Bo White

iTrader: (59)

IMO the exhaust port gains stability with a pipe because of its short port length. The exhaust port itself is so short that the spent gasses/air doesnt have enough time to have a defined direction, its kinda like washin your car... when you pull the trigger when you are using the water hose the more you pull it the further the piston inside gets out of the way for water flow but look past that. When the piston is moving back out of the way its making the outlet deeper and in a sence making the port longer for which the water to travel through and gain direction. That is why it comes from a shower spray to a more defined jet of "defined direction" when its opened all the way. Sure the pressure of the water helps but its the "length" of the port of which the water is exiting that makes the water follow a more defined direction after it leaves the port. So this is my idea of what happens when you add a pipe to the exhaust port on the flow bench, adding the pipe helps define the direction of which the air must travel and making the port that much more effiecient. Just a thought

gomer

iTrader: (13)

One thing that I've always thougth about is this.... when you flow an exhaust port on a flow bench, your are pumping ambient temperature air thru it. When the engine is in operation, it has VERY high temperature exhaust gasses exiting out of it. Think of it as opening a chilled Dr. Pepper vs a hot one that has been shaken up. When you think of it that way, you'll see that a flow bench can only be used to measure one variable in the equation. It doesn't take into account the actual dynamics of a running engine.