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Thread: Back to basics....L vs. HD Pulley Combo's...Explained in Chart/Graph Form

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  1. #31
    World's Fastest Street HD
    Name: Josh

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    Quote Originally Posted by BlairTruck View Post
    my boost test was done the same days only hours a part
    i love your typically and usually gains, its guessing
    It's not guessing. Do you realize these trucks have been out for a DECADE now, and the "typical" and "usual" gains are exactly that. Those numbers aren't my guesses lol. Start reading into the archives on here, NLOC, and F-150 online and you'll see a heaping amount of posts that back those up directly. You know how many dozens and probably hundreds of people have done the exact same "same day tests" where they go WOT, then add an intake and go WOT and see where the boost increased to? Or added an exhaust and go WOT and see where the boost decreased to? Heck its been done thousands of times, pretty much every time a L gets a mod and hits a dyno the boost level increase/decrease is checked. That part certainly isn't rocket science! Heck do it yourself, throw an overdue intake on the truck and see what you gain in boost. I bet you its 1.5-2 lbs

    Apparently you have a freak magical truck that makes more boost without increasing blower RPM, with a precision calibrated boost gauge thats not off by even a tenth, and with exact ideal conditions during your one time test, to create 12 lbs with a 6 lower and 100% bone stock everything else, even though most of the other guys on here with a 6 lb'er also only make 12 lbs along with intake mods. Funny coincidence there huh?

    The accepted boost values for the lightning with various sized pullies could be wrong....although the boost sizes for the pullies have been the accepted values for the last decade without dispute, and why 9" lowers are called 6 lb lowers, 8.5" lowers called 4lb lowers, etc.. My table is based upon that, but you can even strip away all talk of boost levels, you could call it X, Y, and Z levels if you want and it wouldn't make a difference with that table.

    You have to have a basic understanding of physics to understand the table, which I can't think of how I can possibly dumb it down any more for you, but I'm sure you can agree its pretty common sense that increasing the pulley ratio by a larger lower or smaller upper directly increases the supercharger RPM. Your entire arguement saying a 6 lb lower adds 6 lbs on a L or HD, when the L and HD have different size uppers defies the fundamentel laws of physics. What you are saying is that the HD supercharger doesn't need to be spun as fast as a L supercharger to create an additional 6 lbs of boost over stock, and that is just absurd lol Its the exact same supercharger.

    If the uppers were the same, and say the lowers were what came different to decrease the boost on the HD from the factory, THEN adding a 6 lb'er on a HD would put the blower RPM equal to the same blower RPM on a L with a 6 lb lower. But since the HD has a larger upper, the supercharger is always spinning proportionally slower no matter what the lower, so its impossible that the HD blower spinning slower can create the same or more amount of boost than a L blower spinnng at equal or more RPM's.

    Quote Originally Posted by BlairTruck View Post

    im sure graphs can be wrong sometime and maybe even you could be wrong for once
    I have no problem admitting when I'm wrong, but I'm not wrong on this one, if I'm wrong on this, then Newton and the Laws of Physics are also wrong
    Last edited by Harley#356; 05-28-2010 at 11:13 PM.

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