Fast Talk With Jeff Smith: Compressed Air Supercharging

There are very few ideas in the performance world that are new – and this next one isn’t new either! But the execution is definitely new and that’s what makes it so exciting. The idea is compressed air supercharging. The idea is as old as compressed air but the problem has always been how to manage the air properly. Mickey Thompson tried it back in 1971 on both a fuel dragster and a Funny Car but abandoned it when it was too difficult to manage.Jeff SmithEnter entrepreneur Dale Vaznaian and engineer Karl Staggemeir. If their names are not familiar – they should be. Dale was partnered with Mike Thermos and the two pioneered what became the biggest nitrous system company on the planet – Nitrous Oxide Systems or NOS. Karl went to work for them as an engineer and after Dale and Mike sold the company, Dale and Karl soon started work on what they thought would be an interesting new product. Little did they realize how difficult the idea would be to execute.

It has taken them a solid five years and more money than they want to admit spending to perfect this system – but it works. There’s not enough room in this short column to get into all the details. I’ll just hit the highlights and you can do some internet searching to find more information from a story I recently wrote for Hot Rod that gets into the mechanics of the system. The company Dale and Karl started is called Compressed Air Superchargers (CAS).

The big picture goes like this: Take a large, pressurized container that looks like a Scuba tank for Andre the Giant and hook it to a very sophisticated pressure regulator. Run a -20 AN line up to a series of electronic valves that are used to feed the pressurized air directly to the engine. Under boost pressure from the tank, the engine will run only on the air from the tank. For a typical drag strip pass, the large tank has enough compressed air to feed the engine for one full quarter-mile pass. Electronic regulation of the air reduces the tank pressure of 3,300 psi down to something more manageable like 10 psi.

So far, you’re probably thinking, “So what? I can do that with a simple supercharger – I don’t need all this high-tech stuff.” And you’d be correct –except for one critical aspect – inlet air temperature.

A typical supercharger compressing air to 10 psi will generally heat 70-degree F ambient air up to around 150 degrees F. When air is heated, it becomes less dense. That means that if we could somehow compress air, cool it and then stuff it in the engine – the engine would make more power. That’s also been done with intercoolers. But still the air is probably around 120 to 130 degrees F. Now let’s look at air exiting a tank where it is compressed to 3,300 psi. While the air is compressed to a ridiculously high pressure, it is allowed to cool back to ambient temperature.

The compressed air cylinders are hidden behind the engine. The large tube feeds the compressed air. On the right are the series of valves that manage the compressed air as it enters the engine. The system can manage the pressure so it can be ramped up from 1-2 psi up to max pressure – all commanded by a simple laptop program. The gray device sitting on the white boxes is the 12-volt power supply for the ECU (blue box). The power supply will not be needed when installed in a car.

The compressed air cylinders are hidden behind the engine. The large tube feeds the compressed air. On the right are the series of valves that manage the compressed air as it enters the engine. The system can manage the pressure so it can be ramped up from 1-2 psi up to max pressure – all commanded by a simple laptop program. The gray device sitting on the white boxes is the 12-volt power supply for the ECU (blue box). The power supply will not be needed when installed in a car.

Keep in mind that we have put quite a bit of energy into the air to compress it. The first rule of thermodynamics is that energy cannot be created or destroyed but merely converted from one form to another. So when we put energy into compressing air, some of the energy is converted to heat, but the majority of the energy is stored as pressure. When the air is released, the genie comes out of the bottle (the energy is released) very quickly and it is ridiculously cold.

Karl told me that the air exiting the bottle should be somewhere in area of -140 degrees F! It will pick up heat from the valves and hose materials in transit to the engine, but ultimately, the engine will see inlet air pressure of 10 psi at a temperature of roughly 0 degrees.

Let that one sink in for a minute. That means that the engine is ingesting much more dense air than from a supercharger. So we tested this idea on a 355c.i. Small Block Chevy at Westech Performance Group in California with Steve Brule at the controls of the dyno. The small block was using an Edelbrock EFI system that could handle boost pressure, so we limited the boost to the size of the injectors. After a couple of normally aspirated pulls, the engine made 423 HP. We then connected the compressed air supercharger system to the engine. It uses a flapper valve upstream of where the compressed air is inserted so that the pressure is not vented to the atmosphere.

With the system installed, we set the boost control at 10 psi max and then merely hit the button – just like a nitrous system. The engine responded much like a nitrous system and peak power jumped to 833 HP. This is nearly a 100-percent power increase over normally aspirated with only 10 psi of boost. With most superchargers you get about a 50-percent power increase with this same level of boost.

The best news was that engine appeared to not be overly stressed. The spark plugs looked like they had just run down to the corner grocery store – unfazed. We were using Rockett Racing Brand 114 octane race gasoline, but I think it’s possible to run this CAS system on lower octane numbers– much lower.

We learned all kinds of things from that test and I really want to go back up on the dyno to try a bunch of other ideas. From the photo the system appears to be a bit cumbersome – but I think once it’s in the car, the control mechanism is small enough to fit easily under the hood without being obtrusive. The guys are currently working on installing a CAS system on a ’68 Camaro so they can do some track testing to verify the system’s performance potential. One of the advantages is that the power can be pulsed to begin at a lower boost level and then the boost may be ramped up as the vehicle runs down the track.

This is cutting-edge stuff and as soon as Dale and Karl have something more, I will keep you up to date.

– Jeff Smith

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