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Compact and light-weight, the Z21 was a pocket-sized rocket that wasn't mean to be. That doesn't mean you should stop dreaming of one though.

The Caterham 7 is a no-nonsense sports car that's been around for longer than probably any other car on the market, without its basic structure and purpose witnessing change. But it's also one of those cars that'll tickle you pink when you give it the beans.

The Z21 was a BMW's reaction to the Caterham, and it was brought to life by the same engineers who lead the Z18 project. And the Z21 was no regular BMW roadster; it was a one-off concept that offered performance from a rear-mounted engine, sending power to the rear wheels. There was more to this car than its removable door panels and exposed components. The Z21 was all about going fast, thanks to its lightweight frame.

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The Ariel Atom seemingly was inspired from this concept. The BMW Z21 Concept looks sharp, and with its F1 car-like open-wheel design, it meant the car was up to the job of being raced at the Spring Mountain Motor Resort in Nevada. It even came with exposed shock-absorbers and two motorcycle-like exhausts poking out of the back. The suspension and wheels were not a part of the main body, and the front and rear suspension mounting points and the rollover hoop were carried by its naked frame design. The Z21 did not feature a roof or a windshield, but BMW assured decent protection from the weather because of the car's aerodynamics that were honed in a wind tunnel. It clearly had intentions to pip the Caterham 7, the Z21. At least when it came to the looks of the car.

The cockpit used a minimalist design philosophy. The steering wheel design of the Z21, that was once considered simple, can now be had as an aftermarket fitting in just about any car. The white-dials-with-black numbers, on the other hand, evoke nostalgia while the carbon-fiber seats look cool, although not very comfortable because of the limited cushioning. Then there's the stubby all-aluminum gear lever that's a thing of the past these days.

The Z21 was powered by a four-cylinder engine from the BMW K1100 bike, making 100hp. That's unlikely to make your eyes pop, but the fact the Z21 weighed in at just 1,212 lbs, meant this was going to be a hoot to drive with its impressive power-to-weight ratio. BMW was itching to take it for spin, and the team managed to reach a top speed of 112mph, going from 0-62mph in just 6 seconds. Most cars with a similar engine capacity these days, can barely hold a candle to the Z21.

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BMW never took the Z21 seriously much to our displeasure. Had it made it to production, the Z21 could have evolved in design, and looked like it has potential be developed further with additional performance upgrades. Updates perhaps in the form of a bonkers V8 to take on the Ariel Atom and the KTM X-Bow. Having said that, it was a great project but came with a silly nickname, 'Just 4-2'.Z

Rehan got published for the first time at the age of 17, having written a feature on a Triumph Herald in print. He uses his writing as a tool to express his fondness for all things automotive even today, aged 28. Collecting scale models is a hobby close to his heart, and he wishes to sprinkle pixie dust on them only to see them grow into full-sized cars. He now represents HotCars.com.