If you are interested in this topic, you might like to check out Raptor Aircraft on Youtube if you haven't already. Raptor Aircraft is a guy named Peter Muller, an Aussie living in the USA. He has designed a high-performance and very spacious 4/5 place canard pusher aircraft pretty much from scratch (although it looks a lot like the Velocity), and its power is provided by the Audi 3 litre twin-turbo diesel V6. With a reduction drive of course - pretty much essential for any car engine to drive a propeller. He has been working on this for 4 years or so and is on the brink of first flight - I think the test pilots are booked for the end of July.
It's an interesting story. Peter had no background in aircraft design (he's a computer nerd like me), but when he did his training for his pilot licence some years ago he was taken aback by how cramped and uncomfortable small aircraft were (are), and how expensive. He reckoned that if he could buy a high-end car like an Audi for (say) $60K or so, why was a decent aircraft 4 times that price, or more? After looking around he decided the Velocity was the closest to what he was looking for, but it still didn't tick all the boxes. So he decided he would design and build his own. He has made a lot of mistakes, but has been completely open about all the failures as well as the successes, with 2 videos per week almost every week since the project started. He does intend the Raptor to go into production, and has hinted at some negotiations which have taken place, but I'm guessing nothing will be revealed until it has flown. I stumbled across the channel about 18 months ago and have been following the ups and downs ever since - I find it quite compelling, and I certainly admire Peter's persistence and tenacity.