SecProbe.io

August 27 , 2012

Via E -mail
Mr. David R. Demers
Chief Executive Officer
Westport Innovations Inc.
Suite 101, 1750 West 75th Avenue
Vancouver, British Columbia, Canada  V6P 6G2

 Re: Westport Innovations Inc.
  Form 40-F for the Nine Months  Ended  December 31, 201 1
Filed March 1, 2012
  File No.  1-34152

Dear Mr.  Demers :

We have reviewed your filing  and have the following comments.   In some of our
comments, we may ask you to provide us with information so we may better understand your
disclosure.

Please respond to this letter within ten business days by amending your filing, by
providing the requested information, or by advising us  when you will provide the requested
response.  If you do not believe our comments apply to your facts and circumstances or do not
believe an amendment is appropriate, please tell us why in your response.

After reviewing any amendment to your filing and t he information you provide in
response to these comments, we may have  additional comments.

Form 40 -F for the Nine Months Ended December 31, 2011

Exhibit 99.2

Note 21.  Investment in Joint Ventures, page 37

(a)  Cummins Westport Inc., page 37

1. With r espect to your relationship with Cummins, p lease tell us how you considered the
disclosure requirements for such a supplier concentration.  Refer to ASC 275 -10-50-16
through -22.

Mr. David R. Demers
Westport Innovations Inc.
August 2 7, 2012
Page 2

 2. With respect to your accounting for CWI, your 50:50 joint venture with Cummi ns, please
tell us how you considered whether a reconsideration event occurred and whether CWI is
a VIE and whether you remain the primary beneficiary.  Refer to ASC 810 -10-35-4.

3. With respect to your disclosure for CWI, p lease tell us the following:

 The company’s methodology for determining that the company is the primary
beneficiary of CWI, including, but not limited to, significant judgments and
assumptions made.
 Whether the company has provided financial or other support (explicitly or
implicitly) dur ing the periods presented to CWI that the company was not
previously contractually required to provide or whether the company intends to
provide that support.
 Qualitative and quantitative information about the company’s involvement
(giving consideration to  both explicit arrangements and implicit variable interests)
with CWI, including, but not limited to, the nature, purpose, size, and activities of
CWI, including how CWI is financed.

Refer to ASC 810 -10-50-5A and discuss your consideration of providing these
disclosures.

Note 23 – Segment Information, page 40

4. Your definition of segment net operating income (loss) excludes depreciation.  In future
filings, please clarify by revis ing the description of the line item for segment net
operating profit or lo ss in the segment table to clarify that it does not include depreciation
expense.

5. Please tell us how you considered the disclosure required by ASC 280 -10-50-25 related
to your segment assets.

6. We note that you report revenues for the Americas, Asia and ot her.  Please tell us how
your disclosure considered ASC 280 -10-50-41 which requires disclosure of r evenues
from external customers attributed to your country of domicile and attr ibuted to all
foreign countries either in total or, where material, attributed  to individual foreign
countr ies separately.  Also, it requires disclos ing the basis for attributing revenues from
external customers to individual countries.

Mr. David R. Demers
Westport Innovations Inc.
August 2 7, 2012
Page 3

 Exhibit 99.3

Disclosure Controls and Procedures and Internal Control Over  Financial Reporting, page 13

7. We note that management’s conclusion regarding the effectiveness of your disclosures
controls and procedures refers to March 31, 2011 and not December 31, 2011.  Please
amend your Form 40 -F to comply with General Instruction B(6)(b) of Form 40 -F  to
disclose the conclusions of the company’s principal executive and principal financial
officers regarding the effectiveness of the company’s disclosure controls and procedures
as of the end of the period covered by the report - i.e., December 31, 2011 .

 We urge all persons who are responsible for the accuracy and adequacy of the disclosure
in the filing to be certain that the filing includes the information the Securities Exchange Act of
1934 and  all applicable Exchange Act rules require .  Since the company and its management are
in possession of all facts relating to a company’s disclosure, they are responsible for the accuracy
and adequacy of the disclosures they have made.

 In responding to our comments, please provide  a written statement from the company
acknowledging that:

 the company is responsible for the adequacy and accuracy of the disclosure in the filing;

 staff comments or changes to disclosure in response to staff comments do not foreclose the
Commission from taking  any action with respect to the filing; and

 the company may not assert staff comments as a defense in any proceeding initiated by the
Commission or any person under the federal securities laws of the United States.

You may contact Gary Newberry, Staff Ac countant, at (202) 551 -3761 or Kate Tillan ,
Assistant Chief  Accountant, at (202) 551 -3604 if you have questions regarding these comments.
In this regard, do not hesitate to contact me at (202) 551 -3671.

        Sincerely,

        /s/ Kate Tillan for

        Martin James
        Senior Assistant Chief Accountant