Exhibit 16.1

September 18, 2017

Securities and Exchange Commission
100 F Street N.E.
Washington, D.C. 20549

We have been furnished with a copy of the response to Item 4.01 of Form 8-K for the event that occurred on September 18, 2017, to be filed by our former client, Clean Diesel Technologies, Inc. We agree with the statements made in response to that Item insofar as they relate to our Firm.

Very truly yours,

/s/ BDO USA LLP
Los Angeles, California