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Is there more pressure on an SOHC exhaust?

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  • 22-01-2007 9:55am
    #1
    311
    Closed Accounts Posts: 5,332 ✭✭✭


    Is there more pressure on an exhaust system from an SOHC engine, compared to a DOHC engine?


Comments

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    #2
    JHMEG
    Closed Accounts Posts: 7,686 ✭✭✭JHMEG


    That depends on the exhaust system and not the type of valvetrain.


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    #3
    311
    Closed Accounts Posts: 5,332 ✭✭✭311


    The engine has a 140hp output and the cat converter is attached directly onto the engine block.
    It's the new honda 1.8 civic engine ,with lift technology.

    I'm getting a sound from the exhaust system and I can't help thinking theres movement between either the block and the converter or the converter and the exhaust.


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    #4
    jayok
    Registered Users Posts: 1,907 ✭✭✭jayok


    Ohhh... you asking the right person there (JHMEG) _Brian_ !

    Care to elaborate on the noise (growl, rattle, groan, etc)?


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    #5
    311
    Closed Accounts Posts: 5,332 ✭✭✭311


    Its like a dry groan/growl and it's mostly between 1700-3000rpm.
    Regardless of whether I take off or sit still.

    It's like when the valves are wide open I get the noise.


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    #6
    jayok
    Registered Users Posts: 1,907 ✭✭✭jayok


    Isn't that as a result of the variable timing? You can normally hear such "groans" as the cam-phase or valve timing is changed (well you can on i-vtec CR-V and vtec Civic).

    Also isn't the new Civic drive-by-wire? You won't know what the engine timing is really up to...


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    #7
    JHMEG
    Closed Accounts Posts: 7,686 ✭✭✭JHMEG


    Just had a look at pics of that engine (have never seen on in real life). Interesting in that it's SOHC and therefore doesn't have cam phasing and therefore also does not qualify for the original definition of i-VTEC, but i-VTEC can mean anything now.

    Looking at the valve train the VTEC operation is on one intake valve only. Other valves are not affected.

    As jayok says it is possible you are hearing the differences between VTEC on and VTEC off. It's more likely tho that you're hearing this through the induction system than though the exhaust (as VTEC is on an intake valve). On previous SOHC VTEC engines this change is very subtle and can't be heard too easily. (DOHC is easier to hear as the exhaust valves are also affected)

    According to Honda VTEC is "on" (in this case for economy) between 1000 and 3500 RPM on this engine (your rev counter may not be 100% accurate).

    PS. I wouldn't describe the VTEC sound as anything other than a change in engine note! ;-)


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