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Old 03-02-2004, 02:06 PM   #1
extasy
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Default Turbo v Supercharger facts...Do Not Reply

PLEASE DO NOT REPLY TO THIS MESSAGE, THIS IS FYI ONLY.

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It is inevetable that this subject will come up again at some point so I decided to clarify the matter. I am making no assumptions as to which is better as you can see below there are many variables I am merely stating the FACTS gathered from numerous websites. Some of us have a good understanding of what each of them does but for those of you who have some misconceptions hopefully this will answer many questions.

Turbo vs Supercharger

1. Definitions (as defined by "Merriam Webster" dictionary.
Supercharger: a device (blower or compressor) for pressurizing the cabin of an airplane or increasing air volume to the combustion chamber of an internal combustion engine

Turbocharger: a centrifugal blower driven by exhaust gas used to supercharge an angine

2. Similarities
Both create boost, ie.. compress more air molecules into an engines combustion chamber then normally allowed at atmospheric pressure (14.7psi @ sea level). More air molecules means more fuel is used to create energy to make power. Both normally increase power output between 40% and 100%.

Supercharger is mounted to the engine and is driven by a belt/pulley set-up. Air is compressed by an impeller(centrifugal) twin rotating screws or counter rotating rotors (roots), peak operation is between 15,000-40,000 rpm

Turbo is a centrifugal supercharger mounted to exhaust side of the cylinder head, paek operation is between 75,000 -150,000rpm.

3.Cost
Cost is approximately the same for the same engine and is not a factor.

4. Lag
With a turbo exhaust gasses must spool before the impeller will turn, this creates a downtime before the turbine reaches full throttle and creates the desired boost, since a supercharger is driven directly from the crankshaft it does not suffer from this.

5. Efficiency
The turbo is more economical to operate since it is powered by energy in the exhaust gasses that would otherwise be lost out the exhaust.

6. Heat
Because the turbo is mounted to the exhaust which is typically hot thus causing the air to expand an intercooler is reccomended to bring the intake air charge down. However superchargers are also subject to heat especially the roots type which may require an intercooler on fairly low-boost applications.

7. Back pressure
Since superchargers typically do not interrupt the exhaust flow associated with have a turbo mounted in the exhaust stream this is only a concern on a turbo engine

8.Reliability
Due to higher heat turbos can have a shorter life expectancy. When the turbo is off oil on the bearings is heated and if not properly cooled can cause internal damage. Coupled with higher operating speeds (up to 150,000 rpm) can cause damage to internal components.

9. Ease of installation
Superchargers tend to be easier to install than turbo.

10.Maximum power output
Turbo are known for their ability to spin to incredibly high rpm and make very high boost figures (+25psi). Although major engine modifications are required the turbo is capable of producing more peak power than a supercharger.

11. Tuneability
Turbo due to complexity and reliance on exhaust pressure are more difficult to tune although have potential for larger hp figures. Superchargers are typically more "user friendly" to tune.


A performance comparison:

Turbos when properly mated and tuned to an engine can create maximum boost conditions as low as 2500 rpm (example). Since turbos until mechanical limits are reached are capable of unlimited amounts of boost and thus need to be regualted by a wastegate to bleed off the excess pressure.
Superchargers on the other hand require power to make power, for example (due to it's exponential nature) you have a supercharger rated for 8psi at 6000rpm, as rpm drops so does boost so you could have as little as 2.5psi at 3000rpm. Because of this factor a turbo rated at 8psi will create more hp than the supercharger.

Conclusion:
If you ask 2 people which is better you will get 3 answers. There are many factors to determine which to use and what you want it to do. You must take into consideration engine size, engine configuration(inline or "V"), where in the powerband you desire the power etc... so there is no right and wrong answer as to which is better.

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