| Here's some light on the subject: Roots Blower : Produces a constant boost at all RPMs. They are bound to engine RPM which means their CFM output increases at the same rate as engine CFM consumption. Therefore you get the same boost throughout the powerband. The mechanics behind roots blowers is such that they follow a linear progression in air delivery. I dont believe that roots can be intercooled. Centrifugal Supercharger : Also attached to the engine RPM like the roots even though its air delivery is designed like a turbo. Ever read a compressor map? Familiar with the line on the left called the surge line? Well, this is the problem with centrifugals. At low rpm (regardless of throttle position) the SC wont be able to produce boost. You must rev the engine on low RPM power before the boost 'kicks in'. These do have one advantage over turbos, however. Since they are not powered by exhaust gasses, they wont choke. Small AR on turbine sides of turbos usually makes the turbine flow less raw CFM and halts your top-end power delivery. Tubos : Ahhh. The free HP tool. Exhaust gasses have a ton of wasted energy in them in the form of heat. The heat combined with the ballistic properties of a moving fluid, drives the turbine to give yourself more air. This has less to do with engine RPM however. If you open the throttle body air will flow and it will immediately power the turbo. There is that magic surge line which limits the compressors abilities at low compressor RPM, but if the compressor is spinning quickly and you stomp the throttle at low engine RPM, you will get boost quickly. They have no parasitic loss and they run completely on a "waste" product of the engine. Couple that with the facts that it can be intercooled (unlike roots; stop me if I'm mistaken) and that it doesn't require engine RPM to operate and you have one hell of a good air delivery system. Also, you also need to remember about displacement. If you ever tried to build a turbo system from an engine that is only 3 liters of displacement, you would find the HP is not as easy to get. Forced induction, in any form, is just a displacement enhancer. I also like my A/C.
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10:33:23 08/02/03
