Originally Posted by ianthegreat
would the fact that they focus more air into the engine bay be a plus? would this lower IAT temps?
I am skeptical of how much impact this really makes.
At a certain temperature differential, this might be true, but not with the temps in the engine bay when the car is moving and experiencing air-flow. It's actually much cooler in there than what you would think.
Next time you come off the highway or constant cruising (ie not stop and go traffic) pop open your hood and feel the intake pipes and surrounding components (not the oil filter housing which will be hot due to oil circulation).
They will be cool to the touch.
What does that tell you about temperatures in the engine bay?
And to add more substance, consider that once your cool intake air gets into the turbocharger housing, it has two things working to superheat it:
1. The exhaust turbine is subjected to temps approaching 1000 degrees. Some of this heat will conduct over to the compressor side and induce heat-transfer to your incoming charge of cool air.
2. As you spin the turbo, the spinning effect will create friction as a result of compressing the air to produce boost.
I think that both of these factors will add tons more heat to your intake temps than the engine bay ever will.
So any cooling effect from drawing outside air will no doubt be negated by the relatively larger temperature increase induced by the turbo's.
Remember, this is not a normally aspirated engine. so some of the standard performance equations do not apply when it comes to intakes. N/A cars do not have their intake charge pass through hot turbo's, so cooler air will have some effect in this type of engine.
If you are still not convinced, then ask yourself this - Why does BMW install an intercooler even with a stock cold air intake?
The answer is in their technical papers:
Air Ducting Overview
The fresh air is drawn in via the air cleaner and the charge-air suction lines and then by the compressors of the turbochargers and compressed.
Because the turbochargers can get very hot during operation, they are connected with the engine's coolant and engine-oil circuits. The charge air is greatly heated when compressed in the turbocharger, making it necessary for the air to be cooled again in an intercooler
The turbine and the compressor can rotate at speeds of up to 200,000 rpm.
The exhaust inlet temperature can reach a maximum of 1050°C.
The charge air heated in the turbocharger by its component
temperature and by compression is then cooled in the intercooler by up to 80°C.
But maybe I'm wrong
So step in Mr. Burger = resident myth buster and click on the above link to draw your own conclusions.
(Flame suit is now on)