[apk919]

Originally Posted by Drmike

Just thinking/musing out loud:

As we are concerned with heat transfer shouldnt we be looking at mass flow rate of the air not just pressure?



Air pressure P1 entering the scoop depends on vehicle speed and its aerodynamics
Air pressure P2 in engine bay (non moving air not from scoop) depends on vehicle speed its aerodynamics and resistance for flow to exit




Flow through scoop depends on all the losses in the system

- Roof scoop dimensions, length and shape
- Resistance to flow from the intercooler matrix
- Difference if any between roof scoop air pressure, P1, and engine bay air pressure P2 (exit resistance)


So all things considered we should see the following:

at low car speeds air pressure P1 and P2 is high but flow is low
at high car speeds air pressure P1 and P2 is low but flow is high


The mass flow rate is a function of pressure (density) and flow rate


So you can have a low pressure high flow air giving same mass flow rate as high pressure low flow air



Nothing ever moves from low to a high pressure zone. its physically impossible, Its always the other way around




opss coffees kicked in

I agree that the mass of air flowing though the intercooler is more important, that's why the most significant graphs are those which show the volume of air (in cfm) vs. vehicle speed. The pressure drop in P2 with speed (which is the significant measurement with regards to volume) seems to be quite small (only a few hundredths of an inch of Hg).

On the other hand I'd say that P1 increases with speed (since the scoop is actually flowing less air than it would be if the ducting presented no resistance... imagine sticking a tapered cone vs. a tube out in the airstream). That's significant when considering how air will flow when combining ducted air from other sources (i.e. the side scoops).