WCKDVPR
Viper Owner
Re: VIPAIR™ Dyno Results on 99 RT 16 RWHP!!
I know this is all about being the longest post and I have not read all of the replies so the answer may be in here somewhere. But based on the last few pages I scanned where technical assumptions are being made, it looks like the jury is still arguing about ram air - real or not.
Well, here is the answer for all of you as this problem can be easily solved using Bernoulli's Equation.
Bernoulli's equation states along any point on a streamline the relation between Local static pressure (P), density (p) and Velocity (V) is: P/p + (V*V)/2 = constant
Applying this to a moving car, the local air velocity increases due to the car deforming the local streamline as it flows around/over the body. Therefore, we can write the equation for a point at infinity in front of the car and a point at the car and as such the constant equals the same because we are only comparing the velocity and pressure at these two points in the flow. Using Pinf=Pressure Ambient, Vinf=vehicle speed, PA=static pressure near the vehicle surface, and VA=local air speed, the equation becomes: PA/p + (VA*VA)/2 = Pinf/p + (Vinf*Vinf)/2
Looking at a position/opening at the front of the car where local velocity approaches zero (ram air box leading to a throttle body, radiator, etc), this gives us a VA=0, solving for this gives you:
PA/p = Pinf/p + (Vinf*Vinf)/2
If the vehicle is traveling at say 30m/sec (67mph) and using density of air at 1.22 kg/m3 (20 C and 1 atm), solving the equation yields PA - Pinf = (Vinf*Vinf)*p/2 = (30*30)*(1.22/2)= 549N/m2 = 0.08 psi.
Going 60 m/sec (134 mph) yields a positive pressure of 0.32 psi.
Going 90 m/sec (201 mph) yields a positive pressure of 0.72 psi.
There you go - ram air is real. It is free HP and I'll take it.
Hope this helps
P.S. If you still don't believe, you never will as this is the exact principle that pitot tubes rely on to measure air speed on airplanes. It has been around for a while (Henry Pitot invented it in the late 1700's and it was refined into its modern form by Henry Darcy in the early 1800's) and we are still using it today on pretty much every aircraft built.
Regards,
I know this is all about being the longest post and I have not read all of the replies so the answer may be in here somewhere. But based on the last few pages I scanned where technical assumptions are being made, it looks like the jury is still arguing about ram air - real or not.
Well, here is the answer for all of you as this problem can be easily solved using Bernoulli's Equation.
Bernoulli's equation states along any point on a streamline the relation between Local static pressure (P), density (p) and Velocity (V) is: P/p + (V*V)/2 = constant
Applying this to a moving car, the local air velocity increases due to the car deforming the local streamline as it flows around/over the body. Therefore, we can write the equation for a point at infinity in front of the car and a point at the car and as such the constant equals the same because we are only comparing the velocity and pressure at these two points in the flow. Using Pinf=Pressure Ambient, Vinf=vehicle speed, PA=static pressure near the vehicle surface, and VA=local air speed, the equation becomes: PA/p + (VA*VA)/2 = Pinf/p + (Vinf*Vinf)/2
Looking at a position/opening at the front of the car where local velocity approaches zero (ram air box leading to a throttle body, radiator, etc), this gives us a VA=0, solving for this gives you:
PA/p = Pinf/p + (Vinf*Vinf)/2
If the vehicle is traveling at say 30m/sec (67mph) and using density of air at 1.22 kg/m3 (20 C and 1 atm), solving the equation yields PA - Pinf = (Vinf*Vinf)*p/2 = (30*30)*(1.22/2)= 549N/m2 = 0.08 psi.
Going 60 m/sec (134 mph) yields a positive pressure of 0.32 psi.
Going 90 m/sec (201 mph) yields a positive pressure of 0.72 psi.
There you go - ram air is real. It is free HP and I'll take it.
Hope this helps
P.S. If you still don't believe, you never will as this is the exact principle that pitot tubes rely on to measure air speed on airplanes. It has been around for a while (Henry Pitot invented it in the late 1700's and it was refined into its modern form by Henry Darcy in the early 1800's) and we are still using it today on pretty much every aircraft built.
Regards,
