Head Porting Recomendation?
After years of being driver/engineer we deal with Critical Velocity in fire hose sizes, as well as the Laminar flow of water. For us the concern was the nominal amount (GPM) of water that we could flow through a given hose size before the efficiency went away. This is to say I could increase the engine pressure but at some point your going to have to deal with the 6 principal's of hydraulics in order to increase Water flow.
From listening to the head porters and gurus in this thread, the obstacles seem quiet similar? I am right?
Bernoulli 101!!!!
For some reason this man's concepts aren't very common yet they impact what we do greatly..... so THESE ARE THE LAWS OF PHYSICS WHICH ARE NOT QUESTIONABLE... smart people figured these out centuries ago:
First... air is a COMPRESSABLE fluid, oil and water are INCOMPRESSABLE. If we don't start with that statement people get lost down the line
Second... the principle of conservation of energy requires that the sum of kinetic energy and potential energy remain constant. Energy can't be created just transformed.
Third.... fluids only move from a area of high pressure to a area of low pressure. Period. The best example we can relate to is a piston, as it moves down a bore it is creating a lower pressure than that of what is in the port above it so the air fills the lower pressure void until it's pressure is higher than that of what is filling it. FWIW the pressure increases in the cylinder because the mass of air increases and the volume to store that mass stops increasing in size. Basically it's filled up at that pressure level.
Fourth.... a orifice can only flow so much volume thru it at a set pressure drop. Think of a orifice plate used to calibrate a flow bench. It is set at a certain diameter so that at a given depression 28" of H2O it will move a set CFM level, then you adjust the bench to read what it should.
Pressure and Temp...
Higher pressure = Higher temp...... Lower pressure = Lower temp
Think about it this way, why do we need an intercooler on a supercharged engine? Because the air is being compressed increasing the pressure which is putting energy INTO the air (since it's a compressable fluid) which causes the air molecules together and they make HEAT. So we need to cool that higher pressure air down before we put it in the motor with a intercooler.
Same applies to your compressed air tank, when you put the air gun on the line and use it to dry or clean off parts... it's colder NOT BECAUSE of evaporation (you can actually measure this with a temp gun) but because of the expansion of the air. Conversely when you compress the air into the air tank the tank gets warmer again something you can check with a temp gun.
Velocity and Area...
Area effects the speed of the air, the larger the area the slower that same volume of air passing thru it will be. I know there are some guys who don't get this because I have seen the crap they grind on, but when you need the velocity in a cylinder head to decrease you increase the area at that point. Which leads into....
Pressure and Velocity...
The faster the velocity the lower the pressure. The hood scoop or carb venturi on a race car is a perfect example of this...
A carb only draws fuel into the air stream because as the area decreases (going into the venturi), the speed increases and the pressure drops. Then it expands again due to the larger area which increases the pressure and slows the velocity.
In terms of the hood scoop the set area only allows a set volume into the scoop. (4th rule above) The air exits the scoop orifice and slows down into the larger area of the scoop the pressure INCREASES due to the conservation of energy. You are turning the kinetic energy of the velocity into the potential energy of PRESSURE. As started above in the 3rd rule... the more pressure you have above the valve the more you can put in the cylinder... hence why a good hood scoop will increase the speed/HP of the car going down the track.
So.....
Higher Pressure = Bigger Area = Lower Velocity = Lower Temp
Lower Pressure = Smaller Area = Higher Velocity = Higher Temp