Turbocharger

[firefighter jim]

Does a tractor with a turbo help fuel economy or hurt fuel economy? Thanks.

 

[Ductape]

Help, since it makes them more efficient.

 

[Duffster]

Help, since it makes them more efficient.

What he ^^^^^^^^^ said.

 

[Treemonkey1000]

Do they really help that much though? I know they help the torque curve once you get them spinning up to speed.

 

[Opti-Mist]

Specifically, adding a turbo or supercharger helps to achieve more complete combustion of the fuel avaiable thus releasing more energy (less wasted unburned fuel) by forcing more air (oxygen) into the combustion chamber. So, the short answer is yes, by reducing waste.

The increase in power usually is due to increasing the fuel. Of course doing that will lead back to increased waste as evidence by the black smoke that we used to love to see.

 

[whistlepig]

Do they really help that much though? I know they help the torque curve once you get them spinning up to speed.

They do help that much. And it's a very noticeable difference. The "spinning up to speed" you refer to is called turbo-lag. One can feel this turbo-lag in the motor. This lag is only a couple of seconds. Then you can feel the turbo spin up. The turbo then more than makes up for the few seconds of the lag. Opti-Mist's explanation of turbo efficiency is about as good as it gets. I couldn't have said it better. Turbo's are nice. Not everyone needs a turbo.

 

[SPYDERLK]

You may be able to get something for next to nothing with a turbo but you definitely cant get something for less than nothing. A turbo vs non turbo engine the same size and each optimized for efficiency would be virtually equally efficient up to the power point where the normally aspirated one began to smoke. At that point the turboed engine, previously lagging very slightly under the efficiency of the NA one, would overtake and surpass its efficiency and continue to widen its advantage, still burning cleanly as more HP was demanded. The same amount of fuel would be being burned by each, but a lot more would be being injected into the NA and an excess coming out as unburned/smoke. Such is the price of getting enuf to burn to reach the max power. When the NA gives up the turbo will still be burning clean and efficient and be capable of several percent more, or greater depending on boost.

A bigger NA engine designed to produce the same HP of the turbo will easily equal its efficiency anywhere on the power curve.
larry

 

[Redneck in training]

A bigger NA engine designed to produce the same HP of the turbo will easily equal its efficiency anywhere on the power curve.
larry

I am not sure about that. There is lot of energy in the exhaust gases. The turbine uses the energy to run compressor that in turn helps to overcome suction losses. If you measure velocity, temperature and pressure upstream and downstream of the turbine you would see that the gases downstream have lower pressure, temperature and velocity (recalculated to the same cross-section of the exhaust pipe). The difference is energy recovered by the turbine. Therefore turbocharged (not supercharged) engine is more efficient and also cleaner burning. Turbocharged and supercharged engines can develop significantly more specific power (HP/cid or kW/L). The limits are mechanical because in order to achieve it the engine would have to be designed for high combustion pressure and high rpm. It all boils down to mass flow of O2 and fuel (energy input) burned and converted to mechanical power in given period of time. Power versus efficiency is a design compromise. Most efficient engines are diesels with specific power so low that they don't require cooling and in fact are insulated to limit energy dissipation.
8,000 miles per gallon British car enters for fuel-economy world title - Bath University Press Release 12may2006
I can't find the article talking about the engine anymore.

Perhaps you noticed that almost all new tractor engines are turbocharged because they have to comply with clean air standards. The efficiency and power increase is a side effect in this case.

I also noticed that some manufacturers use the same engine producing power from in example 67 to 90 HP. That is apparently possible by changing, among other things, turbocharging pressure. Turbocharging allows for power as well as torque increase without rpm increase.

 

[niemeyjt]

The issue with a turbo is, as others have said, it pushes extra air into the cylinders. How much extra? The boost figure tells you that - 0.6 bar means another 60%.

Turbo engines gain most of the extra power not because of the extra air and a more complete burn, but because extra fuel is also injected as well.

I agree they make use of otherwise waste energy - but I predict that the ongoing "green" legislation (in Europe at least) will give them a bad name in years to come - at least in the domestic / car market.

As others have explained, the turbo needs good, clean oil at all times - it spins at up to 100,000 RPM in very hot exhaust gasses.

The four rules on longevity for a Turbo (my LR Discovery is on its original after 180K miles) are 1) allow engine to run for a few seconds to get clean oil to the bearings at start 2) allow engines to run for 30 seconds to a minute to get clean, cooler oil to the bearings before switching off (simmering) 3) use the best oil (e.g. fully synthetic Mobil 1) 4) change it frequently.

Fleet operators already cut corners on 3 and 4. Now we see cars like the new LR Freelander (I think you call it LR2 in US) which stop engine when you stop and do not restart until you depress the clutch to engage gear to move off. Imagine a hot turbo - come to a red stop light - engine cuts without simmering (rule 2 broken); light goes green, clutch down, engine starts and move off (rule 1 broken). This is a recipe for blown turbos.

We shall see - but I hate seeing consumers being ripped off, or facing extra charges they are unaware of, on the grounds of "being green". Sorry - rant and thread hijack over.

J

 

[Egon]

1) allow engine to run for a few seconds to get clean oil to the bearings at start

Not sure I understand this statement?

 

[niemeyjt]

apologies - should have written "run at idle"

J

 

[SPYDERLK]

I am not sure about that. There is lot of energy in the exhaust gases. The turbine uses the energy to run compressor that in turn helps to overcome suction losses.
[snip]
I also noticed that some manufacturers use the same engine producing power from in example 67 to 90 HP. That is apparently possible by changing, among other things, turbocharging pressure. Turbocharging allows for power as well as torque increase without rpm increase.

Absolutely, and its very good to make use of that energy. By doing it in this manner tho, running a turbine, you have to look at any energy offsetting cost it has. This use increases the exhaust backpressure on the engine making the engine do more work on its exhaust strokes. With a NA engine the exhaust can be tuned to help evacuate the cyls completely - - and also the compression ratio is significantly higher leaving very small remanent exhaust gas in the cyl to corrupt the intake. The turboed engine runs at a slight disadvantage because of this, and hence a lesser fuel efficiency, but in comparison to NA, gets it back in the higher parts of its power range because it does not have to be run "rich" to get there.

In your example, that NA engine running comfortably within its range producing 60HP is slightly more fuel efficient than that same turbo optimized engine is when it is producing 60HP. The turbo one tho has plenty in reserve before its efficiency falls, while that of the NA is already falling as more fuel is added to get as much burn [power] from the limited air charge as possible.
larry

 

[Redneck in training]

What you are saying might be true about automobile engines. Tractor engines are virtually constant speed. Therefore the valve timing and turbocharger size can be optimized. The turbo increases backpressure but the exhaust downstream of the TC has less resistance due to lower velocity of the gases and since a lot of energy was removed by the turbo the muffler can also be less efficient (restrictive) for the same noise level. In addition to it the timing of the exhaust valve can be such that some air is actually blown to the exhaust completely flashing the combustion chamber. I think that TC engines are in overall more efficient. But that is just my opinion.

 

[Chilly807]

In my experience, which is mostly marine diesels, turbocharging gets you more power out of a given displacement, fuel economy will be better for the same rated horsepower delivered as well.

The amount of boost you can safely apply depends on the engine design, it has to be built to withstand the extra stress the increased power brings with it. It's why turbocharging an engine that was designed around natural aspiration (non-turbo use) is discouraged. Most of the stuff I work on has anywhere from 20 to 45 psi of boost at full load. At lower loads the intake manifold runs in a vacuum state, as power output and exhaust gas flow increases, turbo speed rises and a pressure develops in the intake.

Most vehicles are built to accomodate an engine of X x Y x Z dimensions, turbocharging or supercharging that engine allows you to deliver more power per litre of displacement. Marine use is no different. When you have an engine room of a given size depending on the size of the ship, and you need a given horsepower value to give you X knots, it definitely limits your choices.

I'm not a big fan of turbo-charged tractors, at least not the smaller displacement ones most of us here have. I believe the added complexity and cost outweighs the benefits. I don't burn enough fuel for the increased economy to make an appreciable difference, and there's plenty of room under the hood anyway.

Tractors that are primarily used for steady load ground engagement, such as plowing, tilling, etc, will see the most benefit, while those that are used for loader work or off-on load will see the least advantage.

Chilly

 

[Redneck in training]

In my experience, which is mostly marine diesels, turbocharging gets you more power out of a given displacement, fuel economy will be better for the same rated horsepower delivered as well.

The amount of boost you can safely apply depends on the engine design, it has to be built to withstand the extra stress the increased power brings with it. It's why turbocharging an engine that was designed around natural aspiration (non-turbo use) is discouraged. Most of the stuff I work on has anywhere from 20 to 45 psi of boost at full load. At lower loads the intake manifold runs in a vacuum state, as power output and exhaust gas flow increases, turbo speed rises and a pressure develops in the intake.

Most vehicles are built to accomodate an engine of X x Y x Z dimensions, turbocharging or supercharging that engine allows you to deliver more power per litre of displacement. Marine use is no different. When you have an engine room of a given size depending on the size of the ship, and you need a given horsepower value to give you X knots, it definitely limits your choices.

I'm not a big fan of turbo-charged tractors, at least not the smaller displacement ones most of us here have. I believe the added complexity and cost outweighs the benefits. I don't burn enough fuel for the increased economy to make an appreciable difference, and there's plenty of room under the hood anyway.

Tractors that are primarily used for steady load ground engagement, such as plowing, tilling, etc, will see the most benefit, while those that are used for loader work or off-on load will see the least advantage.

Chilly

If I understand it right to meet TIER II standards the manufacturers use TC without intercooler. To meet TIER III they use TC and intercooler. Therefore all new tractors are turbocharged.

I also read somewhere that some WWII piston aircrafts had engines with turbines not only running the compressor but were also coupled with the cranckshaft. The turbine added about 10% of power at low altitudes when the compressor was not needed.

 

[niemeyjt]

I also read somewhere that some WWII piston aircrafts had engines with turbines not only running the compressor but were also coupled with the cranckshaft. The turbine added about 10% of power at low altitudes when the compressor was not needed.

Certainlythe Rolls Royce Merlin engines were supercharged - which is what you describe - as fitted to the likes of Spitfires, Hurricanes and Lancasters.

Rolls-Royce Merlin - Wikipedia, the free encyclopedia

The sound is amazing when they fly over from time to time.

J

 

[Chilly807]

Generally speaking, any engine which uses a form of compressor on the intake system is said to be "supercharged", turbocharging is a variation of that which uses a turbine to drive the compressor, usually driven by exhaust gas.

Detroit Diesel engines (2 stroke variety) use a mechanical supercharger driven off the geartrain to provide scavenging air and a mild boost effect. Some of those also use exhaust gas turbochargers in series with the supercharger to further increase the intake pressure. A "blower bypass" system is used to circumvent the mechanical blower at higher loads when the turbos are able to provide more air flow and higher pressures. Most of those are also intercooled.

Larger engines often use sequential turbocharging to provide better performance from a smaller turbo at lower loads, then gradually change over to a larger turbo at high loads. Getting more complicated here..

Which way does the "tier" system work? If higher numbers mean later requirements, my non-turbo Kubota engine is "interim" tier 4 compliant as of now. Diesels are problematic with clean air requirements to begin with, making them cleaner is going to be more difficult than gas engines.

As someone else mentioned, supercharging allows more fuel to be burned effectively, with better (meaning more power) combustion. How much cleaner they actually run, environmentally speaking, is another question.

Sean