Turbo/Super Charging

[daepp]

Engine gurus - all other conditions being equal, can the additiion of a turbocharger improve efficiency and mpg? Does the capture of the heat and exhaust and harnessing it for better induction lead to hgiher efficiencies?

Now I know most everyone on this board was put that additional power to use and save no fuel at all, but if it does lead to higher efficiencies why don't auto makers use them to increase fleet mpg?

[Mulhollanddose]

Originally posted by daepp
Engine gurus - all other conditions being equal, can the additiion of a turbocharger improve efficiency and mpg? Does the capture of the heat and exhaust and harnessing it for better induction lead to hgiher efficiencies?

Now I know most everyone on this board was put that additional power to use and save no fuel at all, but if it does lead to higher efficiencies why don't auto makers use them to increase fleet mpg?

No, a turbocharger, if used will increase fuel consumption. The only higher efficiencies obtained would be horsepower and torque. If one stays off boost, the engine will consume as any other similarly displaced engine. One must take into account the bottom end when considering forced induction, as it may not be strong enough to handle the combustion.

[cowtown]

Originally posted by daepp
if it does lead to higher efficiencies why don't auto makers use them to increase fleet mpg?

They do - With a turbo, you can have a smaller-displacement engine that uses less fuel while cruising, but delivers a lot of power and torque when it's needed. Turbodiesel big rigs are an example.

[Dantilla]

Turbochargers are not free from drawbacks-

A few generalizations:

-Turbo engines run hotter
-Turbo engined need more frequent oil changes
-Turbo engines have poor throttle response
-Turbo engines are costly to build
-Turbo engines have poor low-end torque

But- Turbo engines are a hoot to drive! Great for enthusiasts, not so great for soccer moms.

[Jims5543]

My next car when the lease is up on the Audi

http://www.mazdausa.com/MusaWeb/displayPage.action?pageParameter=modelsSpecs&vehicleCode=MS6

3600 lb curb weight Mazdaspeed6 Vs. 4100 lbs for the A-6
19/25 City/Hwy MPG Mazdaspeed6 Vs. A-6 17/23 MPG
274HP 280Tq. Mazdapeed6 Vs. 255/243 A-6
30K Mazdapeed6 Vs. 50K A-6

I cannot wait for my lease to be up.

[legion]

Originally posted by Mulhollanddose
No, a turbocharger, if used will increase fuel consumption. The only higher efficiencies obtained would be horsepower and torque. If one stays off boost, the engine will consume as any other similarly displaced engine. One must take into account the bottom end when considering forced induction, as it may not be strong enough to handle the combustion.

When the turbo is not spooled up, it is actually a restriction in the intake and less fuel has to be injected into the engine and it produces less power than a similar naturally aspirated engine of the same displacement.

When the turbo is spooled up, it is forcing air into the engine and therefore more fuel is required, making it produce more power than a similar naturally aspirated engine of the same displacement.

[notfarnow]

Then there are diesels... A whole different kettle of fish.

Any turbo diesel I've ever driven gets better mileage than it's not turbo equivalent. Same displacement, same gearing.... but better mileage by about 10%. Heck, I've even swapped over the injection pump and the injectors to see if it was just my imagination. They tend to be a lot quieter too.

[beepbeep]

Hello.

Turbo engines do have their drawbacks but in theory, they are more fuel efficient as turbochargers live off the entalpi of EGT before/efter the turbine.

There is a penalty of higher exhaust back-pressure and low C/R off boost but they are usually more efficient fuel-wise than N/A engines. Turbo-diesels certainly so.

Just check the history of reciproc airplane engines (before they got killed by jets).

First it was all pistons, then pistons + supercharger, then piston + turbocharger then piston + turbocharger + turbocompound.

So yes, they are more efficient if you make them so.

Unfortunately, not all manufacturers are able to make them more efficient.

[notfarnow]

Originally posted by SoCal911SC
I think he is asking *if all things are kept equal* would the addition of a turbocharger improve mpg. In other words, if you take a car and bolt a turbo on it, will you get more MPG.

I think the answer is no.

If that's what he's asking then I think you're right, with these exceptions:

-You may get better mileage, in some application, from not having to downshift.
-Turbo diesels. I'm willing to bet if you slap a turbo on a diesel your mileage will increase. You'll be using less fuel because you're pumping in more air and getting more complete combustion. Less smoke too.

[cstreit]

Also keep in mind that turbo motors typically have lower compression ratios than NA motors so off-boost I bet they are also less efficient as a rule...

[daepp]

What I meant by all else being equal is to eliminate what all pelicans would do with a turbo - drive the snot out of it.

Obviously an engine must be designed for the turbo - I simply wondered if the capture of the heatr and flow of exhaust produced a possibly more efficicent /more mpg engine if driven for mpg.