re rejetting carbs now i am jumping into the middle of this thread so i may not know what y all been talking about but i have a few comments in rec motorcycles davet interceptor cds tek com dave tharp cds writes unless an engine is supercharged the pressure available to force air into the intake tract is atmospheric at the time the intake valve is opened the pressure differential available to move air is only the difference between the combustion chamber pressure left over after the exhaust stroke and atmospheric as the piston decends on the intake stroke combustion chamber pressure is decreased allowing atmospheric pressure to move more air into the intake tract at no time does the pressure ever become negative or even approach a good vacuum there are a number of other factors that are very important the three biggest being air velocity air momentum and shock waves velocity stacks have been used for years and are now being used inside of stock airboxes on a number of bikes at a tuned engine rpm the stacks can greatly increase the speed and thus momentum of the air rushing in air momentum is critical in getting good air intake the momentum of the air stack outside the combustion chamber will force its way inside long after the piston has begun its compressive up stroke shock waves are used to induce air intake and to prevent fresh air from escaping out the exzhaust ports shock waves are the product of expansion chambers or any other means of presenting a wall opening or closing to the air in motion beyond this i am lost in the mystery of how they design for shock waves rich sturges h nswc carderock division w i speak for no one else and listen to the same
