Which will yield higher MPG: Supercharger or Turbocharger?

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Dart270

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PostPosted: Wed Dec 21, 2011 5:44 am

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Board Sponsor & Moderator

Joined: Mon Oct 21, 2002 11:08 am
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Location: Blacksburg, VA
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Well said! Defeat is necessary for the appreciation of sweet victory. My Dart is sitting in the garage with a busted torque converter, but will be faster and badder than before, after I fix it.

Multi-port EFI is the way for best mileage. Forget boost if you want best MPG. Go for higher comp - at least 9:1.

Lou

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FrankRaso

Post subject: Re: Which will yield higher MPG: Supercharger or Turbocharge

PostPosted: Wed Dec 21, 2011 11:15 am

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Turbo Slant 6

Joined: Fri Apr 16, 2004 10:50 am
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Location: Stevensville, ON
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Hi all,

I'm seriously considering converting my car to Multi-point EFI and, possibly, adding either a Supercharger or Turbocharger. I was wondering, everything else being equal, which would give better fuel mileage? My gut feel says a Turbocharger, since the parasitic drag associated with turning the belt would be eliminated. What do you guys think? Is there any real-life experience here on the board? Thanks in advance.

Roger

Dan made a good reply to your question. If you are after higher fuel economy, you need to increase the thermal efficiency of the engine and reduce its losses. Running higher compression (easier with natural aspiration) and improving fuel distribution (with MPFI) will improve thermal efficiency.

With a a higher compression ratio, the trade-off is higher efficiency vs higher fuel costs for premium fuel. In Los Angeles, 87 octane gasoline is selling for about $3.29/gallon and 91 is selling for about $3.49/gallon. Higher compression to use premium fuel would have to improve your fuel economy by 6% to break even.

Reducing the engine's volumetric efficiency can reduce pumping losses and super/turbo-charging serves to increase volumetric efficiency. Although EGR was mainly introduced to reduce NOx emissions, it also helps to reduce pumping losses by requiring the throttle to be opened further.