Types of superchargers

zfokaiz

ok so go ahead and start the "flame fest" but im wondering as to what exactly the difference is between say, a twin screw, whipple, roots, and positive displacement superchargers. (maybe a link to another site if its just too much to type.)
sorry for the noob question but i've never got into forced induction and have always been a fan of N/A.

Edit: on second thought maybe im looking for more Pros and Cons than anything else.

2fast4thelaw

No problem, I will answer this to the best of my knowledge but dont hold me to being exact.

All superchargers are positive displacement and all this means is that at idle the supercharger as producing some amount of air pressure above what the engine would if it where naturally aspirated.

Roots Type:
Twin Screw and roots are very similar and are what most of us easily recognize as a big crome blower sitting on top of the engine between the valve covers of V engine. These units have 2 long cylindrical looking lobes that counter-rotate each other and they sort of interlock "without touching each other" thus squeezing the air and forcing it downward into the intake manifold. This design is efficient because the rotors are large and have relatively high air displacement without having to turn 50,000 to 100,000 rpm like centrifugal superchargers.

The difference between twin screw and roots is just the shape and design of the rotor. The the twin screw rotors are tapered at one end like a cone and the rotors ride opposite of each other. (I may be wrong on this so anyone else with expertise please correct me if I am)

Looking at the photos the roots type supercharger is pictured on the bottom left.

Examples are: Stillen, Kenne Belle,Eaton, and Whipple.


Centrifugal:
Now the other design that is commonly used is the Centrifugal chargers. These units compactly fit under the hood with little to no hood modification. Centrifugal chargers are basically the compressor half of a very large turbo that has been geared up to like 7:1 to turn very fast up to 115,000 rpm. These units are less efficient becasue the engine has to work harder to turn the impellor, which is known as parasitic loss.

Examples are: ATI-Procharger, Vortec, Paxton.

Traction Drive Centrifugal:
Some of these designs are better than others. The best designed units use a traction type planetary drive that use sets of rubber like rollers instead of gears and belts inside the drive unit. The drive system is variable based on demand. The harder the engine accelerates the more pressure is put on the rollers to spin the compressor faster. When driving at the speed limit around town the compressor is not spinning in direct link to the crankshaft so there is less load to the engine under normal driving. This not only reduces friction, but it makes for a quiter unit and ultamately more efficient.

The Traction drive supercharger is pictured on the right.

Examples are: HKS, GTM

Attached Images

	roots super-charger-fix.jpg (36.0 KB, 40 views)
	traction-drive-diagram.jpg (48.9 KB, 50 views)

__________________
To the optimist, the glass is half full. To the pessimist, the glass is half empty. To the engineer, the glass is twice as big as it needs to be.

zfokaiz

Thanks a bunch I really should've looked more into all this sooner.
Anyways thanks man
+1

1slow370

No hard feelings guy but much of the earlier response is wrong

centrifugal's are not positive displacement guy they are a dynamic supercharger meaning that they flow different amounts of air compared to engine rpm. Positive displacement superchargers pump the same amount of air relative to engine rpm (almost). Positive displacemnts are generally preferred as the power and torque produced is made at nearly the same time as the power and torque curves were before supercharging so it feels more linear.

Centrifugal's produce almost no power in the lower rpms but it steadily builds creating a take-off feeling compared to the instant bang of pos. displacement. Centrifugal superchargers are generally cheaper than a twin screw but more expensive than a roots.

Centrifugal: Vortech, Rotrex, Paxton, Procharger

Twin-screw:Whipple, Vortech VTS, Eaton made OEM Lysholm, Kenne Bell

Roots:Weiand, Magna-charger(resells Eaton chargers for the aftermarket including the Eaton Twin Vortices Series or TVS, Eaton made OEM

There are other types of superchargers mainly used by volkswagen but they suck and are expensive so hell if i am mentioning them.

Edit: As to why twin-screw and roots are not the same they have totally different types of rotors inside them and while a twin screw actually compresses the air inside it like a piston a roots blower just pushes it into the manifold where it jams up against the valves and makes pressure there.

Positive displacement is like putting in a big v8, where as centrifugals are like high horse power 4 cylinders- they make power higher in the driving range.

zfokaiz

Thank you for the clarification. You've really help spark my interest in forced induction.
Thanks

2fast4thelaw

None taken, i gave it my best shot from what I learned on this site. I appreciate the correction the new light shed on the subject.

__________________
To the optimist, the glass is half full. To the pessimist, the glass is half empty. To the engineer, the glass is twice as big as it needs to be.

1slow370

Aight. I've had a supercharger addiction for almost a decade now so it happens.

2fast4thelaw

I am about to have one this summer I will most likely choose one of the three: Stillen, HKS, GTM. I want the new traction drive Centrifugal supercharger. I have a feeling this is the route Stillen will be choosing. The twin screw is a no go from everything I have read.

__________________
To the optimist, the glass is half full. To the pessimist, the glass is half empty. To the engineer, the glass is twice as big as it needs to be.

1slow370

a twin-screw is a great unit with higher a/e and v/e then most centrifugals but the damn vvel screwed it up. Would require an extra throttle body be mounted in the car. Centrfugal would be cheap and easy on our cars but i hate the way they provide boost. A good whipple or kenne bell twin screw would have done it for me seeing as they have a unit sized for 500-850hp.

2fast4thelaw

I am not looking for gigantic gains my car is already fast. I would be happy with 100 rwhp boost with potential for 150 rwhp. i am most concerened with the unit delivering boost safely, reliably and not nickel and diming me constantly. I am thinking the centrifugal units are going to fit best with the least amount of modification. They may not be the most efficient and optimal performing units but thier better than nothing at all.

__________________
To the optimist, the glass is half full. To the pessimist, the glass is half empty. To the engineer, the glass is twice as big as it needs to be.

nd4spd

bump

2fast4thelaw

Superchargers are belt driven from the engine much like a water pump or airconditioner. The faster the engine is running, the faster the supercharger turns in which more air is forced into the engine which = more power.

__________________
To the optimist, the glass is half full. To the pessimist, the glass is half empty. To the engineer, the glass is twice as big as it needs to be.

nd4spd

bump

nd4spd

thats cool

1slow370

technically the word supercharger encompasses both engine and exhaust driven "turbochargers" as a device wich compresses intake air for an engine originally turbochargers where turbine-superchargers but that was ghey so we call them turbochargers.

edit: just wanted to throw out that a centrifugal supercharger is in every way inferior to a a proper turbocharger setup where as positive displacement supercharger far excced the low rpm output of a turbo charger but but lose on the top end.