Help support WeTheArmed.com by visiting our sponsors.

Author Topic: turbo for gas mileage?  (Read 5730 times)

kunkmiester

  • Senior Member
  • ***
  • Posts: 671
  • The Purple One

  • Offline
turbo for gas mileage?
« on: August 06, 2009, 11:20:03 PM »
Moving to Wyoming, if I'm going anywhere much at all, I'll probably be spending a good bit of time driving at a steady speed on a highway/something like that.  The thought occurred to me tonight that a proper turbocharger would help to improve gas mileage to some extent.  I wouldn't want the massive things used to boost performance, it'd just be to negate the drag on the engine from sucking in the air it needs.  Trying to shop for a turbo for an Impala is going to be fun though, plenty of superchargers, but all the turbos I found were for diesel pickup engines.

Would it make sense to put a turbo on?  I'm not sure what kind of mileage boost I'd be getting, anyway.
WyomingEvil is Evil, no matter how small


Help support WeTheArmed.com by visiting our sponsors.

GeorgeHill

  • Co-Founder
  • WTA Staff
  • Senior Contributor
  • *****
  • Posts: 19993
  • The Ogre
    • MadOgre.com

  • Offline
Re: turbo for gas mileage?
« Reply #1 on: August 06, 2009, 11:56:27 PM »
Not really.  A turbo will help you on acceleration... not really at a steady cruise.  You could add one, but I don't think you will get the overall gain you want. 
What you need instead is to lose weight and work on your aerobics.   
Things to do:  Remove everything not essential in your car.  Junk in the trunk etc.
Change your tires to Low Rolling Resistance Tires... narrower, harder.  You sacrifice handling, but will gain mileage.  Change your wheels to units that are as light as possible.  You could lower your car, get a better ground effect.  Air flowing under your car can drag as much as air over your car... you lower it, less air gets dragged. 
Change your airfilter to a K&N.   More air in.  Change your plugs to some good platinums.  Change your cat and muff to less restrictive units.  Run Premium Fuel.
Now after this, your car should be much more efficient... maybe you've already done these things.... but what you really need to work on is driving techniques... Slower accelerations, more coasting and some drafting when possible... shift higher earlier... put car into neutral and coast going downhills when possible.
South CarolinaCo-Founder of WeTheArmed.com
The Ogre from MadOgre.com.

Vires et Honestas
Malo periculosam, libertatem quam quietam servitutem.
http://www.madogre.com/

FluffyHitman

  • Senior Contributor
  • *****
  • Posts: 2351

  • Offline
Re: turbo for gas mileage?
« Reply #2 on: August 07, 2009, 12:04:24 AM »
How much difference does running premium make? Does it depend on the engine? I don't see how running a turbo would help, either. For the best mileage, you won't be running high enough revs to have the turbo kick in.
"Sometimes it's better to light a flamethrower than curse the darkness." - Terry Pratchett

AR lover

  • Senior Member
  • ***
  • Posts: 742

  • Offline
Re: turbo for gas mileage?
« Reply #3 on: August 07, 2009, 12:07:07 AM »
Another thing you can try is vortex generators, basically, they shift air from heading straight out over the back of the car and put it in the vacuum behind the car.  This reduces your drag, and so increases fuel milage.  (at least, this is the theory, I have never tried them personally)

GeorgeHill

  • Co-Founder
  • WTA Staff
  • Senior Contributor
  • *****
  • Posts: 19993
  • The Ogre
    • MadOgre.com

  • Offline
Re: turbo for gas mileage?
« Reply #4 on: August 07, 2009, 12:10:11 AM »
Another thing you can try is vortex generators, basically, they shift air from heading straight out over the back of the car and put it in the vacuum behind the car.  This reduces your drag, and so increases fuel milage.  (at least, this is the theory, I have never tried them personally)
They don't work.  And neither do the fuel line magnet gadgets.  The intake tornado gadgets.  If some gadget that you could buy and just bolt in would really help anything - All the car makers would be putting them in.
South CarolinaCo-Founder of WeTheArmed.com
The Ogre from MadOgre.com.

Vires et Honestas
Malo periculosam, libertatem quam quietam servitutem.
http://www.madogre.com/

JesseL

  • Gun Mangler
  • WTA Staff
  • Senior Contributor
  • *****
  • Posts: 11827

  • Offline
Re: turbo for gas mileage?
« Reply #5 on: August 07, 2009, 12:13:20 AM »
How much difference does running premium make? Does it depend on the engine?

It depends very much on the engine. If it runs a high enough effective compression ratio, and is new enough to use a knock sensor, and is configured to run as much ignition advance as possible without knocking, you can get some respectable gains from high octane gas.

Quote
I don't see how running a turbo would help, either. For the best mileage, you won't be running high enough revs to have the turbo kick in.

That depends on how the systems is tuned. You can run a relatively small turbo that will make boost at low rpms (and just get in the way at higher rpms) and allow you to run cruise just above idle with the throttle wide open, as long as you run really tall gearing too. Not exactly a formula for good acceleration, but it would give good mileage.

It would also tend to put a lot of strain on the engine by running very high cylinder pressures and low oil pressure (unless you went to a higher volume oil pump too). This is the kind of running diesels are built for.
Arizona

g.willikers

  • Senior Member
  • ***
  • Posts: 804

  • Offline
Re: turbo for gas mileage?
« Reply #6 on: August 07, 2009, 11:23:30 AM »
It's nearly fraudulent that way some car makers advertise turbo engines as gas savers.
Lots of folks believe them and think a turbo powered engine automatically will get better mileage.
What's left out of this advertising is the obvious truth.
Turbo charging makes horsepower and horsepower uses fuel.
If they were honest, they would say that a small engine with a turbo, that makes the same power as a larger engine without a turbo, can get better mileage.
But only if the driver is not using the full potential of the engine and is happy cruising in a gas saving mode.
Then the mileage will be better than the large, non turbo engine under the same conditions.
When more power is needed, it's there - with the penalty of less gas mileage.
Hopefully this did not add to the confusion.
Trust No One


Help support WeTheArmed.com by visiting our sponsors.

kunkmiester

  • Senior Member
  • ***
  • Posts: 671
  • The Purple One

  • Offline
Re: turbo for gas mileage?
« Reply #7 on: August 07, 2009, 01:46:14 PM »
The thought was to remove the drag on the engine caused by having to suck in air.  More air=better running, or so the thought went.  The intake manifold runs at a negative pressure, and by getting it closer to zero or just a bit higher, the engine wouldn't have to work as hard to get power.

It's mostly tender loving care as I understand it, but my 3.4L does give me 35 MPG on the highway.  I've yet to try a higher octane effectively, prices have been high, and city mileage varies enough, it'd be a highway thing for testing which I can never remember to feed the higher octane stuff often enough to tell.  That and I'm not sure that the mileage boost would compensate for the higher price.
WyomingEvil is Evil, no matter how small

JesseL

  • Gun Mangler
  • WTA Staff
  • Senior Contributor
  • *****
  • Posts: 11827

  • Offline
Re: turbo for gas mileage?
« Reply #8 on: August 07, 2009, 02:00:41 PM »
The thought was to remove the drag on the engine caused by having to suck in air.  More air=better running, or so the thought went.  The intake manifold runs at a negative pressure, and by getting it closer to zero or just a bit higher, the engine wouldn't have to work as hard to get power.

The missing piece in your chain of logic there, is that for an Otto-cycle gasoline engine; more air requires more fuel to maintain the appropriate fuel air mix and avoid engine damage. This of course would mean producing more power, but that's not what you're after.

What you want is to maintain the same air flow (air flow tracks with power output) with a lower vacuum. You can do this with a smaller naturally aspirated engine running closer to its peak output, or an even smaller turbocharged engine running closer to its peak output.

Yet again, this is something that diesel engines do well. They don't have any manifold vacuum to speak of, no throttle plate, and modulate power output purely with how much fuel is injected. Trying to do that with a gas engine would be disastrous.
Arizona

Nelson

  • Member
  • **
  • Posts: 201

  • Offline
Re: turbo for gas mileage?
« Reply #9 on: August 07, 2009, 02:35:28 PM »
It's nearly fraudulent that way some car makers advertise turbo engines as gas savers.
Lots of folks believe them and think a turbo powered engine automatically will get better mileage.
What's left out of this advertising is the obvious truth.
Turbo charging makes horsepower and horsepower uses fuel.
If they were honest, they would say that a small engine with a turbo, that makes the same power as a larger engine without a turbo, can get better mileage.
But only if the driver is not using the full potential of the engine and is happy cruising in a gas saving mode.
Then the mileage will be better than the large, non turbo engine under the same conditions.
When more power is needed, it's there - with the penalty of less gas mileage.
Hopefully this did not add to the confusion.

The way I look at it,  a turbo turns a smaller  engine into a larger one in terms of its ability to burn more fuel.  You don't always need the power that a large engine can give you but a turbo gives you the option of higher power output when you may actually need it.  On the other hand, there are some V8 engines with the technology to run on only 4 cylinders for improved fuel efficiency. I think this is a better option than a V6 turbo since it eliminates the lag while still giving you the option of better fuel efficiency or more power.
Over grown military establishments are under any form of government inauspicious to liberty, and are to be regarded as particularly hostile to republican liberty.
George Washington

Worry is the interest paid by those who borrow trouble.
George Washingto

Skeptic49

  • Contributor
  • ****
  • Posts: 1620

  • Offline
Re: turbo for gas mileage?
« Reply #10 on: August 07, 2009, 03:30:25 PM »
Don't forget the altitude effect.  Modern Turbo engines adjust the waste gate to control boost, if you head over Wolf Creek Pass  10,500 ft amsl, in a normally aspirated car you lose power, in a modern turbo you have the same power that the engine had at mean sea level.

Note also the quality of fuel changes the engine control computer's solution.  Just make sure you put premium in an engine designed for it.  "Premium Fuel Required."

Geoff
Who notes his wife's Subaru Forester crossed Wolf Creek Pass without a problem, but it did burn some gas on the upgrade.  ;D

FluffyHitman

  • Senior Contributor
  • *****
  • Posts: 2351

  • Offline
Re: turbo for gas mileage?
« Reply #11 on: August 07, 2009, 06:03:07 PM »
I would expect a 1.8 subaru to be able to make it up over 10,500 feet, let alone a new 2.5. Wouldn't be at the best power, and I wouldn't want to go on a short on-ramp in it (wouldn't want to go on a short on-ramp with one period, especially since the 1.8s tend to be old and poorly maintained), but it shouldn't have any trouble doing it.
"Sometimes it's better to light a flamethrower than curse the darkness." - Terry Pratchett

THE NORSEMAN

  • To preserve liberty, it is essential that the whole body of the people always possess arms, and be taught alike, especially when young, how to use them. - Richard Henry Lee
  • Moderator
  • Senior Contributor
  • *****
  • Posts: 4955

  • Offline
Re: turbo for gas mileage?
« Reply #12 on: August 07, 2009, 11:02:17 PM »
As noted turbos don't really help mileage, just power output.  And just driving down the road with minimal load they run no boost at all, so the only help on mileage would be more power quicker giving you less time in the throttle heavy with your right foot.

Best bet for mileage? Keep your filters clean, ignition system in top-notch shape, and drive it gently.  The ex-wife could never break 22 mpg with her Taurus, yet on several road trips(including runs over Wolf Creek and Slumgullion passes) I averaged 32 -33 mpg.  
« Last Edit: August 08, 2009, 12:48:10 AM by THE NORSEMAN »
This may be considered as the true palladium of liberty. . . . The right of self defence is the first law of nature: in most governments it has been the study of rulers to confine this right within the narrowest limits possible. Wherever standing armies are kept up, and the right of the people to keep and bear arms is, under any colour or pretext whatsoever, prohibited, liberty, if not already annihilated, is on the brink of destruction- St. George Tucker, Blackstone's Commentaries

Avenger29

  • Senior Contributor
  • *****
  • Posts: 3944
  • It's party time, chumps!

  • Offline
Re: turbo for gas mileage?
« Reply #13 on: August 12, 2009, 09:17:38 PM »
They don't work.  And neither do the fuel line magnet gadgets.  The intake tornado gadgets.  If some gadget that you could buy and just bolt in would really help anything - All the car makers would be putting them in.


I don't think he was talking about the (worthless) intake gadgets, actually a vortex generator on the outside of the car.

They help on airplanes, don't know anything about putting them on cars. I'm not looking to improve the STOL performance of my Silverado.

http://en.wikipedia.org/wiki/Vortex_generator
I don't THINK I'll ever have to face down routers in the streets.

I should hope not. Mobs of rogue woodworking tools would suck to repel.


Help support WeTheArmed.com by visiting our sponsors.

bmitchell

  • WTA Guest
  • Senior Contributor
  • *****
  • Posts: 2317

  • Offline
Re: turbo for gas mileage?
« Reply #14 on: August 13, 2009, 11:12:07 AM »
Quote
What you need instead is to lose weight and work on your aerobics.

How did you know.

Ben

jimspur

  • Member
  • **
  • Posts: 172

  • Offline
Re: turbo for gas mileage?
« Reply #15 on: August 13, 2009, 01:20:47 PM »


They help on airplanes, don't know anything about putting them on cars. I'm not looking to improve the STOL performance of my Silverado.

http://en.wikipedia.org/wiki/Vortex_generator
[/quote]
 
  We still put them on Boeing 777-300's, they're pretty new designs, I'm not sure if the 787's are going have them. 
Good night Chesty, wherever you are!


Help support WeTheArmed.com by visiting our sponsors.