End product and an impromptu heat shield for turbo:

 

http://forum.miata.net/vb/showthread...72#post4624172
here is a great thread where everyone clamors for fans rather than ducting, lol.

 

I have been following your RAP battle in there. I am siding with you on it. Once I get my new motor in in a few weeks I am planning to finally do some ducting.

 

I only read the last page. It was interesting. A cooling fan shroud is great when you have fans that can't pull enough air to cool the coolant. My two 2200 or 2400 cfm fans bring my temp down by like 10* with a quickness with no shroud. I think a shroud would **** up the airflow when driving unless there were many flaps.

 

True, but no one in that thread drives a car fast on the track. I only use the fans when the car is parked in the pit to avoid heat-soak, that's the only time my head's water temps go overr 180* according to my gauge.

 

That is much cooler than I run, what's your secret!?

 

I have a 2nd gt40r turbonator just to force air through the radiators with a custom shroud.

 

Aah, I have been using twin turbonators. I now see the err of my ways. Do you have an intercooler on it so the air being forced through actually cools?

 

I just wanted to ask a Q,

Correct this if it is wrong, The reason the duct opening is one quarter the size of the exchanger is because the air flows into the duct at 'X' mph but due to the restrictions of the exchanger it only flows through the exchanger at 1/4 'X' mph?

Thanks,
Dann

 

vaccum to the rear of the exchanger has a much greater effect on greating positive airflow than pressure to the front.

 

Not true. The flow is only determined by the pressure difference across the exchanger (and the restriction of the exchanger itself, assumed to be constant). 1 psi more at the front or 1 psi less at the rear will produce the same change in flow.

 

Actually the opposite is true. Blowing through a restriction is more efficient than sucking through a restriction. Higher pressure makes things more dense thus able to do more work and carry away more heat with it.

As an example the same sort of thing happens with throttle body sizing on turbo versus positive displacement super chargers. A restrictive throttle body with a turbo blowing through it doesn’t make much difference the same restrictive throttle body with a super charger sucking through it makes a huge difference.

Bob

 

I can speak to that ^^^ with direct experience. I went from a duct like this on my smic:



To this one:



and the IC core went from warmish at the outlet to downright cold. No change at the back of the core was made from one duct to the other to create a vacuum.

 

I need to mount my oil cooler to get more air becuase the 2.5" hose is not cutting the mustard.

 

I will add this info to my ethuggery repertoire.

 

And what are the key points?

 

I doubled the inlet size of the duct in the aluminum one vs the plastic factory piece, and sealed it around the IC core using HVAC tape. I opened up the hole in the bumper cover accordingly, and overall it cooled much better. I did not make any before/after temp comparisons, as the IAT in a DSM is in the MAS, but to the touch it was vastly cooler.

I figured if I could essentially make a huge hole/duct in a high pressure area (ie: on the front of the bumper cover), that it would increase the pressure on the front side of the IC core and more air would have to move through it...not really any more complicated thought behind it than that. Sure, the air is going to back up in the duct and probably create some unpleasant aero side effects at that corner of the car, but I didn't notice anything untoward while racing around the mountains here.