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Admitted, this is sex for geeks – but then, they should be entitled to some to: So today ViaRETRO is going to be all about the sexiest of air intakes – which was in fact once widely used and equally popular.

In my schoolboy years, I was really more interested in airplanes than I was in cars. The change came around 1979 I think – perhaps along with ground effect cars beginning to dominate Formula 1. The reason could very well be that I could now geek about aerodynamics just as much as I had previously done within aviation. It also wasn’t long until I noticed that the fastest and most extreme sportscars sported the same fancy air intake which I knew from jet aircraft: The NACA duct. Say it out loud and taste it – it just sounds so right.

Even more so if you are familiar with the abbreviation, which stems from the source of the invention: National Advisory Committee for Aeronautics – the predecessor of NASA. Needless to say, such a NACA duct is both hightech and topdollar. In the unlikely event that someone doesn’t know what it looks like, this is it in all its glory:

The NACA duct. Simple, efficient, sexy.

As the picture clearly illustrates, it’s an air intake which is flush with the bodywork – contrary to the more conventional automotive air intakes which are stuck on top of the bodywork and protrude into the airflow to varying extents. In simple terms, the advantage of the NACA duct is that it “catches” passing air without increasing the air friction. Originally NACA developed them back in 1945 when jet aircraft were new, modern and all the rage. Their goal was of course to improve the jet aircraft and make them even faster, by feeding the air-gulping jet engines through a more aerodynamic and efficient intake.

A simple sketch of what the NACA ducts was originally developed for in 1945: A more aerodynamic air intake for jet aircraft.

However, they didn’t work for that use. Granted, aerodynamics was better, but they also supplied less air. Even worse was the fact that air entering through a NACA duct was found to be inherently turbulent rather than a laminar airflow, which just doesn’t suit a jet engine at all.

But all was not lost, as the NACA duct was instead found well suited for other functions – in particular within motorsports and thereafter on road cars too. For the later of course starting off with the most extreme sportscars and then gradually filtering down through the system to more ordinary cars. From there it naturally wasn’t long before the NACA duct found huge popularity within the broad world of tuning. It’s from here that I best remember the presence of the duct, and I was hugely fascinated by mixing aviation technology with automotive technology.

The big question was of course whether it actually worked? The answer to which is Yes. – and No. The NACA duct is good at leading relatively small amounts of air in from a relatively undisturbed airflow. From the pointy nose of a fighter jet for example. But regardless, it looked damned sexy when RUF placed a massive NACA duct on top of the curved rear wing of their famous “Yellowbird” from 1987.

A period picture of a fantastic automobile; the RUF Yellowbird. On many newer pictures of the Yellowbird, you will note that the NACA ducts have been either deleted or at the very least plugged.

But it just doesn’t work particularly well here, and many Yellowbirds have subsequently had the duct removed. The Ferrari F40 from the same period took it all to another level by simply having so many NACA ducts (and various other holes in the bodywork) that it frankly didn’t matter whether they all worked – air was bound to both enter and exit the car either way. In stark contrast, you won’t find a single NACA duct on the illustrious Porsche 959, and the supercar above all other supercars, the McLaren F1, built and developed to be the very best and not for bling, doesn’t have one either.

This is where I slowly started to question the functionality of the world’s most sexy air intake.

NACA overdose.

And that dear reader is probably the essence of it all: The NACA duct was often chosen because of its visual impact. In that context I suppose it still makes some sense, as they truly do look fabulous – even more so on designs from the seventies and eighties, where the softly inward curving opening of the duct perfectly supplements the typically sharp-cut designs of that era. But it’s also painfully obvious on something like the Renault 5 Turbo below, that aerodynamic efficiency was hardly ever a factor. The frontal area has exploded and the aerodynamics of the basic design spoilt by massive arch extensions and all the rest. The NACA duct can only be relevant because it’s sexy. But at least it’s sublime at that.

A rather silly place to fit a NACA duct: This flying brick will no doubt have highly turbulent air passing over the wide rear wings.

The first Countach prototype didn’t have them, but was given a huge dose of NACA down the flanks before production commenced. Maybe because the Italians suddenly learnt something aerodynamics? I seriously doubt it! Even later versions of the Countach received massive air intakes shaped mostly like an oversized postbox right behind the small rear side windows. They probably displayed similar aerodynamic efficiency to an oversized postbox too. On the subject of Italians: Alfa Romeo placed a beautiful NACA duct centrally on the nose of their Montreal. This actually looked highly efficient. But it was a dud. The air intake was for show only.

The prototype Countach was NACA-less.

– and the Montreal’s NACA was all show and no go.

Porsche equipped their 924 Turbo with a small NACA duct. It was even placed by the book, towards the very front of the nose where the airflow is still largely laminar before it separates from the bodywork and becomes turbulent. I tend to regard it as a stamp of approval when anything makes its way – from factory – onto a product from Zuffenhausen: That’s because it works.

Porsche don’t equip their cars with things which aren’t necessary. So the ordinary 924 was always sans NACA, while the Turbo got it.

Several years ago, I was somewhat surprised as I took in all the beauty of a replica Jaguar XJ13. I considered the presence of the NACA duct for a short while, and quickly made up my mind that the person who built this replica was clearly as fascinated by the aeronautical air intakes as me, and had thus messed up his otherwise perfect replica by fitting such a modern intake on a car from 1965. But when I got home, I did my homework and found I was in fact wrong: The sole example of the real Jaguar XJ13 did in fact have a NACA duct.

There is something fabulously wrong about the little modern air intake on the shapely and classic Jaguar. BUT! The XJ13 was indeed born with a NACA duct.

Up until now, this was the earliest example of the NACA duct being used on a car, which I knew of. But for today’s article I dug a bit deeper into the archives. Which car was the very first to use a NACA duct?

My research concludes that it’s the car from the cover picture: Aston Martin Project 214 from 1963. Another race car, and one which was specifically constructed with the main objective of improving the aerodynamics of the classic DB4 design.

But what say you? Have I missed something? Were there others before the Project 214? If so, please share your knowledge in the comments area below. Or have any of our readers ever owned a car with a NACA duct? And was it a better car for it? I’ve personally dreamt of owning a car sporting a NACA duct ever since the eighties. It’s still on the list.

And NO! Mine will not be some cheap aftermarket duct crudely grafted into the bodywork of a car that was never intended to have it.

 

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About The Author

Broad car taste. Prefer them working, though. Coupés, estates, racing cars - and so on. Origin less important, but I love Italy. And Britain. Germany. And so on. By the way, I believe everything was better in the old days. Except the internet. Claus' keeper is a 1978 Reliant Scimitar GTE. As a true Scandinavian of course he also has a Volvo - a 445 of the 1956 vintage.

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