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| Article | Things That Blow 1/1/2006
Superchargers, turbochargers, and nitrous oxide all pack more air into head chamber areas. All three types increase your volumetric efficiency in different ways.
The first of these is the superchargers. These are mechanically driven from crank shaft rotation. This is usually accomplished with a belt and pulley arrangement. The belts and pulleys can be increased or decreased in size, for more or less charge air being forced to intake system. The intake system must accommodate positive charge air pulse on overlap cycle of engine rotation when both intake valves are closed. Plenum area (of adequate size) calculated for the amount of boost the supercharger will provide, creates a holding area so when intake valves open constant pressure charges the head chamber once again. Whatever you choose, pulley or gear driven supercharger, the trade off will be a parasitic loss of horse power it takes to spin the charging veins. The higher the boost you squeeze into the engine, the larger the horse power demand is to drive the supercharger.
Turbochargers are another forced air mechanism for pressurizing intake track. The turbo uses exhaust to drive its impellers, which share an axle with the inlet impellers in a separate compartment. The exhaust, when the machine is under heavy load, will become very hot expanding rapidly causing the exhaust impeller to spin faster. The faster the impeller spins the more boost will be available for intake side. Some turbochargers will have a lag in time from demand to power delivery because revolution per minute (RPM) spool time to reach desired charge rate of boost pressure. Some turbochargers are capable of spooling up quickly, but must have pop off valves to bleed over pressure of the boost out of the system to prevent damage. There is a new turbo being experimented with that can vary boost pressure by charging vein orientation. The obvious advantage to turbo is no parasitic loss of horse power to drive it. The turbo is reclaiming power that would otherwise be lost out the exhaust pipe. The trade off for turbo use is the large amount of exhaust pipe plumbing all around the engine; because, the more efficient a turbo system becomes the more support plumbing needed.
Nitrous oxide systems (NOS) are numerous in design and applications. Nitrous is a cryogenic oxidizer - meaning it goes in very cold hitting hot parts and steam flashes, expanding rapidly. NOS working pressure is from 900 psi to 1500 psi and likes to be kept at temperatures from 70 to 90 degrees Fahrenheit through the use of bottle warmers or insulators. One system is a fogger system, which blows NOS only in your intake. This system is difficult to manage. You control the amount of NOS going in your engine by jetting it, but the difficult part is getting your engine enough fuel and backing the timing off in the correct amount to coexist with the NOS charge. This system is inexpensive and has been responsible in part for the destruction of many engines, but it looks cool. Best NOS systems will be the WET NOS kits which are never cheap! This is where you have an additional outlet fuel valve that feeds both carburetor and an additional electric fuel pump. The gasoline line and NOS line will go to a jet nozzle which will spray both into the intake track. This system is very manageable by way of jetting either NOS or gasoline, as needed, independent of the existing set up that is being added to. Some systems allow accessing at any engine RPM that may cause detonation problems from too much advance timing at low RPM. Some systems have pulse counters not allowing access to NOS until after 4100 RPM has been achieved, keeping you out of this potential trouble spot. The upside of NOS is versatility. The ability to utilize electronic control to interface with other systems can be piggybacked in stages and its tune ability, as well as, light weight. This system can get complicated, and tuning must be on a Dyno with an O- 2 sensor and load control. Today, systems are also electronic fuel injected capable, but all previously mentioned still apply.
So, if you are looking for a little more power, or a lot more power, remember an engine is an air pump and more air in equals more power out. For the people who have gone with big bore or long stroke engines to achieve a larger cubic inch displacement, then superchargers, turbochargers or Nitrous oxide are excellent ways to get your engines volumetric efficiency back up.
Good Riding and God Bless
Steve Caldwell - steve@precisionvtwins.com
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