Superchargers A-Z (Part 1 of 3)

In this series we’ll take a slightly more in depth look at the fundamentals of supercharging that were introduced in our “Supercharger Basics” article. This is part 1 of a 3-part series. After reading these three articles you should have a fairly strong understanding of what the supercharger does, what the advantages of each type of supercharger are, and how superchargers make so much damn power.

This article lays down the foundation of how superchargers came into being by taking a look at the fundamentals of creating more power, and looking back in history at where and how the technology originated.

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 and fuel delivery, reducing intake and exhaust restrictions, reducing rotating mass, enhancing spark energy, and tuning engine timing. This is the purpose of most aftermarket modifications, like air filters, ignition programmers, exhaust systems, etc. These modifications are very popular because they provide added power, they look good, and they sound good. Moreover, they can be done piece by piece, so your car can build with your budget. The problem with these kinds of modifications is that performance gains are small – often negligible and unnoticeable. This is because most engines today are tuned fairly well from the factory, and are not equipped with highly restrictive intake or exhaust 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 modifications essentially have one goal in mind – make the engine more efficient so it can burn more air and 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 (and expensive) engine parts that can withstand the torture from the rapid rotation. Furthermore, the increased RPM substantially increases wear and tear on the engine resulting in decreased reliability and shorter engine life. Most street cars and 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 and 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 lengthening 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 (duh!?), increased weight, and 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, and would require extensive modifications to mount it to the vehicle. Again, though, the goal of this technique is to (yep you guessed it) help the engine burn more air and fuel per time.

4.) The final way to make more power is to pack more air and 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 and 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, as you probably noticed on your last skiing / snowboarding trip, 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. You’ve probably already figured out that this is exactly what a supercharger does – it compresses air to pressures above atmospheric pressure (boost), thus packing more air into the engine. And you’ve probably also figured out that the goal of this technique is to burn more air and fuel per time. By utilizing this technique, a small engine can act like a big engine. It is more efficient because it has less weight and rotating mass. In addition, because you can control when the compressor (supercharger) is sending compressed air (boost) to the engine, and 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?” Don’t run to the library just yet. We’ll tell you!

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 exhaust 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 (from Indiana) 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 utilized twin rotating shafts that compressed. This technology would go on years later to become the foundation of the Lysholm twin-screw compressor used in today’s automotive applications.

One of Lee Chadwick’s early supercharged rides.

Soon thereafter 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 adding device.

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 utilizing 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 and more success. By 1924, superchargers made their way to the Indy 500. Around the world, racers in Mercedes, Fiats, Bugattis, Alfa Romeos, Buicks, and 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.

Robert Paxton McCulloch in the early days.

Supercharged WWII Spitfire.

By 1950, McCulloch had formed Paxton Engineering as its own entity, which took over the supercharger development and 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 and models, but that’s the way we like it!

Paxton’s first shop.

Paxton VS57 supercharger.