Drag racers are ditching superchargers for scuba-style tanks and compressed air

Posted by PaulHoule 4/3/2025

Drag racers are ditching superchargers for scuba-style tanks and compressed air(www.thedrive.com)

57 points | 93 comments

Aurornis 4/7/2025|

This article gets the concept slightly wrong.The compressed air becomes very cold air when it expands rapidly in the intake.

Colder air is more dense and therefore carries more oxygen. More oxygen allows more fuel, which allows more power.

Here's a better explanation in a single paragraph on the company's website:

> The end result of these expansion processes is that the charge air temperature entering an engine is dramatically lower than can be achieved with conventional MAP increasing technologies (supercharging and/or turbocharging with after-cooling). Hence very high charge densities can be attained at relatively low MAP levels.

The goal is to increase the amount of air going into the engine by making it very cold and dense, not by pressurizing it like a supercharger. Low MAP means low manifold absolute pressure. In other words, it's not boost like a turbo or supercharger.

EDIT: It looks like the website is also unclear. There is some mention of a secondary valve shutting off the intake valve to prevent air leaking out from the air filter.

Their website is strangely unclear. This isn't mentioned in the "Theory of Operation" section but does get mentioned later as an "isolation valve"

See here: https://casupercharging.com/tech/#system-overview

hnuser123456 4/7/2025||

Some cars have a system to spray water into the intake manifold to cool the air and increase power, this seems like the next step up from that.

lttlrck 4/9/2025|||

WWII era planes such as the Bf109 injected water and methanol into the supercharger to allow higher boost, side effect of that was charge cooling (and engine cooling).

A very cool aircraft.

RandomBacon 4/8/2025||||

My understanding is that the water is mixed with the fuel to help atomize the fuel as it's being sprayed out of the injector. If the fuel is atomized, it burns all at once which increases efficiency. I doubt a little bit of water is going to cool any meaningful amount of air.

genewitch 4/8/2025|||

In to the cylinders! Water injection.

maximilianburke 4/7/2025|||

It is boost pressure in the sense that the air going into the intake manifold is above ambient pressure. It isn't like nitrous where air still comes in the intake, with compressed air systems there is a valve that's closed to prevent the engine from ingesting ambient air, it runs entirely on the compressed air.

exabrial 4/7/2025|||

It says they're boosting to 10psi, in addition to the colder intake charge

Aurornis 4/7/2025||

I know what the article says, but the author seems to misunderstand how the system works.

The systems has regulators that step the air pressure down from thousands of PSI in the tank to a much smaller, regulated number at the nozzle that gets sprayed into the intake.

From the source company that sells the system:

> The very low temperature medium pressure air stream is then throttle one more time in the Electronic Pressure Regulator before being discharged into the engine air intake tract. The throttling effect that occurs here is small compared to that which occurs at the Mechanical Pressure regulator but, similar in nature.

The tuner can adjust the pressure that is being discharged into the intake tract, but that's not equivalent to the pressure in the manifold.

The system works by having the air expand rapidly in the intake, causing a rapid cooling effect.

The company describes it better on their own site: https://casupercharging.com/tech/#system-overview

EDIT: There is some mention of an "isolation valve" but not within the "Theory of Operation" section of the company's own description: https://casupercharging.com/tech/#system-overview

So there might be some scenario where the system shuts off the intake valve, too, but it's weirdly unclear from their own system description.

mjan22640 4/8/2025|||

The 10psi is still essential, saying 'it's not boost like a turbo or supercharger' is not entirely correct.

aspenmayer 4/8/2025||

I guess in some ways that matter they are different. I’m not super familiar with turbo/superchargers, but aren’t they driven by belts in the engine or linkages? I would think that turbo lag shouldn’t happen with a compressed air system, for example.

But to your point, I agree. Once the boost is achieved, the effects of the boost occur, because they aren’t really related to the source of the boost or how it is implemented. However, systems that use the engine for power like turbos may lose efficiency compared to compressed gas at the same boost level, depending on how much the gas system weighs compared to your turbo. It’s an interesting idea, especially for drag racing.

mjan22640 4/8/2025||

I guess the cooling alone cannot reach the density (and oxygen amount) necessary for the designed power output.

Yes, they put in the energy to compress the air 'offline' and then have that free to propel the vehicle. The cooling of the charge also improves the efficiency, the useful energy output is proportional to the temperature difference before and after the combustion.

A high capacity intercooler would be an interesting experiment also in utility vehicles.

maximilianburke 4/7/2025||||

The air can't go out the filter because a valve prevents air from going back through the filter.

thatcat 4/8/2025|||

Probably just a check valve for one way intake when from filter

johnatwork 4/7/2025||

I worked at a speed shop in my youth and at the time I was into Paintball so I had an idea.

We tried something similar to good effect, but we unfortunately had no good knowledge on how to refine it. It's hard to just shoot compressed air into the manifold and not have it blow back out of the intake. Either way we figured out a way to increase the volumetric efficiency as well as gains from running cool dense air. We were very close to pre-spinning the existing turbo/super setups and experimented with that as well. We gave up because Nitrous oxide at the time was much easier to work with and popular, and the tanks we had to experiment with was tiny compared to the large scuba tanks.

We also tried using compressed CO2 bottles to spray towards the intercooler to cool that down considerably, that worked decently as well, but no good data to support.

arprocter 4/7/2025|

Volvo came up with a way of spooling the turbo by injecting compressed air into the exhaust manifold

https://www.carmagazine.co.uk/car-news/tech/volvos-turbo-lag...

munchbunny 4/7/2025||

Reminds me of this piece of motorsports history: https://fordauthority.com/2017/12/how-ford-cheated-the-rules...

Take, for instance, Ford’s car from the 2003 FIA World Rally Championship. Through a knowledgeable automotive tuner and journalist named Stav from the UK (Facebook page), we learned that the 2003 Ford Focus RS WRC used an ingenious, mostly-hidden system to store excess pressurized air from the turbocharger in a titanium tank until it could be advantageously crammed into the engine on straight portions of the course, elevating power beyond what would otherwise have been possible.

magicalhippo 4/7/2025||

What blew me away was that the high-end engines[1] turn just a few hundred RPM during a race, which to me seemed ridiculous when you see wall of flames from the headers when they release the car at the line.

Also how they use aluminum for the connecting rods instead of stronger and stiffer metals like titanium, as they can then act as shock absorbers protecting the crankshaft bearings.

Lots of interesting tech to eek out performance and lifetime.

I've been enjoying watching Steve Morris's YouTube channel[2], he shares a lot of such information. He's mainly making drag and drive engines, which has the additional constraint of having to survive thousands of miles of regular roads between races.

I've also enjoyed Brian Lohnes channel[3] for interesting historical accounts from the early days.

[1]: https://en.wikipedia.org/wiki/Top_Fuel#Performance

[2]: https://www.youtube.com/@stevemorrisracing/videos

[3]: https://www.youtube.com/@brianlohnes3079/videos

hnuser123456 4/7/2025||

From your first link, they turn at around 3800 RPM, but the race only lasts a few seconds so they only complete a few hundred revolutions:

"This calculation assumes an average racing engine speed of roughly 3,800 revolutions per minute over a period of 3.8 seconds."

magicalhippo 4/7/2025||

Yeah, obviously they don't use a CVT so the RPMs are anything but the same throughout the race.

I don't know the details of Top Fuel and such, but Steve with his SMX[1] wagon[2] keeps his car at 2000 RPM at the lights, so seems reasonable to assume Top Fuel is around there too.

On the top end the Top Fuel cars are limited to just over 8000 RPM[3], with the red line at 8500 RPM.

So an average of 3800 RPM seems reasonable.

As a cross check, given that Top Fuel cars are single-speed[4], I guess one could calculate the same using the diameter of the wheels, keeping in mind that the tire expands a lot compared to its size at rest.

[1]: https://www.enginebuildermag.com/2024/12/4000-hp-twin-turbo-...

[2]: https://www.youtube.com/watch?v=LnrZdrp77Cs

[3]: https://www.enginebuildermag.com/2023/03/top-fuel-and-funny-...

mjan22640 4/8/2025||

> Also how they use aluminum for the connecting rods instead of stronger and stiffer metals like titanium

The 7000 aluminium alloys are similar to titanium in strenght/weight

magicalhippo 4/8/2025||

Yes but they have lower Young's modulus[1] so compress more under the same force. Thus acting as a shock absorber to reduce peak loads on the rod bearings.

Again no expert but from what I can see, high-end aluminum rods can use 7075 aluminum[2], which has a Young's modulus of about 72 GPa, while titanium has a modulus of about 105 and up[3][4], depending on grade.

At least that's my understanding.

[1]: https://en.wikipedia.org/wiki/Young%27s_modulus

[2]: https://www.enginebuildermag.com/2017/03/racing-rods-builder...

[3]: https://titanium.com/alloys/titanium-and-titanium-alloys/gra...

[4]: https://titanium.com/alloys/titanium-and-titanium-alloys/ti-...

mjan22640 4/8/2025||

An aluminium part with 105/72 cross section of the titanium will have the same modulus and incidentally the same weight.

Aluminium is also significantly cheaper, and easier to machine.

Titanium (or high strength steel, which is the strongest both per area and per weight and also the most expensive and difficult to machine) would be used where the volume of the part would be a concern.

magicalhippo 4/8/2025||

Perhaps I misremembered. Seems difficult to find some written sources on this.

In my quest I stumbled upon this[1] article where they discuss composite connecting rods for Fop Fuel dragsters:

Designed for Top Fuel engines, this connecting rod is half the weight of a conventional aluminum rod, yet is projected by company engineers to last an entire season instead of just 12 to 15 races.

Seems they're still at it, perhaps it'll be the next thing?

[1]: https://www.performanceracing.com/magazine/featured/08-01-20...

linsomniac 4/7/2025||

Some facts about top fuel dragsters: the supercharger uses around a thousand horsepower to run, but that's ok because the motor puts out over 10x that. It uses around 15 gallons of fuel for a single quarter mile run, but that also includes the burn-out.

WalterBright 4/8/2025|

If you're anywhere near the pits, and the crew fires up the motor, and then just blips the throttle, the sound waves generated are like physical blows to your chest.

The only sweeter sound is a V12 Merlin coughing into life.

I snagged a ride in a P51 once. OMG. That machine just leaped into the air. I was smiling for a week.

linsomniac 4/8/2025||

Story of coincidences, I guess: I'm adopted, but a total car nut. My adoptive family weren't really car people except my uncle. A couple years ago I found my birth family, and they are all car nuts. My half sister was a test driver for Audi, my mom and much of the family worked at the local drag strip.

WalterBright 4/8/2025|||

When very little, I thought I wanted to be a farmer, and tried growing crops in the back yard. Total failure. I threw an entire bag of grass seed in my yard 6 weeks ago. Not a single seed sprouted (a flock of birds ate every one). Total failure.

But by age 7 I knew that I was a born engineer. Engines, electronics, software, structures, all of it.

bn-l 4/8/2025|||

That’s amazing how influential your genes were on you

JKCalhoun 4/7/2025||

> Compressed air is stored at 3,300 psi in carbon fiber tanks that weigh roughly 30 pounds each when full

When are the kids in California going to grab a tank, point the nozzle down, and ride that thing like a rocket from the beach, parachuting into the ocean?

We could call them "beach jumpers".

m463 4/8/2025||

Isn't this basically cheapo nitrous?

is it skirting some kind of rule and being specifically NOT nitrous?

Or maybe it is just cost - scuba compressor to fill tank.

ck2 4/7/2025||

Aren't there stock electric cars now that do quarter mile under 10 seconds?

When battery weight gets cut in half next decade and capacity doubles, the only reason why they will race ICE engines is for the noise

mikestew 4/7/2025||

Our Hyundai grocery-getter does a 1/4 in 13s, the "N" go-fast version does it in 11s. And those are Hyundais with full-sized, heavy-ass batteries, and abysmal stock tires. Porsche Taycan GT (with a full-sized, heavy-ass battery) turns 1/4 in 9.3s.

Now cut those heavy batteries in half because you're not driving from SF to LA, and I could see that Porsche turning 8s if you could get the power to the ground (IOW, launch control and much better tires than stock).

SideburnsOfDoom 4/8/2025||

If you want to get into electric small-batch performance cars, BYD has you: https://en.wikipedia.org/wiki/Yangwang_U9

josefresco 4/8/2025|||

I don't believe there's anything even remotely competitive in the electric world to Top Fuel dragsters. You could also make the same argument about F1 vs E1

https://en.wikipedia.org/wiki/Top_Fuel

> Top Fuel is a type of drag racing whose dragsters are the quickest accelerating racing cars in the world and the fastest sanctioned category of drag racing, with the fastest competitors reaching speeds of 338.94 miles per hour (545.5 km/h) and finishing the 1,000 foot (304.8 m) runs in 3.641 seconds.

fanatic2pope 4/8/2025|||

AFAIK the fastest "production" EV is the McMurtry "Spéirling" that does a quarter mile in under 8 seconds. Watching it set the record for goodwood is mind blowing, because it looks like the video is being played in fast forward, but it isn't.

https://www.youtube.com/watch?v=5JYp9eGC3Cc

Although you can in theory buy one, it uses down force fans so I don't know if it would even be street legal in most places. Personally, I find car like this to be way more interesting than drag racers.

jonfw 4/8/2025||

I don't know if you understand just how much of a difference there is between a 4.5 second car and a 7.5 second car- it is orders of magnitude.

Even with half weight and double capacity- the worlds fastest EV will get walked by a fast gasoline street car

kazinator 4/7/2025||

The properties of air that you care about are basically immutable, so why not pre-compute a bunch of compressed air instead of compressing it on the fly, and then having to carry the equipment to do that.

There is an energy cost to supercharging. While you get an overall horsepower boost, it's less than what it would be if the compression cost nothing.

hex4def6 4/7/2025|

Question -- why not go with liquid oxygen? Does that push the danger-meter too high? On the plus side, you're not dealing with 3000 psi compressed gas.

I'm assuming the costs involved in making engines capable of withstanding cryogenic temperatures probably make that impractical (?)

everforward 4/7/2025||

I think it becomes easier to just use a different fuel that is partially self-oxidizing. E.g. Top Fuel uses nitromethane rather than gasoline. Gasoline's stoichiometric ratio is 14.7:1 air:fuel, nitromethane is 1.7:1. Nitromethane in Top Fuel is already so volatile that the superchargers have to be wrapped in kevlar because the fuel blows up in them sometimes.

https://en.wikipedia.org/wiki/Top_Fuel

https://en.wikipedia.org/wiki/Nitromethane

toomuchtodo 4/7/2025|||

Nitrous oxide is the safer equivalent, relatively speaking. Pure O2 would make things burn that normally don't burn, and increase engine detonation.

chongli 4/7/2025|||

And instead of gasoline carry liquid hydrogen. Dragsters are practically horizontal rockets anyway. Might as well stop pretending!

lupusreal 4/7/2025|||

Liquid hydrogen is very bulky, the tank might be large enough to impact the aerodynamics. Use kerosene instead, and maybe use RFNA instead of oxygen, just to bump the danger level up to Abjectly Stupid.

wiml 4/8/2025||

I'll just flip my copy of Ignition! open to a random page and build a car around that...

dabiged 4/8/2025|||

Liquid hydrogen can also cause hydrogen embrittlement. Not ideal in a high performance machine.

shitpostbot 4/8/2025||

[dead]

a_shoeboy 4/7/2025|||

If you're going to cheat, way cheaper to put nitrous oxide in the tank and claim it's compressed air. 50% boost in oxygen content without having to engineer your engine to not burn when pure O2 hits it.

alnwlsn 4/7/2025|||

3000psi gas is the easy way. You just need a couple valves instead of a bunch of insulated stuff that has to not freeze up at -200C.

Aurornis 4/7/2025|||

You can't have liquid oxygen at room temperature. It's physically impossible. It would have to be stored at extremely cold temperatures at all times.

Look up "critical point" and a phase chart to understand why. It's an interesting physics topic that isn't obvious if you've never seen it before.

shipp02 4/8/2025|||

Liquid oxygen will oxidize anything it comes in contact with. You have to use specific metals for the connections and piping.

kazinator 4/7/2025||

Think: would a drag race last long enough that you need to cram that much more oxygen into a small tank?

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