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Originally Posted by UncleBob
hehe, I like some of the claims there: "worlds most powerful ....road legal car"
not even close guys.
"world record torque of 1300 ft/lbs"
yawn
But anyway....that is a rather impressive redline for a motor that big. One of the basic fundimentals, no matter how light weight the pistons, no matter how strong the crank and rods, the piston average speed can only go so high. For race application, 5000 fpm is cutting it close. Most stock applications keep it under 4000fpm. Even the most high tech engines in the world, such as motorcycles, never get over 5500 fpm.
The formula isn't too hard, all you need is the stroke. Lets take a 3" stroke for example: 3X2/12 = .5 X RPM = fpm. 3" stroke at 10000RPM = 5000 fpm.
Take a 6" stroke, and as the simple formula shows, 5000 RPM's is playing with fire no matter what you got.
Since we don't know what the stroke is on this 780ci engine, we're guessing, but I assume its going to be a large bore AND a large stroke engine. 5+ inches. In that case, I have to say, its either a short lived time bomb, or its a big fat lie.
But large bore does have its disadvantages....the bigger the bore, the less efficient the flame front is, the harder it is to get enough valve flow to support the cubes. The general rule is, anything over 4" bore is losing efficiency.
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very informative post. so basically, what you're saying is that a certain ammount of stroke is required to take advantage of bore, and when we increase bore, we get to a point where the engine simply needs more stroke to be effective, in the way of physically pulling, pushing, and igniting fuel.