Do some vendors/companies not know the difference between Twin Screw and Roots?

[UNRIVALED SS]

Hmmmm. Not sure these discussions are fruitful because it seems 90% of the people involved do not know the difference either. Because of marketing and just uninformed opinion the misinformation grows.

For example. The term roots doesn't refer to design or component of any type. It's just the man's name who invented the supercharger for Diamler . Smart German who like horsepower. Anyway. Bottom line , the difference doesn't matter. Buy one! Either one. Run the car hard and have fun with it. It'll make the car the way everyone expected it to be when it came from GM.

The difference is . The twin screw has a tapered design which compresses air inside the manifold forcing air through the inlet into the ports on the head. That's why they whistle so loud , it's becUse of the air exciting the manifold outlets.

The roots type build pressure just by simple volume of Air building up outside the mainifold waiting to go into the ports by sheer volume.

What does this mean ? Not much. Centris are great! Twin screw superchargers are great! Roots type are great! All these make great power. Get one big enough that you don't need to upgrade if you want more power. Enough said.

[2010SSRSM6]

Roots type blower:



Twin Screw"




Both spin. Both compress air between the vanes. The difference is the shape the rotating parts are cut. The primary difference in the Maggie and Edelbroc 2300's are the runners that lead to the motor from the blower (Maggies are shorter).

Anyone selling them SHOULD know the differences between them. If they don't, they would not get my money.

[ayousef]

Originally Posted by 2010SSRSM6

Roots type blower:

Attachment 607351

Twin Screw"

Attachment 607352


Both spin. Both compress air between the vanes. The difference is the shape the rotating parts are cut. The primary difference in the Maggie and Edelbroc 2300's are the runners that lead to the motor from the blower (Maggies are shorter).

Anyone selling them SHOULD know the differences between them. If they don't, they would not get my money.

no roots blowers do not compress the air between the rotors, and are pretty different than twin-screws. Roots blowers move the air towards the outside of the case, note this image:



Twin-screw blowers force the air BETWEEN the rotors, one rotor spins faster than the other rotor (unlike roots which spin at the same speed), they also compress the air as shape of the lobes cause the cavity between the rotors narrows down towards the discharge side.



- roots is a PD blower

- Twin-screw is a PD blower that also compresses the air

On paper, twinscrews are more efficient, whether you will notice that or not in real life depends on so many things. You could have a MUCH better designed roots blower than a twinscrew, for example compare a Kennebell twinscrew to an Eaton roots blower and the roots wins. The new roots blowers don't seem to die off at higher rpms as one might think, yet I do agree that twinscrews sill make a little more top-end vs a little less low-end compared to roots.

The total power output of a 2.3 Eaton vs a 2.9 Whipple isn't very different either, yes in this example the roots displaces less volume PER REVOLUTION however can be spun at a higher speed. Spin a 2.9 at 18,500rpms at redline and it will be extremely unefficient, whilst a TVS2300 at 24,000rpm isn't unheard of.

This is also exactly how the new Corvette manages to get away with a 1.7 liter blower, im sure the efficiency of that little blower is up there with the best.

[old motorhead]

One rotor spins faster than the other on the t'screws? You sure about that?

[cdjnight]

True roots style blowers pull air in one side draw it around the outside of the lobes and stack it into the intake manifold creating pressure, They're relying on a restriction to create pressure. They also have an equal number of lobes on each rotor. (Eaton, Wiend, B&M, 6-71, 8-71 etc..) The lobes can be straight or twisted(Helix cut)

A twin screw is similar in design, as it has two rotor but the main difference you will notice is the number of lobes on each rotor are different and they draw air in from one end and return it to engine from the other end of the lobes. The reason for this is because the lobes have a tighter clearance as they move from on end to the other (creating pressure before it leaves the supercharger). (Whipple, KenneBell,)

A roots blower typically has a huge parasitic drag on engine by comparison. But newer designs added bypass valves that essentially let them freewheel.

Hope this helps.

Originally Posted by old motorhead

One rotor spins faster than the other on the t'screws? You sure about that?

And Yes a "Twin Screw Blower" turns the lobes at different speeds. It has to because there is a different amount of lobes on each rotor.


"Q: What’s a Twin-Screw supercharger and how is it different from an Eaton roots type supercharger?
A: All Eaton superchargers use the roots type supercharging principle. The roots supercharger is a positive displacement pump that moves air in pockets from the inlet to the outlet of the supercharger with no internal compression. The supercharger creates “boost” by moving more air into the intake manifold than the engine is utilizing, thus creating higher than atmospheric pressures in the intake manifold. When boost is not desired on an Eaton roots supercharger, the bypass valve allows the supercharger to spin with negligible parasitic loss as there is no internal compression. The Eaton roots supercharger uses 3 lobe (“M”) or 4 lobe (“TVS-R”) meshing rotors that are similar (but reversed) in geometry. The rotors operate at a 1:1 speed ratio.
The Twin-Screw type supercharger is also a positive displacement pump in that it moves a fixed amount of air per revolution. The Twin-Screw uses 2 non-similar screw type rotors that mesh together to compress and move the air pocket axially along the rotors. This internal compression ratio will lead to greater parasitic losses when boost is not required as you cannot turn this compression “off” by simply using a bypass valve. These rotors will have different rates of rotation due to their non-similar geometry and lobe quantity. The rotors of a Twin-Screw will commonly operate at 3:5 and 4:6 speed ratios. This means as the drive rotor spins at 15,000 rpm, the driven rotor will rotate at 25,000 rpm with a ratio of 3:5. This limits the Twin-Screw to lower rpm limits than the roots due to bearing life concerns."

[old motorhead]

I do like to learn something new every day. The rotors of a twinscrew blower turning at different speeds certainly qualifies. Thanks guys!!

[OneSickS10]

Originally Posted by nbrigdan

First off thanks to everyone for their replies!



I was under the impression that their only similarity was that they were both positive displacement, and that whether they were roots or T'screw was based on the style/design of the rotors. No?



Really? I don't think so, they use the rotors from Eaton, and those I'm very sure are a 2.3L roots, at least I think so.

http://www.edelbrock.com/automotive_...chargers.shtml

Call me crazy but these look like twin screws to me... as one of the other guys pointed out both roots adn twin screws utilize the same twin screw design. It's the direction they spin that is different. My understanding of the roots style blower was antiquated. I was picturing non "screw" lobes that are teflon coated :-)

[RankSS]

Originally Posted by OneSickS10

http://www.edelbrock.com/automotive_...chargers.shtml

Call me crazy but these look like twin screws to me... as one of the other guys pointed out both roots adn twin screws utilize the same twin screw design. It's the direction they spin that is different. My understanding of the roots style blower was antiquated. I was picturing non "screw" lobes that are teflon coated :-)

It says in the first paragraph.
Therefore I take that as meaning it is not a twin screw.


Eaton Gen VI 2300 TVS® Supercharger rotating assembly. Eaton's assembly features a four lobe design with 160° of twist for maximum flow, minimum temperature rise and quiet operation for excellent drivability.

[Euthanasia]

Originally Posted by old motorhead

One rotor spins faster than the other on the t'screws? You sure about that?

They do indeed... This is a Lysholm 1600ax I was working with.

[ayousef]

Originally Posted by old motorhead

I do like to learn something new every day. The rotors of a twinscrew blower turning at different speeds certainly qualifies. Thanks guys!!

lemme give you a small piece of information as well, goto whipples website youll find the 5.0 and the 8.3 liter blowers, they are BOTH basically the same blowers, with the only difference being that one is driven by the faster rotor and one driven by the slower rotor.

In the case of Whipples at least one rotor spins 66% faster than the other rotor. so:

The 5.0L blower is driven by the fast rotor, and displaces 5.0 liters per rev.

8.3L blower on the other hand (5.0 x 1.66 = 8.3) is driven by the slow rotor, and one revolution of the slow rotor displaces 8.3 liters.

Hence both blowers flow the same max CFM and have the same volumetric and adiabatic efficiency.

Hope this helps, we all like to learn something new everyday.

[old motorhead]

Originally Posted by ayousef

lemme give you a small piece of information as well, goto whipples website youll find the 5.0 and the 8.3 liter blowers, they are BOTH basically the same blowers, with the only difference being that one is driven by the faster rotor and one driven by the slower rotor.

In the case of Whipples at least one rotor spins 66% faster than the other rotor. so:

The 5.0L blower is driven by the fast rotor, and displaces 5.0 liters per rev.

8.3L blower on the other hand (5.0 x 1.66 = 8.3) is driven by the slow rotor, and one revolution of the slow rotor displaces 8.3 liters.

Hence both blowers flow the same max CFM and have the same volumetric and adiabatic efficiency.

Hope this helps, we all like to learn something new everyday.

I'm just damn glad this "lesson" didn't cost me anything. That's not often the case.....at least for me anyways

[376LS3]

Originally Posted by Euthanasia

They do indeed... This is a Lysholm 1600ax I was working with.

Are you the same Euthanasia that did all the work on the Cobalt M62s? I bought the MP90 kit you created.