Hot intake manifilt





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  1. #1
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    Default Hot intake manifilt

    (gona try post in english so most can understand, please excuse grammer)
    I have noticed that the intake manifilt on my Prado 3.4 V6 gets quite hot. From what I have heard, cold air can get compresed more so more air can go into motor, better power ect ect. So I assume the oposite is also true? Hot air that go into motor will have a negative effect on power. Am I right? Is this occurance seen on other engins aswell? Or might it be a design flaw? How big an effect wil the hot air have on power? I would have liked to have cooler air go into te motor but is an intercooler the only selusion? I realy dont want to fit a intercooler if I can help it.
    Pat

    Hilux 3.0 D4D 4x4

  2. #2
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    The air passes through the manifold waaayyyy to quickly to heat up significantly. I would guess less than 1 C.
    Everything is a hammer.
    Unless it is a screw driver.

    Then it it a chisel.

  3. #3
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    Quote Originally Posted by Die Skim View Post
    So I assume the oposite is also true? Hot air that go into motor will have a negative effect on power. Am I right?
    Yes.
    But with some "terms and conditions".
    Air is a very good insulator.
    Air moves into the engine at a pretty decent speed.
    So there's not a lot of time to heat the air by the manifold.
    Hence intercoolers are generally only fitted to engine with turbos. The air in those systems are subject to more heating (From the exhaust side housing, compression heat etc etc) than the air on a naturally aspirated engine.
    Last edited by RedLineR; 2011/03/30 at 01:28 PM.
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  4. #4
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    Quote Originally Posted by Uys View Post
    The air passes through the manifold waaayyyy to quickly to heat up significantly. I would guess less than 1 C.
    Then please explain why intercoolers work: (assuming air volume passing through intercooler = air volume passing through intake manifold) how much does the intercooler cool down the air and why would air cool down faster than heating up?

  5. #5
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    The air is not heated by the turbo charger's heat, it is heated by the compression of the air(mostly - like 99% I guess) The same principal applies in reverse, if you blow on your hand with a compressor the air is cold.

    The reason why an inter cooler works well is that is much much larger than the supply pipe or manifold, so the air has time to exchange heat. Also the air channels in the inter cooler is small so that flow is very turbulent due to it's high velocity in the channel. The more turbulent the air, the better the heat exchange. The channel wall are also very thin so that heat can easily pass to the other medium , weather it is also air, or water.
    Last edited by Uys; 2011/03/30 at 01:23 PM.
    Everything is a hammer.
    Unless it is a screw driver.

    Then it it a chisel.

  6. #6
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    Look at this, and some values are guessed, but it will give you an idea. Working on a 3.4 straight six (I know your's is V6, but bear with me please).

    A 3.4 litre engine will suck in half of it's displacement per revolution. 1.7l/rev

    At 3000 rpm that is 5100 l/min = 85 l/sec

    Lets assume a manifold cross sectional area equal to a 60mm ID tube.

    That means that your air velocity is just over 30m/s in the manifold.

    Lets assume a length of 600mm with entry in the middle. The air moving towards piston 1 and 6 (the furthest two) will move more or less 300mm - that is 0.1seconds! Like I said, not enough time to absorb heat.
    Everything is a hammer.
    Unless it is a screw driver.

    Then it it a chisel.

  7. #7
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    Uys, I want to have your manchild!

    Jus sayin'
    Last edited by RedLineR; 2011/03/30 at 01:46 PM.
    SWAMBO
    2009 Suzuki Grand Vitara 3.2i V6 Auto
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    2003 Ford Focus 2.0

    Eurard: For T=2; T=1 but, 1/2T=

  8. #8
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    Default

    Thanks Uys! Make a lot of sense when you explain it. I didnt realise that the volume of air going in is that much, but at that speed I agree that heat exchange would be minimal. Just didnt make sens to me to have a hot intake manifilt.
    Pat

    Hilux 3.0 D4D 4x4

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