Turbo performance vs non-turbo

[John Doe]

Ok, another turbo question:

Can someone please explain to me the performance gain by going above 30" MP
(say, during takeoff) on a turbo'd engine.

How much better performance are you getting from the engine at say 35"MP on
takeoff vs a non-turbo'd engine that's going to max out around 29"?

Is it worth the strain put on the engine? I understand the turbo being able
to maintain power at high altitudes, but I haven't heard it explained to me
why I would need such a high power setting on takeoff/climb (assuming sea
level field).

[Newps]

John Doe wrote:
> Ok, another turbo question:
>
> Can someone please explain to me the performance gain by going above 30" MP
> (say, during takeoff) on a turbo'd engine.
>
> How much better performance are you getting from the engine at say 35"MP on
> takeoff vs a non-turbo'd engine that's going to max out around 29"?

Reduce manifold pressure to 23 inches on takeoff and tell me what it
feels like. that's the difference.

>
> Is it worth the strain put on the engine?

Only if you need it.


I understand the turbo being able
> to maintain power at high altitudes, but I haven't heard it explained to me
> why I would need such a high power setting on takeoff/climb (assuming sea
> level field).

For the same reason being able to maintain the sea level power is
desirable, it's more power.

[[email protected]]

: Can someone please explain to me the performance gain by going above 30" MP
: (say, during takeoff) on a turbo'd engine.

Lots.

: How much better performance are you getting from the engine at say 35"MP on
: takeoff vs a non-turbo'd engine that's going to max out around 29"?

As was mentioned before, try taking off in with a regular engine at less than
full throttle.

: Is it worth the strain put on the engine? I understand the turbo being able
: to maintain power at high altitudes, but I haven't heard it explained to me
: why I would need such a high power setting on takeoff/climb (assuming sea
: level field).

There are two different types of turbo systems. The former that you're
familiar with is a "turbo-normalizer." It allows for sea-level manifold pressure at
altitude. That does not add much more "strain" to the engine, although the inlet air
temperature and cylinder cooling in the thinner air at altitude will still make it run
hotter. That *can* be detrimental to longevity.

The other type is "full-time turbo." With that, the engine is designed to
withstand the additional stress of a larger load of air/fuel per power stroke.
Basically, you get more power per cubic inch of engine. These types tend to run even
hotter than their turbo-normalized siblings since they are producing more power.

Unfortunately, in order to prevent a turbo'd engine from destroying itself due
to detonation, the compression ratio of full-time turbo'd engines must be lowered.
That reduces engine efficiency.

For example, my mechanic's turbo Arrow has an TIO-360 Continental that's rated
at 210hp at something like 35" MP. My carb'd O-360 Lycoming is rated at 180hp. If it
were fuel-injected with angle-valve cylinders, it'd be rated at 200hp. That extra
10hp is all that is gained from 6" more MP because the compression ratio was lowered
from 8.5:1 to 7:1. That's not a tradeoff I would be willing to make for any aircraft
I owned. Turbo-normalized, yes... full-time turbo, I don't think so, but to each
their own.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[Robert M. Gary]

I live out West were many airways are above 10,000 feet. When I'm at
14,000 in my non-turbo Mooney and only able to pull 18" of power, I can
understand the benefit of a turbo. :)

-Robert

[soxinbox]

You should get 35/29 the power.
Subtract a bit from that to account for the increased temperature of the
input air, which is counteracted by an intercooler if you have one.
The horse power increase is minimal, but every bit helps on take off. The
real advantage is flying high. I don't fly over mountains, but I will try to
fly at 14500 on cross countries because the speed gain is so much. On a
standard day my arrow does 150Kts IAS = TAS at sea level. Take it up to
14000 and the TAS goes up to 180Kts and it lets me fly over low clouds
instead of under them.
The trade off in cost is significant. There is not much difference in
initial cost or normal maintenance; It's all in overhaul.

"John Doe" > wrote in message
news:2Hf0f.228$L24.111@lakeread01...

[[email protected]]

On Mon, 3 Oct 2005 15:32:04 -0400, "John Doe" >
wrote:

>Ok, another turbo question:
>
>Can someone please explain to me the performance gain by going above 30" MP
>(say, during takeoff) on a turbo'd engine.
>
>How much better performance are you getting from the engine at say 35"MP on
>takeoff vs a non-turbo'd engine that's going to max out around 29"?
>
>Is it worth the strain put on the engine? I understand the turbo being able
>to maintain power at high altitudes, but I haven't heard it explained to me
>why I would need such a high power setting on takeoff/climb (assuming sea
>level field).

I'm not sure exactly what you are asking for. If you are taking off @
sea level on a standard day the performance difference between a
turbo-supercharged engine rated @ 300 HP and a normally aspirated
engine rated @ 300 HP is ZERO.

During cruise flight, the performance difference between both engines
at 65% or 75% power is ZERO.

The "better performance" is derived by being able to develop rated TO
power on the turbo-supercharged engine above sea level on a
non-standard day. It also allows you to use cruise power settings at
higher altitudes than a normally-aspirated engine.

As one responder indicated, if your engine is rated @ 300 HP/36"
MAP/2700 RPM, reducing either the MAP or the RPM is reducing the HP
developed.

TC

[John Doe]

> wrote in message
...
> On Mon, 3 Oct 2005 15:32:04 -0400, "John Doe" >
> wrote:
>
>>Ok, another turbo question:
>>
>>Can someone please explain to me the performance gain by going above 30"
>>MP
>>(say, during takeoff) on a turbo'd engine.
>>
>>How much better performance are you getting from the engine at say 35"MP
>>on
>>takeoff vs a non-turbo'd engine that's going to max out around 29"?
>>
>>Is it worth the strain put on the engine? I understand the turbo being
>>able
>>to maintain power at high altitudes, but I haven't heard it explained to
>>me
>>why I would need such a high power setting on takeoff/climb (assuming sea
>>level field).
>
> I'm not sure exactly what you are asking for. If you are taking off @
> sea level on a standard day the performance difference between a
> turbo-supercharged engine rated @ 300 HP and a normally aspirated
> engine rated @ 300 HP is ZERO.
>
> During cruise flight, the performance difference between both engines
> at 65% or 75% power is ZERO.
>
> The "better performance" is derived by being able to develop rated TO
> power on the turbo-supercharged engine above sea level on a
> non-standard day. It also allows you to use cruise power settings at
> higher altitudes than a normally-aspirated engine.
>
> As one responder indicated, if your engine is rated @ 300 HP/36"
> MAP/2700 RPM, reducing either the MAP or the RPM is reducing the HP
> developed.
>
> TC

The previous responder answered my question. You actually have to be at 36"
to get 300HP out of the engine. I wasn't sure how that worked, but the way
he explained it makes sense.

Seems like the turbo-normalized system is a better system.

Either way, it's been good learning....thanks

[Matt Barrow]

"John Doe" > wrote in message
news:2Hf0f.228$L24.111@lakeread01...
> Ok, another turbo question:
>
> Can someone please explain to me the performance gain by going above 30"
> MP (say, during takeoff) on a turbo'd engine.
>
> How much better performance are you getting from the engine at say 35"MP
> on takeoff vs a non-turbo'd engine that's going to max out around 29"?
>
> Is it worth the strain put on the engine? I understand the turbo being
> able to maintain power at high altitudes, but I haven't heard it explained
> to me why I would need such a high power setting on takeoff/climb
> (assuming sea level field).

A turbo'ed engine is built more "solidly" than a normally aspirated.

The contrasts/advantages can be learned here:
http://www.aopa.org/pilot/bonanza/turbo_primer.html

For example:

"As all pilots are taught, the atmosphere is piled up on the earth's
surface. The weight of the atmosphere is determined by a barometer, or in
airplanes, by the altimeter and the engine manifold pressure gauge. As an
airplane ascends during a climb there is less atmosphere above it so the
weight is less. This is important because it's the weight of the atmosphere
that determines how much ambient air is pushed into the engine during the
intake stroke.

This means that a normally aspirated airplane loses power as it climbs — for
instance, a Cessna 182 engine (a Continental O-470) can no longer deliver
65-percent power above approximately 7,000 feet msl."

and

"

Advantages
There are a number of advantages. The ability to climb strongly at any
altitude between sea level and 20,000 feet gives the pilot amazing latitude
for operation. First, he can safely operate out West, where there are some
tall mountains. For instance, .the MEA (minimum en route altitude) between
Portland, Oregon, and Yakima, Washington, is 14,500 feet. A normally
aspirated airplane would not have much, if any, climb ability at that
altitude — the turbonormalized (and the turbocharged) airplane could easily
climb up there, and could climb smartly over most weather. The pilot also
can comfortably operate at altitudes that are too high for normally
aspirated airplanes and too low for economical operation of turbine
airplanes — generally this is the 10,000- to 14,000-msl band. This means
less conflicting traffic.

The ability to fly at these altitudes also means the pilot can almost always
find a smooth ride. This makes the airplane more comfortable for squeamish
passengers who interpret every turbulent bump as a nudge from the devil.

The ability to climb strongly means that, should in-flight icing be
encountered, the pilot can usually climb up out of the icing band of
weather. Studies show that the icing band of clouds is generally
approximately 3,000 feet thick. Normally aspirated airplanes that encounter
a quick buildup of ice are often faced with having to descend to avoid the
icing layer, which limits safety options.

Finally, the ability to deliver sea-level power up where the atmosphere is
thin means that the engine can deliver a lot of thrust in a flight regime
where the drag on the airplane is less. Thinner atmosphere = less drag. Less
drag with the same power translates into higher true airspeeds. Tornado
Alley Turbo advertises TAS of more than 200 knots at 18,000 feet. That's
fast."

--------------------------------------

For sea level and flat landers, there is limited advantage for a turbo,
unless you want to attain high altitudes to climb above weather. For those
of us in the Rocky Mountain west, it's virtually a necessity. People in here
talk about occasionally taking off from high altitude airports (5000 feet on
up); when you do it ALL the times, especially during summer's high density
altitudes, you quickly appreciate it.


--
Matt

TN Bonanza 36

---------------------
Matthew W. Barrow
Site-Fill Homes, LLC.
Montrose, CO

[George Patterson]

Matt Barrow wrote:

> A turbo'ed engine is built more "solidly" than a normally aspirated.

This would not be true of an engine which has had a turbo-charger added, would
it? I see, for example, that the Commander that AOPA is renovating this year
just had a turbo added via STC.

George Patterson
Drink is the curse of the land. It makes you quarrel with your neighbor.
It makes you shoot at your landlord. And it makes you miss him.

[Matt Barrow]

"George Patterson" > wrote in message
news:ZQl0f.5376$MO2.3022@trndny09...
> Matt Barrow wrote:
>
>> A turbo'ed engine is built more "solidly" than a normally aspirated.
>
> This would not be true of an engine which has had a turbo-charger added,
> would it?

It would be true for a factory turbo, but not an STC add-on I imagine.

The IO-520 in the Beech F33's is different internally from the TSIO-520 in
the B36-TC. Unfortuantely, it was not ideal, so the best upgrade is the
TNIO-550, especially ones from such engine shops as Superior Airparts or
Western Skyways.

>I see, for example, that the Commander that AOPA is renovating this year
>just had a turbo added via STC.

I believe that's a Turbo Alley turbonormalizer, not a Turbo "supercharger".
If not, I suspect the STC might require some "beefing up" of certain parts.


--
Matt

---------------------
Matthew W. Barrow
Site-Fill Homes, LLC.
Montrose, CO

[George Patterson]

Matt Barrow wrote:

> I believe that's a Turbo Alley turbonormalizer, not a Turbo "supercharger".
> If not, I suspect the STC might require some "beefing up" of certain parts.

According to the article, it's a RCM turbonormalization package which contains a
turbocharger. The turbocharger is made by Kelly Aerospace. They say they have
over 1600 hours on one Commander with it.

This unit keeps the manifold pressure at or below 28 PSI. I take it you were
describing systems that do not have this limitation.

George Patterson
Drink is the curse of the land. It makes you quarrel with your neighbor.
It makes you shoot at your landlord. And it makes you miss him.

[Matt Barrow]

"George Patterson" > wrote in message
news:pUm0f.35172$wb3.22707@trndny03...
> Matt Barrow wrote:
>
>> I believe that's a Turbo Alley turbonormalizer, not a Turbo
>> "supercharger". If not, I suspect the STC might require some "beefing up"
>> of certain parts.
>
> According to the article, it's a RCM turbonormalization package which
> contains a turbocharger.

That sounds like being "sorta pregnant". A TN system has a TC, but the
popoff keeps it from running beyonf normal sea level pressure internally.


> The turbocharger is made by Kelly Aerospace. They say they have over 1600
> hours on one Commander with it.
>
> This unit keeps the manifold pressure at or below 28 PSI.

That's about typical for a TN system. Mine keeps MP at or below 31.5 inches.

> I take it you were describing systems that do not have this limitation.

A TN system will been a TC Lite :~)


--
Matt

---------------------
Matthew W. Barrow
Site-Fill Homes, LLC.
Montrose, CO

[jmk]

Right. A turbonormalized engine never sees any more pressure than one
that is normally aspirated - it just sees it up to a high altitude.
Cooling (at high altitudes) may be an issue, but not cylinder pressure.

[[email protected]]

jmk > wrote:
: Right. A turbonormalized engine never sees any more pressure than one
: that is normally aspirated - it just sees it up to a high altitude.
: Cooling (at high altitudes) may be an issue, but not cylinder pressure.

Actually, technically speaking, running the same MP at higher altitudes will
produce a little more power than at lower altitudes. The lower ambient pressure
reduces backpressure on the exhaust, so there's more scavanging and a bigger intake
air/fuel charge for the same MP.

I saw that in the performance specs on a friend's normally-aspirated
PA-24-250. Something like equal power is between 1-2" different MP at 12000' vs. sea
level (RPM constant). I don't remember the exact numbers, but that's in the ballpark.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[Mike Rapoport]

> wrote in message
...
> jmk > wrote:
> : Right. A turbonormalized engine never sees any more pressure than one
> : that is normally aspirated - it just sees it up to a high altitude.
> : Cooling (at high altitudes) may be an issue, but not cylinder pressure.
>
> Actually, technically speaking, running the same MP at higher altitudes
> will
> produce a little more power than at lower altitudes. The lower ambient
> pressure
> reduces backpressure on the exhaust, so there's more scavanging and a
> bigger intake
> air/fuel charge for the same MP.
>
> I saw that in the performance specs on a friend's normally-aspirated
> PA-24-250. Something like equal power is between 1-2" different MP at
> 12000' vs. sea
> level (RPM constant). I don't remember the exact numbers, but that's in
> the ballpark.
>
> -Cory
>
> --
>
> ************************************************** ***********************
> * Cory Papenfuss *
> * Electrical Engineering candidate Ph.D. graduate student *
> * Virginia Polytechnic Institute and State University *
> ************************************************** ***********************
>

It doesn't work that way with a turbocharged engine since the ingested air
is heated by compression.

Mike
MU-2

[[email protected]]

Mike Rapoport > wrote:

: It doesn't work that way with a turbocharged engine since the ingested air
: is heated by compression.

I would argue that it still works that way. In addition, however, the heating
of the intake air reduces the effective mass on the intake charge. Whether one or the
other dominates or they cancel each other out depends on lots of factors... in
particular an intercooler.

I'm not being argumentative... just sharing info that I'd never thought of
before. It doesn't make a huge difference, but it does make a difference. Running
24/24 doesn't *always* make the same power or burn the same fuel. Altitude and
mixture both have 10-20% adjustment fudge factors in there.... throw in a turbo with
heating and there's another 10-20% in the mix as well.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[Mike Rapoport]

> wrote in message
...
> Mike Rapoport > wrote:
>
> : It doesn't work that way with a turbocharged engine since the ingested
> air
> : is heated by compression.
>
> I would argue that it still works that way. In addition, however, the
> heating
> of the intake air reduces the effective mass on the intake charge.
> Whether one or the
> other dominates or they cancel each other out depends on lots of
> factors... in
> particular an intercooler.
>
> I'm not being argumentative... just sharing info that I'd never thought of
> before. It doesn't make a huge difference, but it does make a difference.
> Running
> 24/24 doesn't *always* make the same power or burn the same fuel.
> Altitude and
> mixture both have 10-20% adjustment fudge factors in there.... throw in a
> turbo with
> heating and there's another 10-20% in the mix as well.
>
> -Cory
>
> --
>
> ************************************************** ***********************
> * Cory Papenfuss *
> * Electrical Engineering candidate Ph.D. graduate student *
> * Virginia Polytechnic Institute and State University *
> ************************************************** ***********************
>

The heating of the intake and the consequent reduction in density is the
reason that I think it will take more MP to produce the same HP at higher
altitudes with a turbocharged engine. At the same MP/RPM a tubocharged
engine is effectively running at a higher density altitude than a normally
aspirated one. The turbocharged engine is also running at a higher density
altitude as altitude increases at the same PM becasue there is more
compression required, therefore more heating. The intake air is heated
*substantially* and its density is reduced substantially. Natually, the
effect is strongest at high manifold pressures and high altitudes. I agree
that reduced pressure at the exhaust helps and an intercooler certainly
helps too.

I don't have a flight manual for a turbocharged airplane here but hopefully
somebody here does.

Mike
MU-2

[[email protected]]

: The heating of the intake and the consequent reduction in density is the
: reason that I think it will take more MP to produce the same HP at higher
: altitudes with a turbocharged engine. At the same MP/RPM a tubocharged
: engine is effectively running at a higher density altitude than a normally
: aspirated one. The turbocharged engine is also running at a higher density
: altitude as altitude increases at the same PM becasue there is more
: compression required, therefore more heating. The intake air is heated
: *substantially* and its density is reduced substantially. Natually, the
: effect is strongest at high manifold pressures and high altitudes. I agree
: that reduced pressure at the exhaust helps and an intercooler certainly
: helps too.

: I don't have a flight manual for a turbocharged airplane here but hopefully
: somebody here does.

I agree completely. The heating can be quite substantial from what I've read.
If there's no intercooler, I suspect that you probably always lose the added
scavanging HP to lower density incoming air at the elevated temperature as you
suggest. If there's an intercooler, things might trade off differently and equiv
MP/RPM combination at altitude might be less than, more than, or equal sea-level power
at the same MP/RPM combination.

Between the (substantially) higher inlet air temperature, decreased cooling
due to thinner air flow over the cylinders, and the ability to maintain very long,
high-power climbs, it's no wonder turbo'd engines eat cylinders routinely. The stock
turbo Arrow system is particularly bad... throttling full boost at the inlet? Pretty
stupid to compress the intake only to throw away most of it.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[Paul kgyy]

This is sort of OT, but the new Aviation Consumer this month has an
article on an SMA diesel installed in a C182. The SMA diesel uses 85"
MP on takeoff and pretty much stays there for the entire flight.

[John Doe]

sort of OT?

"Paul kgyy" > wrote in message
ups.com...
> This is sort of OT, but the new Aviation Consumer this month has an
> article on an SMA diesel installed in a C182. The SMA diesel uses 85"
> MP on takeoff and pretty much stays there for the entire flight.
>

[Greg Copeland]

On Tue, 04 Oct 2005 15:44:16 +0000, Mike Rapoport wrote:

> The heating of the intake and the consequent reduction in density is the
> reason that I think it will take more MP to produce the same HP at higher
> altitudes with a turbocharged engine. At the same MP/RPM a tubocharged
> engine is effectively running at a higher density altitude than a normally
> aspirated one. The turbocharged engine is also running at a higher density
> altitude as altitude increases at the same PM becasue there is more
> compression required, therefore more heating. The intake air is heated
> *substantially* and its density is reduced substantially. Natually, the
> effect is strongest at high manifold pressures and high altitudes. I agree
> that reduced pressure at the exhaust helps and an intercooler certainly
> helps too.

Just tossing this out there...

The final rise in temp is always relative to the ambient air temp. At
altitude, where temps can be quiet cool, you are getting a modest
"intercooler" effect. Additionally, amount of boost provided by the turbo
dramatically effects the temp delta.

As an example, a turbo pushing 10 psi, with no intercooler, may cause a
temp delta of 100' F (real world number), measured at the intake. If you
are at altitude, where ambient is quiet cold, say, 40-50' F., then the
intake temp, given the same boost, may only be 140-150'. Compare this to
take off, at sealevel, on a 95' F day, the intake charge may measure ~200'
F, given the same boost.

Turbonormalized is a little bit different because the boost is going to be
much lower at take off than at altitude...nonetheless, you are still
getting an intercooler-like effect from the cooler ambient air.

Greg

[[email protected]]

Greg Copeland > wrote:
: Just tossing this out there...

: The final rise in temp is always relative to the ambient air temp. At
: altitude, where temps can be quiet cool, you are getting a modest
: "intercooler" effect. Additionally, amount of boost provided by the turbo
: dramatically effects the temp delta.

: As an example, a turbo pushing 10 psi, with no intercooler, may cause a
: temp delta of 100' F (real world number), measured at the intake. If you
: are at altitude, where ambient is quiet cold, say, 40-50' F., then the
: intake temp, given the same boost, may only be 140-150'. Compare this to
: take off, at sealevel, on a 95' F day, the intake charge may measure ~200'
: F, given the same boost.

10 psi is a lot for a GA aircraft. 5 psi is more typical maximum boost (i.e.
40" MP)

: Turbonormalized is a little bit different because the boost is going to be
: much lower at take off than at altitude...nonetheless, you are still
: getting an intercooler-like effect from the cooler ambient air.

Only in the context of comparing the engine to ground-based racing
applications. In the context of aircraft and density altitude, temperature rise is
temperature rise. Barring unusual thermal lapse rate, the *effective* density
altitude takes into account the decreasing temperature with altitude.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[Mike Rapoport]

As you point out, the more compression the higher the temperature rise.
..The turbo is called upon to compress the air *more* as altitude goes up
(and temperature goes down). Since the compressor efficiency of a
turbocharger is less than 100% (actually about 70%), the air in the intake
manifold is hotter then higher you go at any given manifold pressure. When
I had a Turbo Lance with an aftermarket intercooler, there was a gauge that
measured temperature before and after the intercooler and could give the
difference as well. It was pretty apparent that all temperatures
(CHT/TIT/intake before intercooler/intake post intercooler) went up with
altitude if power was held constant.

Mike
MU-2

"Greg Copeland" > wrote in message
...
> On Tue, 04 Oct 2005 15:44:16 +0000, Mike Rapoport wrote:
>
>> The heating of the intake and the consequent reduction in density is the
>> reason that I think it will take more MP to produce the same HP at higher
>> altitudes with a turbocharged engine. At the same MP/RPM a tubocharged
>> engine is effectively running at a higher density altitude than a
>> normally
>> aspirated one. The turbocharged engine is also running at a higher
>> density
>> altitude as altitude increases at the same PM becasue there is more
>> compression required, therefore more heating. The intake air is heated
>> *substantially* and its density is reduced substantially. Natually, the
>> effect is strongest at high manifold pressures and high altitudes. I
>> agree
>> that reduced pressure at the exhaust helps and an intercooler certainly
>> helps too.
>
> Just tossing this out there...
>
> The final rise in temp is always relative to the ambient air temp. At
> altitude, where temps can be quiet cool, you are getting a modest
> "intercooler" effect. Additionally, amount of boost provided by the turbo
> dramatically effects the temp delta.
>
> As an example, a turbo pushing 10 psi, with no intercooler, may cause a
> temp delta of 100' F (real world number), measured at the intake. If you
> are at altitude, where ambient is quiet cold, say, 40-50' F., then the
> intake temp, given the same boost, may only be 140-150'. Compare this to
> take off, at sealevel, on a 95' F day, the intake charge may measure ~200'
> F, given the same boost.
>
> Turbonormalized is a little bit different because the boost is going to be
> much lower at take off than at altitude...nonetheless, you are still
> getting an intercooler-like effect from the cooler ambient air.
>
> Greg
>