Topic: Venturi Divider mod. Real deal?

[GroovieGhoulie]

http://richstaylordporting.com/vintage_Venturi.html

Thoughts on this modification?  It makes sense on the surface, but I'm not 100% sure.

[evan77]

this is interesting

looks good to me. i will wait until the experts weigh in to determine whether i do this or not.

thanks for posting though

[mlinder]

Looks pretty much like bull#$%* to me. Ruins actual venturi flow characteristics, especially at more than half throttle.
The airflow diagrams are a tad laughable.

[evan77]

not sure how a super thin plate ruins “actual venturi flow characteristics” past half throttle. i suppose you are probably right but i would just like to challenge some thought. i would think the venturi flow characteristics would actually be less affected past half throttle as once the slide is above the (air foil) it allows the top half to open up. the air then is simply being sliced by a knife. perhaps you could come up with a air flow diagram that would explain this that isn’t “laughable”. please share your knowledge.

here is my idea.
what do you say we reshape our single venturi carbs into two. one venturi directly above the other, resembling boobs of a girl lying on her side. i think this is the ticket to really unleash some air-flow.

thoughts?

[turboguzzi]

well, at least CB500's have this built-in into their carbs in the shape of the rotating choke plate

I am with mlinder on the explanation blowing a lot og hot air and thick smoke. Interesting? sure, but so is the life of microscopic elefants 10,000 bellow sea level. not sure any will improve performance.

That said, MV Agusta has a patent on similar split but in the PORTS, the idea there being much more interesting: keeping flow attached to the short side radius to obtain better top end flow

[napoleonb]

I unfortunately do not have a comprehensive history of tuning and porting but had some theoretical classes about flow.
A splitter can alter your flow from (turbulent to laminairor) and could provide a much better or quicker fill and is best used in corners.
On the downside, if i understood correctly, the mixture can also change which make you lose power.

Try and find out i would say.

By the way, those splitters are used in most pump which pump fluids and they seem to boost the results quite effective for it is common knowlegde there.

[Sam Green Racing]

not sure how a super thin plate ruins “actual venturi flow characteristics” past half throttle.

here is my idea.
what do you say we reshape our single venturi carbs into two. one venturi directly above the other, resembling boobs of a girl lying on her side. i think this is the ticket to really unleash some air-flow.

thoughts?

Sorry Evan but this is not your idea It's old hat and is known as a twin choke carburetter (not to be confused with the racing instruments made by Weber and Del-Orto ) but what you're saying does work.

Let's not knock Rich down though, it's happened before when people start slagging off peoples ideas and thoughts only to have it back fire on them when the person in question joins in on the debate.

Over the years there have been some real innovation's in carburation, take for example the Wal Phillips fuel injector, the Gardener Carburetter and the turbo thingy that fits in the same place as Rich's plates.
If all these ideas were the bees knees, why has the big carburetter companies not bought them out and incorporated them into their own carbs ? (or has it already been done as with Evans idea for a twin choke carb.)

Sam.

[Sam Green Racing]

Have you got plenty of popcorn?    this could be a long one. 

[turboguzzi]

Have you got plenty of popcorn?    this could be a long one. 

i'm pretty sure the pop corn will start flowing when you move this to the regular forum or does improved throttle response = hi-perf?

 

[Sam Green Racing]

We're not exactly over run with posts these days, anyway, if a motor responds quicker to your turning the grip, then it and you should move quicker = performance maybe not high performance though.

Sam.

[bwaller]

I hate to be sceptical but if something appears too good to be true......it usually is.

[Markcb750]

I think it would need these on the exhaust to really work. 

http://www.spiralmax.com/tet.htm

[Sam Green Racing]

The same company that made the gadget that I reffered to in the inlet tract.

http://www.spiralmax.com/

Sam.

[MidnightLamp]

From an engineering standpoint...this does not make much sense. One key point to remember is that air is not being "pushed" into the carb, it is being pulled through. Those are very different problems from a fluid mechanics perspective. Also the introduction of a D shaped runner is good in many instances, but only after flow has developed (further on down the intake tract). Introducing this plate upfront causes significant entry losses as well as a slower overall inlet speeds.

As an aside....anything that tunes for a specific throttle position is probably not all that desirable. Assuming this worked in the first place, what happens when you're not at "half" throttle or wherever it's set at. According to the "theory" presented, this would only make problems worse, not to mention the losses at full throttle associated with this plate.

I wouldn't bet my lunch money on it...

[mlinder]

I didn't have time to get to this til now. Lamp hit a major point there.

I'll come back as I have time today to point out other issues.

[Sam Green Racing]

I'm off home to enjoy the evening sun shine (we don't get a lot over here)
Rich knows about the thread and will get on here when he has the time meanwhile, keep on poppin the pop corn.

Sam.

[Bob Wessner]

I'm off home to enjoy the evening sun shine

Sun? What's that? 

[simon#42]

these things where very briefly all the rage on two stroke gp bikes a couple of years ago , the idea was up to half throttle the engine
 ' thinks ' it has a carb of half the size , thus improving low speed fueling . i fitted one to a 125 aprilia that was running a 43-mm  carb to see if it worked . on the dyno it seemed much the same low down but lost 5-hp  up top . on the track the rider reckoned it was a bit better low down , but in an area that he never used when racing so off it came .

[MidnightLamp]

The same company that made the gadget that I reffered to in the inlet tract.

http://www.spiralmax.com/

Sam.

The audacity of people like APE and CycleX...selling big bore kits when one could just fit four of these puppies (one per carb, of course, special order) and gain 140HP right there. I'm sold, I'm just very concerned if that's 140WHP or BHP.... I'll take all four plus a stuck tickler valve Wal Phillips setup.

[TwoTired]

It occurs to me, that air flow straighteners are not new.
But, they only perform a real function when the airflow is turbulent.  Which sort of begs the question, why is it turbulent?
Maybe someone tossed the inlet stacks?  Or, put an air filter membrane in the air path close to the carb?  Or, well ...I just don't why the turbulent inlet flow assumption is made.  So, the addvert sort of makes the reader do a "leap of faith" that is actually exists, which it may.  But, I'd like to know root cause or that a problem exists before looking at approaches that "fix" it.

Some other observations:
I noticed the "artist's rendition" uses slides without an entrance cutaway.  I think that matters to the air pressures in the carb throat driving the fuel jet flow rates.

I suppose this device doesn't apply to carbs that have choke plates at the entrance, right?

Assuming air turbulence can't be corrected before reaching the carb entrance, the entrance plate divider actually causes turbulence as it draws and mixes stagnant air from the "quiet" or slower flowing side of the divider plate.

Also, it appears that the entrance divider plate doesn't meet up with the slide face to block air flow from above and adjacent to the slide.  Funny that the artist's rendering doesn't show that path of flow and the turbulence that induces.

Just 'cause I think that it's cool, I'm going to add a drawing that illustrates a way to deal with turbulent flow in a duct.  It's from the Harrier, where they installed an inflatable boot at the inlet area on the outside, so airflow inside will stay laminar.  The boot is inflated only while hovering.  When the duct has forward motion in the air, it isn't needed, or wanted, as air isn't really drawn from that area when the aircraft is flying on the wing lift instead of jet engine thrust directed downward.  In both cases, flying and hovering, the duct inlet velocity is comparable.  But, the relative airspeed outside the duct still has an effect on the airflow inside the duct.  As an aside, this is why a velocity stack entrance lip radius design is important to the internal stack air flow capabilities.

Cheers,

[Sam Green Racing]

Lloyd, I was kinda hoping you would chip in, now everyones head is totally messed up. Let's wait until Rich puts his claims forward, this is a proven theory and we should wait to hear his take on the subject.

Sam.

[MidnightLamp]

Is rich a member on here?

[Sam Green Racing]

I don't know but he's sent me a few emails.

Sam.

[racerclam]

Hi guys, Im Rich Gagnon . Sam E mailed me and asked me to get involved in this discussion on the venturi dividers that I build. No they are not a miracle but they do work. With them installed on the rear of the slide at 1/4 and or 1/2 throttle positions at those particular throttle openings the air does not tumble at the back of the slide as it makes its way under it thereby flow and velocity is improved and response is improved and by building them also on the front of the slide the air is prevented from rapid expansion for a greater length of time, so velocity is kept up and cylinder filling is improved, on a two stroke this is very significant since there is no intake valve slamming in its face and the ram effect of the air column will keep filling the crank case for a longer period of time before crank case pressure closes the reed valve or the piston closes of the crank case, but either 4 stroke or 2 stroke turbulent air is not our friend. Also I will mention that on both sides of the slide the dividers conform to the shape of the slide to no more than 1mm gap. And on a flow bench using just a 1/2 throttle divider on both sides of the slide shows increased cfm , but with 1/4 and 1/2 positions a slight loss of Wot cfm is found but the trade off is worth the improvement for the ability to pull out of a corner after the throttle is backed of such as in a MX bike. But to gain the Wot cfm back one merely uses a slightly larger carb with the 4 dividers and has the best of both response and total cfm. And with the addition of a UFO ( ultimate flow optimizer ) made by thunder products improvements are made every where. It is a plastic disc that fills the cavity on the bottom of the slide, it can be seen by going to the links page on my web site and click on thunder products web site. Recently I improved the design of the 1/2 throttle divider at the rear by making a concave scallop type cut in the back and that showed an increase in Wot cfm since air actually rolls into the carb from the sides and not directly from the rear. If I can be of any help please ask.

Respectfully, Rich

[Markcb750]

Rich & others:

I know it is possible to tune the size and shape of the intake stack for any given throttle position which would improve flow through the venturi created by the slide for a given RPM.  I assume this divider creates a situation where the intake side is tuned to a given throttle position/rpm.

When the throttle is moved away from that tuned point the intake tuning that was effective becomes less effective.  I assume this is why you talk about 1/4 & 1/2 position dividers, to improve the flow around these particular throttle positions.

Motors must operate at other throttle settings:

When the throttle slide crosses the divider what happens to the system?  Is there a point where the engine looses response because air is tumbling around this additional edge? 

Is fuel and air mixing impacted at throttle settings above the divider plate because of the directed flow across the lower section of venturi?

Mark