ScaryFast Power Now Intake Baffle

Discussion in 'Thumpers' started by vrago, Jan 12, 2005.

  1. vrago

    vrago Plays with dirt

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    OK, I may be a sucker, but nothing ventured.

    Since I have and FCR on my 640 (hear that, cult of the BST), I figured I'd do some extensive research on more response from the FCR. I checked out some of the reviews on the Power Now intake baffles.

    Maybe Snake oil, like the perpetual motion machine spinners in this months Cycle World.

    Vendor says, baffle on intake side of carb reduces turbulence at less than half throttle and improves responsiveness on lower end. The also have a power now plus which is a baffle for the head end, which reportedly acts much like porting and polishing in that it aids top end.

    I will give it a try. I'll even have some witnesses at this weekend's tech event. Look for a report to follow.
    #1
  2. meat popsicle

    meat popsicle Ignostic

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    Don't believe the hype... :evil

    This came up on another thread; why would Weber put dual CV carbs on his custom rally twin bike? For $68,000 I expect nothing to be "second rate" :nod

    http://www.rallytwin.com/

    Specifications

    Engine:
    Kawasaki EX 500, liquid cooled
    parallel twin, 498cc, DOHC,
    4 valves per cylinder, threaded
    adjusters, electric start
    74mm x 58mm
    10.8:1
    375 Watt
    Wet sump, 3.6 quart capacity
    50hp (approx)
    35ft-lb (approx)
    Dual 34mm Keihin CV
    6 speed
    Chain, 520 X-ring
    Aluminum air box with dual foam
    element filters
    Custom tuned stainless steel headers
    and mid-pipe, with 86dB USFS spark
    arrestor
    45-50 mpg (dual sport use)

    Frame:
    4130 Chrome Molybdenum, TIG welded, single
    backbone, double cradle
    4130 Chrome Molybdenum, TIG welded, removable
    Aluminum, KTM, linkage suspension
    WP 4057 upside down cartridge, adj. comp/rebound,
    11.8” travel
    Ohlins, adj. pre-load, comp/rebound, 12.6” travel
    27.5 degrees
    62”
    39.5” (unlaiden, 4” less with rider)
    12.5”
    6.1 gallons
    KTM hubs, Excel rims, 21” front, 18” rear
    Brembo, 290mm disc (fr) 210mm disc (rr)
    350lbs (wet, without gas or aux. components)

    Controls:
    Answer hi-carbon steel, with Enduro Engineering
    aluminum hand guards
    Magura
    Magura
    Honda
    custom instrumentation

    (This message paid for by the Cult of the BST) :D
    #2
  3. Jinx

    Jinx Call me Renzo

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    Turbulence is the result (or is rather predicted by) the Reynold's Number of the gas flowing through your intake tract.

    I won't bore you with the math, but let's just say that all intake flow is turbulent all the time, and there is not a damn thing you or anyone else can do about it, because you can not have laminar flow at the velocities, pressures, temperature, and density combinations that we are dealing with.

    But WTF, Dirt Bike Magazine loved it. :dunno

    But all is not lost. If it isn't the next great thing, get your money back and send for my latest leaflet:

    "How not to be a sucker" by sending $49.95 +$6.95 S&H to

    Jinx
    c/o Cardboard Box near Statue of Lenin
    Seattle, WA 98112

    Sorry, mate. :rofl
    #3
  4. Mack

    Mack Gone, but never forgotten. RIP, Mack...

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    They are quite popular and seem to wake bikes up on the bottom end. I gave a lot of thought about trying one, but decided to go with an FCR-39 rather then a FCR-41 and a Power-Now. No way to know without trying one, but I think I will get just about the same results for less money. The two factors that made me decide against one, were the fact that IMHO, the LC4 already has plenty of grunt down low, and I noticed that it was advised that you drop down one main jet size. This lead me to believe it might slightly reduce airflow at higher engine rpms, and on an LC4 I felt more need for top end then more bottom end.

    It seems to me these make a lot of sense on a MX or Hare Scrambles bike, where power output is becoming less and less of an issue, but throttle control seems to be paramount, but not so much so on a big honk'en D/S........... (Heck I've groundlooped my ADV a few times, by getting a bit more grunt then I needed for the available traction)

    It would be nice to have some seat of the pants real world experience with one of these. So why don' you try it out for us? :nod Cheers, Mack

    PS: I know some guys on KTM talk installed them on their LC4's, and a large number of EXC owners as well.
    #4
  5. creeper

    creeper Still alive...

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    I believe the idea of the Power Now is not so much to direct air flow, as to reduce the turbulence that occurs when the column of intake air contacts the exposed face of the partially open slide.
    As the “vane” resides very close to the slide face, turbulent air above it (at part throttle openings) is restricted from mixing with the relatively laminar air flow below the vane.
    In theory, the flow is improved at throttle openings where the slide cutaway is below the vane (potentially the best available flow is when the cutaway is parallel or in line with the vane) and this is why they recommend a slightly leaner mixture.
    The less turbulent, more laminar, higher velocity air flow creates a stronger than usual vacuum signal (negative pressure), pulling more fuel thru a given jet size.

    Or… I am completely full of shit, and made all this up as I went.
    #5
  6. viverrid

    viverrid not dead yet

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    Power Now caused the most vicious flaming session I ever saw on the New England Dirt Bikes site. Some guys love them and run them and claim it makes their bikes livelier, and others ridicule them and say there is no way it could work and point out that dyno tests show no improvement.

    Only way I can see, is get a few bikes together, lets somebody take them into a garage and put Power Nows in some of them but not tell anybody which ones (that person goes out the back door so he can't even give away the answer unintentionally with a non-poker face). The riders go ride them and declare which ones have it and which don't. (They can all ride their own bikes). Then a lunch break, back into the garage, some get it taken out or in, some are left alone - and back out again and let the riders say if they still have it or don't.

    Then we'll see if it really does anything.
    #6
  7. vrago

    vrago Plays with dirt

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    Mack,
    I'm runnin the FCR-39.

    #7
  8. Gregg Wannabe

    Gregg Wannabe Just killing time

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    Reminds me of that infomercial product for cars called Tornado or something like that. Its a vane that goes in the intake just BEFORE the filter supposedly to increase power and MPG. My local TV news guy (consumer watchdog dude) did a test on a variety of cars and MPG was DECREASED.
    #8
  9. potatoho

    potatoho Cheese and Rice!

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    I put an intake vane on my bst40 intake. It was nice. Mainly an improvement on 1/4 throttle. Then one day I gave it some good throttle and it sucked my vane loose. I had to stop and fish it out through the airbox. I used very thin brass for the vane and it caved due to the pressure.

    Without the vane, I just couldn't ride the bike the same. I got used to creeping around turns, and without the vane I always felt like falling over. The off-idle torque was gone.

    So instead of making a bigger/stronger vane, I ordered a pumper. I got an oversized 42mm since I plan on putting both intake and engine side vanes. So that should leave me with 40mm give or take and dual vanes. Sweet.
    #9
  10. ChrisC

    ChrisC Amal sex?

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    :nod :nod :nod :nod :nod :nod :nod :nod :nod :nod
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  11. dagwood

    dagwood Banned

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    My idea on that (back talking to Gumbydave and flanny was to go with the fcr39 or even the fcr34 for excatly that reason. higher velocity air flow at lower throttle opening.
    same results with a cheaper and more readily used carb than the 40/42.
    #11
  12. vrago

    vrago Plays with dirt

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    I'm in learning mode now,

    What do velocity stacks do exactly?

    Tuned for what?
    #12
  13. Jinx

    Jinx Call me Renzo

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    Velocity stacks are used to smooth the flow, and prevent the inlet stream from separating from the inlet tract walls on entry. Which would actually reduce the effective area.

    This is a typical piece of crap velocity stack beloved of Harley riders and VW builders. Note the sharp entry. Avoid them.

    [​IMG]

    Now here is the business. Note the fully radiused lip. That's what you want. This allows the full inlet area to be used, and as the diameter gets smaller downstream, the gas flow is gradually accelerated.

    [​IMG]

    Tuned length is a different subject, Sort of, as velocity stacks are often used to vary the tuned length of an inlet system. My own preference is to see the inlet tract either shortened or lengthened downstream of the carb or throttle body, but to each his own. But either way, every inlet should have a full radiused entry, or as close to one as we can get.

    An inlet system is tuned as follow: When the inlet valve opens there is (hopefully) a lower pressure in the combustion chamber. When you open a valve and there is a pressure differential in the adjacent chamber, a wave is created. In this case, the higher pressure inlet tract creates a negative, or suction wave that travels back up the inlet tract. At full throttle, as long as the inlet tract is otherwise unobstructed, this negative pressure wave travels right through the carb or throttle body, and to the end of the inlet tract where we have just installed our velocity stack.

    So what happens when a negative wave reaches an open end? It also reflects back, but this time as a positive pressure wave. And what we want is to have the length of the inlet tract just long enough so that this reflected wave arrives at the valve just before it closes and shove a little extra fuel/air mixture in, where the closing valve traps it. The math is pretty straight forward, the speed of sound (which is the speed that all our waves travel, which is why it is often called acoustic tuning) is @1100 ft/sec. All you have to do is figure out your cam timing, and what RPM you want this effect to happen.

    The waves are pretty much a full throttle only thing. Waves will move quite nicely through smooth cross sectional changes, but a throttle slide sticking halfway through the bore will kill them dead.

    And there are two big flies in the ointment. The first is this only works at specific RPM, or multiples thereof.

    The second problem is that there is not always room for a single pulse to travel up and back. Inlet tracts tuned for that tend to be pretty long. But you can always cut them in half. A system tuned for 16000 RPM will also work at 8000 (the waves just travel twice up and down, but the pressure phasing is almost the same), and it will fit a lot better.

    The effect of all this is great at 8000 RPM if that is what we have tuned for. But it pretty much sucks at 6000 because it is now out of phase (though it may be back on the job at 4000). But there is hope.

    Modern airboxes are also frequency tuned (the term is Helmholtz Resonator if you want to do some more reading), and they are tuned to take out the flat spots created by inlet length tuning. Waves resonate in an airbox system just like they do in the inlet tract. And these can be tuned to have the airbox have it's highest pressure at any RPM you want. Modify a modern airbox at your own peril. There is a lot of engineering behind them these days.

    Pretty much the same thing happens on the exhaust side, except everything there is tuned to give the lowest pressures (as opposed to our inlet example where we want the highest pressures). But, in general, longer primary pipe lengths work at lower RPM, and shorter ones at Higher RPM. In fact, a two stroke's expansion chamber is nothing but a bunch of tuned lengths with diffusers and convergent tapers designed to amplify and lengthen the effect of these waves bouncing back and forth.

    But watch that wave speed. Due to temperature, the speed of sound, and of our waves, in the exhaust system is @1700 ft/sec.

    If you space these events out (inlet tuned for 8000 RPM, Airbox tuned for 6000 rpm, exhaust tuned for 7000 RPM) you get a nice wide powerband with few flat spots. If you bring them together (everything tuned for 8000 RPM) you get a rocket with no powerband at all. It's like turning on a light switch. And it will have a flat spot you could shoot pool on.

    Lot's of good info in books and on the web if you want to dig into the subject in depth. Cheers.
    #13
  14. PASSMORE

    PASSMORE Just the last name...

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    Hi all,

    I was there for the installation of this on vrago's bike. To say the least I was skeptical as well of this, but given that he seems to have his gear pretty well sorted and it was his C note on the line, I was very curious about it's effects.

    Frankly I do not recall if I rode his bike prior to instll or not, but I was able to ride it after install.

    WOW!

    I cannot verify any hp increase or otherwise, but what was VERY impressive was the INSTANT power upon throttle! With my FCR41 I have to get into it a bit before wicking it up rapidly. That was eliminated with Power Now.

    I will definitely be adding this to my list of to-do's for my bike.

    Thanks for being the guinea pig vrago :thumb

    M
    #14
  15. vrago

    vrago Plays with dirt

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    Sooooooooo...

    I put the nicely machined matte gold anodized intake bell witha a vane down the center of it onto my FRC-39 carb equiped LC4.

    I had dyno runs from jetting (Factory Eddy current dyno) indicating it had 40+ HP at 7000 RPM. I was very pleased with the jetting and found the power fine. I did notice that the FCR did not seem to like to be "thwacked" open, for lack of better term, instead it seemed to respond better to a more linear roll on.

    Since I'm a bit uptight and edgy, I wanted my throttle response to be that way as well. THat's why I tried the Snake Oil out.

    Sicne I do not have a dyno handy and am ot sure how you would run a test on such a modification since its purpose is not really to add any hp. But You all will just have to take my subjective assessment.

    IT ROCKS! :thumb

    No really, it does change things a bit, like instantaneous throttle responsiveness. My favorite sensation on a bike (OK, tractor, truck, or anything else powered ) is torque and It made the torque come on earlier and possibly longer.

    Say what you will, but that c note made me smile. :D I'd recommend the device to any other heretics who have abandoned the much championed BST.

    Oh yeah, Since there is so much energy on this topic, I made creeper ride it so he could get dragged into the drama.

    Jokes aside, I think it did move the start of the torque rise down a bit and am very pleased with the result.

    The unit is just slightly longer than the intake bell I got from sudco when I got the fcr for conversion. It made no diffrence on install.
    #15
  16. Esteban

    Esteban Banned

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    Velocity stacks increase the length of the intake tract. This increases momentum of the column of air entering the engine which allows greater combustion chamber filling even when the piston is rising. The inertia of the air column will force more air into the combustion chamber even as the pressure within the combustion chamber rises.

    BTW turbulent air rushing into the combustion chamber gives better mixing and more power than smooth air. Makes for a better more complete burn within.

    (I have not read this whole thread so my next comment may have already been addressed.)

    Beware what you put in your intake tract !! Thin metal vanes could fatigue, crack and get sucked in. I have not seen the ones I read briefly about here, but I have seen cheap poorly designed air filter housings and components do this. Just a note of caution as the results can be expensive.

    Steve
    #16
  17. meat popsicle

    meat popsicle Ignostic

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    You should be able to compare the HP and torque curves with the snake oil on and off the bike to see if there is a change in the onset of torque. That is if you wanna pay for more dyno runs.


    much championed BST!?! we are the underdogs vrago! it is YOU with the fancy-pants FCR and velocity stack w/ wind vane... we are the faithful! :pot
    #17
  18. creeper

    creeper Still alive...

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    Made is the appropriate term. It was difficult to ride with my hands tied behind my back and a farm impliment aimed at my head... but ride it I did.
    It felt very much like a BST as far as tractability... but with better snap. :D
    Vrago has lower than stock gearing, so his bike would be snappier anyway, but I was able to lug it down to a what amounted to a fast idle in 4th gear, and pull from that fairly cleanly with just a quick fan of the clutch.
    If this is an uncommon occurance with a FCR... then it appears to be money well spent. :nod

    Creep

    uptight and edgy? you?... :lol3
    #18
  19. tcate

    tcate old enough to know better

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    Gents -
    I'm an AdvRider newbie and scared to get into the fracas, but...
    I ride a YZ250F offroad and, being old, fat, and slow, tend to lug it around a bit more than it was made to do. A friend added a powerNow to his WR and I couldn't believe the difference. I read all the verbage on ThumperTalk - why it will and won't work - and then installed one on my YZ. No jetting changes or anything. Without question, it was the best money I've ever spent. The throttle response, particularly on the bottom-end was unbelievable. The only thing I've noticed is that I lost some of the high rpm snap - it tends to hit a wall at high rpms. But, being a low-rpm-kinda-guy, that hasn't really bothered me much. The bottom line is that it ain't snake oil. Don't know why it works, but don't really care why, just that it does. And it does well....

    TC
    #19
  20. vrago

    vrago Plays with dirt

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    :pot
    #20