twin srew or radix....
Apr 4, 2005 | 01:51 PM
#1
twin srew or radix....
Ok I'm torn.... The radix is a complete deal.. but the twin screws are just tooo tempting for the off idle boost. Is there any one that has driven both that can tell me if there is much low end difference between the kenne bell/whipple and the radix
Apr 4, 2005 | 01:56 PM
#3
Originally Posted by PSM
Ok I'm torn.... The radix is a complete deal.. but the twin screws are just tooo tempting for the off idle boost. Is there any one that has driven both that can tell me if there is much low end difference between the kenne bell/whipple and the radix
Apr 4, 2005 | 01:59 PM
#4
Radix:
A common, but perhaps more correct, term for a Roots supercharger is "blower. One defining characteristic of a Roots is that charge air compression occurs outside the supercharger, in the space between it and the intake valves. In effect, it blows air into the intake manifold where it becomes compressed due to the system's pushing more air in than can flow out.
The Roots blower was patented in 1860 by two brothers, Philander and Francis Roots, as a ventilating device for blast furnaces, grain elevators and coal mines. In the last half of the 19th century they were quite common in those applications and that ancestry is key to understanding that a Roots is a device which moves air rather than compresses it.
In the early part of the 20th Century, engineers perfected supercharging in motorsports and aircraft applications using primarily centrifugal superchargers. In the '30s, Roots blowers gained acceptance in Grand Prix and Indianapolis racing and on some expensive, high-performance sports cars of the period. Starting in the late-'30s, General Motors began using large Roots blowers on the diesels it built for its GMC heavy-duty trucks, its marine customers and its Electromotive Division locomotives. In the 1950s, drag racers and Bonneville Salt Flats competitors adapted GMC blowers to racing engines. Today, Roots blowers are still quite common in motorsports, especially drag racing.
The Magnuson "Radix" supercharger in GM, Vortec truck engine trim. Magnuson makes both the intake manifold and the blower case. The drive and the guts of the blower are Eaton parts used in Eaton's model-M112 supercharger, the largest unit Eaton makes for O.E.s.
Later, the Roots idea transferred to the street high-performance aftermarket and the Eaton Corporation developed a small, compact Roots blower for original equipment use on some performance cars, luxury sedans and, yes, pick-up trucks. Buick, Pontiac, Ford, Lincoln, Jaguar and Mercedes Benz are just a few brands using the Eaton blower, the design of which is now in its fifth-generation.
These are the rotors from the fifth-generation Eaton supercharger. The frosty-looking, matte-black color is the APC with partially-abrades away during break-in leaving an enhanced lobe-to-lobe seal. The lobes mesh as they turn and that pulls the air through the supercharger.
There are some concerns with blowers and one is cost. A properly developed, aftermarket supercharger kit runs several thousand dollars. Add installation labor and you're past five large pretty quick. Because a supercharger increases both the engine's cylinder pressure and charge air temperature, two causes of detonation or "knock", blowers mandate use of at least 91-octane fuel which may increase operating cost. A "boosted" engine produces a higher volume of exhaust gases, so engines equipped with superchargers usually need a low-restriction exhaust system.
With aftermarket superchargers on computer-controlled engines, the "calibration" in the computer, software which tells the computer how to set the fuel curve, spark curve, emissions controls operation and a host of other operational parameters, can be a significant development issue. In fact, proper engine controls calibration of a aftermarket supercharger system requires almost as much work as developing the supercharger hardware, itself, so a key factor in the difference between a good aftermarket blower kit and a bad one is, often, calibration. Lastly, don't be surprised if there is a reduction in fuel economy. How much depends on how the engine is driven. If boosted operation is infrequent and the blower has a bypass (which we'll discuss momentarily), fuel mileage will be close to stock. If you're "on boost" regularly, expect a noticeable decrease in mileage.
Let's take a closer look at some features of the Magnuson Radix Supercharger as used on the THR Silverados. The word "Radix" is Latin for "root" or "origin," an appropriate name, indeed. Radix are based upon Eaton, fifth-generation, M112 superchargers but they're not simply "rebadged" Eatons. Magnuson uses many of Eaton's internal pieces but manufactures its own supercharger case, intake manifold, charge air cooler and drive system.
What actually moves the air through a Roots blower is a pair of contrarotating, tri-lobe rotors which mesh as they turn. The tighter the fit of the lobes, the more efficient the blower is, however, there must be some clearance or the rotors won't turn. If the clearance is too great, the supercharger is inefficient because of leakage past the lobe edges. If the clearance is too tight, there is a high level of resistance to rotation. To both tighten rotor clearance and reduce friction, one trick Eaton began using with its fifth-generation Roots is to coat each rotor with an abradable powder coating or (APC). During the break-in period, in the first few hundred miles of operation, a small portion of this coating abrades away, leaving the contact areas at the tips of the rotor lobes perfectly matched to each other and able to run extremely close. This is Magnuson's Radix case. At top left, just inside the blower inlet is the bypass valve butter fly. At lower right, on the side of the blower case if the vacuum motor that operates the valve.
Eaton rotors are twisted 60 degrees. Helical rotors, along with specially designed inlet and outlet port geometry in the blower case, help to reduce pressure variations resulting in a smooth discharge of air and a lower level of noise during operation. This arrangement, also, improves efficiency. With helical rotors, the supercharger can run at up to 14,000 rpm, making for a small blower for a given boost and air flow output. The Eaton's axial intake further reduces package size.
Another "secret of the Radix" its bypass valve. This small valve, between the the throttle body and the intake manifold, increases fuel economy and reduces parasitic power loss. The bypass is operated by a vacuum actuator and is normally closed. When manifold pressure is low (high vacuum typical of light throttle operation) the actuator opens the valve, allowing charge air to flow from the throttle body directly into the intake manifold, bypassing the blower and equalizing pressure in the system. The bypass valve open at low manifold pressure eliminates parasitic loss in a practical sense. Magnuson superchargers running with an open bypass consume only about one horsepower. When the supercharger begins to make boost, the bypass valve snaps closed, allowing pressure to build in the intake ports.
All Radix have a "charge air cooler" which some call an intercooler. During compression, charge air temperature rises. Because a temperature increase reduces air density, negating some of the effect of compression, and makes the engine more prone to detonation; there is an advantage in cooling the air after it exits the blower but before it goes into the cylinders. The Radix charge air cooler is built into the intake manifold.
A common, but perhaps more correct, term for a Roots supercharger is "blower. One defining characteristic of a Roots is that charge air compression occurs outside the supercharger, in the space between it and the intake valves. In effect, it blows air into the intake manifold where it becomes compressed due to the system's pushing more air in than can flow out.
The Roots blower was patented in 1860 by two brothers, Philander and Francis Roots, as a ventilating device for blast furnaces, grain elevators and coal mines. In the last half of the 19th century they were quite common in those applications and that ancestry is key to understanding that a Roots is a device which moves air rather than compresses it.
In the early part of the 20th Century, engineers perfected supercharging in motorsports and aircraft applications using primarily centrifugal superchargers. In the '30s, Roots blowers gained acceptance in Grand Prix and Indianapolis racing and on some expensive, high-performance sports cars of the period. Starting in the late-'30s, General Motors began using large Roots blowers on the diesels it built for its GMC heavy-duty trucks, its marine customers and its Electromotive Division locomotives. In the 1950s, drag racers and Bonneville Salt Flats competitors adapted GMC blowers to racing engines. Today, Roots blowers are still quite common in motorsports, especially drag racing.
The Magnuson "Radix" supercharger in GM, Vortec truck engine trim. Magnuson makes both the intake manifold and the blower case. The drive and the guts of the blower are Eaton parts used in Eaton's model-M112 supercharger, the largest unit Eaton makes for O.E.s.
Later, the Roots idea transferred to the street high-performance aftermarket and the Eaton Corporation developed a small, compact Roots blower for original equipment use on some performance cars, luxury sedans and, yes, pick-up trucks. Buick, Pontiac, Ford, Lincoln, Jaguar and Mercedes Benz are just a few brands using the Eaton blower, the design of which is now in its fifth-generation.
These are the rotors from the fifth-generation Eaton supercharger. The frosty-looking, matte-black color is the APC with partially-abrades away during break-in leaving an enhanced lobe-to-lobe seal. The lobes mesh as they turn and that pulls the air through the supercharger.
There are some concerns with blowers and one is cost. A properly developed, aftermarket supercharger kit runs several thousand dollars. Add installation labor and you're past five large pretty quick. Because a supercharger increases both the engine's cylinder pressure and charge air temperature, two causes of detonation or "knock", blowers mandate use of at least 91-octane fuel which may increase operating cost. A "boosted" engine produces a higher volume of exhaust gases, so engines equipped with superchargers usually need a low-restriction exhaust system.
With aftermarket superchargers on computer-controlled engines, the "calibration" in the computer, software which tells the computer how to set the fuel curve, spark curve, emissions controls operation and a host of other operational parameters, can be a significant development issue. In fact, proper engine controls calibration of a aftermarket supercharger system requires almost as much work as developing the supercharger hardware, itself, so a key factor in the difference between a good aftermarket blower kit and a bad one is, often, calibration. Lastly, don't be surprised if there is a reduction in fuel economy. How much depends on how the engine is driven. If boosted operation is infrequent and the blower has a bypass (which we'll discuss momentarily), fuel mileage will be close to stock. If you're "on boost" regularly, expect a noticeable decrease in mileage.
Let's take a closer look at some features of the Magnuson Radix Supercharger as used on the THR Silverados. The word "Radix" is Latin for "root" or "origin," an appropriate name, indeed. Radix are based upon Eaton, fifth-generation, M112 superchargers but they're not simply "rebadged" Eatons. Magnuson uses many of Eaton's internal pieces but manufactures its own supercharger case, intake manifold, charge air cooler and drive system.
What actually moves the air through a Roots blower is a pair of contrarotating, tri-lobe rotors which mesh as they turn. The tighter the fit of the lobes, the more efficient the blower is, however, there must be some clearance or the rotors won't turn. If the clearance is too great, the supercharger is inefficient because of leakage past the lobe edges. If the clearance is too tight, there is a high level of resistance to rotation. To both tighten rotor clearance and reduce friction, one trick Eaton began using with its fifth-generation Roots is to coat each rotor with an abradable powder coating or (APC). During the break-in period, in the first few hundred miles of operation, a small portion of this coating abrades away, leaving the contact areas at the tips of the rotor lobes perfectly matched to each other and able to run extremely close. This is Magnuson's Radix case. At top left, just inside the blower inlet is the bypass valve butter fly. At lower right, on the side of the blower case if the vacuum motor that operates the valve.
Eaton rotors are twisted 60 degrees. Helical rotors, along with specially designed inlet and outlet port geometry in the blower case, help to reduce pressure variations resulting in a smooth discharge of air and a lower level of noise during operation. This arrangement, also, improves efficiency. With helical rotors, the supercharger can run at up to 14,000 rpm, making for a small blower for a given boost and air flow output. The Eaton's axial intake further reduces package size.
Another "secret of the Radix" its bypass valve. This small valve, between the the throttle body and the intake manifold, increases fuel economy and reduces parasitic power loss. The bypass is operated by a vacuum actuator and is normally closed. When manifold pressure is low (high vacuum typical of light throttle operation) the actuator opens the valve, allowing charge air to flow from the throttle body directly into the intake manifold, bypassing the blower and equalizing pressure in the system. The bypass valve open at low manifold pressure eliminates parasitic loss in a practical sense. Magnuson superchargers running with an open bypass consume only about one horsepower. When the supercharger begins to make boost, the bypass valve snaps closed, allowing pressure to build in the intake ports.
All Radix have a "charge air cooler" which some call an intercooler. During compression, charge air temperature rises. Because a temperature increase reduces air density, negating some of the effect of compression, and makes the engine more prone to detonation; there is an advantage in cooling the air after it exits the blower but before it goes into the cylinders. The Radix charge air cooler is built into the intake manifold.
Apr 4, 2005 | 01:59 PM
#5
One more for Radix
The modified roots type is the best type of supercharger to use until the boost pressure exceeds 13 PSI. At that point the pressure in the manifold starts to exceed the pressure in the supercharger housing and it starts to backflow into the supercharger and decreases its output and the heat generated really goes up. Above 13 PSI the better supercharger would be the Lysholm type. It is said that the compression of the air occurs in the plenum after it leaves the supercharger in the modified roots type supercharger unlike the Lysholm where the air is compressed inside the blower and then decompresses as it leaves the blower and enters the plenum. The advantage with the modified roots type is that it has less parasitic drag on the engine when boost is not needed. The Eaton superchargers also use a bypass valve that equalizes the pressure on both sides of the impellers when the engine is operating in vacuum. This takes more load off the engine and reduces the heat generated in non-boost conditions. The Lysholm is still compressing air internally even during non-boost conditions and this generates heat and has more parasitic drag on the engine during non-boost even with a bypass valve. Mercedes Benz does use some Lysholm superchargers on their super cars and they employ a clutch to disengage the supercharger from the crank shaft during non-boost conditions to counter the negatives of the Lysholm superchargers.
Overall the modified roots type supercharger is the much better choice if you are staying under 13 PSI of boost. This is why most of the OEM producers choose the Eaton modified roots type superchargers for their production cars.
The modified roots type is the best type of supercharger to use until the boost pressure exceeds 13 PSI. At that point the pressure in the manifold starts to exceed the pressure in the supercharger housing and it starts to backflow into the supercharger and decreases its output and the heat generated really goes up. Above 13 PSI the better supercharger would be the Lysholm type. It is said that the compression of the air occurs in the plenum after it leaves the supercharger in the modified roots type supercharger unlike the Lysholm where the air is compressed inside the blower and then decompresses as it leaves the blower and enters the plenum. The advantage with the modified roots type is that it has less parasitic drag on the engine when boost is not needed. The Eaton superchargers also use a bypass valve that equalizes the pressure on both sides of the impellers when the engine is operating in vacuum. This takes more load off the engine and reduces the heat generated in non-boost conditions. The Lysholm is still compressing air internally even during non-boost conditions and this generates heat and has more parasitic drag on the engine during non-boost even with a bypass valve. Mercedes Benz does use some Lysholm superchargers on their super cars and they employ a clutch to disengage the supercharger from the crank shaft during non-boost conditions to counter the negatives of the Lysholm superchargers.
Overall the modified roots type supercharger is the much better choice if you are staying under 13 PSI of boost. This is why most of the OEM producers choose the Eaton modified roots type superchargers for their production cars.
Apr 4, 2005 | 02:01 PM
#6
OK, lets anylize this a bit. We always hear about the Radix/Roots supercharger's main weak point right? "Heat". Specifically, heat at higher boost levels. Now, what about the Twin Screws main weak point? "Off Boost Conditions". Specifically, The Twin Screw is still compressing air internally even during non-boost conditions and this generates heat and has more parasitic drag on the engine during non-boost even with a bypass valve. Now, thinking about this logically, do you really think when sitting at idle (i.e. off boost) that the Twin Screw supercharger is able to overcome its biggest disadvantage fast enough to build boost quicker than a modified roots/radix supercharger in its most ideal condition? Meaning, off idle, a modified roots, only has productive boost to build, while a Twin Screw, has to overcome its biggest drawback before producing productive boost (even though once it starts to build boost, it is more efficient).
Hence, the reason Mercedes Benz does use some Twin Screw (Lysholm) superchargers on their super cars and they employ a clutch to disengage the supercharger from the crank shaft during non-boost conditions to counter the negatives of the Lysholm superchargers.
Lastly, on daily driven vehicles, how often are we at an "Off Boost Condition"? I say, half of the time, like when we come to a stop light, idle, or have to slow down for traffic. Advantage, Radix!
Food for thought...why have roots blowers become "modified" by twisting the impeller lobes?
This is why the rotors are twisted:
Eaton rotors are twisted 60 degrees. Helical rotors, along with specially designed inlet and outlet port geometry in the blower case, help to reduce pressure variations resulting in a smooth discharge of air and a lower level of noise during operation. This arrangement, also, improves efficiency. With helical rotors, the supercharger can run at up to 14,000 rpm, making for a small blower for a given boost and air flow output.
They leak air
A roots based supercharger does not "leak air". It is a different design, that's all. It pushes air, not much else to say about that really. However, In essence, what Eaton has achieved, is to bring the adiabatic efficiency up from a low 50% to over 60%.
Where a roots supercharger suffers from reverse flow, or pulse, the Eaton has a 60° twist designed into the rotors to effectively reduce this problem. By introducing the opening lobe cavity at an angle, as well as the introduction of an extra lobe to increase the frequency of this event, less reverse flow is experienced.
Really? This is what came off of one of your sources. "The primary reason that blowers aren't optimized by their manufacturers is that the tooling necessary would push the cost into an area which would make the units prohibitive to the OE marketplace, which is "the" big consumer". I know this was taken a bit out of context as they were mainly describing why the housings and such of blowers are not hand finished. But the tooling needed to make a twin screw lobe is several more times the cost of a roots lobe.
BTW: If that were the case, then why is Eaton getting liscense to sell twin screw compressors instead of roots blowers? Why does the new Pherd GT use a twin screw compressor?
As for production vehicles, my thoughts are: there is no more reliable way to supercharge a vehicle than with a roots type blower, this is fact.
So reliability is my #1 reason
Cost is #2. Note: however, if the Twin Screw was mass produced at the level the Roots type are they would be cost effective as well.
With its low production cost and its improved efficiencies, the Eaton dominates the world's production, accounting for over 90% of the superchargers produced.
Lastly, I am not saying a Radix is more efficient, I am saying it produces the quickest off idle boost..........which.......IMO........for street vehicles is the most rewarding
Hence, the reason Mercedes Benz does use some Twin Screw (Lysholm) superchargers on their super cars and they employ a clutch to disengage the supercharger from the crank shaft during non-boost conditions to counter the negatives of the Lysholm superchargers.
Lastly, on daily driven vehicles, how often are we at an "Off Boost Condition"? I say, half of the time, like when we come to a stop light, idle, or have to slow down for traffic. Advantage, Radix!
Food for thought...why have roots blowers become "modified" by twisting the impeller lobes?
This is why the rotors are twisted:
Eaton rotors are twisted 60 degrees. Helical rotors, along with specially designed inlet and outlet port geometry in the blower case, help to reduce pressure variations resulting in a smooth discharge of air and a lower level of noise during operation. This arrangement, also, improves efficiency. With helical rotors, the supercharger can run at up to 14,000 rpm, making for a small blower for a given boost and air flow output.
They leak air
A roots based supercharger does not "leak air". It is a different design, that's all. It pushes air, not much else to say about that really. However, In essence, what Eaton has achieved, is to bring the adiabatic efficiency up from a low 50% to over 60%.
Where a roots supercharger suffers from reverse flow, or pulse, the Eaton has a 60° twist designed into the rotors to effectively reduce this problem. By introducing the opening lobe cavity at an angle, as well as the introduction of an extra lobe to increase the frequency of this event, less reverse flow is experienced.
Really? This is what came off of one of your sources. "The primary reason that blowers aren't optimized by their manufacturers is that the tooling necessary would push the cost into an area which would make the units prohibitive to the OE marketplace, which is "the" big consumer". I know this was taken a bit out of context as they were mainly describing why the housings and such of blowers are not hand finished. But the tooling needed to make a twin screw lobe is several more times the cost of a roots lobe.
BTW: If that were the case, then why is Eaton getting liscense to sell twin screw compressors instead of roots blowers? Why does the new Pherd GT use a twin screw compressor?
As for production vehicles, my thoughts are: there is no more reliable way to supercharge a vehicle than with a roots type blower, this is fact.
So reliability is my #1 reason
Cost is #2. Note: however, if the Twin Screw was mass produced at the level the Roots type are they would be cost effective as well.
With its low production cost and its improved efficiencies, the Eaton dominates the world's production, accounting for over 90% of the superchargers produced.
Lastly, I am not saying a Radix is more efficient, I am saying it produces the quickest off idle boost..........which.......IMO........for street vehicles is the most rewarding
Apr 4, 2005 | 02:07 PM
#7
If you want what I think is the best whipple setup out today retail look here:
https://ls1tech.com/forums/showthrea...hlight=whipple
https://ls1tech.com/forums/showthrea...hlight=whipple
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Apr 4, 2005 | 04:55 PM
#8
TECH Resident
Joined: Sep 2004
Posts: 941
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From: Ennis, Texas
The biggest set back on the Whipple and KB as already said is the lack of intercooler. However, if I you could get a very good deal on one of the twin screw chargers it would be worth getting. From what I have read, the non-intercooled blowers make little extra power in hot weather.
Apr 4, 2005 | 05:48 PM
#9
Originally Posted by PSM
Ok I'm torn.... The radix is a complete deal.. but the twin screws are just tooo tempting for the off idle boost. Is there any one that has driven both that can tell me if there is much low end difference between the kenne bell/whipple and the radix
A local guy (bigguy74inches) used to have a Whipple on his truck pushing 12psi on a 6.0. He went for a ride in mine and said his wouldn't have held a candle next to the Whipple'd 6.0. My truck has a 5.3 pushing 8psi at that time.
Apr 4, 2005 | 06:00 PM
#10
servey says... RADIX 
On a side not Flyer... how is the low end torque of the tiny 5.3 w/ the radix.... I'm coming from a 454 so I'm used to low end grunt... this truck stock is way faster than the 454 was, but you gotta really rev it up. Thats not something I'm used to
On a side not Flyer... how is the low end torque of the tiny 5.3 w/ the radix.... I'm coming from a 454 so I'm used to low end grunt... this truck stock is way faster than the 454 was, but you gotta really rev it up. Thats not something I'm used to