Diff. between turbo and supercharger?

[alphalanos]

whats the difference

[Polygon]

Turbo: This is a device that is driven by the exhaust. The exhaust causes a turbine to spin. There is a shaft connecting it to another turbine which then forces air into the cylinders. This uses no power to make power. Also because of this you will have turbo lag allowing you to retain good gas mileage when you aren't getting on the gas.

Super: This is a belt driven device. It has to use some of the power from the engine to force air into the cylinders. Also the power is instant as soon as you hit the gas; this will affect your gas mileage.

I feel that the turbo is better but it is all personal preference.

[454Casull]

Originally posted by Polygon
Turbo: This is a device that is driven by the exhaust. The exhaust causes a turbine to spin. There is a shaft connecting it to another turbine which then forces air into the cylinders. This uses no power to make power. Also because of this you will have turbo lag allowing you to retain good gas mileage when you aren't getting on the gas.

Super: This is a belt driven device. It has to use some of the power from the engine to force air into the cylinders. Also the power is instant as soon as you hit the gas; this will affect your gas mileage.

I feel that the turbo is better but it is all personal preference.

A turbo does take a little bit of power, but not so much as a mechanically-driven supercharger. Remember, there's nothing in life that's free.

Mechanically-driven superchargers (either by belt, chain or gearset) are driven off the crankshaft and directly pressurize the intake charge with a compressor wheel (a centrifugal supercharger), two 3-lobed rotors (Roots supercharger), or two screws (Lysholm/twin-screw supercharger). Because the crankshaft drives these kinds of superchargers torque is spent running this as an accessory, much as turning on A/C slows down weak engines.

Just a little reminder as to why I wasted time putting "mechanically-driven" in front of "supercharger" - turbochargers are classified as superchargers. Kind of like how squares are always rectangles but not all rectangles are squares.

EDIT: I forgot to mention another supercharger type - the Wankel. Yup, before the rotary was an engine, it was a pump.

[ivymike1031]

A turbo does take a little bit of power, but not so much as a mechanically-driven supercharger. Remember, there's nothing in life that's free

True, but a large portion of the power to drive the turbo would have been wasted otherwise. All that enthalpy in the exhaust... Turbos are wonderful for engines that aren't compression (knock) limited. They're a whole lot less impressive in applications where max cylinder pressure is severely restricted (ie gasoline engines). A good turbo improves the overall efficiency of a diesel engine (vs no turbo at all), which is a sure sign that it's giving "work for free" when compared to blowing the exhaust energy straight out the pipe.

There are some applications where a supercharger can yield "work for free" too. Some Miller cycle engines take advantage of a supercharger to facilitate over-expansion of the cylinder gases. The intake duration is shortened, so the compression stroke is effectively shortened, but the intake charge is denser (due to the S/C), so the power output is still good. Overall efficiency is said to be pretty good.

[Sean]

A turbo can decrease the ease at which exhaust comes out, but if you have the proper equipment you can overcome it. Anyone want to explain blowoff valves and wastegates? im too lazy

[ivymike1031]

Originally posted by Sean Quinn
A turbo can decrease the ease at which exhaust comes out, but if you have the proper equipment you can overcome it. Anyone want to explain blowoff valves and wastegates? im too lazy

..but it ends up giving you positive pumping work, so who cares?

no.

There's an article about all this in the "articles by Texan" portion of this site.

[454Casull]

Originally posted by ivymike1031
A turbo does take a little bit of power, but not so much as a mechanically-driven supercharger. Remember, there's nothing in life that's free

True, but a large portion of the power to drive the turbo would have been wasted otherwise. All that enthalpy in the exhaust... Turbos are wonderful for engines that aren't compression (knock) limited. They're a whole lot less impressive in applications where max cylinder pressure is severely restricted (ie gasoline engines). A good turbo improves the overall efficiency of a diesel engine (vs no turbo at all), which is a sure sign that it's giving "work for free" when compared to blowing the exhaust energy straight out the pipe.

There are some applications where a supercharger can yield "work for free" too. Some Miller cycle engines take advantage of a supercharger to facilitate over-expansion of the cylinder gases. The intake duration is shortened, so the compression stroke is effectively shortened, but the intake charge is denser (due to the S/C), so the power output is still good. Overall efficiency is said to be pretty good.

Yeah, the Miller cycle engines are pretty interesting. Compression does take a lot of energy to accomplish.

[rxtacy]

wastegate regulates amount of exhaust allowed to drive the turbine (boost), and the bov releases pressure from the system when there is excess air headed for the tb (like when you let off the gas real quick). see, that wasn't so hard now.