now I know several guys with turbo and supercharged engines and a few had issues with what they assumed was valve float ,at lower rpms than they experienced valve float before the engine was supercharged, sometimes with the same cam and valve train, when using basically stock valve trains, after checking geometry and clearances it became rather obvious that the valves were not seating correctly under high boost, and the reasons simply that if you've got a pressurized intake runner and lets say a 10 lb boost pushing on the back surface of a 2.02" intake valve thats about 3 sq inches of area with about 30 lbs of force trying to hold it open, off the valve seat, that a similar non-boosted engine doesn,t deal with, so an increase in valve spring seat pressure is mandatory to maintain a good solid valve seat seal.
obviously a cam and valve train designed for the application is going to be closer to ideal , especially in valve timing as a super charger cam usually has a wider LSA and a longer exhaust duration, but guys forget that theres other factors besides the valve timing that changed and things like ring gaps, increased fuel flow,pressure and jetting or larger injectors, bigger radiators and more effective lubrication systems, and valve seat pressures need to change, you can,t just slap a centrifugal super charger on a stock engine and expect it to run at max efficiency
yes your supercharged engine DOES tend to show a slightly richer plug color and fuel/air ratio meters do tend to indicate your effective mixture is a bit richer for the exact reason you stated.
thats one reason super charger cams tend to have a wide 112-116 LSA, so that theres a bit less overlap time where compressed boost could enter and partly exit into the exhaust port while both valves were open
obviously a cam and valve train designed for the application is going to be closer to ideal , especially in valve timing as a super charger cam usually has a wider LSA and a longer exhaust duration, but guys forget that theres other factors besides the valve timing that changed and things like ring gaps, increased fuel flow,pressure and jetting or larger injectors, bigger radiators and more effective lubrication systems, and valve seat pressures need to change, you can,t just slap a centrifugal super charger on a stock engine and expect it to run at max efficiency
yes your supercharged engine DOES tend to show a slightly richer plug color and fuel/air ratio meters do tend to indicate your effective mixture is a bit richer for the exact reason you stated.
thats one reason super charger cams tend to have a wide 112-116 LSA, so that theres a bit less overlap time where compressed boost could enter and partly exit into the exhaust port while both valves were open
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