I like the idea of using the Briggs & Stratton Vanguard engine, especially since there is so much racing experience and aftermarket parts. I am installing a new engine in my Q1 and going in a similar -- though not identical -- direction. I'm
replacing the 22-hp Super-Onan with a pretty generic two-cylinder 870 cc Chinese direct-injection diesel rated for 25 hp at 3600 rpm. I'm turbocharging the engine with a tiny IHI turbo (the smallest sold) and an intercooler. I'm aiming for a turbo-normalized
30 hp, which should give me some really interesting performance numbers at my 17,999-foot cruise altitude.
The engine is all aluminum and air-cooled. I've removed a bunch of extra parts and material like the OEM exhaust, intake, and fuel tank and have the weight down around 55 kg. The new parts are mainly titanium, but that's because we use titanium at my day
job and have a welder who does beautiful work. Guessing that the crankshaft is a casting, I'm installing a 1-to-1 belt drive to isolate the prop loads while raising the thrust line. The engine, turbo, and intercooler come from China, the redrive is from India,
so the complete powerplant (minus prop) was under $2000 including shipping.
I built the new engine so I can commute to work in San Luis Obispo, CA. My company is right at the airport there and I can even park inside. Presently I fly my Thorp T-18, which takes about 90 minutes for the 222 nm flight from Santa Rosa. I don't expect
the Q to go any faster (or slower) than that, but hope to drop the fuel consumption from 10 gallons down to three. Even at 10 gallons it is cheaper to fly than to drive my car, in part because I skip the toll on the Golden Gate Bridge.