Six Sigma actually contains a specific project methodology when working with projects that will produce a new product as opposed to improving business practices:
DMADV System:
Define design goals that are consistent with customer demands and the enterprise strategy.
Measure and identify characteristics that are Critical To Quality, product capabilities, production process capability, and risks.
Analyze to develop and design alternatives
Design an improved alternative, best suited per analysis in the previous step
Verify the design and hand it over to production

As you can see many of these concepts overlap with the PMBOK standards. Six Sigma does offer a number of quality management tools that may help keep the project running smoothly.