The G37 Coupe and Convertible share a powerful engine, along with a rear-drive chassis, a manual or automatic transmission, and an independent suspension.
The 3.7-liter V-6 in the Coupe churns out 330 horsepower with an enthusiastic growl all the way to its 7,500-rpm redline. Car and Driver says the engine's a "version of Nissan's venerable VQ V-6 engine," and notes "torque output at 270 pound-feet." The now-defunct ForbesAutos reports "acceleration was strong and smooth" during their test, and "the engine makes great music as it happily revs to the red line." Edmunds finds in testing that a "G37 Journey accelerated to 60 mph in 5.5 seconds, while a Sport 6MT coupe pulled a nearly identical 5.4 seconds to 60 mph." The Convertible makes 5 hp less due to exhaust tuning, and it carries an extra 450 pounds of folding hardtop. LeftLane News confirms the engine is "a 325-horsepower, 3.7-liter V-6 yanked from the hardtops," which Popular Mechanics asserts is "nearly identical to the Coupe." Car and Driver contends its Convertible's 0-60 mph time of 5.5 seconds is something of a letdown, though it matches Edmunds' numbers: "Kick down the 3.7-liter V-6, and the car seems to think hard for an instant before committing its considerable heft forward." The problem? As Car and Driver notes, "Our scales measured it at 4136 pounds, which is 454 more than a manual coupe."
Both the G37 Coupe and Convertible can be ordered with either a slick six-speed manual with a clutch that has a high uptake point, or a marvelous seven-speed automatic that gets paddle shifters and a sport driving mode with the optional Sport package. It's a delight to flip around through the gears in most driving modes with the automatic and a relief for most urban drivers. While TheCarConnection.com's editors prefer the automatic, other reviewers are impressed with both transmissions. ForbesAutos says "both gearboxes work precisely and are well matched to the potent engine." Automobile's "choice is distinctly for the 6MT," where the "tail-out antics and fun factor outweigh the coarseness" that they feel comes with the manual transmission. "Manual shift drivers will like the positive shifter feel, smooth clutch take up, and quicker 3.9:1 final drive," LeftLane News observes, but also praises the automatic's "downshift rev matching, Drive Sport (DS) mode and Adaptive Shift Control (ASC)" which give it quicker shifts and better fuel economy. A later review from Automobile reverses course; this time, they "prefer the automatic, which dampens much of the V-6's roughness and provides better off-the-line acceleration, thanks to delightfully short gear ratios." Edmunds is "happily surprised by [the automatic's] intuitive and responsive nature when placed in Drive Sport (DS) mode. On a twisting roadway it held gears, downshifted when braking for turns and consistently did exactly what we wanted without any driver input."
On fuel economy, the Convertible's 17/25 mpg (automatic) or 16/24 mpg (manual) is bested by the Coupe's 17/25 mpg (manual) or 18/26 mpg (automatic) fuel economy. Cars.com reminds shoppers this is an improvement over the last two-door; it's "about 1 mpg better gas mileage than the 3.5-liter V-6 in the G35."
The G37 steers nicely and has a well-damped ride, even with the Sport package's 19-inch wheels. Directing all this high technology is rack-and-pinion steering gear with electric, as opposed to hydraulic, assist. The feel of the steering isn't ideal, as it sometimes varies steering effort unexpectedly, but roadholding is fantastic. The ride quality can get a bit nervous in the Coupe, especially in versions with the optional 19-inch wheels. Motor Trend says "through all but the most aggressive curves, the car stays as flat as the Arizona desert." Car and Driver reports even with the sport package, "the chassis soaks up road bumps without the slightest chatter, and the steering remains precise and communicative." While a "four-wheel active steering (4WAS)" system is available, according to Edmunds, they recommend sticking "with the standard steering setup," as the 4WAS system "fails to weight up properly in the corners and provides limited feedback." At the corners are massive disc brakes that stop with impressive power. Motor Trend finds that the brakes are "stellar-exhibiting excellent response and pedal feel and no fade." In all, Kelley Blue Book affirms that "performance-focused drivers hoping for a more sophisticated, premium-badged Nissan Z will find satisfaction in" the Infiniti G37.
As for the heftier Convertible, it feels slightly less nimble and not as quick to accelerate. "Does this additional structure mean the G37 has lost its deft handling? Not really," Popular Mechanics concludes. "The Convertible is certainly fun to bend into a corner, but perhaps there's a bit less capability to execute those curves at the same speeds as the hardtop model." Edmunds agrees: "It's not easy to hide 453 pounds, but the Infiniti engineers did a remarkable job of managing the added weight... even the base model riding on standard 18-inch wheels manages its weight in a controlled manner, avoiding excessive wallow or undulation under all but the most aggressive driving circumstances." Infiniti does offer the Sport option on the G37 Convertible, which adds "14-inch discs up front and 13.8-inch units in the rear, up from the standard 13-inch setup at each corner," Popular Mechanics explains, along with "quicker steering, aluminum pedals, sport seats and wide 225/45R19 front and 245/40R19 rear tires." That package "gives the G37 convertible unexpected responsiveness and confidence for a 2-ton machine (4,095 pounds)," Edmunds observes.