In my idle hours whilst dreaming about wish-list powerplant ideas for my soon-to-be RV-8, I wondered why the O-320 doesn't appear to give anywhere near the fuel consumption advantage over its O-360 cousin.
Having a look at the bore-stroke ratios of the engines, it is easy to see why this might be. An O-320 has an estimated combustion chamber surface/volume ratio of more than 10% greater than the O-360, which translates pretty much directly into a 10% greater loss of heat during the combustion cycle -> inefficiency!
If I was to take an O-290 head and barrel (and all other things being equal etc) but with an O-360 crank, I can get an O-327 within 1% of the surface/volume ratio of the O-360, so I might start to see some of the fuel consumption gains that a smaller engine should offer, not to mention better knock resistance and potentially lower weight.
So, does anyone know much about the O-290's? There doesn't seem to be a wealth of info on the web about them, although a VAF search suggests that replacement parts may be hard to come by, except as second-hand GPU's
I wonder if the results could be good enough to convince some of the Lycloners to do a 4.875" bore kit to suit an O-360 crankcase?
Thoughts?
Andrew
Having a look at the bore-stroke ratios of the engines, it is easy to see why this might be. An O-320 has an estimated combustion chamber surface/volume ratio of more than 10% greater than the O-360, which translates pretty much directly into a 10% greater loss of heat during the combustion cycle -> inefficiency!
If I was to take an O-290 head and barrel (and all other things being equal etc) but with an O-360 crank, I can get an O-327 within 1% of the surface/volume ratio of the O-360, so I might start to see some of the fuel consumption gains that a smaller engine should offer, not to mention better knock resistance and potentially lower weight.
So, does anyone know much about the O-290's? There doesn't seem to be a wealth of info on the web about them, although a VAF search suggests that replacement parts may be hard to come by, except as second-hand GPU's
I wonder if the results could be good enough to convince some of the Lycloners to do a 4.875" bore kit to suit an O-360 crankcase?
Thoughts?
Andrew
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