Author Back pressure  (Read 592 times)

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  • Offline Smithy404   gb

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    Offline Smithy404

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    Back pressure
    on: Feb 18, 2023, 02.05 pm
    Feb 18, 2023, 02.05 pm
    I have a full Akrapovich exhaust, think itís called a stubby or something no pun intended.

    Headers/down pipes and the silencer. Part number for the silencer is S-K9SO7-ASZT

    Thereís no baffle but I have ordered one today. I know the bike is running lean, just how lean I donít know. It snaps crackles and pops and initially I loved it but itís worn off on me hence the ordering of the baffle today. I also have a 16T front sprocket so the gearing is slightly taller.


    My question is how much back pressure/torque have I lost and am I harming my bike?

    Would anyone be able to suggest a route to recovering low end grunt as most of my riding is in the city. Would a power commander be a good option?

    L
    I also have a K&N high flow air filter which I have not fitted as Iím worried I might add to the already out of tune A/F ratio. Donít know what filter is on the bike, as I brought the bike already set up like this by the previous owner.

  • Offline superpig   gb

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    Offline superpig

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    Re: Back pressure
    Reply #1 on: Feb 18, 2023, 04.05 pm
    Feb 18, 2023, 04.05 pm
    *Originally Posted by Smithy404 [+]
    I have a full Akrapovich exhaust, think itís called a stubby or something no pun intended.

    Headers/down pipes and the silencer. Part number for the silencer is S-K9SO7-ASZT

    Thereís no baffle but I have ordered one today. I know the bike is running lean, just how lean I donít know. It snaps crackles and pops and initially I loved it but itís worn off on me hence the ordering of the baffle today. I also have a 16T front sprocket so the gearing is slightly taller.

    From my experience of having the full system the baffle won't stop any pops or bangs. It'll just make them sound like farts in a bean tin instead. If you really want to stop the bangs you need some block off plates.

    Like you I initially loved the noise. But it got old within about 3 weeks  :745:
    I hated how it sounded with the baffle so went back to stock + link pipe and can.
    Last Edit: Feb 18, 2023, 04.07 pm by superpig

  • Offline Gerrit   za

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    Offline Gerrit

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    Re: Back pressure
    Reply #2 on: Feb 19, 2023, 12.58 pm
    Feb 19, 2023, 12.58 pm
    Hi Smithy, read my post.
    These bikes are very lean, and can run too hot, depending on your climate.
    RAPID Bike Easy made a huge difference to my my bike

    https://www.z900forum.com/index.php/topic,5670.0.html

  • Offline Cazzy_R   england

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    Offline Cazzy_R

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    Re: Back pressure
    Reply #3 on: Feb 19, 2023, 03.59 pm
    Feb 19, 2023, 03.59 pm
     If it's a 2017-19 it won't be lean or at least anywhere in the rev range that will cause any damage.
     2020 onwards might be a different kettle of fish. I wouldn't know.
     The popping and farting can be drastically reduced by plugging the PAIR valve feed hose from the airbox. Block off plates are a tidier solution to achieve the same objective but not absolutely necessary.
     Baffles/db killers also kill power as well as noise. My bike lost 6 bhp with 30mm dia db killer.

  • Offline rcannon409   us

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    Offline rcannon409

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    Re: Back pressure
    Reply #4 on: Feb 20, 2023, 06.33 pm
    Feb 20, 2023, 06.33 pm
    The exhaust stem also needs to be air tight to stop the cracks and pops

    When you installed the header, did you use new gaskets?  If those gaskets leak, even a small amount, a perfectly tuned bike will crack and pop.  Even with block off plates.

    Drove myself to insanity a few years back until I figured this out. 

    .

  • Offline Rollin540s   us

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    Offline Rollin540s

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    Back pressure
    Reply #5 on: Feb 20, 2023, 06.52 pm
    Feb 20, 2023, 06.52 pm
    I bought my z with the akra headers and pipe, power commander 5 and the akra map. It was outrageously loud, to the point where I was embarrassed to ride in my town. I installed the db killer and I feel like it sounds just right. It still pops and barks, especially when it's still getting warm, but less so after it gets to running temps. The db killer did nothing to stop the pops. The PAIR plate (or other DIY solution) is the way to stop the pops.

  • Offline Lcfour   us

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    Offline Lcfour

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    Re: Back pressure
    Reply #6 on: Feb 20, 2023, 10.24 pm
    Feb 20, 2023, 10.24 pm
    Re-flash,re-flash,re-flash,etc

  • Offline Smithy404   gb

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    Offline Smithy404

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    Re: Back pressure
    Reply #7 on: Feb 21, 2023, 01.44 pm
    Feb 21, 2023, 01.44 pm
    Thank you all some very interesting points raised.

    Baffle is due to arrive tomorrow and Iíve also ordered a blanking plate kit which comes with the resistor plug to avoid CEL.

    Watched a few tear down videos of the bike and even though I wouldnít minding giving it a go Iím a little apprehensive ripping her guts out.

    Seriously not happy with the out of balance A/F ratio. Not too bothered about slight power loss or gain, I just want the bike to run right. No choppy throttle and no excessively hot running temps.
    Called Road and race performance and booked her in for some custom mapping. They said they will be happy to install the block off plates and the K&N for me for a little extra £..


    Exciting times. Hopefully, as soon as these block off plates arrive and I get her on a dyno I will have a more capable machine all round.

     



    rockbound