Supercharger/Increased MPG?

[bowtieguy]

to confirm the thoughts of "no" here, take this illustration...

my oldsmobile had an option of a supercharger, w/ the same motor. according to the EPA, fuel efficiency was in fact decreased w/ that option.

[GasSavers_bobski]

Yep. The issue with superchargers is that they're on all the time and boost pressure is dependent on engine RPM rather than load. As such, adding a supercharger is not much different from going to a larger displacement engine. As is generally understood, going to a larger displacement engine means more energy wasted to pumping losses and such since most of the engine's peak power output goes unused under the great majority of driving conditions.
On the other hand, turbochargers only spool up when there is sufficient exhaust flow (which is dependent on engine load), make use of what would otherwise be waste energy and present little restriction to the engine (which could affect efficiency) under low intake/exhaust flow conditions such as when cruising. Rather than increasing the engine's effective displacement by a fixed amount, turbochargers provide displacement on demand.

[theholycow]

Turbochargers do not make use of waste energy. That energy is pumped by the pistons.

[GasSavers_BEEF]

most turbo systems have a much more freely flowing exhaust system so the net difference in the turbo vs. a stock exhaust system (restrictive) is basically nothing.

that is just the way it has been explained to me. not sure if it is right or not but turbos usually have a much larger diameter exhaust as far as I have seen anyway.

[bobc455]

Originally Posted by bowtieguy

my oldsmobile had an option of a supercharger, w/ the same motor. according to the EPA, fuel efficiency was in fact decreased w/ that option.

The non-supercharged version of the motor also had a higher CR, which could explain some of the difference.

No doubt that spinning an extra accessory will draw some parasitic HP, however. Even if it is freewheeling.

-BC

[GasSavers_goldie]

Thanks for all the input and information. Because of your help, I have saved myself some grief and and a lot of money and have now given up the idea of installing a supercharger. I was hoping with all the mods on my truck (MSD coil, E3 plugs, Taylor wires, under drive pulleys, headers, Gibson exhaust, and a K & N FIPK) to add to my fuel economy. Some folks on this subject made mention of turbo's. While they sound interesting to research, I haven't found a company that makes a unit for my 4.3 engine. Any ideas?

[GasSavers_BEEF]

for the kind of money you would spend on a turbo or supercharger setup on your truck, why not just buy a beater honda, saturn, or old chevy (maybe even a cavalier). maybe spend $2k or so on it.

I have a friend that has a BMW M3 (fast little thing with that straight 6) and he was in a similar dilema. he bought an '89 civic hatchback and is getting high 30s in it. he spent $1800 on the car. can't beat a beater

[theholycow]

Originally Posted by BEEF

for the kind of money you would spend on a turbo or supercharger setup on your truck, why not just buy a beater honda, saturn, or old chevy (maybe even a cavalier). maybe spend $2k or so on it.

...or just buy $2000 worth of gas.

[imzjustplayin]

Originally Posted by theholycow

...or just buy $2000 worth of gas.

but that would only last you a year....not the same thing.

[i-DSi]

Originally Posted by theholycow

Turbochargers do not make use of waste energy. That energy is pumped by the pistons.

Hi Holy cow,
Turbochargers put indead a small load on the pistons, but this is only for a small part of the exhaust stroke true.
Major part of pressure for the turbine is delivered by the waste energy in the exhaust gas, as there is a relative high pressure and temperature in the combustion chamber that wants to come out and pushes on the turbine.
Only the last part of the exhaust stroke the piston has to do some effort to push it out, but that's really minor.
You can not tell me the piston has to push out all the exhaustgas into the turbine, do you?
Greets