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Removing Catalytic Converter Question

Discussion in 'Scrambler How-To's and Guides' started by Scrambler Larry, Sep 19, 2016.

  1. Scrambler Larry

    Scrambler Larry New Member

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    Was a a bike meetup recently and a guy had an aftermarket slip on exhaust pipe with CAT removed. Was wondering if the will mess up airflow/performance?
     
  2. jkblaq

    jkblaq New Member

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    If by mess up you mean improve, then yes. :)

    Joking aside, you will make a lean bike even more lean, by adding a slip-on. You have a few options:

    You can get a factory Termi slip-on that comes with a Race "tune".
    Lots of other people get a slip on with a Rexxer tune OR
    Slip on with Boosterplug (increases fuel in mixture by lying to the ECU about outside temp).

    If you search the forums, there are details on all these options.
     
  3. TC3

    TC3 Well-Known Member

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    In my case it affected the spread of torque so did a remap and runs better than any stock bike now :)
     
  4. Scrambler Larry

    Scrambler Larry New Member

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    I was concerned about changing the back pressure, affecting the sensors, etc
    It looks like the CAT is attached to the stock muffler, am I right?
    Should be an easy swap.
    Yes, lean is the way to go, already took off the EVAP cannister
    This on looks badass

    LeoVince LV One EVO Slip-On Exhaust Ducati Scrambler 2015-2016
     
  5. jwaythedj

    jwaythedj New Member

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    so. I've read the whole thread. My question: is the cat converter inside the can or in the pipe? If I take off the OEM can and put on a slip on (3rd party, no cat), am I not going to have a cat?
     
  6. Hui

    Hui Well-Known Member

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    Correct, no cat.
    The Cat resides in the phat box in front of the rear wheel, the box and tail-pipe are all one unit so by removing the exhaust /silencer will remove the Cat.
    Back pressure is of no relevance to this engine as the valve overlap is quite short. On the Panigale engine for example back pressure can help stop the inlet fuel charge from falling out into the exhaust by pushing back before the valve has a chance to shut as the valve overlap (ie. inlet & exhaust open) is nearly a fortnight.
     
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  7. jwaythedj

    jwaythedj New Member

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    awesome reply, thank you. That's why I was figuring...so I shouldn't worry about back pressure on this particular engine. I should be fine with just the slip on and no ECU flash/remap
     
  8. markstar

    markstar Active Member

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    10000kms with slip on and spark plugs look good Screenshot_2017-04-21-12-21-02.png
     
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  9. jwaythedj

    jwaythedj New Member

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  10. chesterburnet

    chesterburnet New Member

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    Lean is not the way to go. Runs too hot. Not good. There are a lot of warnings throughout this forum warning of damage to the bike. If you do a slip on you should be doing a remap. I wouldn't trust the products that say no remap is necessary.
     
  11. Max Kool

    Max Kool Active Member

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    Heck, a remap on a totally stock bike would ever freshen the engine up I guess. :eagerness:

    But I gotta say, the scrambler seems pretty choked on the intake side; single throttle body and the airbox seems very "closed". More so than on the exhaust side. Hence the results with the MWR Power Up Kit.

    The stock exhaust has quite some volume and the cat itself is a big 80mm unit with a three chamber design and some small blowby holes.

    I would really like to see an A/F graph from a stock bike, and one with just a slipon with the DB killer installed.

    I would never run an open pipe -too loud-, and to make a smaller, lighter aftermarket pipe reasonably quiet, the manufacturer has to build in some "choking" or even a resonance chamber. Chances are they have to choke the exhaust flow even more than on the stock exhaust to get the noise down.


    I know from previous bikes that changing just the end can, and nothing else (so no air filter and/or airbox mods) hardly changes the fueling and or power output. And the other way around, change the airbox and the fuelling while leaving the exhaust stock could lead to interesting gains already.
     
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    Last edited: Apr 21, 2017 at 12:09 PM
  12. Hui

    Hui Well-Known Member

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    The problem is, the many warnings on this forum about tuning are as far as I can tell are made by well meaning people who have read other forums who have also read other forums written by somebody who listened to a mate's mate who's never worked on an engine.
    The way I can usually tell how much the author knows is when the 'back pressure' statements along with tuned lengths, rich, lean etc get thrown in with no technical explanation of any or all of them.
    I've been tuning engines and fabricating exhausts for many years and never have a problem.
    I will agree though that a re-map of a stock ecu will always show improvements without the factory compromises.
    Anyway to free the exhaust of restrictions will mean no lost power trying to push and sqeeze the elephant up a stair. As far as making the mixture too lean, please will somebody explain HOW? on this particular engine with 11degrees of overlap. Don't waste time explaining a tuned 43 degree engine etc. I already know.
     
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