These concept cars appeared on the NY Auto Show.

The Civic Si has a " 200-horsepower, 16-valve, DOHC i-VTEC engine with an 8,000 rpm red line, mated to a close ratio 6-speed manual transmission. Helping to put all that power to the ground is a helical-type limited slip differential for improved launch traction and cornering performance. 18-inch cast aluminum wheels, 225/40R18 high performance tires and 4-wheel, with large cross-drilled brake rotors and 4-piston Brembo calipers."

No given data for the Nissan.

Both companies gave no word if these cars would be produced.