Kenne Bell or Centrifugal?

2000xp8 said:

Any supercharger adds power down low, most of the time more than you need.

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Not exactly. Most centrifugals (the ATI Prochargers with the 4.10:1 ramp up ratio being an exception) aren't able to move enough air in the lower regions to add anything to the power curve. If they're not pressurizing the intake, they're not adding any additional power. Furthermore, until that point where positive manifold pressure is achieved, they're actually costing slight amounts of horsepower as it is being taken away from the wheels and directed into spinning the head unit.

gt40_2003wes said:

and contrary to to popular belief centrifugal chargers do make boost below 4k rpms...on that point aswell who races below 4k? what are you guys doing 50 mph rolls in 4th? as soon as you hit the gas in first or second it spins past that 4k mark.

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I think you're missing the point here.

For starters, who spends 100% of their time at WOT on a predominantly street driven car. Racing at the track is one thing, but I would bet that 95% of the posters in this thread spend about 1% of their total driving time running WOT down the track.

Where the power made with a centrifugal supercharger is only useful under hard throttle at higher RPM, the power made by a positive displacement supercharger is useful at all RPM and much more moderate throttle levels.

As someone who's owned a positive displacement blow car and who's driven/ridden in both, I can tell you matter of factly that the car with the positive displacement blower makes for a much, much nicer all around driver.

Pulling away briskly from a stop, merging into traffic or even highway passing doesn't require hard stabs of the throttle, or downshifting into more appropriate RPM friendly gear. The grunt provided by all that extra airflow down low truly makes the owner feel as though they're driving a big block V8 from the 60's. The power is instant, seamless and 100% controllable by your right foot….none of which are an option with most centrifugal set ups. Sure, swapping out to a steeper set of gears will help centrifugal guys get into their power bands more quickly, but it’s still only a partial improvement and it comes with a hefty highway fuel mileage penalty.

If I had the additional displacement to make up the low end torque deficiency of the stock 302 HO down low and a light enough car, then I would most certainly consider a centrifugal, but without that added engine displacement to help move things along, or for guys saddled with full weight cars, auto transmissions and who quite frankly don’t want to compromise their low highway cruise RPM, there’s really no other alternative to a PD set up.