Another thing I would say to anyone developing any kind of Sim/Game/application, and this is from experience of a semi-failed dev cycle for a sim (not racing but principals apply), if you develop a sim and there are some stand out elements, as soon as the other elements are workable, but not exceptional, release a free version, let people experience it.
Even if there's not a lot of content, it will enable you to get peoples' attention if you have a sim that let's say, does realistic damage, but the tire physics model is using some off the shelf bit of code, that can be updated over the next updates. Once you nail the content generation pipeline then start whacking out the content.
Main thing is just getting the sim's name out there, building up the community and whilst you're refining elements, update as regularly as you can without burning yourself out.
One of the biggest lessons I learnt was that just because a sim doesn't look like the latest big budget version out there, it doesn't matter if it never get's released as there is nothing to show for the hard work.
Hope that helps, I have to admit writing this has been rather cathartic!