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Turbocharging for economy
#1085048
09/29/11 11:41 AM
09/29/11 11:41 AM
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Joined: Aug 2003
Posts: 4,481
Mesa, AZ
Pat_Whalen
OP
super gas
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OP
super gas
Joined: Aug 2003
Posts: 4,481
Mesa, AZ
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I know that a turbocharged engine has the potential to be more fuel efficient than an equally spec'ed N/A engine. Is that something that is easily done? I've got a late 70's low compression 440 in my 80 Ramcharger (3.23 gears) and was wondering if there was any feasibility to adding a turbo (without any internal engine mods) and seeing an increase in highway economy. Point me in the right direction if you will 
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Re: Turbocharging for economy
[Re: Pat_Whalen]
#1085051
09/29/11 02:58 PM
09/29/11 02:58 PM
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Joined: Jan 2003
Posts: 28,067
Irving, TX
feets
Senior Management
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Senior Management
Joined: Jan 2003
Posts: 28,067
Irving, TX
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The turbocharged engine will get more energy out of the fuel it burns when compared to a similar output n/a engine.
The turbo engine has a more fuel efficient cam profile in most cases.
However, dropping a turbo on an existing engine will not return better mileage on the street.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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Re: Turbocharging for economy
[Re: feets]
#1085052
09/29/11 06:25 PM
09/29/11 06:25 PM
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Joined: Jan 2005
Posts: 2,540
Milwaukee WI
TRENDZ
master
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master
Joined: Jan 2005
Posts: 2,540
Milwaukee WI
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I gotta dis-agree with you, Feets. You will never see bsfc numbers in the .4s with any turbo engine(with the exception of direct injected engines). It's not all that uncommon to see .45 in a well thought out n/a engine.
The myth of economy with a turbo engine comes from, as previously stated, a smaller engine that is capable of making the hp of a larger engine. If you were to use that smaller engine in boost all the time though, you would be no further ahead in economy. It's the time out of boost with a smaller engine that you see your gains in economy.
"use it 'till it breaks, replace as needed"
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Re: Turbocharging for economy
[Re: Pat_Whalen]
#1085054
09/29/11 11:04 PM
09/29/11 11:04 PM
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Joined: Feb 2003
Posts: 21,318
Manitoba, Canada
DaytonaTurbo
Too Many Posts
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Too Many Posts
Joined: Feb 2003
Posts: 21,318
Manitoba, Canada
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Quote:
I can only guess that what is to follow is a direct result of not knowing much about turbos:
My understanding was that because a turbocharged engine will produce an equal amount of power more efficiently than a similiar N/A engine that there could potentially be a higher efficiency at highway speeds. For example, if it takes 100HP to keep my truck moving at 65MPH on the freeway (~2100rpm), the turbo'd engine will be able to produce that 100HP more efficiently using less fuel.
Is this inaccurate?
On the highway at a steady speed, you will have no boost. Your engine will be under vacuum just like a n/a engine. The turbo engine sees no benefits from the turbo itself in this scenario because you are just taking the turbo along for the ride. The only difference is the turbo engine may have a milder cam, resulting in better economy during normal driving. However the turbo engine may have a lower compression ratio, offsetting or partially offsetting the gains of the milder cam.
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Re: Turbocharging for economy
[Re: TRENDZ]
#1085055
09/30/11 12:03 PM
09/30/11 12:03 PM
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Joined: Nov 2006
Posts: 2,255
IL
furious70
top fuel
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top fuel
Joined: Nov 2006
Posts: 2,255
IL
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Quote:
I gotta dis-agree with you, Feets. You will never see bsfc numbers in the .4s with any turbo engine(with the exception of direct injected engines). It's not all that uncommon to see .45 in a well thought out n/a engine.
The myth of economy with a turbo engine comes from, as previously stated, a smaller engine that is capable of making the hp of a larger engine. If you were to use that smaller engine in boost all the time though, you would be no further ahead in economy. It's the time out of boost with a smaller engine that you see your gains in economy.
Herb's old book shows bsfc in that range with water injection and turbos. I believe Booster is seeing that kind of results with his TT340, but he's spent 20yrs engineering that systems to be as good as any OEM setup for the street.
Would have to talk to Tom Vaught on tmf, but I wouldn't be surprised if Ford's Ecoboost systems are among the most efficient engines out there right now (they are direct injected though)
To the OP's concerns, if you wanted better mpg you'd probably replace that 440 with a boosted 318. OR, if you wanted to make 600hp with your 440 and have good street manners, you could boost it rather than put big heads and cam in it. Corky's book explains it well saying 'at best the turbo system is a mild restriction in the system under light load and will cause a small loss in efficiency'. The 'gain' in mpg is not over the existing engine but in any upgraded NA engine that would compete with it for equal power.
Last edited by furious70; 09/30/11 12:05 PM.
70 Sport Fury
68 Charger
69 Coronet
72 RR
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Re: Turbocharging for economy
[Re: HotRodDave]
#1085059
10/01/11 09:26 AM
10/01/11 09:26 AM
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Joined: Jun 2008
Posts: 10,847
Oakdale CT
gdonovan
I Live Here
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I Live Here
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Posts: 10,847
Oakdale CT
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Quote:
Since the engine is not under boost at cruise
If I may? This is a falsehood.
As someone who has spent a LOT of time boosting engines I see boost with the cruise control on all the time.
Hills gentlemen, hills. Some cars like the SRT-4 see boost off idle, ridiculous. You can size a turbo so large that you almost never see boost at cruise but that does take some of the fun out the package.
I agree with the poster who already pointed out that the mpg gains come from the ability to run a smaller motor at cruise and a "larger one" as needed under boost.
An example I would use would be the 2.2 engine at 0 boost would be using as much air as a 135 CID engine. At 14 psi indicated boost (twice atmosphere) using as much air as a 270 CID engine and so on.
Simplistic, but you get the general idea.
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Re: Turbocharging for economy
[Re: gdonovan]
#1085060
10/01/11 10:20 AM
10/01/11 10:20 AM
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Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck
Not enough dumb comments...yet
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Not enough dumb comments...yet
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
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Quote:
Quote:
Since the engine is not under boost at cruise
If I may? This is a falsehood.
As someone who has spent a LOT of time boosting engines I see boost with the cruise control on all the time.
Hills gentlemen, hills. Some cars like the SRT-4 see boost off idle, ridiculous. You can size a turbo so large that you almost never see boost at cruise but that does take some of the fun out the package.
I agree with the poster who already pointed out that the mpg gains come from the ability to run a smaller motor at cruise and a "larger one" as needed under boost.
An example I would use would be the 2.2 engine at 0 boost would be using as much air as a 135 CID engine. At 14 psi indicated boost (twice atmosphere) using as much air as a 270 CID engine and so on.
Simplistic, but you get the general idea.
a turbo 4 banger might pull boost at cruise but a BB will not. I had many many highway and cruise miles on my old S/C'd 440. It never pushed any boost at speed. With vacuum readings of 20+ how can it? It would go into boost until vacuum was near 0.
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Re: Turbocharging for economy
[Re: Mr.Yuck]
#1085061
10/01/11 10:25 AM
10/01/11 10:25 AM
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Joined: Jun 2008
Posts: 10,847
Oakdale CT
gdonovan
I Live Here
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I Live Here
Joined: Jun 2008
Posts: 10,847
Oakdale CT
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Quote:
a turbo 4 banger might pull boost at cruise but a BB will not. I had many many highway and cruise miles on my old S/C'd 440. It never pushed any boost at speed. With vacuum readings of 20+ how can it? It would go into boost until vacuum was near 0.
Will all depend on how the turbos are sized.
We are talking turbos, NOT superchargers as you have indicated in your post.
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Re: Turbocharging for economy
[Re: gdonovan]
#1085062
10/01/11 11:34 PM
10/01/11 11:34 PM
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Joined: Nov 2006
Posts: 2,255
IL
furious70
top fuel
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top fuel
Joined: Nov 2006
Posts: 2,255
IL
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IIRC it took a pretty good hill for my old 90 Daytona with a 2.5 in the tiny mistu turbo to go into boost, if that car didn't do it often I don't know what one would? I know my 86 Shelby Charger took more to do it. Haven't been on any 'big' hills yet with the Fury, but so far it's never in boost unless I put my foot into it more than necessary, and it's got pretty tiny turbos on it.
70 Sport Fury
68 Charger
69 Coronet
72 RR
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Re: Turbocharging for economy
[Re: furious70]
#1085063
10/02/11 08:29 AM
10/02/11 08:29 AM
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Joined: Jun 2008
Posts: 10,847
Oakdale CT
gdonovan
I Live Here
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I Live Here
Joined: Jun 2008
Posts: 10,847
Oakdale CT
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Quote:
IIRC it took a pretty good hill for my old 90 Daytona with a 2.5 in the tiny mistu turbo to go into boost, if that car didn't do it often I don't know what one would?
My 89 Shelby Daytona with a 2.2 would do it all the time with the stock Garrett.
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Re: Turbocharging for economy
[Re: gdonovan]
#1085064
10/02/11 09:49 PM
10/02/11 09:49 PM
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Joined: Jan 2005
Posts: 2,540
Milwaukee WI
TRENDZ
master
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master
Joined: Jan 2005
Posts: 2,540
Milwaukee WI
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What year was the switch from throttle plate before the turbo to after the turbo? This could be the difference in your experiences...
"use it 'till it breaks, replace as needed"
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Re: Turbocharging for economy
[Re: TRENDZ]
#1085065
10/03/11 06:22 AM
10/03/11 06:22 AM
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Joined: Jun 2008
Posts: 10,847
Oakdale CT
gdonovan
I Live Here
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I Live Here
Joined: Jun 2008
Posts: 10,847
Oakdale CT
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Quote:
What year was the switch from throttle plate before the turbo to after the turbo? This could be the difference in your experiences...
89 and 90 have the same intake and throttle body.
I have seen this in other turbo applications including the old log intake cars.
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Re: Turbocharging for economy
[Re: gdonovan]
#1085066
10/03/11 09:26 AM
10/03/11 09:26 AM
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Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck
Not enough dumb comments...yet
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Not enough dumb comments...yet
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
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Quote:
Quote:
a turbo 4 banger might pull boost at cruise but a BB will not. I had many many highway and cruise miles on my old S/C'd 440. It never pushed any boost at speed. With vacuum readings of 20+ how can it? It would go into boost until vacuum was near 0.
Will all depend on how the turbos are sized.
We are talking turbos, NOT superchargers as you have indicated in your post.
boost is boost doesn't matter how it's made. Unless you don't have a bypass or POV it's not going to push air until the engine is under load. A 440 w/ 3.23 gears is not going to create load at 75mph on the highway.
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Re: Turbocharging for economy
[Re: Mr.Yuck]
#1085067
10/03/11 05:14 PM
10/03/11 05:14 PM
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Joined: Jun 2008
Posts: 10,847
Oakdale CT
gdonovan
I Live Here
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I Live Here
Joined: Jun 2008
Posts: 10,847
Oakdale CT
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Quote:
boost is boost doesn't matter how it's made.
If I may, you are showing an appalling lack of knowledge regarding turbochargers. Not all boost is created equal, I'm sure several members of the board would be more than happy to point that out.
Superchargers are directly run of the crankshaft, turbochargers are run off exhaust flow. I can hold the throttle at one point and go up a hill and the car would be very happy to go from vacuum to boost just due to the increased load on the engine.
Turbos are NOT superchargers aside from the fact they make positive pressure.
I have owned over a dozen turbocharged vehicles and have worked on thousands of customers cars. Turbo and supercharged.
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