NA or Supercharged?

[eschaider]

Centrifugal compressors need turbine speed to produce boost. That means at idle, you will have little to none, and the car will drive and feel that way. Depending on your installation and your equipment, you can usually get around 8, maybe even ten psi by 2500 to 3000 rpm. That number will vary based on your engine size, compressor size, compressor trim, and, in the case of crank-driven units, the overdrive ratio you elect to use.

The boost delivered by a centri design is based on turbine size and the square of the turbine speed. That means initially, the boost will be very moderate and then come on in a rush as turbine speed increases. This can provide for some exciting driving experiences. In fairness, the belt-driven PD blower will provide an immediate rush as you push on the accelerator, but it is predictable and manageable, with experience.

A belt-driven positive displacement compressor (KB, Whipple, Eaton, Roush, Magnuson etc.) produces immediate boost the moment you push on the throttle. The driving experience is night and day different.

When it comes to modulating engine power, the centri's may or may not be as responsive as you intuitively expect. Throttles placed after the compressors will provide the best modulation. Throttles placed pre compressor (this is not common) will provide the least modulation.

Belt-driven PD blowers will provide you with 90% or more of your maximum torque from throttle tip in through max engine rpm. The effect is a very intoxicating driving experience and the kind of control you need to minimize the number of crashes you might experience when driving a supercharged Cobra aggressively on a road course.

Using a centri compressor and using your clutch pedal to disconnect the engine from the final drive, you can still mitigate the trailing torque oversteer problem a Cobra can induce. For precision torque management control, the PD blower design does a better job, although you can still get yourself into enough trouble that you will still need to push in the clutch.

Neither path is inexpensive. Both are exciting — and dangerous.

Pick your poison ...