Any experts out here that can settle the debate as to the pros and cons of roots vs centrifugal type compressors ?? I am really looking to learn if a roots is equal to the cetrifugal at a power for power gain and/or on a pound for pound scale ??
Hoping for less oppinions here and more experienced replies. No pun :)

 

I'm not expert but I owned several SC cars.

The Roots make great low end power but runs out at the top end. Heat can also be an issue but a well designed one would still be good.

A Centrifugal Blower makes great power further up in the RPM's and is only limited to how fast the thing can spin. Heat can still be an issue.

My Saleen with a Vortech was a little soft in the lower RPMs because of the compression ratio. At about 3.5 grand the car would hammer you into the seat (Miss that 500HP car). The smaller Saleens with the Roots blower felt very strong down low and made great light to light driving.

If I do the Corvette I would take a long look at the new Roots blower because most of my driving around town not down the 1/4 mile.

 

Roots blowers work very well until you go above 10# of boost. Then they produce A LOT of heat.

On a low boost application like ours, it would be just fine. :D

 

My knowledge is that a Roots type is positive displacement, which means it outputs as much air as it takes in. It is mounted directly to the intake manifold thus is highly affected by engine heat. A centrifugal type creates a DP across it from intake to exhaust sides which isn't as effiecient as far as moving air goes, and is mounted on the side of the engine and not as greatly affected by engine heat.


Here is an excerpt from http://www.howstuffworks.com

The most common type of supercharger, the Roots-type blower, compresses the air in the intake manifold. Common examples include the B&M and Weiand supercharers. These systems work great, but the disadvantge is that the air discharge temperature is rather high, meaning that although the pressure inside the intake manifold is increased, the air is hotter and can't hold as many oxygen molecules.

The other type of superchargers are real compressors. They compress the air inside the supercharger unit. Common examples are Paxton, Vortech, and Whipple. These systems usually have lower air discharge temperatures compared to Roots-type superchargers. Superchargers are driven by a belt, which uses engine power to run, and although a supercharger may use about 10-20 percent of your engine's power to run, the good news is that the overall engine output is up to 50 percent greater.

There are a few things you should know when you looking for a supercharging system. Air dischrage temperature is a measure of the air as it exits the blower. A higher tempertaure means a lower density of oxygen and fuel. Boost is the amount of pressure created by the supercharger. Put these two together and you get the supercharger's efficiency. Don't be fooled by high boost levels, they do not necessarilly mean more power. In order to reach higher boost levels, the blower must turn at higher speed, and thus more heat is created. However, there is an answer to heat. Intercoolers can lower the intake temperature. But even intercoolers have a disadvantage: they reduces the amount of boost pressure.

Most supercharger systems produce a mild boost of 5-7 lbs, which can be handled easily by a relatively stock engine. If you have a little technical knowledge, you can perform the installation in your driveway in about a day. Before you add your supercharger, you will need to upgrade your exhaust with a minimum of a cat-back system. A set of headers and a high-flow catalytic converter are also reccomended. You should also use a low-temperature thermostat (160 degree), and an ignition system that will retard timing as the boost pressure rises. If you're not already using high octane gas, you'll need to use at least 92 octane with your new supercharger system. Additional items such as high-flow fuel pumps and computer upgrades may also be necessary, depending upon which supercharger you use.

If you really want the power, advanced systems can produce 25 lbs of boost pressure or more. But these systems expensive and require a specially designed engine that can handle a high compression ratio. For a simple boost, though, a mild system with 5-7 lbs. of boost should a lot to wake up your engine. Best of all, most superchargers are legal in most states, and some systems are legal in all 50 states.

 

I'd go with the roots :jester

 

There's pros and cons for each, all I know is that I want one.

I'm saving my pennies! :yesnod:

 

Okay.... this is what I am looking for :yesnod:
So, when you say power runs out at the top end, are you saying 5k or more like 6k ??
I too am looking for a pocket rocket for daily driving and not so much interested in a screaming 1/4 mile only car. More importantly, I think the dependability and durability of the roots may be higher. Have you ever seen one of the big three offer a centrifugal type as a RPO :nono:
Maybe the serious HP 600+ should stick to the centrifugal and those that what longevity with the overall setup can look closer at the roots ?? I am most interested in hearing more on this matter !!!

 

All I can say is that I want either one, and I want someone else to pay for it!

 

Roots is much less efficient and creates more heat than a centrifugal blower.
The roots compresses the air to such and extent that it becomes much much hotter than the centrifugal (adiabatic efficiency). That is why over 8 or so psi you would really have to have an intercooler on a roots, it just beats up the air too much.
The centrifugal blower also has very few moving parts that can go wrong. THe roots "screws" are under much greater pressure. THe roots also has much more of a drag on the engine. Takes a good amount of hp to turn it.
You get alot of HP from that relativiely small blower. Wheras the roots is usually fairly large and intrusive.
The sentrifugal blower is much like a turbo, but the cent. is run off the crank/engine rpm and not hte exhaust gas like the turbo.

:cheers:

 

actually, in the 60's some of the Shelby Mustang came with a Paxton Supercharger :)

 

I ran the roots supercharged Rx7 up to 8000 rpm at 13 psi of boost. I forget the drive ratio, but the supercharger was overdriven, turning something like 12000 rpm. I built my own water injection system and got phenomenal results. Whether it "beats" the air or not depends on the supercharger design, displacement, and drive ratio.

There is a good (old) book called "Street Supercharging", that fully explains adiabatic efficiency, volumetric efficiency, and various types of supercharging. It also shows the calculations to predict the temperature increase. Anyone thinking of supercharging NEEDS to read this before purchasing.

 

Imxz28,

I have a Weiand 6-71 Blower on my Chevy small block(350) in my Pro Street Chevelle. there were a couple of reasons for choosing it.

1) Tunability of the motors. You have the choice with a roots Blower like the Weiand to tune before the Combustion process. A Centrifigual is after the fact using the exhaust gases

2) Roots blowers gave me the option of underdriven vs overdriven performance. I am unsure if the centri. allows this option.

3) Horsepower....Roots blower gave me the feeling of slamming me in the seat grabbing for the steering wheel and screaming my head off in joy right from the time I hit the gas... :smash: :smash: :smash:

 

Okay, so here is a similar question
I had a Vortech S-Trim on my 95 LT-1. It made 1# at 2000 and was relatively linear. Making about 7# at 6000. Even with only 1# basically from right off idle, it was a significant improvement in power. In the lower gears, it almost didn't matter because wheel spin was a big concern. I haven't got any experience with a roots and keep hearing how much more responsive they are. Can anybody explain how and to what degree a roots makes quicker power. And because I am assuming it makes that power quicker because it makes boost quicker :confused: Anyone with a roots have a boost gauge on the manifold ? How much boost at given RPM ?
Just a huntch... could it be as simple that the compressor is closer to the combustion chamber, therefore quicker response.

 

PoBoy Racer...great stuff!!! :cheers:

 

I have been reading these supercharger posts with great interest and I see alot of what can be looked at as negative opinions about roots/eaton superchargers. All three options, roots/centrifugal/turbo, have pros and cons but the efficiency/heat argument is mute. The reason being is technology has made such great advances in wheel and blade design that for specific vehicle applications, each is a great choice. Of course you have to know what you plan to do with the car and what your looking for.

So basically im just pointing out that when you choose a power adder and its sized right for the application you dont need to worry about efficiency or heat.

8. How does a Magna Charger supercharger compare with a centrifugal supercharger?

A centrifugal supercharger is essentially a belt driven turbocharger. Centrifugal superchargers systems frequently have less horsepower and torque than the naturally aspirated version of the same engine at lower rpm’s. There is a narrow rpm band where a centrifugal superchargers perform well but this makes them “peaky”. The peak horsepower from this narrow band is what centrifugal manufacturers advertise but most experienced people say that the true measure of a supercharger is performance at all engine rpm’s. Magna Charger’s roots hybrid positive displacement superchargers deliver additional horsepower and torque right off idle and maintain horsepower and torque gains through all engine speeds. With the standard integrated bypass system Magna Chargers are less parasitic than centrifugal.

9. I've heard roots superchargers are not efficient, how is the Magna Charger different?

Traditional roots blower design is old engineering, and admittedly is not very efficient, but engines designs from that era were not very efficient either. As engines have improved over the years so has roots supercharger design. The Magna Charger/Eaton supercharger is a hybrid-roots blower pump, with substantial design improvements. The rotors have a unique involute lobe shape and are engineered to a specific L:D ratio. Each rotor has been twisted 60 degrees to form a helix. The two counter rotating rotors have three lobes, which intermesh during operation. These twisted rotors, along with specially designed inlet and outlet port geometry, seal timing, and axial air flow help to reduce pressure variations resulting in a smooth discharge of air and a low level of noise during operation. This arrangement significantly improves efficiency over traditional roots superchargers and reaches a volumetric efficiency near 98%. Magna Charger applications have an adiabatic efficiency that stays above the 50% mark over the full operating range of the engine, from 2000 to 6000 rpm.

:cheers:

 

23 years later.....

When I think quality roots style blowers I definitely think India. Where do I send my money?

 

 

 

Roots chargers are the best if using a modern version like the Magna or Eaton. This is why OE mfgs like using them. They are more efficient and today are well designed. Most include intercoolers today. In the past the old GMC were not the best but they have come a long way.

You just can’t easily bolt the Roots on unless it was designed for the vehicle.

The centrifugal is good as a bolt on as it fits most applications with no hood mods. It is not always the most efficient. Also some use engine oil so if you blow an engine you wipe the supercharger too.

We sell both at work and each has its own deal.

I have had 3 Eaton chargers and they work great. Low maintenance and great durability. All were designed for the vehicle.

 

2002