Airport car rental service Silvercar has raised $14 million in Series B funding to help with expansion. The company, which rents out Audi A4s, is currently available at eight airports around the U.S. Silvercar's downloadable end-to-end app allows users reserve, unlock and pay for a car. Reporting 10,000 new customers each quarter, it has seen 20% top-line growth month-over-month and claims a 40% customer return rate. In late 2013, Silvercar received a valuation of $24 million; it has now raised about $32 million in financing. Velos Partners led the new funding.