Roots Blowers

Roots BlowersAfter writing about forced induction, I thought I would go into more detail on each of them. I am going to start with the traditional supercharger, Roots blowers. As I mentioned before, Roots blowers are named better as a blower than a supercharger since it doesn’t compress the air in the supercharger, it just pushes air into the engine faster than the engine can use it.
The Roots blower was originally intended as a fan to move fresh air into mines. The first use in engines that I am aware of is in the two stroke Detroit Diesel engines that first came out in the 1930’s. With the way the two stroke diesel works, the blower was needed just for the engine to run, and not to add power. What does this have to do with hot rods? The two stroke diesels are were the first hot rodders to use blowers got them from. The original two stroke Detroit Diesel engines were the 71 series. The 71 series is named that because each cylinder has a displacement of 71 cubic inches. So the 6-71 engine were the 6-71 blower comes from is a six cylinder with a total displacement of 426 cubic inches. Likewise the 8-71 blower came from an 8 cylinder engine. The larger the engine, the larger the blower. For most street engines, a 6-71 is a good choice, unless it is a larger higher horsepower engine, then an 8-71 could also be a choice.
The modern 6-71 and 8-71 blowers are capable of moving more air than the original ones, due to improvements to the design. Improvements to manufacturing have made it so the rotor lobes can be closer together, and adding teflon strips to the ends of the rotors allow a tighter seal for improved efficiency. What hasn’t changed is the look and sound. While a screw type supercharger, turbocharger or a centrifugal superchager can be hidden under a hood with maybe a hood scoop, I am not aware of any vehicle where a Roots blower would fit under a stock hood. But Roots blowers hidden, that would be a cool sleeper, at least in looks. ¬†However, I like the look of a blower sticking up through the hood. The other thing is the sound Roots blowers make. I love the whine.

While yes, they are not subtle, some times that is the effect you are going for.
While they lack subtlety, they do have advantages. One is the lack of subtlety. Another is the fact that since they are always pushing more air than the engine needs, there is no waiting for boost. That means they put out more low end power than most turbocharger or centrifugal supercharger. When driving on the street, that means they can be more fun, since even taking off from a stop sign or just cruising around you have power available. That can mean a more enjoyable car to drive on the street, and a more drivable car.
I will say that I love the look of them on hot rods, but I am not sure about the look of them sticking through the hood of a muscle car. I love the look of the engine, but to me it looks better on an old hot rod. But that is my opinion, and I have seen muscle cars with Roots blowers that look good. And it makes for an awesome engine regardless.


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