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aerodynamic and thermal benefits of vent block

Discussion in 'Gen 2 Prius Fuel Economy' started by chronon, Jun 16, 2007.

  1. chronon

    chronon Active Member

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    Hello - I saw graphs of upper vent, lower and upper - lower .. it showed the best gains from the lower 2? vents.

    I blocked the lowest one ( which doesnt even seem to go directly to the radiator nor the a/c radiator ) --
    this could keep the intake manifold warmer and reduce aerodynamic drag - of course , in the summer time
    the thermal gains are less than when implemented in the winter.

    I am in about 80 deg F ave temp .. its less than 80 in the early am, but more than 80 by late morning and until just before sun set. My concern is with the invertor temps - i dont want those to go too high while keeping the engine coolant high.

    Speaking of aerodynamics - has anyone installed rear wheel skirts ?
     
    #1 chronon, Jun 16, 2007
  2. efusco

    efusco Moderator Emeritus
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    If you do not have CAN-View I would definately suggest NOT blocking the lower vent...and probably not even the upper vent...in warm weather (ie over 50-60 degrees). the lower vent is the primary air flow for the lower 1/3rd of the radiator which contains the coolant circuit for the inverters...you don't wanna fry those.

    They definately help, but it's not worth the risk to the car. I already am seeing inverter temps in the 130 degree range with the lower vent open in 80 degree weather here.
     
    #2 efusco, Jun 16, 2007
  3. donee

    donee New Member

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    Hi Ersh,

    In the sumertime, with the humidity and warm temps, aerodynmics are not as important. Humidity actually reduces air density.

    Get you out on a 15 degree day in some wind, on the highway, with some fast trucks, and it will be readily apparent how much more dense the air is. I have had the car pulled out cruise control by trucks in such weather at 70 mpg. Next thing I knew, I was locked into the trucks draft at 75. Had to cancel cruise, and tap the brake to get free of it!

    Yep. I agree with you on the inverter temps. I only block the very top radiator opening on my car in the summer. And my commutes rarely have high speeds for very long, and being on mostly flat Chicagland terain, its probably safe. The temps here are about 65 in the morning and 90 F on the drive home. But the driving in the evening is much more slow and go. So, the engine is turning off.

    At 80 degree F, I would not do any blocking for a long trip. The top radiator opening helps allot in rain. The rain comes in that opening and at highway speed hits the top of the radiator, which is the warmest, and gives off the heat. For a 1/2 hour highway speed trip, or, a 1 hour slow and go trip, blocking the top opening only is probably OK.
     
    #3 donee, Jun 16, 2007
  4. slair

    slair Ubër Senior Member

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    Wth?! Ya, go ahead and block your air flow and see what happens.
    lol.
     
    #4 slair, Jun 18, 2007
  5. efusco

    efusco Moderator Emeritus
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    <div class='quotetop'>QUOTE(Slair @ Jun 18 2007, 08:25 AM) [snapback]463916[/snapback]</div>
    Oh, many of us have already. And with proper monitoring of the critical component temps "what happens" is improved fuel economy. Was this a question or just a smart nice person uninformed comment?
     
    #5 efusco, Jun 18, 2007
  6. JimN

    JimN Let the games begin!

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    <div class='quotetop'>QUOTE(Slair @ Jun 18 2007, 08:25 AM) [snapback]463916[/snapback]</div>
    In addition, what happens is that the fan will start if it gets too hot. So far with partial blockage (never full) the fan hasn't started. My Intrigue has a solid nose and an electric fan and in some 7 years and 80,000+ miles it still runs.
     
    #6 JimN, Jun 18, 2007
  7. F8L

    F8L Protecting Habitat & AG Lands

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    I was curious about this myself.

    Where I live it is generally pretty warm durring the day so I get great milage. Yet at night once temps drop to 60deg my milage tanks hard. IE on my way to a club last night at about 8pm it was 75deg or so and I was getting 50-53mpg instant and averaged 48.9mpg. On the way home it was 61deg and my instant milage sat at about 36mpg then after the warmup crept up to 43mpg which brought my average down to 47.3mpg.

    In cases like this where I am driving home late at night would blocking the upper (only) vent be worth the hastle of carrying the material in the car and installing it for the drive home?
     
    #7 F8L, Jun 30, 2007
  8. JimN

    JimN Let the games begin!

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    <div class='quotetop'>QUOTE(F8L @ Jun 30 2007, 10:58 AM) [snapback]470595[/snapback]</div>
    F8L, based on the temps you mentioned, you should be able to block your upper grill and leave it in.
     
    #8 JimN, Jul 1, 2007
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