Great Video About Engine Fans and HP Loss!
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Thread: Great Video About Engine Fans and HP Loss!

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    Just Some Dude in Jersey My location The Scifi Guy's Avatar
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    Great Video About Engine Fans and HP Loss!

    https://www.youtube.com/watch?v=ZXdLgaFXZzs


    Norbert found this one. It shows a pretty good series of dyno tests of various engine fans on a V8 and compares them to no engine at all and a brief comparison of the effect of the radiator shroud. The comparisons are made solely based upon Max Torque and Max HP, not cooling efficiency, which is a primary concern on GT's. Some interesting points they make that may or may not be true:

    1) They claim an alternator making 30 amps(to power an electric fan) would use only about 1 hp.

    2) I think they must be way off in the one guy's estimation that the parasitic drag(the HP loss) of an engine fan will stay constant, regardless of engine size. The worst fan registered a 30hp loss, if he was correct, then a 90hp 1.9 engine would gain THIRTY HP if you take the engine fan off. I've had GT's with no engine fan and an electric instead, no fan feels like a 3-5 hp gain to me. Take into account that they're testing 18" fans, not our smaller ones. And, of course, The hp loss is the greatest the closer you get to redline.

    3) Interesting to observe that they discovered that no shroud around the fan actually decreases hp. So, if you run your engine fan without a shroud, not only will you reduce your cooling efficiency, you'll also lose a few more horse puppies.


    Nope, I'm keeping my engine fan and my back up electric fan(s). Keeping my engine cool is way more important to me than how fast I can go. I want lots of air to pass through my engine compartment all the time. I'm always stuck in traffic on hot, humid, days where I live.



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    Pedal Smasher Autoholic's Avatar
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    Ya this is the third time someone has shared this LOL.

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    Quote Originally Posted by The Scifi Guy View Post
    https://www.youtube.com/watch?v=ZXdLgaFXZzs


    Norbert found this one. It shows a pretty good series of dyno tests of various engine fans on a V8 and compares them to no engine at all and a brief comparison of the effect of the radiator shroud. The comparisons are made solely based upon Max Torque and Max HP, not cooling efficiency, which is a primary concern on GT's. Some interesting points they make that may or may not be true:

    1) They claim an alternator making 30 amps(to power an electric fan) would use only about 1 hp.

    2) <SNIP>

    Nope, I'm keeping my engine fan and my back up electric fan(s). Keeping my engine cool is way more important to me than how fast I can go. I want lots of air to pass through my engine compartment all the time. I'm always stuck in traffic on hot, humid, days where I live.


    Do the math! 12 volts x 30 amps = 360 watts
    1 HP = 746 watts so 360/746 = .48 HP required
    If you assume the alternator is 50% efficient, then 1 mechanical HP is required to develop 360 watts so the above statement is true! (This is conservative as I believe that alternators are better than 50% efficient, i.e. less HP required.)

    HTH -- Doug
    Last edited by slracer; 6 Days Ago at 11:36 AM.

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    1000 Post Club My location Dale .D's Avatar
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    Very interesting. I believe it . I used to have just a electric fan. Found it a real pain with my loppy Idle. Every time the fan kicked in at Idle it almost killed the idle. Went back to mechanical with the electric as backup , no shroud.

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    "Be Water, My Friend" Bruce Lee, December 9, 1971

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    Yeah, yeah, yeah! This was all very interesting, but pretty much USELESS!

    1. The amount of air a fan moves is strongly related to the pitch of the blades and the 4 fans tested all had different pitch on their blades.
    2. IIRC, the thrust developed by a propeller (and these fans are all just poorly designed propellers) is also a function of how much area the blades cover vs the total "disc area" which is varies from fan to fan on this "test". It is called "solidity factor"?
    3. Taking the shroud off in the one case just reduced something that was poorly designed to start with. A properly designed shroud will improve the efficiency of a properly designed fan. Are either of these available as over the counter that are universal fit? Absolutely not!
    4. More details all of which were uncontrolled ....

    Bottom line: Ignore the results!
    Next to the bottom line: Ignore the electric fan result above too! If you have to move a certain amount of air through a radiator to cool the engine, it will take the same HP regardless of the method used to drive the fan. There are differences in the efficiency of the different systems which means the input HP will be different, but the required "output HP" (the amount of air moved at a given speed) is constant.

    As usual, this is JMHO, but is based on my education and job experiences with aircraft components for over 32 years. Am I right? Usually! (but not always).

    Doug

    I MAY get interested enough here to dig out some of my old text books and put together a better summary, but don't hold your breath. This brings to mind an old proverb attributed to the Irish (in this case):

    Lord, grant me the serenity to accept what I cannot change, the courage to change what I can, and the wisdom to know the difference. I believe what we are looking at here falls mostly into the first case!
    P.J. Romano and The Scifi Guy like this.

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