I see you made a double post in 2 forum categories, not nice
...any case here is my take on it.
Not enough, and that is the main reason why the current aviation engine technology is so old & expensive, there is not a big enough market out there compared to cars, for designers to put the huge development effort and cost in and be able to get the return, and to drive the price down. Any new aviation engine will be looked at sceptically until it proves itself, limiting your sales uptake.
Currently there are 4,449 RV's flying according to Vans, so that limits you, to say +/- 500 RV engines a year at best? I do not have to old figures to see the increase. So i am guessing the 500 RV's a year.
I've read somewhere (think avweb) the annual new piston aircraft engine market is +/- 2,500 units a year. Tiny and small in comparison to the car engine market where they sell that amount of engines in a month in one country alone.
That is why we all wish a motorcar engine transplant into an airframe would be so easy and feasible, but it is not.
Kind Regards
Rudi