The electric motor in the i3s puts out 184 hp and 199 pounds-feet of torque. That's up from 170 hp and 184 pounds-feet in the base model. BMW says the enhanced drive system in the i3s translates to power and torque improvements of up to 40 percent over the base i3.
For 2018, the base i3 also gets a wider track and design changes to give it a sportier appearance. The i3 originally went on sale in 2014. BMW sold 7,625 i3s in the U.S. last year, down 31 percent from the nameplate's 2015 peak.
Both the 2017 and 2018 models include an optional range-extending gasoline engine.
The 94Ah battery in the 2018 model is expected to be similar to the 2017 model, which has a stated range of 114 miles.
BMW says EPA ratings have not yet been released for the 2018 models and the company is unable to provide any information on battery range.
Automotive News has reported that a bigger battery with significantly longer range -- close to 200 miles -- will be available on the i3 by the end of the 2018.
Both 2018 BMW i3 models will be unveiled publicly in September at the Frankfurt auto show. Prices of the new models will be announced closer to their on-sale dates.