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Thread: Power Adders Explained.

  1. #1
    Got boost?
    Join Date
    Aug 2002
    West Warwick RI/ White Plains NY

    Default Power Adders Explained.

    Below is a paper I wrote a couple years ago for school. Pretty much dumbs down power adders for everyone. I had a 10pg version but I cant seem to find it; this was the inital summary of the paper.

    The automobile engine as we all think of it is naturally aspirated, or breaths air on it’s own using the vacuum created by the moving pistons to suck in air and fuel. This limits the amount of power an engine can make to how big it is. When you want to make more power in a vehicle without changing the motor, you must find a way to add more air and fuel to it. There are the normal engine bolt-ons: larger camshafts, more freely flowing intakes and exhausts, but these have their limits. There are three common methods to add more air and fuel to an engine: turbochargers, superchargers, and nitrous injection.

    The Turbocharger is a device made to increase power in an engine with minimal parasitic (frictional) losses. It contains two compressor wheels and housings connected by a shaft. One of the wheels is placed in the exhaust stream of an engine, and when it is spun by hot exhaust gasses, the other wheel turns sucking in outside air and forces it into the engine's intake. This excess air allows more fuel to be added to the mix, which in turn produces more power. “Boost”, as this additional pressure is called, is controlled by venting exhaust gasses around the compressor wheel when the desired pressure has been reached.
    Swedish inventor Alfred Büchi perfected the turbocharger in 1925, while seeking a more efficient and economical source of power for gasoline engines. It has since been used on countless automobiles, and has more recently become the mainstay of the import 4 and 6 cylinder vehicle tuners.
    These systems are very complicated and must be carefully monitored and maintained or a dangerous condition may occur inside of the engine. As with most technologies, complicated tends to mean expensive, and this is no exception. Turbo charging is by far the most expensive power adder with kits starting at over three thousand dollars and going well over fifty thousand.

    Superchargers, or "blowers" as they are sometimes called, are the oldest, and most recognizable form of power-adder. Driven off of the crank pulley of an engine, they force air into the combustion chamber allowing for higher cylinder pressures, and more horsepower. Some of the first cars came with rudimentary superchargers installed on them, and later during WWII when aircraft manufactures were looking for a reliable way to add power to their fighter planes, they too turned to supercharging. There are several different kinds of charger, each offering different benefits and drawbacks.

    The first, and oldest of the superchargers is the "Roots" type. They are the most recognizable, usually protruding from the hood of a vehicle. This type is basically an air pump using interlocking vanes for pump massive amounts of air into the combustion chamber. They are meant for carbureted applications, and usually are not used with modern fuel injected vehicles, as they completely replace the intake manifold on the engine.

    The second type of blower is the "Screw" type. They look very similar to roots style, but there is a difference on the inside. Instead of using interlocking vanes, this type utilizes two augers that compress the intake charge inside of the blower housing before releasing it to the combustion chamber. This type of supercharger is used mostly on high-performance fuel injected streetcars due to their simplicity and reliability. Screw-types are usually more expensive than the roots type due to their tighter, more precise construction.

    The newcomer in the supercharger scene is the “Centrifugal” charger. They are shaped like a turbo, but instead of being run by the exhaust gasses they have a serpentine pulley driving the compressor wheel. Centrifugal chargers are less than half the size of most roots or screw style blowers, and allow for mounting in many different sized engine compartments without any hood modifications. Their only drawback is that they suffer from "lag" like a tubocharger, usually not making usable boost until higher engine RPMs.

    Nitrous oxide is the final type of power adder. It is simply liquid N20 stored under pressure in a tank that can be injected into the intake through solenoids. It is by far the cheapest way to go faster, as most kits go from three to nine hundred dollars. On demand from the driver, solenoids attached to the nitrous bottle and a fuel line open up, introducing a pre-determined mix of nitrous gas, and fuel in to the engine’s intake track. When the liquid nitrous goes from its stored pressure of 800psi+ to atmospheric pressure, it instantly turns to a gas, and drops in temperature. This is the first benefit of nitrous oxide, as colder air is denser air, and denser air can burn more fuel. Upon reaching the combustion chambers, a chemical reaction occurs splitting the nitrous (N2O) into one oxygen molecule (O), and two nitrogen molecules (N, N). The oxygen molecule is now free to combust with the additional fuel. The function of the nitrogen is to calm the combustion process. If pure oxygen were added with the additional fuel, combustion would be so violent it would destroy the engine. The nitrogen molecules slightly slow the reaction down to a safe rate.

  2. #2
    Trained in the art of psi Krazed's Avatar
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    Sep 2004
    My Boost technique is strong, you are no match!


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  4. #4

    Default Power Adders Explained

    My brochures say the BG had power steering as standard on SE, SE Exec, GT, LX, GLX, and GLX ABS, i.e. all the UK spec models.

    They also had tilt steering except the LX.

    Maybe a non-UK spec had no Power steering.

  5. #5

    Default Power Adders Explained

    Thanks for that Billy, maybe I misunderstood Fabians description or he was talking about some other engine when he was telling me about the power it makes.

    What power do you expect his engine to make?


  6. #6

    Default -

    Im new to bimmer. just looking for my first ride.
    Ive been driving chipped 300-400 hp turbo cars for about 10 years.

    Looking for 500-600hp.
    What is best bmw for this? prefer 3 series size.
    supercharged or turbo?

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