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Thread: SC Exit Temps

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    Eric Ocman's Avatar
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    SC Exit Temps

    I noticed this while I was reading an article. Anyone have any empirical data on Temps with the common type Intercoolers we run???

    For example, if a supercharged engine is pushing 10 psi (0.69 bar) of boost at sea level (ambient pressure of 14.7 psi (1.01 bar), ambient temperature of 75 F), the temperature of the air after the supercharger will be 160.5 F (71.4 C). This temperature is known as the compressor discharge temperature (CDT) and highlights why a method for cooling the air after the compressor is so important.


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    West Texas RXP skoepp's Avatar
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    Quote Originally Posted by Ocman View Post
    I noticed this while I was reading an article. Anyone have any empirical data on Temps with the common type Intercoolers we run???

    For example, if a supercharged engine is pushing 10 psi (0.69 bar) of boost at sea level (ambient pressure of 14.7 psi (1.01 bar), ambient temperature of 75 F), the temperature of the air after the supercharger will be 160.5 F (71.4 C). This temperature is known as the compressor discharge temperature (CDT) and highlights why a method for cooling the air after the compressor is so important.
    By far is the hottest pipe in my hull.

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    Huh? Dyoung's Avatar
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    I always wondered why the water from the pisser off of my i/c was so warm...now I know

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    Eric Ocman's Avatar
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    Found some more data. This has probably already been covered here but Im trying to get a better understanding of it all.

    Total Volume:

    Height x Width x Depth = the total volume of the intercooler, which is an indirect measure of the internal surface area of the intercooler. The larger the volume, the larger the heat exchange surface area, the more heat we can sink out of the air in an extremely short period of time (the 100 milliseconds or so that the air spends inside the core). Obviously the bigger the volume, the better the cooling and the worse for pressure drop. Again this number needs to be controlled.

    How do I know if the intercooler I have now is adequate?

    Intercooler efficiency can be tested in two ways:

    1- Thermal performance

    a. Measure the temperature difference between the intercooler inlet air and intercooler outlet air and use this delta T to compare between the intercoolers you have available to you. The best intercoolers out there can drop air temperature by over 100*F and get you within 20* of ambient air temperatures. If your factory intercooler can already accomplish similar results then there may be no need to upgrade.

    b. Track the temperature of your intercooler in a prolonged power run, or on back to back power runs. The design and placement of the intercooler should be adequate that the temperature rise over time (with say 60+mph air hitting the intercooler) should be controlled, if the temperature rise is too steep then you may need a better ‘radiating’ core with more frontal area, better air guides and air foils, and better placement with high pressure air in front and low pressure air behind it… we’ll explain more about this later.

    2- Flow performance

    a. Measure the flow through the intercooler core at 28” of water (standard for most flow meters), or measure the overall intercooler pressure drop at the flow rate required by your target horsepower. If the intercooler is on the car, measure the differential pressure across your intercooler at peak hp figures.

    The best intercoolers will have less than 1psi of pressure drop (typically 0.5 to 0.9psi) at peak boost and horsepower. If your intercooler is within these power figures then there may not be any need to upgrade.

    Now going back to selecting the best sized intercooler for your application, it would be very tough for me to figure out the exact math of how to optimize your intercooler size, and then I would have to translate that math to ‘car terms’ of power, inlet air temps, supercharger outlet temps, pressure ratios and boost pressures…etc

    Here is another solution; one thing engineers like to do in dealing with this kind of a problem plotting statistical data on a chart and looking for some trends…

    I found some 30 different intercoolers online with either flow tests (CFM), or Dyno tests (HP) or both, and since we know that it takes roughly 1.5 CFM of air to produce 1 HP (depending on density) then I combined both sets of data both for flow tested OEM intercoolers and for aftermarket ‘engineered’ intercoolers to produce the following graphs:

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    Eric Ocman's Avatar
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    Has anyone ever attempted to water jacket the sc housing or would the benefits in the associated charge temp be pointless??

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    home of the dislexic fingers breon's Avatar
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    the rotax housing is jacketed....

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    Eric Ocman's Avatar
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    And it feeds off the exhaust manifold line or?
    Wow I saw that housing.... 2,800 WTF!

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    home of the dislexic fingers breon's Avatar
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    Quote Originally Posted by Ocman View Post
    And it feeds off the exhaust manifold line or?
    Wow I saw that housing.... 2,800 WTF!
    its rotax....everything rotax is WTF...

    i would say you can feet it from anywhere but i would go from the pump...any water comming from the exhast manifold is already hot

    basically a fizzle is good for 13 14 psi ..above that you really should think about a better intercooler especially if wher eyou live is hot and the water temps are high...

    in fla we see 97 deg air with 90 deg water ..not real good for cooling...that is also why i run a 40 la heat exchanger..just because

    i can watch my af get richer and rmp fall as i hold WOT..a bigger intercooler is near the top of my list for the next upgrade..

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