>>>>If you just want to make a VW or Corvair windmill, just lower the compression ratio
Thanks for the input Mark I have often thought about this, particularly when I hear what you guys pay for Corvair spares over there. The Corvair is already a good motor, so de-rating it by 10% will make it bullet proof. Your comment is encouraging and I would be delighted if this can work out - this is however how I see it. The tendency (ability) to wind-mill at cruising speeds is influenced by how much resistance the engine presents to being turned over (CR), as well as the force that is trying to turn it - and that is very much a function of propeller diameter and blade area. Smaller props have less leverage (and inertia). To achieve fair grunt out of any motor, we need to let it get a respectable way up the power curve. In the case of the Corvair I suspect that this will be well over 3000 rpm, restricting the propeller diameters to something like 65" on a direct drive. (not that there is room for much more). My instinct has always been that - by the time you drop the CR to the point that 80mph (approach) will keep a 65" prop turning a 3L engine (approx)- the CR will be such that maybe 30% of the potential power is lost. If the CR reduction required to allow a typical KR prop to wind-mill is such that the power loss is 10% /12%) - this would change things for me. Take care Steve I visited your engine CC'ing site - excellent piece of work, written in a way that that makes me want to do one.
