off as quickly past 12,000 ft. Also - have you seen the amount of exhaust pipe after the turbo? In the Seneca it about a foot of straight, relatively large diameter pipe.

Also, assuming the manifold pressure gauge reads gauge pressure and not absolute, then its essentially telling you the pressure differential between the inlet manifold and atmosphere, ie its incorporating a measure of back pressure.

I think if the engine develops more power at 12,000ft with a 40 inch differential between inlet manifold & atmosphere than it does at ground level, then something else is at play.

[Lumps]

In that case I eagerly await the smart engine people's input!

[gassed budgie]

I think if the engine develops more power at 12,000ft with a 40 inch differential between inlet manifold & atmosphere than it does at ground level, then something else is at play

There may well be other factors at play, but I would have thought that the extra power available at 12,500' could largely/mostly be attributed to the reduction in back pressure at altitude.
If you think of back pressure as a form of resistance, all engines use up power in overcoming this 'resistance' whether it be, internal friction or driving a mechanical supercharger for example.
The engine uses a certain amount of power pumping exhaust gases overboard, so if that 'resistance' is reduced at altitude because of the lower atmospheric pressure, ultimately more power is delivered to the prop.

[Old Akro]

I'm told the MP gauge reads absolute, not gauge pressure. Therefore at 12,000ft the engine is effectively getting more boost than ground level because the pressure differential between the inlet manifold and ambient atmosphere is greater. If I thought about it, I would realise that since the needles don't always point to the same reading depending on variations in QNH.

The question is why Continental allow it? Although its probably academic because CHT and EGT limitations probably mean you can't sustain that power at 12,000 ft. Since the power charts are expressed as % of rated power, then 75% power at 12,000 ft is still 150 Hp (not 161 Hp). The charts are effectively saying the engine will run above 100% power between about 10,000ft and 14,000, peaking at 107% at 12,000ft.

[Lumps]

Akro, I think your gauge theory is in fact another way of saying that there is reduced backpressure. As far as I know the MP gauge is a closed system, it doesn't know what the ambient pressure is unless the engine stops. So 40" is still 40", but as you say the ambient pressure is less, so while on the induction side the engine is copping 40" of manifold pressure, on the exhaust side it only has to push out against 18"

[Old Akro]

In the automotive world backpressure tends to refer to the pressure losses due to plumbing bends, mufflers, pipe diameter changes. I agree with you, but tripped up in the nomenclature.

[aditya104]

Another incongruity between the POH and the Continental publication is of the critical altitude. This discrepancy can be explained by the variation in setting of bypass orifice.
Seneca III POH- 12,000'
TSIO 360KB Publication- 14,500'

The Continental publication on the engines is no doubt the prime document but pilots are better off following the POH, IMHO. :ok:
Also, thanks for Red Sky Ventures Free Aviation Downloads (http://www.redskyventures.org/free_stuff.php).
____________________________________________________________ _______________

The engine uses a certain amount of power pumping exhaust gases overboard, so if that 'resistance' is reduced at altitude because of the lower atmospheric pressure, ultimately more power is delivered to the prop.

Hate to bring this up, but I discovered some engines in the continental publication posted above (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/025cc4fb35e2e9a6862579530051a486/$FILE/E9CE%20rev%2021.pdf) which are rated less at critical altitude than at S.L.. Those engines are:

TSIO-360-A, -AB, -B, -BB
TSIO-360-C, -CB
TSIO-360-D, -DB
TSIO-360-H, -HB
TSIO-360-JB

Then, to our delight:
Note 4 on Page 8 of the publication writes about the exhaust system max back pressure for the engines listed in there. The above list of engines which are rated to produce less power at critical altitude are limited to a Exhaust system max back pressure of 40"Hg abs.

Where as the other engines which are rated to produce the same or more power at critical altitude are limited to a Exhaust system max back pressure of 48"Hg abs.

This information hints to the differences in design of the exhaust system of different models of the Continental engine responsible for rated power at critical altitude.

[43Inches]

12000' DA is the critical altitude where 40' MAP intercepts full throttle movement. Above manifold px will decrease due to maximum throttle position achieved and below the throttle needs to be closed to remain below maximum MAP.

With the throttle wide open it provides the least impedement of charge into the cylinder offering the highest BMEP and highest HP output.

The higher the critical altitude setting for the TC the greater the HP loss to SL operation.

*forgot to add that this is for a fixed wastegate system, most automatic wastegate systems will be able to operate at full open throttle at any altitude and therefor HP remains constant or decreases. ie the density controllers in the PA31-350 automatically acheive 350 hp at take-off by varying wastegate position at full throttle position.

[Lumps]

Thank you! Finally. So does this mean if you stuck a pressure gauge in the exhaust system before the turbine it would read more than 40" on the 200/215hp EB model?

[43Inches]

Note 4 on Page 8 of the publication writes about the exhaust system max back pressure


The backpressure quotes apply to a number of engines including the TSIO-360 KB which does not have increased HP at altitude. The KB is just an EB with increased rating according to the TCDS. It does have a higher HP rating all round by means of higher RPM 5min limit. The difference between the EB and KB holds the answer...

[baron_beeza]

Note 4 on Page 8 of the publication writes about the exhaust system max back pressure
Thank you! Finally. So does this mean if you stuck a pressure gauge in the exhaust system before the turbine it would read more than 40" on the 200/215hp EB model?

Whoa up, - I gave that info days ago.

You must have read it yourself then ?

[Lumps]

I didn't come across the fine print relating to backpressure. Needed it pointed out it seems. Still, no one is much the wiser - or if they are they've failed to translate it to simpleton pilot speak.