The Mighty twin screw Supercharger:

BillyGman

BillyGman

New member
Recently, another board member sent me an e-mail asking me what the difference between the twin screw and the roots supercharger is. Fortunately I was able to give him an answer, but while providing an answer for him, it made me suspect that there might be some other board members here who aren't aware of what the differences are in the two designs so here the an explanation that I wrote to him and some pics too. Enjoy:



Both designs use two internal rotors to push the air into the intake manifold as they rotate in opposite directions. However the rotors that are used are shaped differently in each of the two designs. Those used in the roots design each have three lobes on them. The lobes of each of the two rotors mesh with eachother like the cogs of gears do. But they pull the air around the outside wall of the case. The twin screw design uses two rotors that are shaped like a big screw, and they pull the air in between the two rotors instead of around the side of the case like the ones on the roots design do.

The twin screw design offers more power with less heat. It offers a power curve with as much low RPM power as the roots design, and also as much high RPM power at the centrifugal. So it's suprerior to both the roots and the centrifugal designs in it's power delivery, and is equal to the centrigugal in it's efficiency.

Of the 5 pics below, from left to right, the first and the last are both of the roots design, while the rest are of the twin screw design.....
 
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Thanks, Billy-now I know the difference, too!:) I doubt we'll ever have a twin-screw available for our cars.:(
 
In addtion to the info above^ here below is an interesting pic of an engine with dual blowers!!!!
 
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Tallboy said:
Thanks, Billy-now I know the difference, too!:) I doubt we'll ever have a twin-screw available for our cars.:(
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I doubt it too. There just wasn't enough Marauders produced for some companies to justify the cost of development for the kit needed. I also suspect that there are a greater percentage of Marauder owners who desire to keep their car stock than there are Mustang and Cobra owners.
 
Mary-Kate & Ashley Olsen??? :D ;)

OOPS!...Sorry, I mis-read the thread's title!

I'm hoping that Kenne Bell or Whipple-charger come out with a Mach I kit, the entire kit should would work fine on a Marauder except for the air inlet-to-blower adaptor.
That piece would have to be CNC machined as a mirror image at an additional cost. (Like 'Effster' did with his Kenne Bell one of a kind)
 
Good post Billy. A kid at work asked me why the twin screw was better and all I could tell him was that power delivery was as efficient at both low and high RPMs.... Now I see some of the differences between it and the roots design. :)
 
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Joe Walsh said:
Mary-Kate & Ashley Olsen??? :D ;)

OOPS!...Sorry, I mis-read the thread's title!

I'm hoping that Kenne Bell or Whipple-charger come out with a Mach I kit, the entire kit should would work fine on a Marauder except for the air inlet-to-blower adaptor.
That piece would have to be CNC machined as a mirror image at an additional cost. (Like 'Effster' did with his Kenne Bell one of a kind)
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My latest MM&FF magazine, said Kenne Bell offered one for the Mach, but I yet to find it or even mention of it on their site.
 
Billy


Thanks for your time in posting such useful info. But I would like to add or differ in a couple of areas.

From what I’ve seen here on our dyno where we log boost and of course TQ and HP at the rear wheels…. I’ve found that the true roots type blowers, meaning at this time really only the Eaton’s like what’s on the 99-up Lightning, ’03-04 Cobra’s, our beloved Trilogy kits and a slew of others.
The Eaton’s tend to pull harder and sooner at the real low rpms and early mid-rang area. I’ve proven this to be very true. This is why for the most part the Eaton M-112 is pretty tough to out grow when matched to what I feel are 5.0L or smaller, non-super high revving motors.

I’ve learned that if your going to limit your self to lets say less then 9-10psi of boost on a 4.6L of some kind. The Eaton M-112 will out pull a compriable screw type right out of the gate and hold its own pretty good through the rev range. Yes the screw’s run a little cooler and will pull harder up top, especially if its pullied harder. But if they’re both making the same peak boost… The true roots/Eaton M-112 will do much better down low. Now on a bigger motors such as the 5.4L in the GT-40 or the up coming Shelby Cobra Mustang which is supposed to have also a 5.4L 32V, those have screw type blowers on them. They are also 50 cubic inches bigger too. A screw in this application will produce a very broad TQ curve at probably only 6-8psi of boost because of the cubes coupled to a blower that will come on harder up top and not make as much heat while doing it.

The screw types though over all are in my opining the best thing to happen to 4-stroke engines. I’ve learned that with screws on the popular 4.6L 2V’s in Mustangs that we can safely run 12-14psi on pump gas and get a outrages TQ curve starting right off idle. The beauty of the screws is sorta like a centrifugal, they don’t drop off boost with the higher revs. But they don’t gain as much boost as centrifugals either. Over all though the screw type are the best in my opining for some serious fun on the street and the track as well.

This is why I choose to install a Kenne Bell 2.2L screw type on my 04 Mach-1. Right from the get I decided no less then 18-19psi and use only 100 unleaded full time in this car. It has done what I want so far. With two cats, 3-chamber mufflers, stock gears, Stock torque converter, no weight reduction or any suspension changes, on 315 drag radials it went 10.89 @ 132-MPH last fall. Because of how much over all boost I make with this car, it does make a lot of boost right off idle. But when the screws are only set up for less then 10psi, I feel you get more of your moneys worth with an Eaton M-112 on a little 4.6L.

The dyno graph I’ve posted are a very typical couple of things I do with 03 Cobra’s. The 450 RWHP number is with exhaust and a 2.8” pulley that makes about 13.5psi of boost from the stock Eaton.
The 550 RWHP one is the same car only with the Whipple 2.3L screw type blower on it instead. As you can see they both have the same boost at the beginning and then of course the Screw jumps even higher and continues to climb a little and then pretty much levels off.
A centrifugal like a Vortech S-trim would have kept climbing even higher and higher depending on the combo etc… What I wanted to show here is that had the screw been pullied to make only about 12-13psi at peak like the Eaton, The screw would have been lower boost then the Eaton M-112 at the lower revs. This to some may not mean a lot with what can and cant happen with big or not so big TQ right off idle, but with a heavy car, or a car with a tight converter or just lugging around with a stick-shift and not having to down shift all the time to pass etc…. To some this can make a big difference.

You can’t see it in the graph, but the Whipple is making 16.5 – 17psi which is common place on the Cobras with 93 octane with not trouble, and the Eaton is making about 13.5 at peak. Plus I didn’t start the Whipple’s pull on the dyno quite as low as the Eaton. Which would have showed less boost then the Eaton way down low.

My self these days I like the feel of an 800 cubic inch big block effect that comes from an over boosted Eaton on a MM or a really over boosted KB screw type on my 32V Mach-1, which by the way KB makes a kit for now.


Thanks
 

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Lidio, thanks very much for all of that info. Very intersting!!!! The book where I drew most of that info from does mention that the biggest advantage of the twin screw over and above the roots type S/cer is specifically when high boost pressures are used, since the roots type S/Cer doesn't do as well with real high boost pressures as the twin screw does. Which ofcourse is exactly what you've stated also. Thanks for sharing what you've found while modding your Mustangs, as well as the many Marauders that you've worked on (including your own ofcourse).


I'm very much intrigued with the twin screw S/Cer concept, however, that isn't to say that I'm disappointed in the least with the Eaton M112 roots S/Cer that the Trilogy kit came with. my car performs spectacular now, and has for the past 14,000 hard miles that I've put on it since I installed the Trilogy/Eaton S/Cer. I still highly recommend it for the Marauder. BTW, I think that Jeff (aka "Effster") has done a magnificent job with his Marauder form what I've heard concerning that Kenne Belle twin screw S/Cer that he installed on it. And at the same time, I have great admiration for him simply because of his candid demeanor, and utmost sincerety when him and I were writing back and forth about his Marauder, and he said to me how much of a major hassle it was for him to get everything right with that S/Cer installation.

I'm paraphrasing what he said, but that is what he clearly indicated to me when he said that it took a lot of work, and much time to get everything right, and I replied by saying "Hey Jeff, I'm sure it was all worth it, right?" And he wrote back and said, "I'm not so sure" and that comment was coming from someone who is a mechanic and co-owner of a speed shop!!!

Boy O Boy, Thanks to Joe, I cannot get a certain image out of my mind now, every time I type the words "Twin Screw"....... what a sick guy!!!
 
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Tallboy said:
Thanks, Billy-now I know the difference, too!:) I doubt we'll ever have a twin-screw available for our cars.:(
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Ahem...

If you want a Twin Screw Charger, you can contact Effster.
He has one on his Blue 2003 Marauder...
 
RoyLPita said:
Effster has a home made custom twin screw setup.
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I would call it a "Custom Made" Twin Screw setup.

Home Made sounds as if it was bought with parts from Home Depot.
This was not.

We got to see his installation at out Long Island Meet earlier this month,
and it looks as good as any professional installation I've ever seen.
 
BillyGman said:
he said that it took a lot of work, and much time to get everything right, and I replied by saying "Hey Jeff, I'm sure it was all worth it, right?" And he wrote back and said, "I'm not so sure" and that comment was coming from someone who is a mechanic and co-owner of a speed shop!!!

!!
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But look at what Jeff said about that^
 
The main different between a Roots type supercharger and a Twinscrew is a Twin screw is a true compressure in the fact it actually compresses the air in the supercharger case NOT in the intake manifold as a Roots does.
If you could gauge the case s you would find positive pressure in a twin screw even when not bolted to an engine.
 
cyclone03 said:
The main different between a Roots type supercharger and a Twinscrew is a Twin screw is a true compressure in the fact it actually compresses the air in the supercharger case NOT in the intake manifold as a Roots does.
If you could gauge the case s you would find positive pressure in a twin screw even when not bolted to an engine.
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Very true^
 
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