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?