Fallstar01

I just wanted to inform some people about positive displacement superchargers.
There are several "Brands" out there.

Ford OEM
Ford Racing
Roush
Allen Engineering
Saleen
Kenne Bell
Whipple

Let me clear up some confusion about the compressor (The main part with the screws that has the displacement):
Eaton:
--Ford OEM on the Lightning, both 03/04 and 07 Cobras, and other cars except the Ford GT have an Eaton compressor.
--Ford Racing's 2V supercharger has an Eaton Compressor.
--Roush Superchargers (that I've seen) have Eaton Compressors.
--Saleen Series I and Series II have Eaton Compressors
--Allen Engineering Superchargers have Eaton Compressors.
Whipple:
--Ford GT's supercharger has a Compressor from Whipple
--Ford Racings Cobra upgrade has a Compressor from Whipple
--Saleen Series IV, V and VI all have Compressors from Whipple
Kenne Bell:
--Makes aftermarket kits for most Modular Ford Engines.

The Eaton is referred to as a "Roots" supercharger and the most common compressors on ford engines are the M90 and the M112. Oddly enough, it's screws look much more like twins than the twin-screws.

This is where it gets tricky because they are all interconnected:
SRM liscensed twin screw compressors as early as 1951
SRM formed a sister company: Opcon Autorotor.
Opcon Autorotor parted ways with SRM.
SRM formed Lysholm.
Lysholm formed a partnership in the U.S. with Eaton.
Opcon bought Lysholm.

Kenne Bell uses Autorotor Compressors.
Autorotor is a subsidiary of OPCON, a swedish company.
OPCON bought out Lysholm in January of 2004.
Up until 2005, Whipple used Lysholm Compressors. Now, Whipple makes their own.

Kenne Bell and Whipple have been in competition with eachother since roughly 1991 however they both use a very similar design. Kenne Bell explains why it chose to use Autorotor compressors over Lysholm in the following article this page.
There was a backlog of Whipple orders and rumors that the company may be going out of business. It turns out that Whipple has since moved away from lysholm compressors and now manufacturers their own units in-house.
Here is a great link from Whipple's site on the history of the twin-screw: History of the Twin Screw.

Regarding Lysholm's future:
"The demand for our products on the US aftermarket remains strong and a new sales organization will enable us to meet the increasing demand and further develop the existing potential in the US automotive and Marine aftermarket. We will further develop our distribution channels and our support for these products in the US," says Martin Stenbäck, CEO of Lysholm.

Eaton/Roots:


Autorotor/Whipple/Lysholm Twin Screw (I believe the 4/5 lobe design is more common than the 3/6 pictured below)


It's important to note "Twin Screw" superchargers tend to be more thermally efficient.
Here is a link to a good site with detailed info on how these superchargers work (as well as centrifugal SCs):
http://auto.howstuffworks.com/supercharger.htm

Some Links:
Autorotor
Lysholm
Eaton
Allen Engineering Superchargers
Kenne Bell Superchargers
Whipple Superchargers (site was down when I wrote this)
Saleen Superchargers
Roush (Run a search for superchargers)

Tim37

wow lots of good infor this needs to be a sticky.

Fallstar01

I've made a few updates and corrections. Let me know if anyone else has any input that would be useful.

Birdieman4

Great info, Fallstar.
Folks, notice the helix style rotors on the screw diagram. They make for a much more efficient contact point, and thus less heat is generated.

Good stuff, Fallstar.

KnotBand

my only comment is about terminoligy.....the title says positive displacement and yet, you talk about rotary type compressors....

positive displacement usually refers to something of the piston type.....like your engine, or your shop compressor, or your home AC compressor......they rotary technology (screw and scroll type compressors) is more efficient, more reliable, and more versitile than positive displacement equipment and usually more expensive. Screw compressors are used a lot on large chillers for unloading and on large industrial air compressors for efficiency since compressed air is the most expensive utility...

just thought I would point that out....but as a disclaimer, I don't know anything about superchargers and this might be an industry standard term eventhough it would not be consistant with normal industrial terminology.

tt460

All good information, and you even help to explain the twisted history of the screw compressor (no pun intended), even though I still don't fully understand it.

I have three picks here with some points you made above:

1) The Ford GT's Supercharger *is* in fact assembled by Eaton. The rotating group might have components sourced from Opcon/Autorotor/Lysholm or maybe even Whipple, but the Ford GT supercharger was designed by Eaton engineers, tested by Eaton and manufactured by Eaton. Eaton licenses the screw compressor design and has the right to manufacture and sell them. Why doesn't Eaton sell more screws? Most OE manufacturers still choose the Eaton Roots design over the screw compressor due to cost, reliability, availability, NVH, and low power consumption at cruise due to the lack of internal compression.

2) The rotors of an Eaton are not twins. The image above is very misleading. Eaton superchargers in fact have a left and a right rotor that are mirror images of each other. I think if you'd have a tough time spinning the example of the Roots blower shown above.

3) The diagram referenced above is in fact of a "Roots" compressor, but not an Eaton Roots. Even so, it is incorrect for a plain old Roots. Lets imagine the rotors were correct and that you could actually spin the rotors in the direction shown above. With the rotors moving in the direction the arrows point, the inlet and outlet would be reversed (i.e. "fill side" on bottom, discharge on top). The air travels along the OUTSIDE of the case and then it is discharged as the rotors begin to mesh and the air reaches the discharge port.

What makes the compressor above not an Eaton? Eaton superchargers all have "axial" inlets similar to a screw as they draw air into one end and then discharge air out the top or bottom (depending on orientation).

As for KnotBand's comment: Roots and Screw compressors are both positive displacement compressors. Each revolution they take, they will move a fixed amount of air equal to their displacement (at least in a perfect world, since alot of other things come into play like inlet restriction, clearances, etc). A centrifugal compressor is not a positive displacement compressor since the volume of air it moves is not fixed and varies greatly with RPM.

VARifleman

This is incorrect as positive displacement means there is a certain amount of air displaced in a movement. In the case of a piston, it's the volume that is taken up by one piston stroke, thus moving or compressing that air. The roots and twin screw are positive displacement because they always move the same amount of air in one rotation, just like a piston moves a certain amount of air in a stroke.

itzztrick

Thanks for the info. Appreciate it.

jlauth

It has been a long time since i have put anything on this site, and for this i am sorry, but i have been very busy. On the other hand, good psost man. Great history on the SC’s that are commonly used on the terminator, but im gonna be honest In saying that roots type SC such as the Eaton M112, which can be found on 03-04 in often called a blower as opposed to a compressor. This is because the blowers force the air (at a high velocity) around the supercharger case or housing, thus compressing the air. A twin screw is considered a compressor because it compresses the air at in between the male and female supercharger blades, which were specifically designed to have the correct amount of mass air flow and PSI through the outlet area of the compressor. Both have are reffered to differently because of the diffrent compression process that occurs. NO it is wrong to correct him. Both an engine performing the perfect otto cycle, and the supercharger are indeed both positive displacement. Yes it is more common to refer to the rotary style pump (twin screw and roots superchargers) than the reciprocating pumps as positive displacement, but they are both indeed positive displacement pumps, and yes the superchargers are more efficient, more reliable, and more versitle than than most common air compressors, and even most gas motors (if you dont take into account the ignition of the A/F mixture), thus the price of these supercargers. Chillers often do indeed use screw compressors, which are still of positive displacement and yes i do agree that they are expensive, but the main power sorce of air and electric is coal.

reesmach1

kenne bell makes their own compressors on their big bore kits now.