Radiator/Airflow ducting

[Mr Morlock]

Nitro- by all means post some info that bears out your contention- I don't think the foam on the top of the rad cover of the MX5 will make a jot of difference. Many cars have no ducting around radiators at all.

[NitroDann]

Customers have dríven from as far as Brisbane, 800km away to have me fix track car heat issues that others have no been able to.

If you want flow through any orifice, you need to have a pressure differential, the higher the pressure differential the higher the rate of flow. (assuming the same orifice and linear flow)

To create a pressure differential you need a high pressure on one side and a low pressure on the other.

Low pressure in the engine bay is created by sealing it underneath, and allowing only radiator air to pass into it from the front, and venting it in low pressure locations, such as strategic points on the bonnet, possibly using a gurney flap to further lower the pressure across the vent.

High pressure in front of the radiator is achieved through ducting air into the radiator, and sealing the ducting in order to hold the pressure and not leak any air out, which would of course lower the pressure.

Doing this increases the pressure differential over the radiator and promotes flow through the orifices which are the fins.

This, along with increasing the surface area of the radiator (thicker, more fins per inch) and increasing efficiency (better materials for heat transfer, better cooling fluid, increasing average heat of the core to increase DeltaT-difference in temperature- and increase heat transfer efficiency etc) is the key to cooling.

Also removing restriction to flow (fans and shrouds etc) is the necessary external mods to get fantastic cooling control.

It's all well and good to run without undertrays and foam sealing strips (and also the rear bonnet sealing strip) if you are putting down an average of 20hp cruising on the highway, but when you are putting down 350hp at an 80% duty cycle (equivalent to 280hp@100%) you are asking your track setup for 13 times more cooling than the street car on the highway example.

Dann

PS- Increasing the hole in front of the radiator past stock does nothing to help. The reason the radiator opening is typically 1/3rd of the size of the radiator is because if you look at the front of the radiator its 2/3rds metal and 1/3rd holes. So if you run the radiator mouth opening bigger than a third your radiator becomes the bottleneck anyway. Having a solid understanding of how flow works, and how pressure differential works, along with knowing the relative pressure across all areas of the specific model of car you are dealing with at road speed is how you design effective cooling systems.

[Mr Morlock]

good Dan- I certainly have no problems in staying with an OEM set up for a standard car -afterall automotive engineers and rad a/c specialists are just that.

[NitroDann]

A standard road car with standard road use works very well. Completely agree.

Dann

[StuwieP]

It's all well and good to run without undertrays and foam sealing strips (and also the rear bonnet sealing strip) if you are putting down an average of 20hp cruising on the highway, but when you are putting down 350hp at an 80% duty cycle (equivalent to 280hp@100%) you are asking your track setup for 13 times more cooling than the street car on the highway

Not really relevant to the thread, more my interest but is heat generation that linear? I would have anticipated a much higher rate.

Stu

[NitroDann]

Hard to say, combustion efficiency is probably increased a lot in most performance builds.

dann