With all the confusion between the two and bickering going back and forth over which is better, I figured I would help clear up the "guessing" and "opinion" portion for everyone:

According to Merriam-Webster's dictionary, a supercharger is defined as:
"a device (as a blower or compressor) for pressurizing the cabin of an airplane or for increasing the volume air charge of an internal combustion engine over that which would normally be drawn in through the pumping action of the pistons".
A turbocharger is defined as:
"a centrifugal blower driven by exhaust gas turbines and used to supercharge an engine".


According to Webster's, a turbocharger is included in the definition for superchargers - it is in fact a very specific type of supercharger - one that is driven by exhaust gasses. Other superchargers that do not fall into this category - the kind that we are all used to hearing about - are normally driven directly from the engine's crankshaft via a crank pulley. So in reality, it is not fair to compare all superchargers to turbochargers, because all turbochargers are also superchargers. For the purpose of this discussion, however, a supercharger will be considered all superchargers that are are not driven directly by the engine, while turbochargers will be considered all superchargers that are driven by engine exhaust gasses.

Similarities



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Both superchargers and turbochargers are forced induction systems and thus have the same objective - to compress air and force more air molecules into the engine's combustion chambers than would normally be allowed at atmospheric pressure here on Earth (14.7 psi at sea level). The benefit of forcing more air molecules into the combustion chambers is that it allows your engine to burn more fuel per power stroke. With an internal combustion engine, burning more fuel means that you convert more fuel into energy and power. For this reason, supercharged and turbocharged engines normally produce 40% to 100%+ more power (depending on the amount of boost - check out our horespower calculator) than normally aspirated engines.

How They Work


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A supercharger is mounted to the engine and is driven by a pulley that is inline with the crank (or accessory) belt. Air is drawn into the supercharger and compressed by either an impeller (centrifugal-style supercharger), twin rotating screws (screw-type supercharger), or counter-rotating rotors (roots-type supercharger). The air is then discharged into the engine's intake. Faster crank speed (more engine rpm) spins the supercharger faster and allows the supercharger to produce more boost (normally 6 to 9 psi for a street vehicle). Typical peak operating speeds for a supercharger are around 15,000 rpm (screw-type and roots style superchargers) and 40,000 rpm (centrifugal-style superchargers).

A turbocharger operates in much the same way as a centrifugal (internal impeller) supercharger, except it is not driven by pulleys and belts attached to the engine's crank. A turbo is instead driven by exhaust gasses that have been expelled by the engine and are travelling through the exhaust manifold. The exhaust gas flows through one half of the turbocharger's turbine, which drives the impeller that compresses the air. Typical operating speeds of a turbocharger are between 75,000 and 150,000 rpm.

Head to Head Comparison


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Now it's time to evaluate the turbocharger versus the supercharger according to several important factors.

Cost
The cost of supercharger and a turbocharger systems for the same engine are approximately the same, so cost is generally not a factor.

Lag
This is perhaps the biggest advantage that the supercharger enjoys over the tubo. Because a turbocharger is driven by exhaust gasses, the turbocharger's turbine must first spool up before it even begins to turn the compressor's impeller. This results in lag time which is the time needed for the turbine to reach its full throttle from an intermediate rotational speed state. During this lag time, the turbocharger is creating little to no boost, which means little to no power gains during this time. Smaller turbos spool up quicker, which eliminates some of this lag. Turbochargers thus utilize a wastegate, which allows the use of a smaller turbocharger to reduce lag while preventing it from spinning too quickly at high engine speeds. The wastegate is a valve that allows the exhaust to bypass the turbine blades. The wastegate senses boost pressure, and if it gets too high, it could be an indicator that the turbine is spinning too quickly, so the wastegate bypasses some of the exhaust around the turbine blades, allowing the blades to slow down..
A Supercharger, on the other hand, is connected directly to the crank, so there is no "lag". Superchargers are able to produce boost at a very low rpm, especially screw-type and roots type blowers.

Efficiency
This is the turbo's biggest advantage. The turbocharger is generally more economical to operate as it as it is driven primarily by potential energy in the exhaust gasses that would otherwise be lost out the exhaust, whereas a supercharger draws power from the crank, which can be used to turn the wheels. The turbocharger's impeller is also powered only under boost conditions, so there is less parasitic drag while the impeller is not spinning. The turbocharger, however, is not free of inefficiency as it does create additional exhaust backpressure and exhaust flow interruption.

Heat
Because the turbocharger is mounted to the exhaust manifold (which is very hot), turbocharger boost is subject to additional heating via the turbo's hot casing. Because hot air expands (the opposite goal of a turbo or supercharger), an intercooler becomes necessary on almost all turbocharged applications to cool the air charge before it is released into the engine. This increases the complexity of the installation. A centrifugal supercharger on the other hand creates a cooler air discharge, so an intercooler is often not necessary at boost levels below 10psi. That said, some superchargers (especially roots-type superchargers) create hotter discharge temperatures, which also make an intecooler necessary even on fairly low-boost applications.

Surge
Because a turbocharger first spools up before the boost is delivered to the engine, there is a surge of power that is delivered immediately when the wastegate opens (around 3000 rpm). This surge can be damaging to the engine and drivetrain, and can make the vehicle difficult to drive or lose traction.

Back Pressure
Because the supercharger eliminates the need to deal with the exhaust gas interruption created by inserting a turbocharger turbine into the exhaust flow, the supercharger creates no additional exhaust backpressure. The amount of power that is lost by a turbo's turbine reduces it's overall efficiency.

Noise
The turbocharger is generally quiter than the supercharger. Because the turbo's turbine is in the exhaust, the turbo can substantially reduce exhaust noise, making the engine run quieter. Some centrifugal superchargers are known to be noisy and whistley which, annoys some drivers (we, however, love it!)

Reliability
In general, superchargers enjoy a substantial reliability advantage over the turbocharger. When a a turbo is shut off (i.e. when the engine is turned off), residual oil inside the turbo's bearings can be baked by stored engine heat. This, combined with the turbo's extremely high rpms (up to 150,000rpm) can cause problems with the turbo's internal bearings and can shorten the life of the turbocharger. In addition, many turbos require aftermarket exhaust manifolds, which are often far less reliable than stock manifolds.

Ease of Installation
Superchargers are substantially easier to install than a turbos because they have far fewer components and simpler devices. Turbos are complex and require manifold and exhaust modifications, intercoolers, extra oil lines, etc. - most of which is not needed with most superchargers. A novice home mechanic can easily install most supercharger systems, while a turbo installation should be left to a turbo expert.

Maximum Power Output
Turbos are known for their unique ability to spin to incredibly high rpms and make outrages peak boost figures (25psi+). While operating a turbocharger at very high levels of boost requires major modifications to the rest of the engine, the turbo is capable of producing more peak power than superchargers.

Tunability
Turbochargers, because they are so complex and rely on exhaust pressure, are notoriously difficult to tune. Superchargers, on the other hand, require few fuel and ignition upgrades and normally require little or no engine tuning.

Conclusion


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While the supercharger is generally considered to be a better method of forced induction for most street and race vehicles, the turbo will always have its place in a more specialized market. Superchargers generally provide a much broader powerband that most drivers are looking for with no "turbo lag". In addition, they are much easier to install and tune, making them more practical for a home or novice mechanic.

 

This, "cut and paste" is not only far outdated, but many points are biased and incorrect.

 

It's another turbocharger-supercharger thread. Stop the madness!

 

You tend to find a few of them on a forum devoted to a forced induction car.

 

I agree that some parts are outdated. Especially the "lag" section. Turbo lag is largely a thing of the past with today's variable geometry turbos. All but the largest turbos have no noticeable lag.

 

touche

 

Then perhaps you can add to it instead of throwing out unsupported criticisms?

Not sure how you are "biased" when you are stating how something works mechanically?

The people dropping off the site are correct..there are a lot of ******* on this site.

 

ALL turbos build boost as they gain RPM this is considered "lag". This is fact not fiction Nor is it a thing of the past. This still holds true today. Most car manufacterers have learned how to deminish the "feeling" of lag by changing the torque curves of the motors they match with the turbo. Granted the new turbos are a step up, they still have lag.

 

You mean ******** who copy and paste other people's articles and don't cite them?
For those who haven't read this, the stolen article is not the OP's list of facts, as he states, it came from superchargersonline.com.

One reason that it's biased is because of the source it came from. Another is because most of this criticisms against a turbo is assuming its on a rear wheel drive vehicle.

As far as listing of how it works mechanically......explain this.....

The ease of installation and tunability...how far off could that be? Superchargers don't require fuel and ignition upgrades or engine internals, but for some reason turbochargers do?

 

The Copy Paste has some good basic info, but it is dated.

The Turbo got a very bad rep from the original 911T of the late 70s.

Porshce was able to make an unreal level of HP by sticking a huge compressor on the 911.

The result, unless the car was over 4000 RPM, there was no "Fun"

Basically, if the turbo is balanced to the desired output and size of the motor with propper planning, the lag will not ever be an issue. Only the Novice will be upset, Drop a gear and all lag quickly becomes as little of an issue as this thread.

 

One could tell it was written before turbo designs such as dual scroll or split exhaust housings were big into the gasoline market. Funny thing though, they've always been used in the diesel markets where high flow, high PR turbos were needed with minimal lag. Gasoline markets were for some reason, reluctant to adopt newer turbo designs until somewhat recently.

 

Exactly...the copy paste ******** at least try to help rather than just simply being...well an *******.

Never claimed I wrote it...I was trying to be helpful.

And what drive system it has in it matters how?

Why don't you call a shop and get a quote on how many hours they charge for a supercharger and turbo install?

Nevermind, don't answer that. I would rather not hear from you anymore. In fact I hope this site offers the same ignore button as others do. Instead of offering up facts or saying" hey man, this article is outdated because..." Or "this is wrong because..."

You simply decided to go the route of the 20 year old know it all *****.

 

Gotta love ignore

 

Why don't you offer us your opinions on the subject rather than bash someone who picked out inaccuracies in your copy/paste? If you don't want it discussed, don't post it on a discussion forum IMO.

Not citing copied works is the same as claiming them as your own btw.

As far as calling a shop, I have enough experience installing and tuning in both areas to know whats involved, I choose not to go that route.

 

Here some good stuff for you guys


Supercharger






Turbo

 

Not to pick apart again, rofl, but the first one of a roots blower is incorrect. It shows it compressing through the rotors, which we know isn't exactly what happens.

Edit: That same site that claims on this page that a roots blower compresses air through the rotors on their first flash animation, just as that pic above shows.


Pic courtesy of GM Electro Motive Division showing a roots blower and the correct air path.

 

Just trying to help

 

Whichever method one chooses, boost is boss daddy-o!

 

I am keeping my blower. There aren't many American-made supercharged 4 cylinders out there.

 

What if one chooses both methods?

 

Then that one would be a way gone daddy-o hepcat!!!!!!

 

FTMFW

 

plaigarism!!!!! u got an F!

 

This thread SUX..!

 

If i remember right..I had to get a tune and fuel injectors when i put on my 3.0" supercharger pulley..

The article is definitely biased, although much of what it says can be considered factual. I do agree, however, that it paints turbos in a bad light. The fact that you can control boost levels on a turbo'd car with the touch of a button is proof of where the technology is.