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Discussion Starter #1
I know that SVT use the roots type supercharger and I believe its saleen that uses the Screw type supercharger. but anyways...I have heard that the screw supercharger can hold a lot more psi than the roots and are more reliable than a roots supercharger. Could someone please get the record straight with some hard facts about this?
 

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I've always heard that too, and all the old muscle cars you see with blowers are all the screw type..and it's also the one I'm eventually buying, I don't know any numbers on this however...
 

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i always thought they were the same?? maybe im wrong? i thought there was just centrifical superchargers and roots/screw type ones, maybe im wrong..
 

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Falcon said:
i always thought they were the same?? maybe im wrong? i thought there was just centrifical superchargers and roots/screw type ones, maybe im wrong..
I believe you are correct. The "roots style" charger uses a screw to compress the air just like the "screw style" charger does...so, it too is a screw style.

Saleen has the same style charger as the current cobras. The only difference is that the saleen charger is not an Eaton supercharger. They have the same type of internals but the saleen is a bit more efficient and cooler compression temps. The saleen is more simular to the Kenny Bell type of supercharger as far as efficientcy. The higher the charger's efficiency rating, the more PSI it can take. A whipple is better than a kenny bell which is about the same or a little better than a saleen which is better than an eaton.
 

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Discussion Starter #5
I also noticed that the screw or kenny bell/whipple superchargers are a lot louder than the eaton roots type. there is a lot more rip on them than the say, superchargered 04 cobra. I've heard one with rhe kenny bell screw and it was loud as f**k. I would get a Whipple or Kenny Bell cause I love the sound of them.
 

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its prolly just the brand then because liek procharger and vortech are centrifical and their loudness isnt the same either..
 

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Lots of misinformation in this thread, this will help!

Twin Screw vs. Roots SC arrangement

It's in PDF format so you need adobe reader but I'll post a few highlights here...





TWIN SCREW vs. ROOTS

Because of their ability to produce an abundance of boost (HP and torque) at virtually any engine rpm, the Twin Screw and Roots type are the two
most logical choices for supercharging. Both are essentially positive displacement SUPERCHARGERS (each revolution produces "X" cfm
regardless of engine rpm). Although their appearance is similar, one should not confuse the two. Internally they are as different as night and day.
LOWER POWER CONSUMPTION: The Twin Screw requires 10-16 less HP (depending on boost) to drive, leaving more horsepower for the
engine to transmit to the vehicle wheels for increased acceleration, passing, towing, hill climbing.
COOLER CHARGE TEMP: It also discharges air into the engine at a much lower temperature. The cooler denser air charge from the Twin Screw
equates to even more engine horsepower and torque potential with less thermal stresses on the engine.
INTERNAL COMPRESSION: The Twin Screw compresses the air between the rotors. This "internal compression" means less work to boost the
air pressure and quicker boost delivery to the engine. The compressed (boosted) air resides in the supercharger and makes it behave like an air
tank . . . squeeze the throttle and out comes the boosted air. The amount and boost level depends on throttle depression.
Eaton Corp. who is currently manufacturing the Roots type - and is also licensed to produce the Twin Screw - has this to say in their literature when
comparing them: "A Screw Compressor [Twin Screw] also provides more air for an engine's cylinders but it first compresses the air, thus
providing more boost than a Roots [Eaton] type supercharger. The additional boost allows engine manufacturers to extract more power
from an engine." ...Eaton Corporation


MORE:

It has come to our attention that our potential customers, enthusiasts and the media often confuse the "Roots" style superchargers with the "Twin
Screw." They all labor under the false misconception that both of these positive displacement superchargers are identical in operating principle and
efficiency! Frequently the Twin Screw is referred to as a "Roots." It IS NOT a Roots. These products ARE NOT THE SAME! (see Twin Screw vs. Roots
Operation).
It has been well documented in numerous tests by automotive engineers around the world that the Twin Screw concept is, unquestionably, more
efficient (cooler air charge temperature and lower parasitic loss). Ford, GM, Chrysler, Saab, Volvo etc. are among the many who have tested the Twin
Screw. The Mazda Millenia has used one for years and in 2001 Mercedes selected the Twin Screw for their latest high performance cars.
It is not our intent to knock the Roots type. Both are proven, reliable OEM quality superchargers. However, the Twin Screw is clearly more efficient.
Over 80 companies, including Eaton, have been licensed to produce the patented highly efficient Twin Screw rotors for compressors and
superchargers. Millions have been produced. The Twin Screw is a product who's time has come.
The superchargers tested were the Kenne Bell/Autorotor 3150 (Twin Screw) and a popular comparable Roots type. Both are rated at 1.5L and
recommended for applications up to 450HP. They were tested at 12000 rpm and 70° at sea level with the 3 boost levels indicated. Both are commonly
used superchargers. Two larger superchargers - a Roots type and a Kenne Bell/Autorotor 420 Twin Screw with ratings of 600HP - were also tested.
Again the test results confirmed the Twin Screw enjoyed up to 30% lower air charge temp and 30% less parasitic loss at all 3 boost levels.


Hope that helps, it is from Kenne-Bell (who sells twin-screw) but pretty accurate.
They do include the quote form Eaton, that produces the Roots units, but most
of the Supercoupe community recognizes the superiority of the screw type.
 

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Yeah, they are not the same thing. It's a matter of where the air is compressed in the process.
 

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Actually the term screw type is a Roots blower whether single or twin screw. The design is either attached to the motor ie roots or screw and the centrifical that sits in the air intake side of engine ie. Vortech, Procharger, Powerdyne. The fact is the the Roots or screw type of compressor has more direct PSI building abilities simply because of the design of it attaching to the engine and not being plagued by the expansion of the Tubes attached the Centrifical type supercharger which causes PSI loss.
 

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Danger Dude said:
Actually the term screw type is a Roots blower whether single or twin screw. The design is either attached to the motor ie roots or screw and the centrifical that sits in the air intake side of engine ie. Vortech, Procharger, Powerdyne. The fact is the the Roots or screw type of compressor has more direct PSI building abilities simply because of the design of it attaching to the engine and not being plagued by the expansion of the Tubes attached the Centrifical type supercharger which causes PSI loss.
Well, the Eaton Roots is more like a twin screw than a classical Roots, (IMO)
but it must compress along the outer side of the case. A classical Roots had
2 lobe rotors and they were not twisted or "screwed", but the Eaton is actually
a hybrid design between the Autorotor/Lysholm styles (they are separate) and
the older Roots that was so prolific on the old Detroit Diesels and adapted to
the old Musclecars we all know and love.
 

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Danger Dude said:
Actually the term screw type is a Roots blower whether single or twin screw. The design is either attached to the motor ie roots or screw and the centrifical that sits in the air intake side of engine ie. Vortech, Procharger, Powerdyne. The fact is the the Roots or screw type of compressor has more direct PSI building abilities simply because of the design of it attaching to the engine and not being plagued by the expansion of the Tubes attached the Centrifical type supercharger which causes PSI loss.

Still not quite correct.

The twin screw or the roots type blowers are positive displacement blowers, this means that they basically trap air and push it into the engine.

centrifugal blowers are basically a fan that accelerates the air into the engine. When the air hits the engine it is essentially restricted and this builds up the pressure.

If you look at the inside of both types of blowers you will see the difference. That is why they build boost in different ways. It has very little to do with the pipes on a centrifugal blower setup.
 

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whipster24 said:
Still not quite correct.

The twin screw or the roots type blowers are positive displacement blowers, this means that they basically trap air and push it into the engine.

centrifugal blowers are basically a fan that accelerates the air into the engine. When the air hits the engine it is essentially restricted and this builds up the pressure.

If you look at the inside of both types of blowers you will see the difference. That is why they build boost in different ways. It has very little to do with the pipes on a centrifugal blower setup.
I know the difference between superchargers I have had both on past cars. I was making a statement that the Roots and Screw type SC are the same basic design and work on the same principle. I only put in the Centrifical as to a different design and technology. The fact is a Centrifical SC is nothing more than a Belt driven Turbocharger
 

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Danger Dude said:
I know the difference between superchargers I have had both on past cars. I was making a statement that the Roots and Screw type SC are the same basic design and work on the same principle. I only put in the Centrifical as to a different design and technology. The fact is a Centrifical SC is nothing more than a Belt driven Turbocharger

Ahh, must have read it wrong
 

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the term twin screw... i thought they all had dual "screw" drives or whats up with that?
 

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Welcome Will!

TT-GT would be awesome :D
 

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which would you guys most recommend, a centrigual or a roots/screw supercharger.
 

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Is there even any aftermarket for screw or roots style S/C's on our v6s?? If so I really want a Kenne Bell.
 
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