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  • Writer's pictureKings Of Street Outlaws

Roots And Screw Superchargers In Drag Racing

Jim Howe is a well-known street racer and a prominent member of the Street Outlaws crew. As a master of supercharger technology, Jim has extensive knowledge of the different types of superchargers available for high-performance racing engines. In his video, we will explore the differences between three types of superchargers that Jim is particularly familiar with and know how Howe Motorsports stuff is ran versus the way that other people's cars are doing.


Roots Blower vs. Screw Blower

The roots blower and screw blower are both types of positive displacement superchargers, which means they compress air by trapping it in a small space and then moving it to a larger space. However, they differ in the way they move air through the supercharger.

A set of screw rotors on the left, roots on the right. Photo by PSI Superchargers


In essence, the aim of both roots and screw blowers is to increase engine power by delivering maximum air into the motor. However, the crucial difference between the two lies in their efficiency, which ultimately determines the blower that can produce more power.

The roots blower functions as an air pump with parts that touch inside, causing heat and friction. It can only spin up to 13,500-14,000 rpm before generating more heat than boost. Therefore, roots blowers are much less efficient and cannot move as much air as screw blowers.


On the other hand, the screw blower is more efficient and can be spun up to 24,000 to 26,000 rpm with more room for creating power. However, there are no cylinder heads available that can use the level of air produced by a screw blower. Therefore, screw blowers are the ideal option for generating maximum power because of their efficiency, requiring less horsepower to turn them.


Class rules also play a role in choosing the type of blower to use. The efficiency of screw blowers often comes with a significant weight penalty when used in a specific class, if permitted at all. Hence, roots blower cars can weigh up to 300 pounds less than screw-blown cars. The weight penalty of the screw blower might affect the choice of the blower based on what it would take to make it work at that weight.


Both roots and screw blowers are efficient ways of making significant power in any racing class. The choice of which blower to use depends on the combination, style of racing, and class rules. Each blower has its advantages and can push your racecar to new levels of speed and performance on any race weekend.

Photo by Howe Motorsports


How Jim Howe Uses Different Superchargers


Jim Howe has experimented with all three types of superchargers and has found that each has its own strengths and weaknesses. He uses a combination of roots and screw blowers to get the best of both worlds: the instant boost of the roots blower and the sustained power of the screw blower.

Photo by Howe Motorsports


In conclusion, there are many types of superchargers available for high-performance racing engines, and each has its own unique advantages and disadvantages. As a master of supercharger technology, Jim Howe understands the differences between roots, screw, and centrifugal superchargers and uses each type in the most effective way possible to stay ahead of the competition.

Video by Howe Motorsports


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