It's one of the most common questions we are asked - the answer to which is almost impossible to find
"What is better - a supercharger or a turbo?"
We only wish the answer were that simple, but unfortunately it is not. The simple answer is:
But don't worry, we'll go into more depth than that here. Both superchargers and turbos have distinct advantages and disadvantages. Selecting the right kind of forced induction for your vehicle will depend upon your particular vehicle, your driving habits, your power preferences, and your needs.
Clearing Up Confusion
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.
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
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
Now it's time to evaluate the turbocharger versus the supercharger according to several important factors.
The cost of supercharger and a turbocharger systems for the same engine are approximately the same, so cost is generally not a factor.
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.
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.
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 interooler necessary even on fairly low-boost applications.
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.
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.
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!)
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.
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.
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.
We hope you have found this discussion informative and unbiased. Sometimes when we explain this to our customers, they say that we are biased towards superchargers because that is all we carry. We remind those customers that a turbo is a kind of supercharger and that we truly hope to carry turbochargers someday. The reason we do not currently sell any turbochargers is because we have not yet found a turbo system that is suitable for mail-order / e-commerce sale. We are not prepared to sell a turbo system that is difficult to install and requires the attention of a professional engine tuner or mechanic. If any turbocharger manufacturer makes such a system, please send us the details as we would love to carry such a product.
DuratecTour: Good info on the chargers!! I feel you are a touch lite on the Costs and "Blow OUts" of turbochargers. I haven't met a guy yet who's blown a supercharger, and havent met a guy yet who hasn't blown his Turbo..... The HEAT is the KILLER!
Do you have any idea though, when we might see a SC or TC available for either the four or six cylinder?? Also... what kind of performance(bhp)increase can we look at?? And... will the spare tire compartment fit a bottle of Dentist's GAS?? LOL
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."
Yes, the turbo does spool up to it's maximum. However, boost is constantly delivered. A turbo system does not "wait" before pressue builds to add pressue. Pressure is continuous. The "lag" is merely how the turbo system is tuned. The wastegate does NOT open to let pressue into the engine as you seem to indicate. Rather, the wastegate is used to dump excess pressure at a preset level. So, during normal operation, the turbo is pressurizing the intake air continuously.
There is lag because it takes the engine a time to build up exhuast which is what drives the turbo.
Thus as the turbo is spun quicker and quicker as exhaust pressure builds, the turbo can then build greater and greater boost on the compression side which is continuosly open to the intake.
If the boost reaches higher than the preset which controls the boost pressue, a vacume will then open the waste gate to limit boost pressure.
Further more, turbocharger size dictates how much lag you have. A smaller turbo will spool up faster but will not build alot of boost. A larger turbo will take longer to spool up (more lag) but will build alot more boost. Then there is the sequential twin turbo set up that the Supra used in the mid-90's. Trying to compromise the benefits/pitfalls of turbo size, they paired a smaller turbo with a larger turbo. First turbo spools around 2000 rpm to give you early power and the second comes on around 3500 rpm (been awhile, my numbers might be off) to back the smaller turbo and build more pressure. Stock system is capable of 17-18psi. This system is fairly complicated due to the intake/exhaust setup required for sequential operation and requires fine tuning to control both waste gates for smooth power delivery across the transition from one to two turbo operation.
I've even seen a rare custom set-up of a sequential tri-turbo system!
DJs Six and M-006,
To clear confusion these weren't DuractecTour's words, follow the link for the actual author.
"I haven't met a guy yet who's blown a supercharger, and havent met a guy yet who hasn't blown his Turbo"
I've met both! The only reason for charger failure is improper or failure of lubrication and cooling. We've been running the same t/c on a B16 Civic for a long time with no ill effects. Granted its only pushing about 10psi, but that's because of the high compression of the stock motor.
This article seems biased toward superchargers. For example, they only glaze over the need for crank power to drive the s/c, but are quick to point out exhaust restriction by the t/c's impeller. I think the point is mute. The overall gains from using the "free" exhaust power outweight any restriction. Plus, s/c boost levels below the threshold are completely RPM dependant, whereas one can come to full boost as low as 3000 RPM with a t/c.
Not to mention a properly mapped compressor can almost eliminate lag!
You bring up a good point. If the wastegate opens at 3000RPM, you're gonna lose all that boost!
TURBO baBY! Nothing against super chargers but look at the millions of applications that use turbos vs. s.c. Everything from 3 cyl. sub-compact Japanese econo boxes to V12 Main battle tanks that weigh over 120,000 lbs! Why did top fuel drag racing ban turbo's on cars? because turbos would have been killing super charged dragsters by now.
For a car maker to release a supercharged car instead of a turbo makes no sense to me. Given a SC car vs. a Turbo, to make that Turbo car more powerful is much easier using aftermarket parts than it would be with a SC.
I would prefer a turbo car anyday from a performance standpoint. If I was just trying to squeeze some extra HP out of an engine and did not care about fuel economy or the ability to upgrade then a SC might be worth looking into.