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 Post subject: Reeds
PostPosted: Thu Oct 12, 2017 10:32 pm 
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Joined: Tue Jan 17, 2012 3:19 am
Posts: 7699
Location: Hope, B.C Canada
Anyone here think there is any advantage to re-designing reed valves ??
A couple of years ago I had an Engine on the stand and spun it over with the starter. The Engine was complete minus the carb so I could see the reeds open and close. I was amazed at how little the reeds actually opened, and I would guess they opened less than an 1/8". Now I realize that this is low rpm because the starter was used, but as rpm increases so does the time for an open/close cycle of those reeds. How much flow (cfm's) could actually be getting through that cage ?? I now also believe that reed stops are a non needed item and none of my machines has ever had them installed. I bet money there is no way in hell those reeds open up that far. I did try find videos of operating reeds but found none. So now I come to my idea. Would a cone style reed not flow more cfm's than the current square box style reeds ?? I say that because a cone would be more aero dynamic than a square box, and it would fully open when required. Stuffers in conventional reed cages actually reduce area in my opinion so those would have limited if any improvement in my opinion. Now this cone idea would actually seat in the outlet of the carb or just redesign another reed cage to accept it. A very very light spring would seat it in position. Any back pressure cause by piston position would also seat it.
Anyone think I have lost my mind or am way off base ??
Opinions ??

Edit: Ball style check valve ??


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 Post subject: Re: Reeds
PostPosted: Fri Oct 13, 2017 12:11 am 
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Joined: Wed Jan 14, 2009 2:10 am
Posts: 4678
Location: Carson City NV
2 Stroke Reeds..... quite a bit of science!

It's great that you are thinking outside the box but unfortunately watching reeds flex by just cranking the Engine only gives you an idea on how they work and not their true operating flex. The real deal happens when they are in actual operation (Engine running) and the actual amount of movement depends on the actual Engine rpm.

Remember, there is both a positive and negative pressure wave in the intake pulse sometimes called a pulse wave. The pressure wave coming back from the expansion chamber slams the reeds closed and then the intake pulse forces them open again at blinding speeds with the Ody its up to 8,000 times in a minute! The limiters on the reed cage are there to limit the amount of movement for optimal reed life. Without them the reed tends to flex at the base of the reed itself thus causing the reeds to wear out faster than normal. This extreme flex will eventually cause the reed to not close in a free state.

If you ever want to check out the pulse wave, watch the top of the air box of the Ody at a low idle. You can actually see the top of the air box flex.

Rand


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 Post subject: Re: Reeds
PostPosted: Fri Oct 13, 2017 3:13 pm 
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Joined: Thu Apr 29, 2010 12:53 am
Posts: 1430
Location: Norco, CA
Vforce has twice the number of reeds but I'd bet if you compared a new stock set over the vforce it would be hard to tell much difference, I have them in my cr replaced boysens and was not a major difference.


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 Post subject: Re: Reeds
PostPosted: Fri Oct 13, 2017 3:55 pm 
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Joined: Wed Jan 14, 2009 2:10 am
Posts: 4678
Location: Carson City NV
That's the thing about bolt on performance parts. One small part being bolted on makes little to no difference. It takes a a combination of balanced parts bolted on together to get any kind of substantial gains and even then your only talking a few additional horses.

As the saying goes......

There's no replacement for displacement!

Rand


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 Post subject: Re: Reeds
PostPosted: Fri Oct 13, 2017 4:35 pm 
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Joined: Tue Jan 17, 2012 3:19 am
Posts: 7699
Location: Hope, B.C Canada
Randman wrote:
That's the thing about bolt on performance parts. One small part being bolted on makes little to no difference. It takes a a combination of balanced parts bolted on together to get any kind of substantial gains and even then your only talking a few additional horses.

As the saying goes......

There's no replacement for displacement!

Rand


I completely agree with these statements.
Some guys on here in the past have asked about pipes, clutches, carb size etc and hoping for 1/4 mile dragster speed out of their machine. That's just not gona happen. Your just not gona feel any difference with a single bolt on.


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 Post subject: Re: Reeds
PostPosted: Sat Oct 14, 2017 10:27 am 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
Reeds, lots to consider on choice and again maybe not.
After all there main function is to open and close as a valve. The rest is bla bla bla or is it ?
As far as a valve goes they do there job both static and dynamic. As any valve does they can wear out and not work as well when new.
Static or at rest we look and they lay some what flat on there block in a closed position with no tension or very little depending on type ect. Again no pre load or in some cases pre load. Another debatable subject in deed. If stock stay with stock or close as one can, the Honda engineers done our work for us.
As with any Engine mod one has to do an evuation of the whole intake set up to work with a given Engine configuration. The whole air pump story.
When I read through post I play very close attention to a given set of pramiters to do a quick eval. I break this into three categories, Stock,Low and high. Each will follow a given Engine set up and one will equate an issue with the other depending upon Engine pramiters and bolt on parts.
Many of you may be saying what the heck and others may go ummmmm or right on . I would say to do your home work and choice wisley and please consult your Engine builder before making change.


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 Post subject: Re: Reeds
PostPosted: Sat Oct 14, 2017 11:11 am 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
Ok , took break made coffee and walked around. Hard to set and type anymore.
Why the three you might ask!
What I do is break down reed set up into three categories. Stock
Low
High
Ok I know, said that already so what I'm I talking about.
What I'm referring to is intake velocities. So stock is a base line then you can have a lower or higher than stock.


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 Post subject: Re: Reeds
PostPosted: Sat Oct 14, 2017 11:37 am 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
CO had mentioned the air box flutter. There lys an issue with a giving Engine pramiter. It also gives use a clue to the intake set up and an issue that could arise with certain bolton's. This would require a immeriate change in intake set up for a given Engine operation. In this case sand and or desert. One could resistance to flow. Not good "danger". You 350 guys should really pay attention to that one. Bore to stroke ratio with rod length then add in over bore and exhaust not to mention thin head gasket with stock or stock profile head. Ouch

So what changed in this Engine set to upset the intake set up? Well just about every thing. Again air pump story. There is an acceptable ratio with just about anything. This is about reeds and yes it matters to the dynamic effect on the reeds to Engine intake velocity's, combustion strenghts and pumping efficiency at a given load /rpm. Or as what I like to refer to is throttle position in time/ intake temp and velocity. An home built Adnoh equation. Or babble. Ha ha
So what does the reeds have to do with it. The reeds have a certain area with a given resistance. We can refer to this a tip area ratio. As co mentioned 8000 a second they don't see that for very long, well some do.
Break


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 Post subject: Re: Reeds
PostPosted: Sat Oct 14, 2017 12:15 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
Fingers numb no more.
The reeds have a given material strength to allow them to move or bend at given range of force. In this case it air being sucked past them causing them to bend. I did say suck or the Engine pulling air across and then through the opening it creates. Then air pushing against them to shut tight. Let start with suck or vacume causing them to open . Engine condition in a static form is key here. We can simplefy this into ring seal at changing pressure either cold or hot. I'm not referring to the cranking pressure we measure however it is an indacater of ring condition


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 Post subject: Re: Reeds
PostPosted: Sat Oct 14, 2017 12:40 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
This condition creates a vacume based on the CR of the case and the back of the reed /block area thus opening the reeds. Based on condition of seal and time area. After all our bolt on what did we do to this area most of the time nothing other than change based on bore. After all bore is area. Over bore effects time due to Port change in almost all cases.so not want to dive to deep here I think most get it.
So the Reeds open X according to material properties and vacume according to area will achieve a giving tip area ratio. I pretty sure that's right if not sorry.

Now we have an understanding of open and should move it velocity. I feel that's an easy one. Certain amount in a given time according to area. Or area when open in time.
Easy stuff now.
So if the base line is fixed we can easily or not make some decisions. If the material is weaker it open further and quicker. If stronger not as far and slower. Let refer to this as material and tension. After all we can pre load a reed block. Let stay away from that unless we get into case CR etc port timing bla bla .
That quickly covers velocity which leads us into charge density. More complicated than it sounds with greater effect on the engines life.


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 Post subject: Re: Reeds
PostPosted: Sat Oct 14, 2017 4:04 pm 
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Joined: Tue Jan 17, 2012 3:19 am
Posts: 7699
Location: Hope, B.C Canada
adnoh wrote:
Fingers numb no more.
The reeds have a given material strength to allow them to move or bend at given range of force. In this case it air being sucked past them causing them to bend. I did say suck or the Engine pulling air across and then through the opening it creates. Then air pushing against them to shut tight. Let start with suck or vacume causing them to open . Engine condition in a static form is key here. We can simplefy this into ring seal at changing pressure either cold or hot. I'm not referring to the cranking pressure we measure however it is an indacater of ring condition


This is an interesting comment to me.
Awhile back I put a gauge on the fuel pump line on my brothers Engine and mine.
These are the readings I got on Ralph's Engine: (175psi static). Fuel line pressures - 10" vacuum & 5psi. Mine was (145psi static) 7" vacuum & 5psi. So this is the pressures in the crankcase when using a starter. Maybe these pressures are higher at 8000rpm.
Don't know if this means anything to others but the way I see it the tighter your Engine the more vacuum signal your gona see. In short my brothers Engine pulled 10" of vacuum and mine pulled 7" of vacuum. Both had the same positive pressure of 5 psi. This is what the reeds in our engines are subjected to anyway.
What I was really trying to get to when I posted this thread was that I was wondering if a ping pong ball would work better as it would be very very light and open at the slightest vacuum signal. It would also open the port WAY up. Reeds on the other hand have resistance and would only open up a bit because of that resistance. They would slam shut at the slightest drop in vacuum. The ping pong ball would have a very light spring to keep it in the closed position as well as any pressure from the Engine when the vacuum signal drops off to almost zero. Unlike the reed resistance to bending.
Yes I know the Canuck is coo coo.


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 Post subject: Re: Reeds
PostPosted: Sun Oct 15, 2017 11:53 am 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
sorry got off topic. i will delete if you want


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 Post subject: Re: Reeds
PostPosted: Sun Oct 15, 2017 1:15 pm 
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Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
pic of carb and pressure zones pulled from web. Plays into the velocity and density thing
The case temp all the way back into ambient air temp also plays into this. Yes, i am leading down the path to detonation prevention or points in our favor when it come to gas/fuel choice. I say points because we start with so many points than each item cost us points. Im not much for the point system however easier to tract. Like quantity of mix oil per gallon of gas/fuel it cost points. Better grade of oil means less oil and saves points. The higher the velocity the lower the density and cost of points. Then bring in temperature from ambient to to intake to case to transfer to combustion it cost points. Im not saying high velocity is a bad thing it just needs to be considered along with temperature and few other items. Rand man has touched on this we just have to read through what he said. As temps and time goes up at a given velocity you get closer to deto as you loose points. One might can say density goes down and i mean way down. So how can we at that point make a change. One can do several things easiest being run higher octane and an higher cost. No harm no foul approach. The only foul would be plug yes look for lead spotting on plug and adjust mix if leaded fuel is used. The closer your get to a full on race Engine the greater importance to steady grade of fuel one should consider.
Some other ways are to get more cooler air into the system along with maintain a given Engine temp. Another would be to reduce velocity and thicken up density in way of reduced case CR and or port timing. What about an effective change in tip area ratio according to the natural frequency of the Engine at peak power output rpm. I have talked a little about this in the past its just that relevant in most cases. In big bore high rpm power applications I would say yes it does. Then there is the temperature factor at the intake its self after all that is where it all starts. To be very very generic why do they run inter coolers?
Now a what if: lets say for a minute we can reduce the temp at point of entry through the reeds into a a cooler case (lower part of Engine) then push this up through the ports ( including a boost port alteration) would this have an effect on the point scale in our favor. I would say yes
What if: We change that density to a stronger one or one with a greater density before entering the hotter lower case.
Lets ask our selves what is our reed blocks made of and where do they attach. Most will say aluminum which can wick heat for a warmer source in this case transfer heat for a warm medium to a cooler one. That heat is applied to the density charge at that point and start a point loss.
What if: we has a non conductive body at that point? or a lower conductive body at that point AKA insulater. Would that not save points.
Lets look at the pilot manual a minute under fuel section 4. thumb though the whole thing than pay close attention to the last page 4-16 where it shows reed valve and what ?
There come the idea or what if: two tings come to mind here we have an aluminum cylinder in my case water cooled dissipating heat across it medium. This heat is being transferred to the reed valve its self where a given density is traveling through a given area at a given velocity. Ummmmmm.

getting kinda deep sorry. This will add one more explanation though why one Engine require a different jetting than another. Yes vacuum strength plays a part as CO has noticed him self. A higher velocity will require a low jetting number and lower velocity will require a higher jetting number. This based off of the pressures and tempatures

Now you can read through post and get a idea of whats taken place with a given Engine package and bolt on added.
A simple one why does my 39 mm carb use a 170 and his runs a 190. Can you see the big picture. I can

You should be able to see how the point system is working as the intake charge is traveling through it cycle one can see the point loss. This before it even get to the combustion chamber which has the greatest effect on the remaining charge. You loos to much on the bottom not enough left on top when it matters. I am sure you all have read it I was jetted fat and fouling plugs once i drop down to where it cleans out its cooks off the piston. This is not the whole answer however one step in correcting it. Remember point loss is a reduction in octane rating, get it now.

Here is another one: Shove the weaker now stuffing charge down a pipe with hot spots and cook off a big portion of your points. Remember as a pipe heat up it shift wave pressures so once you get it hot and the density is already low it will steady climb into detonation in some/most cases real quick.

This brings some validity of what CO is always saying "ave gas man". Im not apposed to it as long as it needs it and on the other hand its cheap insurance. Rather ride and pay more than not ride at all. There is a saying and I have said it "fuel cools" same words different meaning when taken in and out of context.

So the big question does reeds and its assembly matter?
Does the intake temperature matter?
Does the available CFM matter?
Does case CR matter?
Does the natural frequency matter?

If so at what velocity and density!

Any way fuel for thought, just think I wrote this because I read three words "air box flutter"
Adnoh


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 Post subject: Re: Reeds
PostPosted: Sun Oct 15, 2017 5:03 pm 
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Joined: Tue Jan 17, 2012 3:19 am
Posts: 7699
Location: Hope, B.C Canada
This reply above by adnoh is one of the most important ones of his that I have read. It touches on many issues and I had to read it twice - slooooow - it gives me ideas.

He said: "Then there is the temperature factor at the intake its self after all that is where it all starts. To be very very generic why do they run inter coolers? "
If I ever find a cheap inter cooler it's going on my oddy LOL.

He said: "This will add one more explanation though why one Engine require a different jetting than another. Yes vacuum strength plays a part as CO has noticed him self. "
AND
"This brings some validity of what CO is always saying "ave gas man". Im not apposed to it as long as it needs it and on the other hand its cheap insurance. Rather ride and pay more than not ride at all."

In other my words -- some of us have girl machines -- AVGAS amen.

This reeds thread started because I thought that reeds were restrictive. I felt that just having an easy opening and FULLY OPEN intake port would be highly beneficial. It may or may not be according to the above ahnoh statements. Yes I did notice that my brothers machine pulled 10" vacuum and mine only 7" but his machine is slightly faster than mine. However his Engine has lots of mods. The previous owner took 2mm off the base of cylinder, has porting, has pipe, has over 170 lbs compression. My initial idea was huge flow huge power. May not be the case unless you do other mods. One mod won't make a 1/4 mile dragster out of your oddy. I was just musing.


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