There is a review of a fine looking RV-9A* in the current issue of Flyer. It is powered by the Wilksch 3-cylinder diesel engine. The engine weight is comparable with a similar Lycoming - the RV-9As fitted with the Wilksch engine are all at the lighter end of RV average weights. The performance is comparable with an RV fitted with an O-235 and it cruises at 117 it's IAS burning 16 lts/ hour of jet A1.
Wilksch currently have over 20 engines flying - 7 of them in RV-9s.
The Wilksch is a 2- stroke diesel with mechanical injection - so it's pretty simple engine.
Dave
* it's mine!