Home
Forum
Gallery
Live Chat
Calendar
FAQ
Memberlist
Usergroups
Member Map
Search
Edit your Profile
Private Messages
DiscountsSupercharger (FAQ)
From Zwiki
Contents |
Intro
A supercharger is a compressor driven by a belt attached to the engine's crankshaft. Since they are powered directly by the crankshaft, they are actually a parasitic loss and actually rob horsepower to drive the compressor. However, as they are directly attached to the crankshaft, the extra power is available at all RPMs and there is no "lag" in the power delivery. There are two basic types of Superchargers, Positive Displacement and Centrifugal. Positive Displacement Superchargers fill a chamber of a fixed volume with air at atmospheric pressure nd move that air to the high pressure side. These superchargers generally provide a flat torque curve boost throughout the RPM range but are generally less efficient and thus produce less peak power. The most common Positive Displacement Supercharger is the "Roots" Supercharger and is used by most factory setups and Jackson Racing. A Roots Supercharger has two rotating, intermeshing lobes that pump air simply by trapping it on one side of the supercharger between the lobes and the supercharger housing and moving it to the other side of the supercharger. The main advantage of a Roots Supercharger is that there is immediate and proportional response to the throttle, because the blower is always spinning and its pumping ability increases proportionately and linearly with engine speed. Therefore, a Roots Supercharger makes the most low RPM power of any Forced Induction system.
A Centrifugal Supercharger (such as Vortech) is basically the compressor section of a turbocharger, but driven by the crankshaft through a step-up gearbox. Centrifugal superchargers often work best over a very small RPM range but provide higher peak power than Roots superchargers. Unfortunately, the power delivery of the boost increases non-linearly with engine speed meaning that they generate tremendous peak outputs, but at unuseably high RPMs. Nevertheless, they are popular with muscle car owners, who have plenty of low end Torque but need high RPM horsepower.
Superchargers can be placed between the throttle body of the carburetor or fuel injection system and the manifold; or at the air inlet before the throttle body. Racing cars usually have it located between the throttle body and the manifold. This design has the advantage that the fuel can be supplied through the throttle body without modification to any part of the system. If the supercharger is placed in front of the throttle body, fuel must be supplied under sufficient pressure to overcome the added air pressure created by the supercharger. The advantage of a supercharger over a turbocharger is that there is no lag time of boost; the moment the accelerator pedal is depressed, the boost is increased.
- Advantages: Instant power delivery
- Disadvantages: Parasitic power loss to system (less peak power)
- Applications: Recommended for low RPM, high torque applications (i.e. V8s)
Z/G Superchargers
Who makes superchargers for my car?
Which one is the best?
Other Mods with Supechargers
Exhaust
Intake
Driverain
Engine
How do you change boost pressure?
What is the maximum boost the VQ can handle?
About Superchargers
What is a supercharger?
To understand what a supercharger is, you must think of a motor as a large air pump. On a 4-stroke engine you have an intake stroke that occurs when the piston moves (typically) in a downward position allowing a charge (gas/air mix) to enter the combustion chamber. This is followed by the compression stroke in which the piston moves upwards compressing the charge. At this point the spark plug receives an electrical current from the ignition system allowing the fuel to burn (not explode) creating the pressure which moves the piston downward there by creating energy, Finally as the piston reaches the bottom of its stroke the exhaust valves open and the piston travels upward again to force out the spent fuel and gas. At redline this entire process happens about 100 times per second. The efficiency with which an engine can receive, burn, and exhaust these gases is measured as volumetric efficiency.
Technically, V/E is the expressed efficiency in which internal combustion engine can move the charge into and out of the engine or more specifically the combustion chamber.
What a super charger does is allow this V/E to exceed 100% efficiency or the theoretical maximum that engine can have otherwise. This is achieved by pumping of air into the engine in volumes and pressures in excess of what the engine could otherwise see. By increasing V/E the engine can produce more power than its displacement would otherwise allow. Superchargers are powered by a belt connected to the crank of the engine therefore allowing uniform volume increases in relation to the engines revolution per minute based on a predetermined gear ratio.
What all this really means is that a supercharger increase the amount of air and fuel an engine can burn there by increasing power.
History of superchargers
Back in 1885 Gottlieb Daimler (yes it’s the same Daimler) received a German patent for supercharging an internal combustion engine. While not very successful he did inspire Louis Renault (seeing a trend?) to patent his much more functional design in France circa 1902. All of this was put to good use in 1908 by a Mr. Lee Chadwick of Pottstown P.A. whose Vanderbilt Racer reached a blistering fast 100 mph using a leather belt to drive the charger.
Types of superchargers
There are three basic types of superchargers identified by the method they deploy in charge delivery.
Roots style
The roots style supercharger is at it’s heart an air pump that in general uses either a 2 or 3 counter rotating rotor lobes (imagine interlocking gears rotating together) which are designed to pump air into the intake manifold. As more air is pumped than can be digested by the engine positive pressure is created in the manifold, not the supercharger itself. Roots superchargers have what is called fixed displacement or the ability to pump the same amount of air per rotation. This ability is what helps roots and twin-screw units to produce comparably flat torque with little or no lag.
The downside of this approach is that due to some relatively complex laws of thermodynamics the roots supercharger will produce more heat due to the supercharger needing to do more work to produce the same amount of air.
Twin screw
This unit, although appearing similar to a roots unit, develops internal pressure and uses a different system to pump air. The name twin screw implies how this process works. Two screw shaped rotors are interlocked and rotate in unison. This rotation pumps the air down the axial length of the rotors and into the intake manifold. Twin-screw units produce pressure more efficiently than roots unit therefore the intake charge temperature with this approach normally is lower (this is a good thing).
Centrifugal
The final and most common type of superchargers are the Centrifugals. Centrifugals produce pressure much like a fan. One rotor is spun thru a set of gears producing a non-fixed displacement. Once again the name implies the method of gas delivery. In this case the blades of the supercharger rotate creating centrifugal force causing the air to move to the perimeter of the supercharger housing where the air is then forced thru a venturi and into a tube that grows in diameter as it travels around the perimeter of the housing. The combination of venturi and enlargement of the tube (scroll) increases the pressure of the air.
Centrifugal superchargers have numerous benefits inherent with there design. They are small in physical size with few moving parts making them easy to install and fairly reliable. The nature of how they produce pressure creates less heat than a Root or Twin-screw.
The downside of a centrifugal design is a significantly higher boost threshold. The very nature of centrifugal designs means that the rotational speed required to produce initial is fairly high in comparison to the other types of superchargers. Centrifugal designs produce boost at the square of its driven speed, this means that that a design producing a maximum of 8lbs of boost at 6500 rpm will produce only 2.8 lbs at 3200 rpm.
Other Questions
Do those electric supercharger/power module chip things work?
Simply put…hell no! They just make noise and are a waste of money. Same is to be said about those so-called power chip modules.
Superchargers 101
from http://www.superchargersonline.com
In order to understand how a supercharger is going to help your car scream, you first need to understand what a supercharger is and how it works. Well... class is in session, so sit down with your note pad pay close attention, because there might be a quiz at the end.
A supercharger is essentially a large pump that compresses air and forces it into the engine's air intake. Turbochargers do the same thing, only they are run by exiting exhaust gasses, while superchargers are powered by the engine's spinning crankshaft, normally via the accessory belt. Originally built for World War II aircraft, superchargers have become very common in today's performance automotive world, and featured as original equipment on some new sports cars straight from the factory!
Superchargers have become popular in recent years for several reasons, including cost efficiency, reliability, and of course, performance. Supercharging an engine often results in huge power increases in the range of 50% to 100%, making them great for racing, hauling heavy loads, or just having fun in your daily driver. Although superchargers carry a fairly high ticket price when compared to other single performance upgrades ($1500 - $4000), nothing provides more horsepower for your dollar... in fact, nothing even comes close. And because of the way superchargers work, they provide power only when the engine is under full throttle or under load... not under normal cruising conditions. This means that the supercharger will not affect the engine's reliability, longevity, or fuel economy under normal driving conditions.
Most of the superchargers sold today are centrifugal-style superchargers, which are internal-compression superchargers, meaning they create the boost (compress the air) inside the supercharger head unit (blower) before discharging it into the engine's air intake. External compression superchargers (roots or screw-type superchargers - Whipple, Kenne Bell, Jackson Racing, Eaton) have become less popular as centrifugal superchargers have evolved. Centrifugal superchargers (Vortech, Paxton, Powerdyne, ATI ProCharger) are more reliable, especially at higher boost levels, and are capable of creating much more boost than external compression superchargers, while creating a much cooler intake charge (which results in an even denser intake charge).
Boost is created at the point when the supercharger's internal impeller pushes enough air through the blower to overcome the vaccuum force naturally created by the engine's air intake, so air is being forced, rather than pulled, into the air intake. Boost is measured in pounds per square inch, or psi. More boost equates to a more dense air charge into the engine's combustion chamber, which allows the engine to burn more air and fuel and create more horsepower. Most street superchargers produce somewhere in the range of 6 to 9 psi, meaning they produce 6 to 9 additional pounds of pressure over the atmospheric pressure at that elevation (at sea level atmospheric pressure is 14.7 psi).
Many people assume that running a supercharger, and hence added intake boost, puts added strain on an engine's engine parts. This is not necessarily true, because engine damage is almost always caused by RPM. Because a supercharger helps the engine produce more power at lower RPM, supercharged engines will make the same horsepower as their naturally aspirated counterparts at substantially lower engine RPM, where today's street engine's are designed to run (around 6000 RPM). Another concern some people have towards using a supercharger is that they think it will increase the engine's compression to the point that it will cause detonation inside the combusion chamber. Detonation exists when the combustion pressure is raised so high that the inlet charge ignites itself before the spark plug fires. When this happens, combustion takes place while the piston is still travelling up in the cylinder bore, which puts tremendous loads on the piston, rod, and crank. While it is true that a supercharged engine creates boost and increases the engine's compression, most supercharger kits include a boost timing retard chip that retards the engine's ignition timing under certain conditions to prevent detonation. With some kits, detonation is not a concern, in which case the kit will not include a boost timing retard chip.
Supercharger impellers on centrifugal superchargers are spun via an external pulley that is normally driven from the engine's accessory belt. Because the supercharger pulley needs to spin at very high RPM, an internal step-up causes the impeller to run at substantially higher speeds than the input pulley. Because the speed that the impeller spins determines how much boost is produced by the supercharger, changing the input pulley size can have a large effect on the amount of boost put out by the supercharger. Smaller pulleys produce more boost, which is why they have become so popular for supercharger owners who are looking to squeeze every last bit of power from the engine. And because they only cost around $70, they are an inexpensive way to test and tune your supercharger at different boost levels.
Because superchargers spin at such high speeds, they often create a substantial amount of heat, and require lubrication to keep friction to a minimum. Different supercharger companies have combatted the problems of heat and friction in different ways. While no single method is the best, each method has advantages and disadvanages. Powerdyne uses an internal belt to spin the internal gears (step-up drive), which minimizes heat, is very quiet, and lasts for over 50,000 miles. This internal belt never slips, and does not require you to tap into your engine's oil supply for lubrication purposes, making it the easiest line of superchargers to install. Vortech, Paxton, and ATI (except ATI's self-contained systems) all use the engine's oil to lubricate the step-up gears and keep heat and friction to a minimum. While this lubrication is the most common and works well, it does require the engine's oil pan to be tapped so the supercharger can draw engine oil from the engine. ATI's self-contained systems also use an oil to provide lubrication and to minimize heat, but they use a proprietary oil that stays inside the supercharger head unit and never requires changing. This system is efficient and does not require the engine's oil pan to be tapped, but is substantially noisier than Powerdyne's belt drive system.
Intercoolers and aftercoolers cool the air after it has been discharged from the head unit and before it enters the intake manifold. The cooler air provides a denser air charge which can make added horsepower, especially under higher boost conditions. Intercoolers and aftercoolers, while popular for racing applications, are not normally needed for street drivers running 6 to 9 psi of boost.
