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