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Air Flow Restriction?

Discussion in 'XJ Technical Chat' started by luvmy40, Jun 20, 2010.

  1. luvmy40

    luvmy40 Member

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    OK, I finally got a Colortune and Carbtune Pro and set to tinkering! From all evidence and prior performance I had been running a little rich and sync was close if not perfect before my fiddling. Sync is as good or better now. She starts with just a bump of the button and little to no choke and idles smooth. The pilot mix is perfect but plug chops show very lean at 4krpm+. I was scratcing my head as to how this would happen from sync and pilot adjustments. I then thought "DOH! What about the K&N High Flow filter you installed to replaced that nasty way dirty OEM filter?" I put the new filter in and new plugs after the sync and pilot adjustments.

    Would the air flow from the K&N be enough to lean out the mains? And, if so how would it work if I fabricated an adjustable restrictor plate for the air box intake mouth. I could restrict the air flow till the chops showed chocolate brown at 5k and readjust the pilot to match air flow.(and resync of course). I realy don't want to rejet before I tear down the carbs this winter.(I don't want to rejet then but will if it is needed)

    I also have a new Mac 4-1 enroute to replace the Kerker 4-1 that thePO installed. Iwould think the two systems would have similar back pressure and performance? I will wait till the new exhaust is bolted on before doing anything.

    Any thoughts or Hell No Don't Do It! warnings?
     
  2. RickCoMatic

    RickCoMatic Well-Known Member

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    You save all the fooling-around and needing to re-jet stuff.

    Just "Trick" the K&N Filter.

    Go to Home Depot and buy a "Shop Vac Filter Saver"
    Filter paper that covers Shop Vac Filters from needing to be replaced.

    Put the scissors to one and make a cover for the K&N.
     
  3. Polock

    Polock Well-Known Member

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    anything that gives less restriction will run leaner
    at 4K i'am not sure your on the main fully yet, it might be still on the needle jet so a shim night work (no pulling the rack :) )
    did you check it any higher, like 6K ?
    wouldn't a restrictor plate defeat the purpose of a high flow air cleaner?
    i think you'll need at least one size bigger main when it's done
     
  4. luvmy40

    luvmy40 Member

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    Rick,
    Thanks, definitely easier than my idea.

    Polock,
    The filter wasn't chosen for the high flow feature. I just wanted a reusable filter and had a good discount coupon from DK so I got the K&N. I havent chopped at 6k but did get 1 or 2 at 5.5k. If I have to re-jet, so be it. But I hope I won't have to.
     
  5. luvmy40

    luvmy40 Member

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    The Mac exhaust arrived today.

    I installed the Mac and changed the oil and filter( I will definitely be getting a spin on oil filter adapter!) Then redid the colortune and carb sync. I was way rich at idle and the Carbtune Pro showed just a bit out of sync. She's purring like a kitten now. I am surprised at the immense difference in the sound of the exhaust.The Mac is much quieter and has a more low end gravely feel. The Kerker sounded like a steriod pumped bumble bee.

    So I will hit some plug chops ASAP but since the pilot was rich after the install, I have to assume(I know!) that the rest will be at least a bit richer.
     

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