I was playing around with some data thinking about intakes and what really matters. What I figured out was that turbo outlet temps is all that matters. Some may not know that air that is pulled in by the compressor has work done to it. This work or energy cannot be created or destroyed, so it is converted from mechanical energy to heat. This heat makes the compressed air exiting the turbo much hotter than the air that entered.
There are three key indicators that control exit temperatures:
Inlet temp
Pressure ratio (outlet pressure (psia)/(inlet pressure (psia))
And compressor efficiency (from map)
In this example I theorized a smaller turbo setup supplying about 12-14 psi to the manifold (14psi at turbo exit), atmospheric pressure of 14.7psi, and since our turbos are tiny they will be on the high side of the map in the 68% efficiency range.
For "stock baseline" I assumed that there was 14.7 psia at the inlet (no restriction) with the same 68% efficiency and 14 psi turbo exit boost.
Then I theoretically put on a restrictive intake reducing the inlet pressure to 12.7 psia from 14.7 psia while all other factors were held constant. This line is listed as "-2 inlet restriction".
Lastly I sprung for some theoretical atp turbos and went from the far end of the compressor map at 68% to the meat of the compressor map at 75% while leaving every thing else as the same as the stock. Labeled as "high efficiency"
As you can see sucking in 20 degree hotter air than ambient resulted in a 26 deg rise in exit temperature. While restricting the intake and have cool air resulted in a 40 degree rise in exit temperature.
Lastly the high efficiency turbos lowered the exit temperature 16 deg on a 70 degree day vs the baseline.
I hope this can illustrate that not only does intake temps matter, but inlet flow matters too as it will raise exit temperatures as much, if not more than inlet temps.
Those sweet atp's may not be worth the cost of you don't plan on pushing past the stockers capability.
John
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