In addition to Honda, which would like to stay in the series, Audi, Fiat, Porsche and Volkswagen are all currently negotiating with the racing league to offer alternative powertrain options. The current engines all displace 3.5 liters and are limited to 10,300 rpm, making about 650 horsepower running on ethanol fuel. The next contract will likely call for engines displacing 2.0 liters and feature turbocharging and direct injection. Both four cylinder and six cylinder options are being considered.
[Source: USA Today]