| Re: 30 dollar 12HP+ air foil? |
Subject: Re: 30 dollar 12HP+ air foil? by jhammons01 on 2009/12/16 15:27:25 Quote:
Let's just play a little game. Let's use Central Coasters CocaCola straw in our game. First let me state that in a condition where the straw is sitting on a counter top all by itself.....there is NO CFM. You have to have a pressure differential on one side versus the other for there to be any measurable flow......but at what point do we find the maximum?? We take 1000psi on one end and no obstructions on the other end.... We open the full 1000psi into the straw (and just for our game we understand the straw doesn't explode). Once the full 1000psi is exposed to one end.......we can measure the CFM coming out the other end..... We want more CFM so we increase the psi to 2000.....Lo! it is still only flowing the measured CFM that came out under 1000psi. OK, so we now know that increasing pressure on one side does not equate to more flow.....let's decrease the pressure on the other side of the straw and see if that helps.. So we pull (to use a Motor head term) 29 inches of mercury on the outlet side of that straw.....will we increase the amount of flow?? Surely we will..... The answer is no. The CFM of the straw is determined by it's physical properties...not by the amount of upstream pressure or downstream vacuum once the amount of flow is measured. Fast forward, let's place that straw into an intake of a motor.....a nice V8. We know that the straw has a measured CFM.....how much CFM would we measure coming out of the tailpipes of our V8?? I'm thinkin' it would be equal to what is going through the straw. So, We take our V8 apart and bore out the cylinder walls and put in bigger valves and larger cam....we put it all back together and we measure the CFM coming out of the tailpipes again....however this time!!! It is equal in CFM to what we can get through that damn straw.... The CFM of the entire system will never ever change until you address the fact that there is a CocaCola straw throttling the system. But But But.....there are no more "Buts" or even "Yeah Buts" "even if".......Even if you stand on your head and do a can can dance wearing a clown suit.....The CFM of that engine will be determined by the physical properties and the CFM of the smallest orifice in that system....in our game that orifice is the CocaCola straw. And don't take my word for it. Google it up yourself...it is called Conductance. You EEs out there deal with electrical conductance all day long....and fully understand it.....this is the exact same thing. |
