turbo for increased fuel economy

[Zorlox]

I saw about a month ago that the next prius will be turbocharged to get around 93 mpg and I also read before that that there was a VW golf or GTI that was turbo and super charged and got ~45 mpg. I was just wondering how turbo/super charging increases fuel economy? Is it just because it gives you better control over the amount of air?

[hightower99]

A big part of the savings is the fact that piston engines are not efficient at compressing air. Turbochargers use otherwise wasted energy to increase volumetric efficiency which can lead to fuel gains and superchargers are more mechanically efficient at compressing air than the piston is.

[lightweight]

If you want an engine that produces 100 hp, it would be more fuel efficient to make a turbocharged 1000cc, than a naturally aspirated 1500cc. Moreover, the 1000cc turbocharged engine will probably (not always) be lighter than the 1500cc naturally aspirated. So, another benefit is the reduced consumption due to the reduced weight.

This is called the downsizing effect

So, the Prius Mk3 will probably be equipped with a smaller capacity internal combustion engine, compared to the Mk2.

[deffenbaugh03]

I know turbos are more efficient because they make use of wasted energy, but it's hard for me to imagine that they are really that much better. The principle of turbocharging is to force more air into the cylinders, but the more air you put into the cylinders the more gas gets put in too.

It makes sense to me that you should use a turbocharged 1000cc rather than a NA 1500cc. But my question is what gets better gas mileage if the displacement of the engine stays the same, and one is turbo'd and one is naturally aspirated, which would get better gas mileage? I would guess the NA one would be more economical, and i would say that turbocharging itself is not more economical, but rather the use of turbo's and downsizing the engine is more economical.

[Dary]

But my question is what gets better gas mileage if the displacement of the engine stays the same, and one is turbo'd and one is naturally aspirated, which would get better gas mileage? I would guess the NA one would be more economical, and i would say that turbocharging itself is not more economical, but rather the use of turbo's and downsizing the engine is more economical.

That's true

Finally it's depends how did you use the car.

[Alastor]

I know turbos are more efficient because they make use of wasted energy, but it's hard for me to imagine that they are really that much better. The principle of turbocharging is to force more air into the cylinders, but the more air you put into the cylinders the more gas gets put in too.

Just because you can put more fuel into the cylinders doesn’t mean you have to.

If it takes a particular car 100 Hp to maintain 60 MPH, than it will take 100 naturally aspirated horsepower or 100 turbocharged horsepower. If the turbocharged engine is more efficient (as you said it is) than it will take less fuel to maintain 60 MPH compared to the NA engine.

[h00t_h00t]

If everything else remains the same, the turbo would use more fuel.

[hightower99]

well that isn't quite true if total output stays the same then the turbo version would be using less fuel. This is the concept that BMW is trying to use in their new series of twin turbo I6s. The turbos are small and peak output is a healthy 300-320hp and the engine is 3L. They have shown that it uses alot less fuel than other engines producing the same output.

[h00t_h00t]

BMWs twin turbo I6s are diesel, and there isn't a 3L none turbo diesel production car that can produce 300hp+ anything that comes close is much bigger and has turbos, so where are you getting your information from?

[johnnynumfiv]

BMWs twin turbo I6s are diesel, and there isn't a 3L none turbo diesel production car that can produce 300hp+ anything that comes close is much bigger and has turbos, so where are you getting your information from?

The same place he gets his "engines" "dynoed".

[aNOBLEman]

BMWs twin turbo I6s are diesel, and there isn't a 3L none turbo diesel production car that can produce 300hp+ anything that comes close is much bigger and has turbos, so where are you getting your information from?

Actually the guy is correct. From Road & Track:

"As we reported last issue, BMW's all-new 3 Series coupe will, in fact, sport a twin-turbocharged 3.0-liter inline 6.
Called the 335i Coupe, this direct-injection engine produces 300 bhp and 300 lb.-ft. of torque, the latter over a range of 1400-5000 rpm. BMW claims 0-60 mph in 5.3 sec., which is probably on the conservative side."

[Equinox]

i read that article on road and track

turbo's are good at fuel economy as lightweight said before and other's

[hightower99]

BMWs twin turbo I6s are diesel, and there isn't a 3L none turbo diesel production car that can produce 300hp+ anything that comes close is much bigger and has turbos, so where are you getting your information from?

...BMW

THe new 335i...

If you are having trouble finding anything about it here: http://www.rsportscars.com/eng/cars/bmw_335i.asp

The same place he gets his "engines" "dynoed"

What is your problem. [personal attack].

[h00t_h00t]

Thats the same engine in a different car.

[aNOBLEman]

Thats the same engine in a different car.

What are you talking about?