Polonius

Recently I've been doing some recreational research into the varying types of superchargers (centrifugal, roots type and twin screw), and having never driven a car with any sort of supercharger, I'm trying to get some feedback from those of you who have as to how different each one "feels". More specifically, what are the best applications for each, how much do they differ in terms of power, where are the most noticeable power gains (RPM wise) for each type, and anything else that you might consider a glaring difference among the types. I know it's a lot to ask, but I'd like to get a driver's opinion, so if I'm considering forced induction in the future I'll have more than a purely academic idea of their differences. Thanks!

angcobra

roots style is great for low RPM and not as effective for high rpm
twin screw is great for the entire range but may have more losses than centrifugal
centrifugal is not very efficient at low RPM but is the most efficient at high rpm

I have both roots style and centrifugal. I like the down low power so I like the roots style and I pulley the centrifugal to boost early. The ideal for me would be the twin screw so I would have the down low and high RPM power.

mustangman02232

most centrifiacals dont make boost until 3k rpm or so, so you get to save some gas milage, also, what mods have you done to your car, the type of blower will also effect the type of gears you put in. centrifical is basically a belt driven turbo charger, where the twin screw and roots are basically always forcing more air into the engine and burning more gas, also, would you be switching to forged internals or no?

OnyxCobra

I love the Kenne Bell... long live twin screw :-) I drove a '97 Cobra with a KB and it was unreal. I'm sure a lot of guys with 03/04 Cobra can vouch for them as well.

Birdieman4

I've owned and driven all three. Roots, screw and centrifugal. First of all, roots blowers are basicly now obselite with the screw technology these days. So it comes down to screw vs centrifugal. If you look at the hp and torque curves for both setups at around 9 psi, you start to wonder why anyone would go the centrifugal route. Yes, centrifugal set ups are less $, but that's the best argument I can make for them. In everyday street driving, the screw outshines the centrifugal bigtime. It's not so much the instant hp, it's the instant torque. Having not to depend on engine rpm for power is why the screw shines so well on the street. On a stock set up, it's not even close. If you went with a centrifugal blower, you could do some things to enhance it's strength, power at rpm. Doing new cams and pistons and increasing the car's redline helps the centrifugal's potential, but the bottom line is that the screw is the best way to enhance an otherwise stock mustang's setup for the street. If you drove a centrifugal car for a week, then drove a twin screw car for a week, you'd want the screw, hands down.

Polonius

At the moment I'm driving a 98 Vert GT w/ no mods, but that wouldn't be the car in question (it was my grandfather's before he passed so that one's kind of a sacred "in family car" anyway). I asked the question just to garner general info, but if I were to pick a particular model to supercharge it'd probably be the 03-04 Mach 1 (though would it be possible to maintain the functional ram-air and still have a supercharger?). So if you were to elaborate on the specifics of the installation, assume we're talking about a stock 03-04 Mach 1.

OnyxCobra

roots style are obsolete? Many cars are still coming from the factory with them...

mustangman02232

sorry to hear about your loss

Polonius

^^^^ Thanks man. It's a shame he didn't live to see me turn into the Blue-Oval fanatic I've become, because I'd say he's definitely responsible for it, but that aside, but I wouldn't say Roots types are obsolete. I know the 03-04 Cobras had roots, and I'm pretty sure the 07 GT500 will. They're torquey and cheaper than a twin screw, so they'll probably be around at least in factory models. Hell, look at the pushrod engine, it's been "obsolete" for years, but automakers still use them. It's all part of the "if it aint broke don't fix it mentality" so prevalent in the auto industry.

Birdieman4

I think you guys misunderstood what I was saying. Compared to twin screw units, roots units are obselite. Name a few cars that currently use roots blowers. The 03-04 cobras aren't current, and the new gt500 was supposed to come with a screw blower, but ford scrapped the it to save $. There is no reason a car maker would use a roots unit over a screw, except to save $.