When it comes to making power, car builders are always looking for the next edge. Compressed Air Supercharging has been around since the 1960s, and allegedly, Mickey Thompson even tested it before it was quickly banned by the NHRA. It resurfaced around 2014 when legendary scribe Jeff Smith (when he was at Hot Rod) tested it. We even dug up this video of him talking about it. Hot Rod also tested “leaf blower supercharging” and other crazy contraptions to remove the “host engine” from the equation when powering the boost-maker.

As they say, what’s old is new again when we spotted CAS at the 2024 PRI Show and then again in this video. It is one of the latest ways to deliver instant horsepower, and it’s nothing like a traditional turbocharger or supercharger. This system feeds high-pressure air directly into the engine. It drastically simplifies boost when you no longer are dependent on the engine to drive the supercharger or turbocharger in any capacity (whether a crank, belt, or exhaust gas). It’s instant power that can be infinitely regulated to optimize for traction. This isn’t science fiction — it’s a straightforward, practical system built for serious performance. Let’s look at how it works.

How Does Compressed Air Supercharging Work?

At the heart of a compressed air supercharging system are the air bottles. These aren’t just regular tanks. They’re built from carbon fiber to handle extreme pressures of up to 3,300 psi. Each bottle weighs around 33 pounds when full, and holds 155 cubic feet of compressed air. Newer models are even larger, holding 200 cubic feet. Systems designed for 1,400-horsepower setups, like those used in drag racing trucks or muscle cars, often run two bottles to keep up with demand.

Here’s a size comparison between a standard 10-pound nitrous bottle and a 155 scf high-pressure air bottle.

The high-pressure compressed air is released from the bottle and passes through a regulator. This critical component steps down the pressure to around 100 psi, or sometimes slightly more. From there, the air passes through a second regulator, that’s adjustable. The beauty of the second regulator is that it gives you control over how much boost you want. Whether it’s 5 psi for a soft launch or 20 psi for maximum acceleration, the regulator ensures the engine sees the exact amount of boost pressure you set.

The air is moved through high-pressure airlines, which are far from ordinary hoses. They are made with aircraft-grade stainless steel fittings. These lines can handle up to 16,000 psi, ensuring no failures under extreme conditions. From the regulator, the air is fed through a standard stainless-braided hose measuring in at AN-20, or 1-1/4-inch in diameter. That line uses standard aluminum AN fittings.

The line from the bottle to the regulator is a special incredibly strong feed line. Post regulator, a more traditional stainless-braided AN line is used, although it’s a -20 size hose.

Once the air goes from the regulator, through the lockoff valve, it hits a Bosch drive-by-wire throttle body that regulates the boost curve of the engine through the run. Finally, the air reaches the ejector valve, positioned near the throttle body. This component ensures that the engine runs exclusively on compressed air during operation, blocking out any outside air, with a throttle-body-style butterfly. This allows the car to drive to the line and complete the burnout naturally aspirated, but switch to the compressed air as soon as the lights drop.

What are the Advantages of Compressed Air Supercharging?

Like nitrous oxide, when the compressed air is released to near atmospheric pressure, it gets incredibly cold.  As the air enters the engine, that cold charge is extremely dense. Actual intake air temperatures as low as -20 degrees Fahrenheit help maximize combustion with the extremely dense intake air charge and keep the engine cool, even during high-stress runs.

The key to the system is the ejector valve. Not only does it direct the compressed air to the engine, but it also closes off the system to outside air and allows the system to pressurize and run on the compressed air alone.

One of the standout advantages of compressed air supercharging is its cooling effect. Traditional turbos generate heat while spooling, but this system delivers ice-cold air without stressing other parts of the car, like the transmission. This means that a compressed air supercharged vehicle is almost burndown-proof at the Christmas tree.  It could also mean less wear and tear throughout the full season of racing. And it’s atmosphere in a bottle – less prone to being affected by weather conditions.

Another advantage is that there is no parasitic loss, like a supercharger, to drive it. And it avoids the massive fabrication time and know-how required for a proper turbo system.

What are the Disadvantages of Compressed Air Supercharging?

Compressed air supercharging is a novel idea, redefining what’s possible in high-performance engines. But it’s far from a proven technology. There is a real learning curve when it comes to tuning. Over the last 10 years, there have been a lot of destroyed engines, which is part of the process.

The system is also very heavy, quite large (will it even fit in a lot of vehicles?), and not legal in most forms of sanctioned racing. In drag racing and land speed racing, though, it’s been a hot topic over the years because of the potential it presents.

Conclusion

Comparatively speaking, conventional superchargers and turbo kits are more reliable and usable for the average racer (t0 say nothing of the streetcar market). Not only can your average shop could be bolt one up and tune it without causing a nuclear disaster, but even the OEMs are producing 1,000hp engines that pass emissions.

Compressed Air Supercharging still has a long ways to go, but it is exciting seeing anyone continue to push the envelope with technology.