UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): September 1, 2015

FUEL SYSTEMS SOLUTIONS, INC.

(Exact name of Registrant as specified in its charter)

Registrant’s telephone number, including area code: (646) 502-7170

(Former name, former address and former fiscal year, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

On September 1, 2015, Fuel Systems Solutions, Inc., a Delaware corporation (the “Company” or “Fuel Systems”), and Westport Innovations Inc., an Alberta, Canada corporation (“Westport”), issued a joint press release announcing the entry into an Agreement and Plan of Merger, dated as September 1, 2015, among the Company, Westport and Whitehorse Merger Sub Inc., a Delaware corporation and a direct wholly owned subsidiary of Westport (the “Merger Agreement”).

A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated herein in its entirety by reference.

The information required by Item 1.01, including a copy of the Merger Agreement, will be filed in a separate Current Report on Form 8-K.

Forward Looking Statements

This filing contains certain “forward-looking statements” within the meaning of federal securities laws. Words such as “anticipates”, “believes,” “expects”, “intends”, “will”, “should”, “may”, and similar expressions may be used to identify forward-looking statements. Forward-looking statements are not statements of historical fact and reflect the Company’s and Whitehorse’s current views about future events. This filing contains forward-looking statements, including statements regarding the anticipated timing for and ultimate completion of the merger, result, timing and financial metrics associated with Westport’s and Fuel Systems’ combined operating business units and consolidated business, revenue and cash usage expectations, the effect of the proposed reorganization and restructuring of our business, continued research and development investment, future of our development programs, timing for launch, delivery and completion of milestones related to the products referenced herein, Westport’s and Fuel Systems’ expected actions and results relating to the key components of its strategy in 2015 and to the integration of Westport’s and Fuel Systems’ businesses, future sales of assets and the benefits therefrom, the demand for our products, the future success of our business and technology strategies, investment in new product and technology development and otherwise, cash and capital requirements, intentions of partners and potential customers, the performance and competitiveness of Westport’s and Fuel Systems’ products and expansion of product coverage, future market opportunities, speed of adoption of natural gas for transportation and terms and timing of future agreements as well as the combined company’s management’s response to any of the aforementioned factors. These statements are neither promises nor guarantees, but involve known and unknown risks and uncertainties and are based on both the views of management and assumptions that may cause our actual results, levels of activity, performance or achievements and ability to complete the proposed merger to be materially different from any future results, levels of activities, performance or achievements expressed in or implied by these forward looking statements. These risks and uncertainties include risks and assumptions related to our revenue growth, operating results, industry and products, the general economy, conditions of and access to the capital and debt markets, governmental policies, regulation and approvals, technology innovations, fluctuations in foreign exchange rates, operating expenses, the availability and price of natural gas, global government stimulus packages, the acceptance of and shift to natural gas vehicles, the relaxation or waiver of fuel emission standards, the inability of fleets to access capital or government funding to purchase natural gas vehicles, the development of competing technologies, our ability to adequately develop and deploy our technology, the actions and determinations of our joint venture and development partners, as well as other risk factors and assumptions that may affect our actual results, performance or achievements or financial position discussed in Westport’s most recent Annual Report on Form 40-F for the year ended December 31, 2014, as amended and Fuel System’s Annual Report on Form 10-K for the year ended December 31, 2014, and other filings made by the companies with securities regulators. Readers should not place undue reliance on any such forward-looking statements, which speak only as of the date they were made. We disclaim any obligation to publicly update or revise such statements to reflect any change in our expectations or in events, conditions or circumstances on which any such statements may be based, or that may affect the likelihood that actual results will differ from those set forth in these forward looking statements except as required by National Instrument 51-102. The contents of any website, RSS feed or twitter account referenced in this filing are not incorporated by reference herein.

Non-GAAP Financial Measures

This filing may contain certain non-GAAP financial measures, which management believes are useful to investors and others in evaluating business combinations. Further detail and reconciliations between the non-GAAP financial measures and the GAAP financial measures are available in the most recent press releases of Westport and Fuel Systems concerning quarterly financial results, furnished to the SEC on Form 6-K.

Additional Information And Where To Find It

Westport will file with the SEC a registration statement on Form F-4, which will include the proxy statement of Fuel Systems that also constitutes a prospectus (the “proxy statement/prospectus”). INVESTORS AND SHAREHOLDERS ARE URGED TO READ THE PROXY STATEMENT/PROSPECTUS, AND OTHER RELEVANT DOCUMENTS TO BE FILED WITH THE SEC, IN THEIR ENTIRETY CAREFULLY WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT WESTPORT, FUEL SYSTEMS, THE PROPOSED TRANSACTIONS AND RELATED MATTERS. Investors and shareholders will be able to obtain free copies of the proxy statement/prospectus and other documents filed with the SEC by the parties through the website maintained by the SEC at www.sec.gov. In addition, investors and shareholders will be able to obtain free copies of the proxy statement/prospectus and other documents filed with the SEC by the parties by contacting Westport Investor Relations at 1-604-718-2046 or invest@westport.com (for documents filed with the SEC by Westport) or Fuel Systems Investor Relations advisors, LHA, at 1-415-433-3777 or fuel@lhai.com (for documents filed with the SEC by Fuel Systems).

Participants In The Solicitation

Westport, Fuel Systems and their respective directors and executive officers may be deemed to be participants in the solicitation of proxies from the shareholders of Fuel Systems in respect of the proposed transactions contemplated by the proxy statement/prospectus. Information regarding the persons who are, under the rules of the SEC, participants in the solicitation of the shareholders of Fuel Systems in connection with the proposed transactions, including a description of their direct or indirect interests, by security holdings or otherwise, will be set forth in the proxy statement/prospectus when it is filed with the SEC. Information regarding Westport’s directors and executive officers is contained in Westport’s Annual Report on Form 40-F for the year ended December 31, 2014, as amended, and its Management Information Circular, dated March 11, 2015, which is filed with, in the case of the Annual Report on Form 40-F, and furnished to, in the case of the Management Information Circular, the SEC and can be obtained free of charge from the sources indicated above. Information regarding Fuel System’s directors and executive officers is contained in Fuel System’s Annual Report on Form 10-K for the year ended December 31, 2014 and its Proxy Statement on Schedule 14A, dated April 14, 2015, each of which are filed with the SEC and can be obtained free of charge from the sources indicated above.

(d) Exhibits.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the Company has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

EXHIBIT INDEX