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Discussion Starter · #1 · (Edited)
I check out howstuffworks.com very frequently while I am at work. Our s/c is twin-screw right?

Howstuffworks "Twin-screw Superchargers"


OH...and btw, if ANYONE wants to know how a s/c works, read up on it here. VERY helpful! I kinda had an idea, but nothing beats simple explanations and detailed pics like the ones you find on this site. This site seems to end my confusion on a topic, rather than create it...
 

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Discussion Starter · #7 ·
Not to sound ignorant, but what the hell here goes. Don't they look similar on the outside? The picture on of the twinscrew looks very similar to the s/c's that ppl have under their hoods that are from comptech (which are supposedly roots)... How can a twin screw and a roots s/c look very similar on the outside, but yet have different internals?
 

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if you read the link i gave you.. it says

Screw type superchargers are derived from the Roots type concept but with vast improvements for street use. Although from the out side, screw type superchargers may look a lot like Roots type superchargers, on the inside you will find a twin-screw design that compresses air unlike Roots type superchargers which pump the air into the motor. Screw type superchargers have an axial-flow design that compresses the air as it moves between the screws to create positive pressure without creating the heat that Roots type superchargers can create. The Screw type supercharger's ability to produce a dramatic increase of power from idle and through out the rest of the power curve make them a great choice for heavy vehicles, towing or commercial use.
 

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Discussion Starter · #11 ·
(Just in case you all didn't come to this conclusion)

Twin Screw > Roots or Centrifugal

and are consequently more expensive.
That's not what the other link said!
It says that (if I remember correctly) that roots are what you use for big power, which kinda makes sense. The ZR1 didn't come out using the twin-screw...

EDIT: "Highest potential for gain" is what it said
 

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That's not what the other link said!
It says that (if I remember correctly) that roots are what you use for big power, which kinda makes sense. The ZR1 didn't come out using the twin-screw...

EDIT: "Highest potential for gain" is what it said
Sorry, when I say "better", I'm thinking for my own use (street, daily driving). Not necessarily the best for HIGH boost.

What I said about the price of the twin screw is true though... they're usually more expensive.
 

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Discussion Starter · #13 ·
They are more expensive because it's pretty intricate inside right? Those two screwed rods are spinning VERY quickly and very close to eachother. You don't want them to hit eachother, especially at 20000-40000 rpm...
 

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Yes, the internals of a twin-screw are more complex, plus there are far more companies selling roots style (harder to come by, market price driven). However, it has more to do with the design, R&D, parts of it that hikes the price up.
 

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I posted this on the Redshift thread, but it is applicable here. Note that the twin screw is for the Lysholm, while the Comptech and Jackson used a Roots style S/C. http://www.8thcivic.com/forums/forced-induction-nitrous/70417-redshift-sc-coming-soon-2.html

The Lysholm supercharger would be a definite upgrade over a basic Roots supercharger. As was mentioned, adiabatic efficiency is greatly improved as well as the ability to run higher boost levels.

Many people confuse the twin-screw supercharger because they look similar to a roots supercharger, especially inside an engine compartment. However, they differ in that as a twin-screw supercharger draws air, the design of the rotors actually compresses air before discharging it from the supercharger. Because the compressing of air is done inside the supercharger, the twin-screw supercharger produces less heat than a roots supercharger.

Upgrades that many would be familiar with are the Whipple supercharger and KenneBell, both of which are famous on Mustang Cobras that want enhanced performance. Mercedes and Saab both use Lysholm superchargers as well.

I found this interesting info on a site comparing a Roots to a Lysholm:

Each of these systems offers some advantage over the other. Each has its srtong points and it's weak points. Here they are:

Roots: OK, we are talking about the MODERN Roots supercharger. A lot of vendors of other types like to compare using efficiency numbers from ancient GMC blowers. The modern Roots supercharger has a few big advantages. First it's the only style that compresses the air outside the unit itself. This means that when its bypass valve is open (standard equipment on all Magnuson kits) it's basically shut off. This means that any adverse effects on fuel economy or emissions during normal driving are negligible. Second, below 10 pounds of boost its efficiency numbers (i.e. power required to drive the supercharger itself and the discharge air temperatures) are really tough to beat. Third is reliability. The Magnuson supercharger requires almost zero maintenance. It only needs an oil change once every 100,000 miles and that's it! It has it's own reservoir so it doesn't heat up the engine oil. Fourth and perhaps most important is power. The Roots type supercharger puts out a lot of power at ALL RPM. Right off idle an engine with a Roots supercharger will typically have nearly full boost and massive power. This power increase will be fairly constant throughout the RPM range.

Lysholm: The Lysholm unit is very comparable to the Roots in most ways. It provides full boost from low RPM. Above 10 pounds of boost it's more efficient then the Roots blower, meaning it has lower discharge temperatures and uses less power to drive it. From a pure horsepower standpoint, above 10 pounds of boost the Lysholm is superior. From an "I actually plan to drive this car on the street point of view" it's not quite as good. The Lysholm has a few weaknesses. First, most street supercharger kits run 8 pounds of boost or less so unless you are talking about a custom built motor with low compression pistons, or you are willing to burn racing fuel, the Lysholm's high boost advantages are lost. The second weakness is that it compresses air internally. That means that a bypass valve can not fully shut it off. The result is your engine burns extra fuel to drive the supercharger at all times, even if you don't need the power. This also means that the supercharger is heating things up all the time which can result in a heat soaked intercooler, totally defeating the lower discharge temps. The fact that it can't be shut off with a bypass valve is the main reason the Lysholm design is not the design of choice among major auto manufacturers. It's worth noting that some attempts at shutting it off with an electronic clutch have been made, none have been successful in aftermarket applications.

This as well from RedShift:

1. What type of supercharger does RedShift use? Answer: We are going to offer several options. We will be offering Eaton Roots blowers as well as Lysholm and possibly Autorotor twin-screw superchargers.

2. Which is better, the Roots or Twin-screw supercharger??? Answer: Roots and twin-screw superchargers are very similar in look at operation, but the twin-screw charger is more efficient at making boost above 8 psi (meaning it creates less heat for the same psi boost). Both roots and twin-screw chargers are positive displacement pumps (meaning they displace the same amount of air per revolution), but only the twin-screw compresses air as it moves through the charger. The roots charger only moves the air from inlet to outlet (without compressing it internally); so the air is compressed only in the intake manifold downstream of the roots charger.

Bottom line is that if a Civic Si is going to be kept fairly stock with lower boost levels, a Roots type is the way to go. If the motor is going to be built up internally and with an injector upgrade, then the Lysholm might be the best way to go. Either way, we enthusiasts have more options now to choose from, which is always a good thing.
 

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Discussion Starter · #17 ·
There really is no best, it depends on your application. Sometimes the price of the more expensive one isn't worth it if you'll be running a low amount of boost
Kinda going off of what you said. There is no best. If there was, there would be no point in making three different types, since the lesser two probably wouldn't sell much. However, once you know what you want, then and only then, is there a best!
 

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Kinda going off of what you said. There is no best. If there was, there would be no point in making three different types, since the lesser two probably wouldn't sell much. However, once you know what you want, then and only then, is there a best!

If you plan on keeping boost levels relatively low, go with the Roots like Comptech offers. If you plan on running above 8 pounds of boost, go with the Redshift Lysholm, which is a twin screw. Note the higher fuel consumption for the Lysholm however.
 

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Discussion Starter · #19 ·
If you plan on keeping boost levels relatively low, go with the Roots like Comptech offers. If you plan on running above 8 pounds of boost, go with the Redshift Lysholm, which is a twin screw. Note the higher fuel consumption for the Lysholm however.
This sounds totally backwards! Don't root s/c offer more poential than twin screw? That's how it's suppose to go...
 

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No the roots "lose breath" above about 8 psi and heat gets high above that for the Roots. The Twinscrew can maintain up to 20 psi without a problem.

Roots=blower
Twinscrew=compressor
 
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