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263 Posts
Good theory but you are missing several key elements of air flow dynamics. First off since an engine is in a state of varying vacuum standard air flow characteristics don't apply but for the sake of arguement your numbers work fine. Second, like every other part of an engine or car for that matter the parts are at the happy medium of things. An engine is a very versitile device that has a wide range of operating ranges. The reason duratecs and shos have secondaries is to take advantage of the better VE available at different engine speeds and loads.
Short large runners are good for air in quick but long narrow runners are better for larger volumes of faster moving air needed for torque. The vulcan uses a middle or the range runner but the sho v6 has both. I think someone posted the measured VE of all the engines before if someone know where they could post it again. VE is pretty much a given in an engine there isn't alot that can be done to improve on it.
On another note bigger is not better. Optimum is best and no bigger. Smaller is better then bigger. Air moves faster through a small passage then it does through a large one. P&P is the best way to get to optimum but for the most part the engineers have used the best size and P&P just gets rid of the extra casting left from mass producing a part with a 10-20% error margin both ways.
Like spyguy I don't get what you are saying with 2 intake valves. You have a vulcan which has one valve per cylinder and only fires one cylinder at a time.
But if you are refering to a duratec it uses 2 smaller valves and runners to accomplish more then one big valve.
Short large runners are good for air in quick but long narrow runners are better for larger volumes of faster moving air needed for torque. The vulcan uses a middle or the range runner but the sho v6 has both. I think someone posted the measured VE of all the engines before if someone know where they could post it again. VE is pretty much a given in an engine there isn't alot that can be done to improve on it.
On another note bigger is not better. Optimum is best and no bigger. Smaller is better then bigger. Air moves faster through a small passage then it does through a large one. P&P is the best way to get to optimum but for the most part the engineers have used the best size and P&P just gets rid of the extra casting left from mass producing a part with a 10-20% error margin both ways.
Like spyguy I don't get what you are saying with 2 intake valves. You have a vulcan which has one valve per cylinder and only fires one cylinder at a time.
But if you are refering to a duratec it uses 2 smaller valves and runners to accomplish more then one big valve.
