Simviation Forums

1. I know it is used to increase the mass of air entering the engine to create more power. So at higher altitude the engine can create more power than a normal engine. Does it mean that with these engines the mixture doesn't has to be leaned like in a normal engine because the charger compresses the air and there's plenty of air like at lower altitudes?

2. On wikipedia I read that turbochargers are not designed to increase manifold pressures above 29.92 inches, as aircraft engines are commonly air-cooled and excessive pressures increase the risk of overheating, pre-ignition, and detonation. "They are designed to hold a pressure in the intake manifold equal to sea-level pressure (29.92) as the altitude increases and air pressure drops. This is called turbo-normalizing." Aircraft with normal engines like Cessna 182 or Baron 58 have a red line just on 29-30 inches of manifold on the manifold gauge and they can't go above it. But a Mooney M20M which is turbocharged has a red line on 37 inches and when you add full throttle it comes to 37.

But on wikipedia it says that it's not designed to increase the pressure above 29.92 and that that can lead to pre-ignition and detonation because of overheating. So what does it mean? Does it mean that Mooney is not only air-cooled?

3. And whats a supercharger? An even more powerfull charger than a turbocharger?

3. And whats a supercharger? An even more powerfull charger than a turbocharger?

The key difference between a turbocharger and a supercharger is its power supply. Something has to supply the power to run the air compressor. In a supercharger, there is a belt that connects directly to the engine. It gets its power the same way that the water pump or alternator does. A turbocharger, on the other hand, gets its power from the exhaust stream. The exhaust runs through a turbine, which in turn spins the compressor

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3. And whats a supercharger? An even more powerfull charger than a turbocharger?

The key difference between a turbocharger and a supercharger is its power supply. Something has to supply the power to run the air compressor. In a supercharger, there is a belt that connects directly to the engine. It gets its power the same way that the water pump or alternator does. A turbocharger, on the other hand, gets its power from the exhaust stream. The exhaust runs through a turbine, which in turn spins the compressor

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3. And whats a supercharger? An even more powerfull charger than a turbocharger?

Turbocharger is short for turbosupercharger. As TSC says, the supercharger is mechanically driven while the turbocharger is powered by exhaust gases. Superchargers fitted to aircraft engines like the Rolls-Royce Merlin would usually be gear-driven from the engine's auxiliary gearbox.

Note to Fozzer: This is not the same as a turboprop.

PS. The turbocharger is more economical as it's not directly driven by the engine.

3. And whats a supercharger? An even more powerfull charger than a turbocharger?

Turbocharger is short for turbosupercharger. As TSC says, the supercharger is mechanically driven while the turbocharger is powered by exhaust gases. Superchargers fitted to aircraft engines like the Rolls-Royce Merlin would usually be gear-driven from the engine's auxiliary gearbox.

Note to Fozzer: This is not the same as a turboprop.

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1. I know it is used to increase the mass of air entering the engine to create more power. So at higher altitude the engine can create more power than a normal engine. Does it mean that with these engines the mixture doesn't has to be leaned like in a normal engine because the charger compresses the air and there's plenty of air like at lower altitudes?

2. On wikipedia I read that turbochargers are not designed to increase manifold pressures above 29.92 inches, as aircraft engines are commonly air-cooled and excessive pressures increase the risk of overheating, pre-ignition, and detonation. "They are designed to hold a pressure in the intake manifold equal to sea-level pressure (29.92) as the altitude increases and air pressure drops. This is called turbo-normalizing." Aircraft with normal engines like Cessna 182 or Baron 58 have a red line just on 29-30 inches of manifold on the manifold gauge and they can't go above it. But a Mooney M20M which is turbocharged has a red line on 37 inches and when you add full throttle it comes to 37.

But on wikipedia it says that it's not designed to increase the pressure above 29.92 and that that can lead to pre-ignition and detonation because of overheating. So what does it mean? Does it mean that Mooney is not only air-cooled?

3. And whats a supercharger? An even more powerfull charger than a turbocharger?

1) With a turbo-normalized engine, you'll still have a range of MPs to deal with, and different circumstances (climb / cruise / descent)... and fuel economy and plug-fowling to manage. So pilot-controlled mixture is still required. And even more so with a Mooney (VERY wide range of MPs).

2) The Mooney has a modified engine (lower compression ratio, o-ringed heads, etc), so it doesn't get as hot during MPs above atmospheric. That extra MP isn't used often. I can't remember the exact times.. but like for take-off you can only hold max-MP for 25 seconds. Great care is taken during power reductions too; as to avoid "shock cooling".

1) With a turbo-normalized engine, you'll still have a range of MPs to deal with, and different circumstances (climb / cruise / descent)... and fuel economy and plug-fowling to manage. So pilot-controlled mixture is still required. And even more so with a Mooney (VERY wide range of MPs).

1. But I don't understant why because if turbocharger increases the mass of airflow at high altitudes wouldn't leaning the mixture give to low amount of fuel for this "increased" mass of airflow? I know that the mixture has to be leaned a bit, but does it have to be leaned "much" like in normal engines? In normal engines above 5000 feet the mixture control has to be set to about half to get the max power of the engine.

2. The way I see a turbocharger is that it creates conditions when flying on high altitudes like that it's flying on lower altitudes. For example if flying in an aircraft with turbocharger on some 15000 feet he will create conditions, that is increase air flow so the aircraft and the engine will "feel" like they're flying on 5000 ft. Is this correct?

1. But I don't understant why because if turbocharger increases the mass of airflow at high altitudes wouldn't leaning the mixture give to low amount of fuel for this "increased" mass of airflow? I know that the mixture has to be leaned a bit, but does it have to be leaned "much" like in normal engines? In normal engines above 5000 feet the mixture control has to be set to about half to get the max power of the engine.

Even if you HAVE 29" of MP available, you're not going to use it while cruising. And even if you're using full throttle for cruising, you can lean a bit for economy and plug life.. and if you have to make a rapid descent (with a corresponding, extended period where the throttle is reduced (maybe even to idle)), you can go EXTRA lean to reduce shock-cooling (running lean makes an engine run hotter.. fuel actually acts as a coolant before it burns).

Even if you HAVE 29" of MP available, you're not going to use it while cruising.

I see what are you trying to say. But what about when flying at 2000 feet? I will have 29'' of MP available or at least 27'' of MP with normal engines but sometimes I won't use all 29''. Sometimes I'will use only 20-23 or even lower depending on what I'm doing. But the mixture will still be set to full rich. And even when standing still on the ground. If on SEA level we'll have the max MP available on the ground and the throttle will be closed, that is minimum MP. And the mixture will be set to rich. So that is what confuses me. :-?

The manifold pressure desired at cruise power depends on the engine and the aircraft. If memory serves me correctly the P-51D  is rated at about 40 inches of mercury at cruise and substantially higher (72") for take-off. This is with an engine-driven supercharger.

Billa (aka Gringo6)

Even if you HAVE 29" of MP available, you're not going to use it while cruising.

I see what are you trying to say. But what about when flying at 2000 feet? I will have 29'' of MP available or at least 27'' of MP with normal engines but sometimes I won't use all 29''. Sometimes I'will use only 20-23 or even lower depending on what I'm doing. But the mixture will still be set to full rich. And even when standing still on the ground. If on SEA level we'll have the max MP available on the ground and the throttle will be closed, that is minimum MP. And the mixture will be set to rich. So that is what confuses me. :-?

I see your confusion..

Beware Martyn... ...!

You are slowly getting "sucked" into another long, never-ending discussion, from which there may be no escape... ....

Have no fear Paul, you'll notice how I've stayed quiet & allowed Brett to get sucked into the never-ending turbocharger/supercharger discussion.



TSC.

Beware Martyn... ...!

You are slowly getting "sucked" into another long, never-ending discussion, from which there may be no escape... ....

Have no fear Paul, you'll notice how I've stayed quiet & allowed Brett to get sucked into the never-ending turbocharger/supercharger discussion.



TSC.

I thought that Brett coped admirably. He's flown the Mooney in RL so should know what he's talking about.

The difference between a supercharger & turbocharger is perfectly straightforward. IIRC the confusion Paul is talking about was turbocharger/turboprop & he was the only one to be confused. I see I didn't manage to convince him that a turbocharged piston engine is not the same as a gas turbine.

Beware Martyn... ...!

You are slowly getting "sucked" into another long, never-ending discussion, from which there may be no escape... ....

Have no fear Paul, you'll notice how I've stayed quiet & allowed Brett to get sucked into the never-ending turbocharger/supercharger discussion.



TSC.

I thought that Brett coped admirably. He's flown the Mooney in RL so should know what he's talking about.

The difference between a supercharger & turbocharger is perfectly straightforward. IIRC the confusion Paul is talking about was turbocharger/turboprop & he was the only one to be confused. I see I didn't manage to convince him that a turbocharger is not the same as a gas turbine.

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Paul...The Atmospheric Pressure is now equal......!

.... ....!

...having owned a 1931 Riley 9, 1087cc, 1-1/2 seater, GP Racing car, which could have a crankshaft driven Roots or Shorrocks Supercharger....I know what a Supercharger is and how it works....

An exhaust driven Turbocharger is the little fan fitted in the exhaust pipe supplying compressed air to a Piston engine....(had one of those as well)....
...and a Pratt and Whitney PT6 is a Turbine engine with a Propeller fitted on the pointy end...(which I never had... makes too much noise).......!

.... ...!

Don't fixate on the altitude when it comes to mixture settings..  It's a situational thing.

I understand. That was confusing me. Because in FS2004 they tought us: 3000 feet MSL mixture rich above 3000 feet MSL lean the mixture. But yes, if I'm standing on the ground even below 3000 feet and the power is set to idle, I can lean the mixture a bit, to save some fuel altough not much only a little bit, and also save the plugs. And even when taxiing leaning the mixture WON'T decrease the power (RPM) of the engine because only little manifold pressure is used during taxiing. But for takeoff mixture must be set to rich because I'm using the max inches of manifold and if mixture is leaned the power of the engine WILL be decreased.