air-filter & intake optimization

Discussion in 'General Questions' started by gone_fishin, May 31, 2007.

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  1. gone_fishin

    gone_fishin Guest

    flow, ports, expansion chambers, boost bottles, reed valves...aaarrrRRGGGH! driving my little gearhead mind nuts :lol:

    after a lot of reading on what you super-freaks have had to say, i've finally developed my question...i don't think it's stoopid, but hey, i'm stoopid, so how would i know?

    most of the engine noise i hear seems to be coming from the intake, so i started wondering...

    is it theoretically possible that our intake needs a bit of restriction (stock instead of free-flow) to help keep that "pulse" in the cylinder where it belongs?

  2. JosephGarcia

    JosephGarcia Guest

    I don't see what you guys are talking about by hearing the intake...

    I never hear a thing and it runs fine.
  3. gone_fishin

    gone_fishin Guest

    i didn't say it was overwhelming or a bad thing, but when i pay attention i can hear the pulse coming back thru, so i was wanting to talk about the theory involved.
  4. gone_fishin

    gone_fishin Guest

    found this in my wanderings, seems like a good primer:

    warning...coupla pop-ups going in & one coming out

    i think i'm gonna try to find the right materials and fabricate a primitive reed. i do believe that's one tweak that will make a difference.
  5. OldPete

    OldPete Guest

    If they say that using the poo-poo pipe gives a pleasent improvement to one's running disposition...Who am I to question that? I kinda agree. :smile:

    A reed block could be had from a m/c wreaking yard. We have one down here for Japanese bikes.
    When I was a child our next door neighbor gave me a hydro-plane boat to repair and good used outboard parts. I went racing locally. :cool: We cheated and replaced the stainless steel reeds with thin phenolic material. That way, if a reed broke the engine could grind it up and spit it out with little harm done.

    I do believe that your piston-port engine would idle better and have a little stronger mid-range with a reed block but top end would die.

    Stroker induction noise is more intense than 4 stroke induction because it happens twice as often for the given rpm and the sound from the exhaust is open all the way back to the air filter. On a 4 stroke this only occurs during valve overlap and this is very brief compared to a stroker's piston dwell time. The piston dwells a VERY long time at BDC compared to TDC.

    For really insane stroker barrels, Google transfer ports and look at images. I looked at racing Yamaha stroker barrels back in the late '70s and wondered "how do these things even run? There is just a small area of stroke that is not open to a port." These were 125cc engines that put out 20+hp.

    NOTE: Reed blocks take up alot of space.
  6. gone_fishin

    gone_fishin Guest

    a reed can't "keep up" at top end is what your saying? because of the small intake? i have a generous amount of room to work with, btw.

    also, i still wonder about my original stupid question...going full free-flow on the aircleaner is having no (negative) effect?

    and OT about the exhaust...i said i was told, not that i know...i have some scrap tubing and such becoming available soon, i'm gonna start experimenting, & i'll use my 12 years as a custom exhaust mechanic to figure it out...then i'll know :)
  7. OldPete

    OldPete Guest

    I have only seen reed blocks used in outboard engines of 2 or 4 cylinders. They are between the cylinders and have 4 pedals on each side of this crankshaft main bearing.
    The only other reed block I've seen 'n touched was used in transfer ported 2 stroke engines. The pedal assist stroker engines we use are piston port 2 strokes, they just have one intake and no tranfer ports.

    I'll Google Gordon Jennings and see what comes up. A good spark plug article and a detailed expansion chamber tech artical.
    Mr. Jennings was Mr. Stroker in the '60s~'70S.

    Never run a 2 stroke w/o an air filter because all air passes through the crankcase. Yes, you know that but lurker does not. :smile:

    I gotta get goin' ttyl.
  8. Guest

    Guest Guest

    A reed would keep up fo' sho'- they work fine at 12,000++ rpm. It would improve the idle and midrange, but I think it will help the top too, just not much.

    As for your question augi, if you open up the air filter say to 100% more media area, (bigger, less restrictive air filter) then you may have to tweak your "mix needle clip" a bit richer. Should open up the mid to top end power a bit.
  9. gone_fishin

    gone_fishin Guest

    well, since all we have is that tiny carby throat, i'd say this is about as free-flow as you can get.
    there's a 5/8" layer of B & S filter foam inside. yeah, pete, i did know that :p

    i bored the jet just a tiny tad & tried all the settings (it only takes a minute)...2nd down for me, & fine performance.
    btw-that's an old pic, the engine is leak-free & spotless now.

    i've mentally invented a primitive valve using a 1/8" plate to match the flange and a "reed" made from a wide gap-gauge. or should i go for a shallow/wide "box" with like 3 of these side by side, then reduced back down to the round? so long as i build it right & the engine doesn't suck it in and trash itself, i believe it could do the trick.
    recommendations on materials or other details would be cool 8)
  10. OldPete

    OldPete Guest

    See the barrel on the left? A home brew reed block will not work in that port @ 12k rpm...betcha!

    See the barrel on the right? That is a for real reed valve port. :grin:

    If you got the time augi a bit of feeler gauge may do in the short term but a thin piece of phonalic would be better. Stainless feeler gauge will not be easily drilled or worked compared to phonalic. Plus phonalic will just spit out if it breaks off.

    I got some 3/16" phonalic here that was used to make carb spacers to insulate them froim heat but no thin stuff.

    augi, summer is here, this is a fall/winter project. :smile:
  11. SlicerDicer

    SlicerDicer Guest

    would it be impossible to fabricate a reed valve thingo intakeo that would mount on the current intake? then have the carb mount onto that just fine like normal?

    It might add 3 inches at most? then it would just be a cage to hold the reed? or would that explode gaskets?
  12. Guest

    Guest Guest

    Maybe a Happy Time conversion is in the future?

    Small reed block machined of aluminum between a Walbro and the jug?
  13. jake

    jake Guest

    so, am i correct in assuming that a ram-air intake would worsen the performance of these engines? it seems like it would just force MORE intake gas out the exaust port.
  14. Guest

    Guest Guest

    Ram air would work if you had a way to adjust the mixture according to the "boost".
  15. SlicerDicer

    SlicerDicer Guest

    augi do you have any close up pictures of that intake? and how that was fabricated? it looks like a bottom of a soda can or something. or maybe a top?
  16. gone_fishin

    gone_fishin Guest

  17. SlicerDicer

    SlicerDicer Guest