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  1. #41
    Senior Member Timmy's Avatar
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    Apr 2014
    Spokane, WA
    Quote Originally Posted by KaiserBill View Post
    You hodor try duuurp derpity on derp derpy and derpy-derp duuurp derpity derp of derp derp.
    You hit the head on the nail KaiserBill. A brilliant little piece of coding if I do say so myself.
    2014 Jeep JKU Sahara, Manual - /OlllllllO\ - 4" Metal Cloak lift, 37" Toyo Open Country's on 20" XD Bully Rims, 4.56 Yukon gears, Mopar High Top Fenders, ARB Front Bull Bar Bumper, ARB Rear Bumper, Teraflex HD Tire Carrier, Teraflex Tire Carrier Accessory Mount, Twin Rotopax mount, Hi-Lift Jack mounted on front bumper, Reverse LED work lights, Warn 9.5ti winch, Synergy Drag Link, Trackbar Relocation Bracket, AMP Power Steps, JK1001 Radio, SpiderShade.

  2. #42
    I t s u i t s y o u r l e v e l o f t e c h n i c a l a b i l i t i e s w e l l ...

  3. #43
    Quote Originally Posted by UselessPickles View Post
    You may think you are raining on my parade. But in reality, my parade has already gone by and the lingering crowds of people are watching as you stand in the middle of the street pissing fiercely into the wind.

    I'm not saying that a centrifugal supercharger in general is not capable of producing big gains at low rpm, ever, on any engine, with any configuration. As you said, it's just a matter of the supercharger's gearbox ratio.

    However, we are speaking specifically about a centrifugal supercharger that is known to produce a peak boost of about 7-8 psi on an engine that revs up to 6500 rpm.

    The boost produced by a centrifugal supercharger is directly proportional to the square of the speed of the supercharger, and therefore directly proportional to the square of the speed of the engine.

    Due to the fact that increasing engine speed reduces the amount of time available for air to flow in the intake valves, the gain in torque of a centrifugal supercharger ends up being approximately directly proportional to the speed of the engine (not the square of the speed of the engine, as the boost pressure is). This means an approximately linearly increasing gain in torque across the entire rpm range.

    Again, that is approximately linearly increasing torque gains, starting with minimal gains at very low rpm, increasing fairly steadily to maximum gains at/near maximum engine speed (gains may taper off a bit near max engine speed due to the compressor falling out of its efficiency range).

    Armed with this knowledge of how centrifugal superchargers work, and within the context of the entire RIPP torque curve across the rpm range, I can quite confidently say that the large bump/hump in the torque curve at low rpms is unexpected. See the following picture where I have circled the area in question, and drawn a line that approximates a reasonable expectation for the shape of the torque curve. I'm not saying the shape of the torque curve is impossible. It could be something about tuning, relative to the stock tune being intentionally de-tuned in that area for various emissions/efficiency reasons, etc.. I'm just saying just that it's unexpected, so I'd like to see whether other people have gotten similar results to see if this "hump" is consistent, or is this just a misleading side-effect of how this specific dyno run was performed.

    The truth is most likely somewhere in between.I'm also a bit suspicious of the dip in the stock torque curve in that same area (I've seen other stock dyno charts without this dip). If we assume that dip in the stock torque curve is a fluke, then this is about what I would expect from the RIPP torque curve:

    So you are saying the RIPP curve is wrong? it should be linear, i get that. but JL has done a bunch of dynos, is it consistent? or is it there sometimes and not others?

    Could any air at all above sea level push the pentastar past its factory power levels?

  4. #44
    I am not and cannot say that the RIPP power curve is wrong. Only that it is unexpected based on how centrifugal superchargers work, and in comparison to dyno charts of other centrifugal supercharged vehicles I have seen.

    Sounds like we need some input from Ross: do all of your dyno pulls for Black Betty have this "hump" in the torque curve at low rpms?

    Also, I vaguely remember something about fixing a small leak and getting more power. Do you have dyno results with more power? If so, please email the dyno run file so I can import the the torque curve data and update my charts, etc.

  5. #45
    Quote Originally Posted by Pznivy View Post
    Could any air at all above sea level push the pentastar past its factory power levels?
    I'm guessing you meant to say "any amount of boost at all above atmospheric pressure"?

    More pressure = more air. So, yes, in general, any amount of boost above atmospheric pressure should theoretically be able to produce some amount of increase in engine output.

  6. #46
    BB has been dyno'd a bunch of times. I'll dig up a file, we should probably start a dyno thread. And post all the charts in one spot.

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