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yep, the air gets VERY hot. First, remember that the turbo is being powered by the hot exhaust gasses. all of the tubing, etc., is being heat soaked by the engine and radiator.

Here is a forumla to estimate the temp. Remember that altitude changes and air temperature changes this forumla!


So for the ideal turbo outlet temp, T2 = T1*((P2/P1)^(0.283))

where P1 is the absolute pressure atmos (14.7 psi), P2 is absolute pressure after turbo (14.7 + 15 psi boost = 29.7psi), T is temp in 'degrees R' which is degrees f plus 460.

For 15psi at 20 degrees c (68 f) you have an ideal outlet temp rise of:

((68+460 * ((29.7/14.7)^0.283)-460)-68 = 115 deg f.

If your turbo is about 70% efficient at this boost level and airflow (figures taken from the compressor map) then the rise will be 115/0.7 = 164 degrees f, 73.33 degrees c. Adding this to the inlet temperature; 164+68 = 232.3 degrees f, 111.3 deg c.

The intercooler, if very good, can cool the air down to 20degrees of ambient air flow. Remember that the air can never cool it down to ambient unless you have a magic intercooler that is 100% efficient.

The only way to cool an air-air intercooler further than ambient is to spray co2 or nitrous in front of the intercooler, thus lowering the ambient air temperature. With a water-air intercooler, you can put ice water or bags of ice around the intercooler for a quick spurt.

Discussion Starter · #4 ·
Here is my addition to the intercooler article: intercooler placement.

Remember that air-air intercoolers have to have airflow moving through it to cool. Placing them in the front of the car is optimal. Some turbo cars like the subaru engines have the intercooler on TOP of the engine. Whenever the car doesn't have ram air moving through the duct on top of the intercooler that duct is acting like a chimney, letting heat out of the engine bay through the intercooler!

Can you say heatsoak?
Also, ducting is most efficient when it is about 2/3 the frontal surface of the intercooler.
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