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air-filter & intake optimization

G

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?
 


J

JosephGarcia

Guest
I don't see what you guys are talking about by hearing the intake...
904_HPIM0486_2.jpg

I never hear a thing and it runs fine.
 
G

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.
 
O

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. :)

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.
 
G

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 :)
 
O

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. :)

I gotta get goin' ttyl.
 
G

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.
 
G

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)
 
O

OldPete

Guest
http://www.dansmc.com/reedvalve.htm

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. :D

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. :)
 
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