When it comes to tuning VW's 2.0L 8V there are many options available. Beginners may opt for simple bolt-on parts but gains are limited. If the basic upgrades aren't enough and a full motor swap isn't an option, the next logical option is forced induction, either supercharging or turbocharging. Recent trends tend to favor supercharging, as the kits are relatively inexpensive and the install can be done in an afternoon.
The main advantage of supercharging is the immediate power increase right off idle without waiting for a turbo to spool. Since a supercharger uses a belt to link it to the engine, stepping on the gas pedal is akin to flipping on a light switch, giving instant power. As soon as the engine starts, the supercharger is working. A supercharger is basically a large air pump. Power is created by increasing the amount of air going into the motor by compressing the air and forcing it into the intake. As the extra air volume is mixed with more fuel, a stronger combustion occurs. The increased combustion pushes harder on the piston, which pushes harder on the crankshaft, which creates more horsepower and torque.
Bahn Brenner Motorsport began its 2.0L 8V supercharger kit development with the latest in supercharger technology: an Autorotor twin screw lysholm-based charger model SR2-2087 manufactured by Opcon. The Autorotor is known for its reliability and longevity. The fact that it is a positive displacement type charger makes it a perfect match for the 2.0L 8V. An added bonus is that it requires less power to drive it, and it doesn't have to turn as high rpm to produce boost.
The Bahn Brenner Autorotor twin- screw compressor features billet aluminum case construction. This manufacturing process allows for a case with virtually zero distortion at any rpm. The billet manufacturing process allows for precision machining of the inlet and outlet ports, resulting in increased airflow and lower air charge temperatures, resulting in less power consumption. It also uses a unique hybrid rotor system; this design profile decreases air leakage, resulting in reduced air charge temps and lower power consumption. The charger utilizes oversized rotor shafts with large 100% ball bearings with a load rating of 2,500 pounds, for increased strength and reliability through the entire rpm range. To combat the whine typical of supercharger operation, the Autorotor charger utilizes precision, low lash, fine metal helical gears for quiet operation and maximum reliability. Additionally, the pulley used to drive the supercharger is made of OEM high-grade steel ensuring longer pulley and belt life.
How's it work?To get a better idea of how a twin- screw supercharger generates boost, let's trace the pathway air takes as it passes through a process known as "internal compression." This process takes less work to produce boost and reduces turbulence, friction, and heat and pressure loss. Air enters the supercharger and is forced to the rear of the housing, where it is then compressed internally between a male rotor rotating clockwise and a female rotor rotating counterclockwise. This allows the supercharger to use a more efficient internal compression. Once the air is compressed and forced through the full length of the rotors, it either exits the supercharger or remains in the supercharger in a compressed state until the engine demands boost.
Once Bahn Brenner decided on what supercharger to use, steps were taken to custom tailor the rest of the kit specifically for the 2.0L 8V engine. The Autorotor supercharger is a universal part, so the first step in the design process was determining how to mount the supercharger. The most critical part lay in the pulley alignment and positioning of the belt to be absolutely straight. If the belt position was off by even a few millimeters the belt would be torn to shreds. Bahn Brenner was able to use the factory belt tensioner and position the charger to maximize the amount of belt contact area. This resulted in 50% drive belt contact, which is critical in preventing belt slippage when the supercharger is under high boost.
The next challenge was designing the plumbing to and from the supercharger. With a positive displacement blower, it is recommended that the throttle body be relocated to the inlet side of the supercharger. This provides a quieter operation and better on-throttle boost response. Since the original location of the throttle body is on the passenger side, it was relocated to directly behind the radiator support. This required an extended throttle cable and fabrication of an intake pipe to mount the throttle body. When the factory MAF sensor harness came up short, it was relocated using a custom fabricated extender harness.
Next was completing the discharge side of the kit. This section of plumbing was critical for optimal performance. If the discharge was too restrictive, turbulence and heat would be created, causing boost distortion. The supercharger discharge flange was designed using the latest in computer-aided technology, resulting in a part that maximized air flow capacity and lowered discharge temperatures. The rest of the plumbing from the flange to the intake manifold was mandrel bent to ensure concentric bends and maximum air flow. Proper working conditions were ensured through the installation of an air bypass valve system (aka diverter valve) to maintain proper boost control. The system is vacuum operated and determines when boost should be retained or released. Since the supercharger requires high pressure oil feed, Bahn Brenner installed an oil feed line and an oil drain line.
Last, but certainly not least, was the issue of fueling and software. If the vehicle has OBD-I, the supercharger kit will include a larger fuel pressure regulator system, a kit to reroute the idle stabilization system and corresponding software. If the vehicle is equipped with OBD-II, the supercharger kit comes with a set of four larger fuel injectors and corresponding software. The culmination of Bahn Brenner's design elements resulted in a stage-one supercharger kit that increases power output by 60%, which equates to approximately 177 bhp and 180 lb-ft of torque.
If after you complete the stage-one upgrade you're still left wanting more, Bahn Brenner offers two additional stages. The stage-two upgrade consists of a custom Bahn Brenner head gasket to lower the compression, a higher lift camshaft, smaller supercharger pulley to increase the boost pressure and a new ECU program. All these parts are said to net an additional 20 whp.
The stage-three upgrade is designed to combat the extra heat generated by the increase in boost pressure. This kit consists of a new intake manifold with a built-in air-to-liquid intercooler, electric water pump, reservoir tank, Setrab heat exchanger, hoses and fittings. Also included in the kit is a stage-three-specific smaller pulley to push boost even higher and new ECU software to complete the package.
Blower 411There are three main types of supercharger designs currently being used in the automotive industry: centrifugal, Roots and screw.
CentrifugalCentrifugal superchargers are basically belt-driven turbochargers. As air is drawn into the snail-shaped compressor housing, the velocity is increased by a high-speed impeller (the high speeds are produced by internally overdriving the input shaft, which is also overdriven by the external drive pulley) and forced out through the scroll of the supercharger.
RootsThe Roots-type supercharger is classified as a positive displacement system. A Roots-type supercharger does not actually compress air, it just moves it very quickly. As air is drawn into the supercharger inlet it collects in the areas between a pair of counter-rotating rotors moving it within the housing and forcing it into the intake manifold at a high velocity.
ScrewThe screw-type supercharger is the latest development of the Roots-type supercharger, the main difference being the way boost is produced. As air is drawn through the inlet it is compressed internally between the rotors. The male rotor rotates clockwise while the female rotor rotates counterclockwise, compressing the air between the rotors and forcing out the discharge.