Attention: TDR Forum Junkies 
rbattelle
TDR MEMBER
Focusing on the intake side...
Anything you can do to make an engine "breathe" better will result in efficiency and power improvements. But Hohn's absolutely right about the flow being limited to the characteristics of the turbine inlet flange (on the exhaust side) and the intake manifold inlet (on the inlet side). If those parts remain unchanged, it makes little difference what you do before that point, except in the case where you're able to change temperature significantly. Remember that flow rate is defined as density*velocity*area.
If you've got a large plenum with convergences at the entrance and exit, the velocity of the flow will decrease as it passes into the plenum, then increase again when it leaves the plenum. If the inlet and outlet areas are similar, the velocities are going to be similar. Then the only benefit you'd get would come from a change in temperature, which has a direct effect on the density term in the definition of flow rate.
All that aside, I'm not sure I'm comfortable with any device that reduces intake pressure. More pressure in your intake manifests an increase in mean effective pressure and peak cylinder pressure, right? And those two parameters are perhaps the most important for defining power output.
Or does the increased volume of air exactly balance with the lower pressure so that MEP and peak pressures are unchanged? Pressure and volume are directly related by the ideal gas law; if temperature remains constant, then increasing either one should result in a proportional decrease in the other.
Hohn is absolutely right - if the manifold pressure tap is located in the plenum it's not going to read "true" manifold pressure, and would neatly explain the massive difference in DHayden's pressure readings.
-Ryan
Anything you can do to make an engine "breathe" better will result in efficiency and power improvements. But Hohn's absolutely right about the flow being limited to the characteristics of the turbine inlet flange (on the exhaust side) and the intake manifold inlet (on the inlet side). If those parts remain unchanged, it makes little difference what you do before that point, except in the case where you're able to change temperature significantly. Remember that flow rate is defined as density*velocity*area.
If you've got a large plenum with convergences at the entrance and exit, the velocity of the flow will decrease as it passes into the plenum, then increase again when it leaves the plenum. If the inlet and outlet areas are similar, the velocities are going to be similar. Then the only benefit you'd get would come from a change in temperature, which has a direct effect on the density term in the definition of flow rate.
All that aside, I'm not sure I'm comfortable with any device that reduces intake pressure. More pressure in your intake manifests an increase in mean effective pressure and peak cylinder pressure, right? And those two parameters are perhaps the most important for defining power output.
Or does the increased volume of air exactly balance with the lower pressure so that MEP and peak pressures are unchanged? Pressure and volume are directly related by the ideal gas law; if temperature remains constant, then increasing either one should result in a proportional decrease in the other.
Hohn is absolutely right - if the manifold pressure tap is located in the plenum it's not going to read "true" manifold pressure, and would neatly explain the massive difference in DHayden's pressure readings.
-Ryan
