Superchargers!

[BoostedFC]

Yes it's not a common practice on our Rotary rides, but there are the guys that do go this route. So for them & anyone else just interested in the idea here we go.

Making More Power - Four Possibilities with One Common Thread

When it comes to extracting more power from an engine, the common goal, simply stated, is to burn more air and fuel per time. There are essentially four ways to achieve this end.
1.) The first way to make more power, is to make the engine more efficient by tuning the air & fuel delivery, reducing intake & exh. restrictions, reducing rotating mass, enhancing spark energy, & tuning engine timing. This is the purpose of most aftermarket mods, like air filters, ignition programmers, exh. systems, etc. These mods are very popular because they provide added power, they look good, & they sound good. They can be done piece by piece, so your car can build with your budget. The problem with these kinds of mods is that performance gains are small are not noticed. This is because most engines today are tuned fairly well from the factory, & are not equipped with highly restrictive intake or exh. components, which would reduce fuel economy. In other words, if you're looking for more moderate power gains, you'll need to get to the heart of the engine where power is really made. Most of these mods essentially have one goal in mind - make the engine more efficient so it can burn more air & fuel in a given amount of time.
2.) You can also make more power by speeding up the engine, i.e. spinning it at a higher RPM. This technique is very effective in producing more horsepower while keeping the engine lightweight and small. If you look at some of the fastest race cars in the world, you will find them spinning at incredibly high RPMs. The only drawback is that to spin at such high RPMs requires very high quality (expensive) engine parts that can withstand the torture from the rapid rotation. Furthermore, the increased RPM substantially increases wear & tear on the engine resulting in decreased reliability and shorter engine life. Most street cars & trucks have a redline RPM of around 4000 to 7000 RPM. Spinning the engine faster than the redline RPM in street vehicles is risky without extensive engine modifications to support the higher rotational speeds. The goal with this option is also to burn more air & fuel per time.
3.) Another obvious way to make more power is to simply use a larger engine. Bigger engines burn more air and fuel, and hence, make more power per revolution. Of course, if it were that simple, we'd all be driving around with V-12s. You can fairly easily increase the size of the engine's displacement by boring the cylinders and running a larger piston, or by increasing the stroke of the crank, but you can only go so far before you've bored the entire cylinder away or your piston is slamming into the cylinder head. To go really big requires a bigger engine, probably with more cylinders. The drawbacks of a bigger engine include their increased size, increased weight, & reduced fuel efficiency. In addition, using a larger engine normally is not practical because it would require an entire engine replacement, which would be prohibitively expensive, & would require extensive mods to mount it to the vehicle. Again, though, the goal of this technique is to help the engine burn more air & fuel per time.
4.) The final way to make more power is to pack more air & fuel into the combustion chamber before igniting it. The end result is the same as using a larger engine. The problem with this technique is that it's not as simple as telling your engine to suck more air & fuel, it's restricted by atmospheric pressure. At sea level, atmospheric pressure is 14.7 psi, which is a measure of how densely packed our atmosphere is with air molecules. As elevation rises, air thins which robs power from the engine. Now imagine if you could trick mother nature by making atmospheric pressure 21psi. You'd be packing around 50% more air, which means you could burn 50% more fuel, meaning you'd be making approximately 50% more power. This is exactly what a supercharger does, it compresses air to pressures above atmospheric pressure (boost), thus packing more air into the engine. The goal of this technique is to burn more air & fuel per time. By using this technique, a small engine can act like a big engine. It is more efficient because it has less weight & rotating mass. In addition, because you can control when the compressor (supercharger) is sending compressed air (boost) to the engine, & when it is not, you can enjoy stock fuel efficiency when the supercharger is not sending boost to the engine (normally at half throttle or less).

In reality there are more than four ways to make more power, but these are the four most conventional ways. You can also use a more potent fuel source that has more potential energy. This is the idea behind Nitrous Oxide and other high-energy fuels, a topic beyond the scope of this article.
A Brief History of the Supercharger
You may be wondering, "Who first thought of compressing air before sending it to the combustion chamber?"

It seems that just before the turn of the century (1900 that is), a German engineer named Gottlieb Daimler (yes, of Daimler Benz, Daimler Chrysler...) obtained a patent for a pump to aid in the delivery of increased amounts of air and fuel to the cylinder, and to aid in the removal of exh. gasses. He didn't call it a "supercharger" in his patent application, but that's what he was describing - this was the birth of the automotive supercharger. But in order to get to the true beginnings, we have to look even further back in history.
Gottlieb's automotive supercharger design was modeled after a twin-rotor industrial "air-mover" invented and patented nearly 40 years earlier by Mr. Francis Roots back in 1860. This technology is the foundation of the roots type "blowers" still used today! Soon after the roots air movers (they were not called "compressors because they did not compress air, they only moved it) were used in industrial applications, a German engineer named Krigar invented an air pump that used twin rotating shafts that compressed air. This technology would go on years later to become the foundation of the Lysholm twin-screw compressor used in today's automotive applications.
Apparently our old friend Gottlieb didn't have much luck in the early stages with his new invention, but the idea inspired French engineer Lois Renault, who patented his own type of supercharger soon after the turn of the century. It wasn't long before superchargers started to show up on American race cars. Lee Chadwick is credited with being one of the first American racers to successfully use a centrifugal supercharger in competitive racing, starting in the Vanderbilt Cup in Long Island, New York in 1908.
Soon after superchargers took to the air as World War I military engineers looked for new ways to make more powerful airplanes. Because airplanes fly at such high altitudes, the internal combustion engines that worked great on the ground, suffered at altitude in the thinner air. Although the technology wasn't successfully used in combat before the war ended, it was clear that superchargers were well on their way to becoming a mainstream power adders.
Meanwhile, back in Germany, Mercedes was hard at work trying to make old Gottlieb's supercharger work. By 1921 they found success and released a glimpse of the first production supercharged vehicle using a roots type supercharger. Mercedes went on to manufacture several supercharged models with great success in the following years.
In the racing scene, supercharged cars were finding more & more success. By 1924, superchargers made their way to the Indy 500. Around the world, racers in Mercedes, Fiats, Bugattis, Alfa Romeos, Buicks, & MGs began using superchargers to help them to the victory circle. Mercedes found great success with their supercharged Grand Prix cars, while Harry Miller's supercharged Indy cars dominated at the Brickyard.

In the mid 1930's Robert Paxton McCulloch started McCulloch Engineering Company & began manufacturing superchargers as the first large US commercial supercharger manufacturer. They began developing superchargers for use on US passenger cars & hydroplane boats. This was the start of the supercharger industry in America as we know it today.
Robert Paxton McCulloch in the early days.
Then came World War II in 1939, & the Allied forces had an ace up their sleeve in the form of the supercharged Spitfire fighter planes & B-29 SuperFortress bomber. These supercharged planes seemed almost unaffected by the altitude to the delight of Allied pilots.
Supercharged WWII Spitfire.
After the war, superchargers took on a new life in the world of racing. Alfa Romeo & British Racing Motors used superchargers on their Grand Prix cars to the horror of the competition before they were eventually outlawed. At Indy, there was no such rule, & centrifugal superchargers howled their way to many victories.

By 1950, McCulloch had formed Paxton Engineering as its own entity, which took over the supercharger development & took on the task of creating an inexpensive supercharger fit for use by the general public. After $700,000 in research, and two years of testing, the VS57 supercharger was ready for the public in 1953. Initially it worked only on 1950-1953 Fords, but by 1954 kits were made for nearly every commercially available 6 and 8 cylinder engine.

The rest is history, as Paxton developed newer and better superchargers until they became a part of life, not only in the world of racing, but also in the street-legal aftermarket world. Today it's hard to keep track of all the supercharger brands & models, but that's the way we like it!