I listened with great interest as Ed described his project. Thousands of people all over the world, especially in the US, build their own plane. Many of them use auto engines, with the Subaru Boxer engine being one of the most popular. Ed should join the EAA, if not already a member. http://www.eaa.org
I am building a RV-7A with a Subaru engine. As with many who have bought the same engine kit I did, I sure wish I’d gone with Lycoming. I’ve got $50k and 5 years into what was sold as a “complete FWF package” and turned out to be FAR from that.
Ed also mentioned that his proposed Subaru engine came with hoses and parts, etc, indicating that he’s planning to buy a FWF (firewall forward) kit, as opposed to buying an engine and making the mount and other FWF components himself. I’d urge “buyer beware” in this area. NPR may block mentioning any particular brands of FWF supplier, so I won’t specify any brands here, but I do urge looking carefully into the customer satisfaction of your FWF kit supplier. There are two Subaru FWF providers that have gone bankrupt after ripping off customers; taking money, but not supplying engines. There are two remaining Subaru FWF providers. One has significant reputation problems, the other does not, as far as I know. I got my FWF from the former.
You can get extensive details of my building experience, and particularly the Subaru FWF experience, on my web site at:
The bottom line in my experience is that a Subaru engine is much better in theory, but if you want to fly your plane, rather than tinker with it endlessly, go with Lycoming. If you’re only considering the Subaru based on price, I’d especially avoid it. Most people using Subaru engines do it for the more modern technology. There are many people successfully flying with Subaru (and other auto) engines, but there are also a lot of us, particularly customers of this particular Subaru FWF supplier, that have been bogged down for years solving technical issues that the supplier overlooked.
If you do go Subaru, make sure your electrical system is bulletproof and redundant, because without electricity, these engines do not run. A Lycoming uses old-fashioned magnetos, but does not require electricity to run. There are drawings on my web site, showing how I did my electrical system.
Avoid any auto engine with factory ECU. The factory ECUs are made for auto use and have many built-in auto safety features that you don’t want in a plane. If an auto ECU detects an anomaly in inputs from sensors, it will go into “limp home mode”, where the engine will run, but will not produce enough power to stay in the air. A German customer of the same FWF kit I have crashed his beautiful RV plane when his Subaru ECU inexplicably decided to go into limp home mode. Since then, most of us customers of that same FWF supplier have torn out the auto ECU and installed a simple reliable aftermarket ECU.
Engine cooling has been another area of concern, problems, and re-engineering our FWF kits.
Lots more info about all this on my RV builder’s web site.
good luck with it,