[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 depends on vehicle speed its aerodynamics engine bay vent pressure and resistance for flow to exit the bay




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 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


The only way you will get reverse flow out the scoop is if the air pressure at scoop entrance is lower than the air pressure in the engine bay AND if the engine bay has high pressure flow entering into it. It doesnt matter how high the pressure or temp is in the engine bay if its not moving/being fed it wont flow anywhere and will instantly balance with scoop exit pressure. As the only air entering the engine bay is coming from the underfloor engine bay vents then I would assume that air would be lower pressure than roof scoop pressure at speed due to aerodynamics? That being the case I cant see how reverse flow can ever happen - but I could be talking bollocks

bottom line I think we need to measure mass flow rate. so we need to record air pressure (in scoop) as well as flowrate (or velocity) through scoop



opss clearly the coffees kicked in


all things being equal:

flow rate through scoop depends on total resistance to flow through scoop

How much the front part of the scoop size contributes to the total resistance to flow through scoop is the question. My guess would be the intercooler matrix is far larger a contributor - which would suggest ading fans after the intercooler wouldnt be very effective

Measuring air velocity, V, after the intercooler may not highlight small changes in flowrate, Q, as the 'area' A is huge (Q=VA) so small changes in flow rate may not be apparent. It might be better to mount the velocity meter inside the ducting before the intercooler if possible or in a duct attached to the front and encompases all the outlet from the intercooler