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can i leave air filter box top open

luciferdxb
luciferdxb
in Ford Focus Club

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need suggestion- 2014 ford focus 1.6 ti vct 4 cylinder, got K&N air filter that fit perfectly in OEM filter box. my question is i saw few RS style box cover available on amazon n other site with open net on top. my question is - can i leave just top of the box open for better air intake or i should stick with factory style full covered box.

  • Quote


    Technically yes, but it won't give you a better intake.  The RS box is sealed to the bonnet so it doesn't suck hot engine bay from behind.

    Leaving the lid off is also an MOT failure now, as it's classed as tampering with emissions system.

    I would recommend just leaving the lid on.

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    • Like 6
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    thanks

    me too felt same when i drove near by as a test drive, leaving lid open. was having rough idle and power response was late in initial acceleration, after few second it was kicking off. so i will leave it on .. 

  • Quote
    • Like 1

    Lid off means less performance (because of the heat coming from the engine) and more dirt into the engine.

     

  • Quote

    depending upon design, you may find the engine breather no longer behaving and this can seriously alter idle speed / smoothness - and might even get you an emission failure on your MOT as the fumes are still kicking around in the crankcase

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