CHICAGO --Yearning for a roadster with the additional 18 horsepower and the Godzilla-like aerodynamic body kit that in-house tuner Nismo added to the Nissan 370Z coupe? Nissan has unveiled such a beast at the 2015 Chicago Auto Show, "created to gauge interest" in what could become the tuner's fifth North American offering.

Like the 370Z Nismo coupe, the Nissan 370Z Nismo Roadster concept's venerable VQ engine, a 3.7-liter DOHC V-6 with Variable Valve and Lift, is tuned for an extra 18 horsepower and 6 lb-ft of torque, to 350 hp at 7,400 rpm and 276 lb-ft at 5,200 rpm. Nismo has retuned the double-wishbone front/multi-link rear suspension, added a Nismo front strut tower bar, plus sportier shock absorbers and larger front and rear hollow anti-roll bars.

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The Nismo Roadster concept is shown with a seven-speed automatic, which was added as an option to the 370Z Nismo coupe for 2015 to join the previously offered six-speed manual gearbox.

What Nismo calls "GT-R-inspired" aerodynamics means a deep front fascia with LED daytime running lights and black headlamp bezels and a big Nismo rear spoiler. The expressive bodywork adds 3.3 inches to the 370Z Roadster's overall length, bringing it to 170.5 inches. The Nismo also is 1 inch wider, at 73.6 inches, and 0.1 inch taller, at 52.2 inches compared with the quotidian Roadster. Headroom is a half-inch greater, at 38.7 inches.

That may be a result of the interior accoutrements. The Nismo's interior features black leather-trimmed Recaros with off-white Ultrasuede inserts, red seat trim and stitching with the Nismo logo, Alcantara and leather-wrapped three-spoke steering wheel, a Nismo-branded tachometer, premium suede-wrapped door panels, Nissan Navigation with 7.0-inch VGA touch-sensitive display, RearView Monitor, and six-speaker Bose audio system with subwoofer. There are also leather-wrapped fixed headrest bars and a cloth power-folding ragtop, Nismo badging and red stripe accents.

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If Nissan's Nismo builds the Roadster, it will cost you; the 2015 Nissan 370Z Nismo coupe has a base price of $42,815. The standard 370Z Roadster is substantially pricier than the standard 370Z coupe, though trim levels between the two don't directly line up. The 2015 convertible runs from $42,630 to $50,210.

If it goes into production, the Nismo Roadster would be the fifth tuner model from the brand sold in the U.S., after the 370Z coupe, the 600-horsepower GT-R Nismo, the Juke Nismo, and the Juke Nismo RS. Unlike most such "concepts," however, the 370Z Nismo Roadster doesn't seem like such a sure thing, considering a sticker likely approaching $50,000, which would price it close to a lot of good, well-established competitors, a problem with noted in our recent review of the 2014 Nissan 370Z Nismo coupe.

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