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Has anyone experimented with reed valves?
https://slantsix.org/forum/viewtopic.php?t=38720		 Page 2 of 3
Author:  olafla [ Fri Jan 22, 2010 12:31 pm ]
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I see your point, but I think a test must be done before we accept or dismiss any claims in either direction. I have actually had this idea in my head ever since the reed valves started to turn up on bikes, but unfortunately never had the means to follow it up. I tried to do some calculations on the theme, but that was before I had access to a PC, so it didn't go very far, but I am convinced that I am right in my statements about the application of reed valves in four-stokes. There was a post in the forum I link to in the initial post about this theme, posted by one Mike Gullatt, who apparently had some kind of Chevy repair shop or similar. His link is not active anymore - maybe he's a victim of the financial crisis? He did exactly what I describe, and apparently with great success. Anyway, here is what he wrote one year ago:
Quote:
We are working on a tech 4 chevy s-10 engine right now putting 4 big reed valves in the intake and 2 big dellorto 2-barrels making an IR setup with a long duration intake timing which usually kills the low end and midrange torque on these engines. The reeds control the overlap and reversion at low speed letting it pull like a short timed cam but able to use the extra cam timing as rpm goes up. Best of both worlds and amounts to poor mans variable valve timing like my wife’s nissan. Mileage is also very good since the intake is tuned length and the reeds stop most all the backflow that usually blows a fuel fog back out the intake on quick throttle. Seems pretty practical so far if reed life isn’t a problem. Anyone playing with this?
That certainly raises the hope of success when trying it out, but only dyno runs with base engine, engine with hot cam, and engine with hot cam and reed valves can tell how good/bad it is. If an engine with a race cam suddenly can idle and potter around in low speed, that should also tell the tales...
Olaf
Author:  olafla [ Fri Jan 22, 2010 8:07 pm ]
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It would be interesting to get some feedback on this subject from some of you guys that are active racers, engine builders, and/or have played around with camshaft design.
Olaf
Author:  ceej [ Fri Jan 22, 2010 8:43 pm ]
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You have feedback from racers already.... :wink:

As you pointed out, atmospheric pressure fills your cylinders. Any restriction in the path creates a "Drop" in pressure. Every time the direction of the flowing air changes, will result in a pressure reduction as well.

Scavenging effect creates a low pressure at the exhaust valve, which makes the pressure that atmospheric is seeking go "Deeper." A vacuum, or lesser pressure than atmospheric is shallow when it is closer to atmospheric pressure, and deeper as it approaches zero pressure. (Absolute) The overlap event couples the low pressure at the exhaust port to the intake port, drawing Fuel/Air charge into the cylinder.

Scavenging is created by the mass of the exhaust gas at velocity. By creating a stoppage in the intake runner, the mass of the mixture going toward the intake valve will stall. It never really stops flowing. You don't want it to. The closed valve becomes a slightly higher pressure than the rest of the plenum because of the tuned property of the runner. By creating a situation where the reed valve is in the way, the restriction in the runner will increase, stalling the effect.

While it may help a wild cam at a dead idle, it will decrease benefit of having a big cam at operating RPM very noticeably. You will be in the same boat as running a very mild cam, or worse.

Keep us posted with your results, but this isn't a two cycle outboard. Your going to tear up reeds. A four cycle engine doesn't breath the same way a two stroke does. It breaths considerably more of it's theoretical displacement on the intake stroke than a two stroke does. The reason for the high horsepower ratings of two cycles is twice the power cycles at the same RPM, and generally the two cycle runs at considerably higher rpm.

HP=Torque X RPM /5252

That's how it works. High RPM engines trump lunger low rpm engines for HP ratings.

CJ
Author:  emsvitil [ Fri Jan 22, 2010 8:45 pm ]
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Let's say you can avoid most if not all restrictions to the flow with reed valves....... Those tepee like reed valves look like they'd fold out of the way into the runner if the runner was designed correctly.

Forget carbs and use fuel injection so you don't have to worry about any weird fuel distribution problems.

Do equal length runners off of a common log plenum chambers so all cylinders have as close to identical flow characteristics.

Have the reed valve at the plenum side so that runner tuning can still be utilized (pressure waves bounce off the reed valve and back down the runner, probably similiar to the bounce you get when it hits the open plenum)

With the reed valve at the plenum side, you'd also get a slight supercharging effect at low rpms.

When the piston is moving back up the bore pushing the mixture out of the cylinder before the intake valve closes, you're pressurizing the runner. When the intake valve opens again, you actually get some air flow before you normally would because of the runner pressurization.
Author:  adiffrentcity [ Sat Jan 23, 2010 8:34 am ]
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Seems like the best way would be to make the runner "D" Shaped with the flat side as the floor. Put the axis of the hinge just under the floor level of the runner, so that when flattened(opened) completely there is nothing to obstruct flow.

CJ has a good point about the reeds being fragile, it would suck to have your wild cam-race motor eat one! No pun intended.

I'm ready to see some testing as this idea logically seems like it has merit.
Author:  olafla [ Sat Jan 23, 2010 12:23 pm ]
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Sorry ceej, I know you fill all the categories :oops: , I just expressed myself clumsily, what I intended to achieve was feedback from different points of view, and the response was great. My affair with two-strokes ended with a Suzuki in '72, after that I have only had four-strokes to play with, so I have never had any personal experience with reed valves in engines. After working with bikes and cars all through the seventies, I got myself an education in combustion engine engineering, but at the time, the reed valve had just started to turn up in bikes, and wasn't even mentioned as a construction element in engines. I hope to get as many ideas and thoughts as possible from you all, in order to try it out in an engine. There is no literature on applying reed valves in a four-stroke engine, so there is also some theory to be formulated in the process.
Olaf.
Author:  SlantSixDan [ Sat Jan 23, 2010 12:28 pm ]
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Remember the guy who made all kinds of fancy claims for his intake valves (or "valvz") equipped with a sliding plate type check valve theoretically acting just like the reed valves in this discussion? Always enthusiastic to talk about the amazing improvements they make, but always ready with a bagful of excuses why he couldn't provide/doesn't have/can't share any actual test data backing up the claims. :roll:
Author:  olafla [ Sat Jan 23, 2010 12:40 pm ]
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emsvitil and adiffrentcity, good thinking. I wonder if a runner should best be made of small sections, so the reed valve can be placed at different levels between the inlet valve and a plenum, to see if a common factor in relation to the known ways to calculate runner length can be applied. I will obviously also have to find out what kind of abuse a reed valve can take without failure.
Olaf
Author:  olafla [ Sat Jan 23, 2010 12:50 pm ]
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Dan, you are absolutely right. There are so many 'fantastic' engine designs that have popped up, and they all have the documentation problem in common. The simplicity of just adding reed valves to an existing engine is what facinates me, no major engineering is involved, just an adaption of ideas.
Olaf
Author:  ceej [ Sat Jan 23, 2010 8:51 pm ]
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One application where a reed valve in the intake runner could be beneficial would be in a naturally aspirated Miller Cycle design. To avoid pumping losses, secondary reed valves would need to be used to dump flow to runners at lower pressures during an intake stroke.

It would reduce pumping loss when the reed valve in the runner that was suffering reversion closed.

Hmmm. It's still a tremendous restriction of the runner. The biggest problem you run into is the "Cage" that holds the reeds has to provide enough surface area for the reed to seal. That presents a large impediment to the runner's flow characteristic.

Miller cycle engines keep the valve open longer and reduce dynamic compression tremendously. One of the problems with them is they don't play well with carburetors. With fuel injection and forced induction, they perform well, and deliver exceptional fuel efficiency though. With a "bypass" method, the reversion could be fed to another cylinder that is still on an intake stroke. Not quite sure how that would look timing wise. Likely it would be a nightmare for a conventional engine, but a swash plate engine would have the cylinders close enough together to take advantage of such an arrangement.

With a variable displacement configuration, which has been achieved with a wobble plate engine already, it could work. I wonder if the metallurgy is up to the task now. It wasn't making the grade fifteen years ago when the technology was being explored actively.

CJ
Author:  emsvitil [ Sat Jan 23, 2010 9:22 pm ]
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Interesting on the Miller cycle....

For a 4 cylinder you'd dump the pressure into the next cylinder in the firing order which is 180 degrees crank rotation. Cylinder at bottom is feeding cylinder at TDC.


For a 6 cylinder would you use the next cylinder (120 degrees crank) or skip it and goto the one after that (240 degrees crank) ?

240 degrees would enable you to have front 3 cylinders, and rear 3 cylinders as a system. 120 would be complicated.
Author:  emsvitil [ Sat Jan 23, 2010 11:39 pm ]
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I think the more reeds you have, and the less angle they move, the less resistance to flow you'd get.

Compare this: (looks like 4 reeds)

http://www.snowmobile.com/products/reed ... n-666.html


to this: (2 reeds)

http://www.gasgasrider.org/html/reed_valve_service.html


A stack of reeds, with vanes to manage airflow may not actually have that much resistance.
Author:  Kevin Johnson [ Sun Jan 24, 2010 6:21 am ]
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"Reed valves" on SAE.org produces 194 hits: http://miniurl.com/27674

KrankVents

Dan, I think I know who you were speaking of. The gentleman I was trying to sponsor for the X-Prize was in contact with the inventor of the valves and wanted to install them in a G10 engine. The inventor is a different person from the person on the internet. Some drama there. I suppose you could track this down with a patent search.

The person I was dealing with was earnest but was trying to do too much to a single engine in too little time with very little funding.

Emissions requirements now are brutal. I spoke with someone not long ago who was mentioning the pending exit of most two stroke designs in even off-road applications.
Author:  olafla [ Sun Jan 24, 2010 6:42 am ]
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Why is the text field in posts on page 2 suddenly half a mile wide? Can someone fix that please, it is very awkward to read the posts.
Olaf
Author:  Kevin Johnson [ Sun Jan 24, 2010 6:54 am ]
Post subject: 
Quote:
Why is the text field in posts on page 2 suddenly half a mile wide? Can someone fix that please, it is very awkward to read the posts.
Olaf
All fixed with mini-url.
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