In Reply to: what is better Turbo or Supercharge ? posted by M5(400hp) on December 07, 2000 at 06:58:46:
for what purpose (CA-smog-legal road use, road use where smog inspection laws are looser, road-course use, dragstrip use)
On what kind of vehicle/engine (M5?)
And where's your financial threshold of pain ($25K, $50K, higher?)
Generally, the slap-on low-pressure centrifugal blowers (e.g. Vortech) are the cheapest and provide great top-end numbers but they provide minimal low-end and midrange oomph. There's a lot of these because they're comparatively cheap, and comparatively easy to smog-certify.
A positive-displacement belt-drive blower e.g. Eaton or the Whipple/Autorotor/Lysholm screw types will add a lot more midrange, generally not as much top-end, and are generally harder to package.
A properly-done turbo installation is usually preferable to all of the above, but now we're talking fabrication of a complete new exhaust system, packaging problems for all that hot metal, and significant smog-certification impact.
Any high-output forced-induction system is going to require charge cooling, which adds more cost and packaging work.
I'd expect $25K to be about entry-level price for supercharging an M5, since the engine will have to come apart first to get the CR down to something that can tolerate boost.
One of the cuter developments to come around in a while are the Eaton hydraulically-driven superchargers - basically the compressor side of a turbo driven by an hydraulic motor. They've been announced, but are apparently not in production, seen no numbers on what they can produce or what kind of pressure/flow it takes to run one...