Positive displacement:
PD/Roots/Twin-Screw blowers are my favorite street car blower. They're moron simple to install and deliver boost as soon as you open the throttle blades far enough for that much air to get in. Twin screws and classic roots blowers work in similar but different exact ways but, they're close enough to lump together.
An Eaton M90 or M112 is what most people think of when they hear roots blower and they're right but those are TINY examples. My old 1970 chebbie stump puller pickup had a BDS 8-71 huffer sitting on top of it. That's about 3x the physical size of an 03 cobra's M112 blower.
Autorotor is a leading manufacturer of twin screw type PD blowers. Twin screws are more efficient than pretty much any other crank driven blower but they're also more expensive than anything but a turbo. They're idiot easy to install and produce buckets of power. In some tests we've seen within a couple % of the same power as a turbo motor would produce from a TS blower equipped engine. TS compressors deliver cooler inlet temps and use less engine power to turn them. They also have that cool looking machined aluminum case. Note: use a flat black coated blower. Chrome makes for unnecessary heat dissipation problems.
Eaton is about the #1 maker of PD blowers. The only real downside to them is that they run out of steam kinda suddenly and have a poor efficiency rating when compared to the other types. What they do have in their favor is price and simplicity. I've installed a PD blower in a car in less than an hour. You get monster low end grunt, good base tq and a nice consistent climb as RPM's increase. Make sure you don't put too small a unit on your engine. 90cid is not enough for a v8. M112's are as small as I'd go on a 4.6. Get bigger for 5.4's.
Last edited by r3dn3ck : 12-17-2007 at 10:28 AM.
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