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  • Aug 03 2010
    12:29 AM
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    SI and CI Engine
    • swadhin sahoo

    Why we use Petrol in SI Engine & Diesel in CI Engine

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    Editorial / Best Answer

    hosam_ozo  

    • Member Since Apr-2010 | Aug 8th, 2010

    First thing you have to know is what is called cetane and octane number.

    The octane number is the percentage of octane in the mixture of fuel
    The centane number is the percentage of cetane
    The octane number expresses the self ignition temperature, as this no. increases the self ignition temperature increases too and this make the knock to be avoidable and the cetane no. is vice verse

    **Octane no. increase self ignition increase and cetane no decrease"" SIE needs high octane no"
    **Cetane no increase the octane no decrease and the self ignition temperature decrease" CIE needs this"

    Case 1: SI engine we dont want the Self Ignition to be reached we use a fuel have a high octane to avoid the knock "which damage the engine"

    Case 2: CI the compression ratio is too high "12:22" and this kind of engine depends essentially on the self ignition temperature so we use a fuel with high cetane no "low octane" as the high cetane "low octane" gives low self ignition temperature and that is we need in the CIE..

    ABHIJAY

    • Jul 10th, 2014

    Si engines means spark ignition engines. With the help of spark plug, spark is produced in engine cylinder. Before this process occurs, mixture of air and fuel entered in engine cylinder during s...

    PRAVIN KAD

    • Aug 9th, 2011

    Si engines means spark ignition engines. With the help of spark plug, spark is produced in engine cylinder. Before this process occurs, mixture of air and fuel entered in engine cylinder during suctio...