Difference Between Supercharging and Turbocharging

If you have any specific questions let me know. http://auto.howstuffworks.com/question122.htmu

Both compress combustion air. The supercharger is a blower run directly from the engine (belt or electric), whereas the turbo is a turbine run from exhaust gases.

Stated as you have done, there is no difference--both are forms of supercharging. The first term that came into being was supercharging, per se: essentially a form of ram-air charging, in which a scoop resting above the carburetor intake (or throttle body intake), above the hood, could cause air to be forced into the intake manifold--the faster the engine moved forward, the greater the pressure forcing air into the engine. Thereby, the limitation on fuel delivery to combustion chambers could be overcome and if fuel could be delivered at a greater rate, and still maintain approximate 14:1 mixture, a boost in engine output performance could be achieved. (By limitation on fuel delivery is meant, that if fuel delivery exceeds the ability of the engine to provide air to mix with the fuel, then the extra fuel cannot burn fast enough: instead, it goes through the engine unburned and actually reduces power.)You can know when a car is equipped with (classic) supercharging whenever you see the air intake projecting up above the engine conspicuously--or you might see scoops/nacelles on the hood. However, the ram-air method of supercharging posed a limitation. It was dependant on the velocity of the engine (that is, the vehicle) throught the air: at low speed, very little boost; beyond a certain speed, diminished boost as the fuel delivery can no longer keep up. Enter a newer form of supercharging: turbo charging. (Note that "supercharging" refers to both types as a class--that is, as a mechanism of air deliver augmentation. However, in common parlance it has become customary to distinguish the two, interpreting supercharging to mean ram-air charging, and turbocharging to mean other than ram air charging. However, supercharging, strictly speaking, refers to both.) With turbo charging--essentially a feedback system--the boost in air intake pressure is provided by a pump actuating turbine that is positioned in the exhaust stream. Thus the boost achieved is decoupled from the forward speed of the engine, and depends only on the fuel delivered to the engine by the driver's opening of the throttle. With wide open throttle (WOT) the engine RPM increases, exhaust flow increases, the turbine kicks in, the pump delivers pressurized air to the intake and the engine performance is boosted in the same manner as ram air supercharging but essentially within the entire range of permissible engine speeds--the faster the engine turns (the greater the exhaust velocity) the greater the boost (within limits). The essential drawback with turbocharging is the lag encountered due to the delay between the turbine's spinning up, and the pressurized air from the pump arriving at the intake. This has the effect--if you've ever driven a turbo engine--that when you mash the pedal, a few, or even several seconds transpires before the engine suddenly takes off. It can be disconcerting--and even a control problem--until you become accustomed to it. Hope this clarifies things for you as to the two types of supercharging.

Munky has introduced an aspect that I had forgotten about. The blower. Thanks, Munky. As I now recall better, the complexity of the blower system and its weight penalty was one of the other reasons that that form of supercharging was largely supplanted by turbo charging. Thanks for jogging my memory.

too wordy. the first guy had it down

Correct in that too many of the words were incorrect. Thanks

I had a really good response written with history, configurations, applications, nomenclature and such to dispel the false data on "supercharger", but now I'm so annoyed at the log-in/password procedure (to avoid the "Anonymous Coward" BS) and other navigation required here (that eventually deleted my erudite missive), that I'm not going to rewrite it (sorry Nishid). The short form is that "blower"/"supercharger" have been used interchangeably for about 100 years although the concepts and configurations are distinctly different. "Ram-air" is not and never has been described as supercharging, and in most cases is totally ineffective in cars. I don't know where CowAnon got this from... rcassidy@usamedia.tv

Thanks for showing some consideration, whoever. Sorry to see that you've had the same problem with signing on but, rest assured, you will get there. (It was helpful to me to pose the information about my frustration--as have you in your posting--to the site administrators. He was very accomodating in helping me to get the sign on routine to work.)
To the rest, please, enough already. I thought I admitted my mistake (read: overhastiness when tired late at night) when I agreed with the follow-on submitter. I know how easy it is to get upset by seeing errors, but I try to make a practice of restraint...because not to do so usually comes back around. That said... ...albeit that ram is another (not an otto) engine application (there, I've atoned again), my other, more basic points, I believe, go to the point of the original question; and do so with the degree of succinctness that the questioner seeemed to require. (Since that post did not state how much was known already about "supercharging," it seemed that the essential question pertained to the difference between the two forms of supercharging (as opposed to the non-super, ambient atmospheric form of charging): by drive-train driven supercharging (supercharging per-se, as originally conceived) and by exhaust-stream driven supercharging (the turbo form of supercharging)--not meaning any disparagement about the "nomenclature" issue. In that aspect, I believe CowAnon's information was not incorrect: that the turbo form is simpler and poses less "engineering" challenge--thus is in more common use in cars(that is to say, I don't recall ever seeing other than a turbocharged engine offered in a standard-issue vehicles on dealer lots). Similarly, the point about what it accomplishes--to overcome the limits on output imposed by mere atmospheric-pressure-level fuel mixing--was succinct to the degree that (it appeared to me that) the original questioner was, or might have been, asking. This is not to say that the other, more detailed information will not be equally, or more, useful to the questioner; however, if you find me still to be misguided, I welcome your specific refutations. Then I will be pleased to stand fully corrected.

Are you an engineer or a lawyer? LOL

AAMOF....Which to you need? And how soon?

I agree w/ Munky. Both are air pump's. It's how they are powered that's the difference. 'S'-charging uses a mechanical drive (toothed belt, roller chain, gears or connected directly to the crankshaft). 'T'-charging utilizes the exhaust gas 'plug'. Essentially free energy. You use a portion of the engine's power output to run the 'S'-charger. That portion increase's as rpm's increase. I had a tooling engineer who was a pilot try to explain to me that an aircraft manufacture advertised that some of their model's utilized an 'Exhaust-driven supercharger'. I think that was a marketing guy who wasn't reined in. Wrong terminology. No such thing.

Quesions about Electric Ram-Air Supercharging/Air Induction (More info at www.electricsupercharger.com)
FAQs below. Answers below them.

1. Why does the e-Ram only come on only at full throttle (W.O.T), and why WOULDN'T I want it on all the time, OR at least to come on at part throttle?
2. How does it work?
3. Will my fuel system respond to the increased density and flow of air?
4. Is it difficult to install?
5. How much HP gain can I expect?
6. How is the e-Ram different than a supercharger or Turbocharger?
7. Don't Most cars have ram air already?
8. What causes most of the intake restriction, and how do you measure how much you have?
9. What is the difference in drawing engine heated air versus cool outside air?
10. If the e-Ram produces a positive pressure in the air box, how does that relate to HP gains.
11. Does the e-Ram cause restriction when it is not on?
12. Does the e-Ram put a large drain on the alternator?
13. I have a very efficient intake system now, can e-Ram still help?
14. I have a stock air box, will e-Ram still work?
15. I have an after market intake tube. Will the e-Ram mount to it?
16. Is their a chance of the e-Ram damaging my engine?
17. What is the life expectancy of the e-Ram device, and does it require maintenance?
18. How quickly does the e-Ram spool up?
19. How will the increase HP from the e-Ram help my quarter mile drag times?
20. Will the e-RAM work on my Diesel engine?
21. Will the e-RAM work on Motorcycle engine?
22. Will the e-RAM work with a carbureted engine?

1. Why does the e-Ram only come on only at full throttle (W.O.T), and why WOULDN'T I want it on all the time, OR at least to come on at part throttle?

Answer: The word throttle means "Choke." Any time the throttle is partially open, it is "choking" the engine and creating a variable pressure drop (that's its job). You do not want to engage the e-Ram to generate pressure when the throttle body is restricting it. If it came on under part throttle, the choking action of the throttle would just remove any gains in pressure created by the e-RAM. Normally, If you want more HP when you are at part throttle, you just press further down on the gas pedal to open the throttle-body, and let more air into your engine. It is only when your throttle is wide-open, and your engine is taking all of the air it is capable of (equal to the total displacement of your engine - CC's or Cubic inches - minus the drop in air pressure created by inherent restrictions in your intake system) that you can realize any benefits from a pressure generating device like the e-RAM. When you press the gas pedal to the floor, the e-Ram engages and gives the added air and HP you need. REMEMBER... THIS IS INDEPENDENT OF ENGINE RPM! IF YOU FLOOR YOUR GAS PEDAL AT 2000 RPM, YOU GET FULL BOOST AT 2000 RPM. This is the reason for the waste gates and relief valves with turbos and superchargers. They run continuously, but the pressure is bled off until the total power of what could be produced through normal aspiration is exceeded. (Manifold pressure above ambient or in other words, above atmosphere) Also, the e-RAM requires very high current, so regardless, it is necessary to use it only during full throttle conditions as to not tax your electrical system, and not cause excessive heat or wear at the heart of the e-RAM... the high-power electric motor. Having the e-RAM engage too early and too often when it is not needed, will lead to premature aging and failure of the e-RAM device. When used and installed properly, the e-RAM will last for many years, and only require service after thousands of hours of operation.

2. How does it work?

Answer: The e-Ram is an electrically powered forced air system that uses a 791 watt axial flow fan to slightly pressurize the intake air while it rids the inlet and filter box of most all restriction. It is designed to operate only at full throttle, since this is when you want the most air pressure available to your engine. By slightly pressurizing the air available to your engine intake system, the air becomes more dense, and is matched with more fuel producing the increased HP to the wheels.

3. Will my fuel system respond to the increased density and flow of air?

Answer: Yes, the small increases of air density are well within the limits of most modern fuel injection fuel system, basically in the same way your engine would respond if you were traveling at high altitude where you loose HP. Here the fuel air metering system is able to respond by sensing the change in density via the mass air flow sensor, air flow meter , or manifold pressure sensor, and keep mixture levels correct.

4. Is it difficult to install?

Answer: The e-Ram can typically be installed in less than 1 HOUR! It comes complete with instructions, wiring, adapter hose, fan inlet, the e-Ram, 50 amp relay, and micro-switch that mounts near your accelerator control linkage. (Other locations are also possible for micro switch position such as at the gas pedal for some of the newest cars with "throttle-by-wire" electronic throttle position control)

5. How much HP gain can I expect?

Answer: Gains on stock 4 cylinder to heavily modified 8 cylinder engines have yielded 4-6% increases. That's 5-15HP depending on your base flywheel HP. If you are removing a stock air-box, gains for cool air tubes and cone filters are up to 5HP by themselves. The e-Ram with its 5-15 HP adds to ALL OTHER MODIFICATIONS, so with an intake tube will give over 20 HP of total gain for the e-Ram + intake system.

6. How is the e-Ram different than a supercharger or Turbocharger?

Answer: The e-Ram is a distant cousin of the full blown turbo or supercharging system which employs a centrifugal impeller that must run all the time. They have to produce matched engine airflow, with high-pressure air compression (4 to 15 PSI is normal). This requires a tremendous amount of HP to drive the device. For example the airflow needed for a 2.5-liter engine at 6000 RPM is 240 CFM. At only 6 PSI, you would need 10 to 15 HP just to create this type of supercharging. Belts driven by the engine or a turbine driven off the engines exhaust gases can produce this type of power. The e-RAM produces a low-level 1 PSI (1.7 PSI for the Super e-RAM). The e-RAM is very efficient in moving lots of air flow (CFM) at small pressures, where traditional turbo/superchargers are very good at making pressure, but need extreme speeds to match flow rates of most engines.

7. Don't Most cars have ram air already?

Answer: No, most manufactures have done everything to make inlet ducts to get air into the engine. The problem is that because of the path the air has to take, by the time it gets to your throttle body, the air doesn't have enough pressure and speed to add any ram pressure to your intake system. Even at speeds of 80 mph, no ram effects can be measured with an almost perfect inlet system (i.e. less than .08psi). At 160 mph , that pressure goes up to .36psi., that's it!! Horsepower robbing vacuum in most air boxes is present due all sorts of restrictions as we cant have dragster style hood scoops on street cars because we would not be able to see over them!

8. What causes most of the intake restriction, and how do you measure how much you have?

Answer: Filters, inlet turns, diameter reductions and obstructions of the intake system create pressure drops depending on the restriction, resulting in vacuum in the air box (less dense air). Using a sensitive pressure gauge, this vacuum can be measured under W.O.T. either statically on the dyno, or on the track as we did.

9. What is the difference in drawing engine heated air versus cool outside air?

Answer: Every 40 degrees makes a difference of 6% HP. The pressure would have to rise 1PSI for this gain in HP. Conversely, the air pressure could drop 1PSI at altitude and the losses would be similar.

10. If the e-Ram produces a positive pressure in the air box, how does that relate to HP gains.

Answer: In the same way that you loose HP when you travel at altitude because the air is less dense, you gain it by increasing the pressure. For example, if you travel at 6500 feet, the air is 3PSI less dense than at sea level.(on average) This 3PSI doesn't seem like much, but can be responsible for up to a 20% HP loss. If you could produce a 3 PSI supercharger, your gains could be in this range too. (Ignoring the heating of air due to compression) At 1/2 PSI, gains are in the 3% percent range.

11. Does the e-Ram cause restriction when it is not on?

Answer: No. Since the e-RAM is over 3.8 inches inside diameter, even with the motor in the center, and its axial blade design, the e-RAM flows the equivalent to a 3.1 inch diameter free-flow intake tube. Also at part-throttle conditions, this not a factor because the flow rates under part throttle condition are much lower as well.
We have dyno'ed the e-RAM when mounted but NOT ENERGIZED at full throttle and measured no losses (see dyno results page for this dyno example).
Many people also have seen actual HP gains by just putting a static version of the e-Ram in line with the intake system claiming better atomization of fuel and air. We have not verified these gains, but if they are real, the e-RAM should be an order of magnitude more effective in HP gains and equal in gas mileage efficiency gains as any of the existing static swirling devices.

12. Does the e-Ram put a large drain on the alternator?

Answer: No, the max current draw is 60 amps for the e-RAM, and 120 amps for the Super e-RAM. This is as much as a high powered stereo, headlights, electric radiator cooling fan, or the starter motor on your car. Most car batteries with over 200 cold-cranking amps can handle draws of over 100 amps while the engine is running with no problems. We have even tested the e-RAM and Super e-RAM on motorcycle electrical systems with no problems. The e-RAM generates up to 15 hp gain from drawing over 1hp (831watts) directly from the battery. This has been verified on the dyno and with Volt Meters and Amp Meters. Charging systems work base on voltage drop of the battery, so the burden of the current draw really depends on the condition of your battery. Most batteries in good condition see very little voltage drop for short duration current draws of 60 or 120 amps for 10 to 15 seconds (full-throttle operation of e-RAM).

13. I have a very efficient intake system now, can e-Ram still help?

Answer: Yes, it makes what you have better. Preliminary tests have shown the best results on modified intakes with aftermarket intakes and filters. The e-RAM adds to any other modifications you have made, or will make to your engine (including addition of a turbocharger or belt driven supercharger).

14. I have a stock air box, will e-Ram still work?

Answer: YES! It also is designed to bolt on to the intake of your existing stock air box with little or no modification and the same 4-6% gains *(except late model Fords, Audis, BMWs, Nissans, and Mazdas equipped with Mass-Flow Sensors).

15. I have an after market intake tube. Will the e-Ram mount to it?

Answer: YES. By using the version of e-RAM with its integral cone filter (e-RAM-FILTER), you mount the e-RAM directly to the intake tube leading to your air flow sensor or MAP sensor. By using the e-RAM with adapters on both sides (e-RAM-INLINE), you can mount the e-RAM in place of a section of your intake tube for cold-air tubes and some MAF equipped cars.

16. Is their a chance of the e-Ram damaging my engine?

Answer: No, the e-RAM system is designed to work with any internal combustion engine, new or old. The low level of boost is safe for all engines and will not provide any major additional stresses on the engine that wouldn't already be happening at full-throttle operation. If anything was to enter the fan and damage it , a metal safety screen is included on the exit of the fan to assure no components enter your engine... no matter what the event... ever.

17. What is the life expectancy of the e-Ram device, and does it require maintenance?

Answer: The only moving parts are the instrument quality rare earth electric motor which is rated for over 800 hours before recommended service (brush replacement) and a metal impeller. It is highly resistant to heat and has sealed no maintenance ball bearings. Because of the low duty cycle (on the race track it is only on for 20 to 40 seconds a lap depending on the road course such as Laguna Seca or Sears Point where testing is done), the e-RAM unit should outlast your engine. We have many e-RAMs in the field since 1998 that are still going strong.

18. How quickly does the e-Ram spool up?

Answer: The highly balanced e-Ram spools up to 25,300 RPM in less than 100 ms (1/10 of a second). This is due to its very lightweight and strong construction.

19. How will the increase HP from the e-Ram help my quarter mile drag times?

Answer: The 4-6% HP gains are roughly equivalent to 1 or 2 tenths of a second for 0-60, and 2 or 3 tenths of a second in the quarter mile. This may not seem like much but, at the finish line, at speeds of 100 mph (146 feet per second), 1 tenth of a second is 14.6 feet, or roughly a car length. If you beat someone by one car length, that race wasn't even close!

20. Will the e-RAM work on my Diesel engine?

Answer: Yes! The e-RAM works on all internal combustion engines (Gasoline, Natural Gas, Diesel, etc.). Since the e-RAM is just providing additional air-density to the intake, your engine management system will automatically adjust to provide the appropriate amount of fuel and provide the additional HP gain expected from your e-RAM installation.

21. Will the e-RAM work on my Motorcycle engine?

Answer: Yes! The e-RAM works on all internal combustion engines (car, motorcycle, ATV, Boat, etc.). You just have to make sure that there will be enough room to mount the e-RAM in the compact area available on a motorcycle. The e-RAM will work with your carbureted engine (see next answer for considerations for carburetors). However, 2-stroke engines with simple membrane style carburetors will not respond to the e-RAM pressure. Your carburetor must have a "float-bowl" for correct fuel delivery. Also, if your fuel delivery is "gravity feed" type, you will need to add a small fuel pump to provide pressurized fuel delivery to the carburetor at a minimum of 2psi.

22. Will the e-RAM work on a carbureted engine?

Answer: Yes! The e-RAM works with carbureted engines. You just have to make sure you follow the following guidelines: An e-RAM-FILTER should be placed on the end of the sealed intake tube that feeds the carb with pressurized air. The area between the e-RAM thrust and the carb will be a pressurized area, and this area will need to be linked with a tube to the float bowl vent of the carb to equalize the pressure between the air intake and the float bowls to assure proper fuel delivery (please contact us by e-mail if you would like a picture diagram of this setup, as we have done this many times with other customers).

NOTE: 2-stroke engines with simple membrane style carburetors will not respond to the e-RAM pressure, as this style carburetor delivers fuel based on vacuum measured by the membrane, and there is no method to equalize the pressure to make this style of carburetor work properly with the e-RAM. Your carburetor must have a "float-bowl" for correct fuel delivery. Also, if your fuel delivery is "gravity feed" type (like on motorcycles with gas tank above the engine), you will need to add a small fuel pump to provide pressurized fuel delivery to the carburetor at a minimum of 2psi.

The idea behind either type of supercharging is to raise the intake manifold pressure to a value that is as close to twice atmosphere as possible. In other words raise it to around 15 psi guage at sea level. This way you could theoretically produce twice as much power from a given number of cylinders in a motor for the same rpm. So if a normally aspirated motor produces 100 hp at 3200 rpm then doubling the charge should double the output or produce the same results you would expect from a motor with twice as many cylinders without the weight penalty. Given that a standard four stroke motor in an ideal situation can be no more than 50% efficient since half of its revolutions are taken up pumping air, it makes sense to use some of the wasted energy from the exhaust to boost the output of the motor. But tremendous losses occur from heating the intake air, both from the compression and heat exchange from the turbine itsef. This can be somewhat overcome by passing the compressed air through a radiator in the fresh air stream. This air to air heat exchanger or intercooler drops the inlet air temp post compression by about 100 degrees F. This makes the air charge slighly more dense than non cooled air but it is still warm enough to cause near instantaneous vaporization of the fuel charge when they meet upon entering a cylinder. Weight saving is the advantage here, but the plumbing can been cumbersome to execute. Turbo lag can be adjusted out by changing the diameter of the turbine itself. Smaller spools up quicker, larger, slower. Since operating speed of the compressor wheel is 250,000 rpm, size is critical. Toyota experimented with using a small belt driven suoercharger in parallel with a turbo. The objective was to let the baby booster bring the pressure up quickly while the papa bear turbine spun up to provide the needed increase in volume. If car manufacturers ever convert to the threatened 42 volt electrical systems then an electrically powered supercharger would be the better option. It could use screw type compression with an accumulator to provide near instant metered boost based on throttle opening speed. It would eliminate a good deal of plumbing and simplify the fuel metering process and since it would run by wire it could be placed anywhere and not be restricted to being located on the motor itself.

Dual stage turbos (turbo superchargers) deliver quite high pressures eg. Cummins QSK 60 dual stage aftercooled engine uses about 30psi boost to develop 2700 hp at 1900rpm from 60 litres. It is pretty much given that diesels are much more efficient and cleaner when coupled to to a turbo and an intercooler, an aftercooler, or both. As an aside 2 stroke diesels mostly rely on supercharging to get the air through the engine. Look up Rootes blower.

My understanding is that a turbocharger is a subset of the term supercharger, although commonly the term supercharger has come to mean a mechanically driven air compressor. The turbocharger captures exhaust gas energy to drive the air compressor. This method has a significant difference vs. the mechanically driven supercharger. The amount of air the turbocharger can deliver is not limited to the speed of the engine. With a turbocharger you can keep increasing the power output of the engine until it breaks.

There is a lot of interesting opinions expressed to this question. I would like to add my comments to the already voluminous information. Essentially both supercharging and turbocharging are the same. The mecahnism by which air intake into the engines, for efficient fuel combustion and increased power performance, is called supercharging. Normally, all engines have been designed with fixed oxygen to fuel ratio for efficient burnng of fuel. Unfortunately, idealism doesnt work with engines. At higher altitudes, at high speeds, and when excess loads are hauled, engines starve of oxygen as there is less amount available within the short span of spark timing or injector cycles and hence there is a need to boost the air intake into the engines. Supercharging was a term coined in 1805 almost along with the inventions of automobiles. First generation supercharges were run by the engines themselves. The supercharger is coupled to the engine and the compressor is driven by a pulley-belt or geared coupling configuration.(Eventhough, ultimately only the pully drives remained in vogue). The problem with this system was that the compressors are bulky, require extra space within the engine confines, adds to more frictional losses, engine has to share the power to run the compressor, over all addition to the weight causing more fuel consumption. The advantage is a gain of almost 40% in power and 50% in torque and almost without lag. (ofcourse there is some lag when the engines throttle and a larger boost is needed). The designers then hit with the novel idea of using the exhaust gases as prime mover for the supercharges to preserve the power from the engine and allow the power entirely for transmission without having to share a part of it with the superchargers. To run the supercharger with the exhaust gases, they have used the same technique of gas turbines used in the power industry. Thus, a supercharges powered by exhaust gases which run a turbine were given birth to. Because these supercharges are run by a turbine, they are called the turbo chargers. The advantages of turbocharges are many and yet , there are many disadvantages also. Mainly, the open throttle requirement to boost exhaust gas emission, leads to higher fuel consumption and hence turbocharged vehicles are fuel guzzlers unlike convetional superchargers.Yet another problem is the enormous heat produced by the turbochargers and this leads to the additon of coolers to cool the turbos. The intercoolers help. However, the turbos need priming which is also known as heat up time or warm up time. You can not accelerate immediately after starting the engine. One can do so by opening throttle for a few minutes, warm up and then race. Turbochargers are also high on maintenance unlike pulley driven superchargers. There is a lot more to supercharging and I am sure we will see much more info and comments from knowledgeable persons on this topic. For cars, supercharges are the best and particulalry well suited are the rear engine types. For heavy vehicles such as Lorries, haulers, trucks, heavy earthmoving equipment, Turbochargers are an essentiality.

How interesting, and informative...yours and the antecedant messages. Another application that would be of interest, would be the use of supercharging in marine engines.

Many thks. It completely slipped my mind to include marine engines. Thanks for the addition.

Bad Week for: ....Hispanic Outreach, after Volkswagen decided to pull billboards promoting its new GTI as a car with "Turbo-Cajones." The company saie it meant to convey that the GTI is "a high-performance sports car," but complainants said "cajones" still means "ball" to them. From: The Week [Vol. 6, No. 252, March 31, 2006, News, pg. 8]

Yeah, I know...it's an oldie...but I couldn't help myself...

1. Electric Superchargers

Imagine strapping a hair-dryer to your engine bay, and plumbing the exhaust into your air-intake. Do you truly believe that you will gain HP from this? These devices are a scam. As it typically requires around 20% of the engines naturally aspirated HP to crank a supercharger, how do you expect your cars electrical system to supply anywhere near that amount of energy?

2. Applications of Superchargers and Turbochargers

Superchargers deliver boost dependant upon the RPM of the engine. Higher rpm = greater boost generated, in a linear fashion. The maximum amount of boost required at the rpm at which the engine will produce the most power is worked out before hand, and the pulley size selected accordingly. Wastegates and Blow-off valves are used in the modern application of superchargers, and the centrifugal supercharger is far more common among street tuners these days than the roots style blower.

Turbochargers generate boost dependant upon the exhaust volumes exiting the exhaust manifold. This is important to note, as a well tuned turbo setup will generate little if any measurable boost free spinning through its rev range. Wastegates and Blow-off valves are still used to control delivered boost.

The application of either turbochargers or superchargers to produce more power and/or torque from an engine is valid in different situations and depend on requirements. There have been cases of tuners and manufacturers using both technologies on the one engine (this really isn't a popular build though). Depending on how you want your engine to produce power or torque depends on which route you would take, and how that application was set up. You can easily set up a turbo on an engine to produce boost from very low in the rev range, but on a single turbo system, this will compromise on your potential max power. By the same token, a setup optimised for max Hp will suffer the effects of turbo lag more.

3. Marine applications

Both superchargers and turbochargers have been used successfully in marine applications. Usually the gain in HP is utilised to drive a larger or more aggressive prop in those vessels that use a propeller, as max rpm is not dependant upon intake manifold pressure.

4. Why charge the manifold?

The intake manifold of a naturally aspirated engine will usually be in a state of negative pressure, as air is drawn into the engine via the action of a piston receding into a block. This introduces the problems of pumping losses, and the efficiency of the engine will be limited by how well the engine can suck air in. When a the manifold is charged with a positive pressure, the engine no longer draws the charge in, but rather it is "rammed down its throat". As long as the fuel system curves are adjusted to maintain the right mixture, power will increase as boost increases, to the point that the engine design can not possible swallow the charge being generated (or the engine experiences failure due to exceeding tolerances).

Well, I'm a little happier now, even if nobody reads my brief overview of positive pressure induction...

I hope nishid Nanvati , that you have got much information regarding Turbo charging and supercharging. But eventhough if you are not satisfied than you can contact me in the College. I will try my best to help you out.