The volume and density of the intake charge actually varies throughout the rev range. It’s not a constant at all.
A lean sieze is rarely, if ever caused by lack of oil from leaning down, provided the correct amount of oil was used to begin with. Generally that amount is decided by the operating RPM of the engine and to an extent, how long full throttle periods are.
A lean sieze is typically from the piston expanding to the point that the film strength of the oil is exceeded In one or more areas. One that happens you have metal to metal contact and no amount of additional oil can help.
Another failure is damaged piston ring landings and/or crown from detonation.
Have a look in the crankcase of an engine that’s seized from being run lean… you’ll find a lot of oil in there as well as the transfer passages and oil doesn’t burn very well at all.
A vacuum is a reduction of pressure. It takes force to create vacuum. The normal air has the force of the weight of the column of air above it. So both the created vacuum and the still atmospheric air has force and both work together to create air movement. Both the Yin and the Yang are necessary. They are a matched pair. Both air and fuel are both pulled and pushed into the engine.
That being said, can we get back to the topic at hand?
RPM changes neither. What changes is the engine receives exactly the same amount of air, at exactly the same density, more often. The cylinder and piston don’t get bigger as RPM increases - the hole in the air left behind by the rising piston is the same size hole.
Anyway, it’s semantics. I’ve read the Weber carb book (carb not carb ) and yes I fully understand it. Regardless how you consider the result is the same, air goes in gets burned n gets kicked out, and were off topic a bit (jetting )
I do love a good debate and good explanation of lean seizure - thanks for that.
Maybe he was referring to the intake charge transferred to the combustion chamber. How much it mixes with exhaust gas varies with RPM. Also some can be lost out the exhaust port and some can be sucked back down into the crankcases if the return diffuser wave isn’t very strong as the piston rises till it closes the transfers. What remains in the combustion chamber as the piston seals off the exhaust port of course would affect jetting needs. As I’ve said before, I eagerly await the day when we can assign the job of making a near perfect 2 stroke calculator to A.I. (hopefully we aren’t too dumb to use AI created software)
I agree with you @tjkoyen when you say lessons learned listed by @Jaguar relates to motor bike and not karting.
Therefore, I´d like to know if any of you have created your own methodology for kart carb jetting. I mean, what to do before starting the session and what to do while you are in the track and you don´t feel you have the optimized jetting?
This is one of the most difficult topic for me, so I´d like to be confident I understand the theory before start practicing to make changes during the session or race.
Any of you regulate just looking EGT like I am doing nowadays?
I realized with my data analysis that, ~475ºC for low revs and ~610ºC for high revs bring me good time laps.
Any tip from the experts in carb jetting?
On my KA or X30, or anything with the adjustable needles, I set them at a baseline setting, then use EGT to tune on the fly. I also use an air density gauge in my trailer. My engine builder will have an EGT number in mind that they want to shoot for. We tweak the carb needles to get to that number and check the pipe coloration to see what amount of unburned mix is getting through the engine.
I try not to overthink it. There is validity in getting the mixture correct, and it’s an integral part of tuning, but the time gains of dialing it in that very last little bit are small compared to having the kart setup properly and driving it properly.
I look at it slightly different, sure big gains can be made with tire work, but the gains become smaller and smaller the closer you get to ideal, same as turning.
Technically you are talking about potential energy not force. A mass at a given distance from the center of gravity has a potential energy relative to its distance and masses. The only force involved is gravity. The first law of entropy states that energy always moves from the higher state to the lower state. In terms of heat, hot air warms cold air, not the other way around. Where as in terms of pressure, the molecules of denser air are pushing out more (higher state of potential energy for a given volume) than the lower pressure air (ergo vacuum) so the molecules rush in (push) until equalization is reached.
To put it simply, if you were in outer space and capped an empty bottle then brought it back to earth, the atmospheric pressure would push the air into the empty bottle. Same in reverse, if you capped a empty bottle on earth with only the air it was exposed to and took that bottle into space, when you opened it, it would push the air out into empty space trying to equalize with it.
As it all relates to karting, I think for the most part getting your jetting as close as you can is important, but less so than your setup or driving. In a perfect world, that last hundredth gained from better jetting might make or break your weekend, but more often than not your setup and driving skills will likely out perform the competition than your jetting.
A vacuum is not an “absence” of pressure. It’s simply a term used to describe the difference between 2 pressures. Anytime you have 2 areas connected, and one area has a lower pressure than the other area, the lower pressure area could be described as a vacuum.
A vacuum has no power whatsoever, none!! Your writing leads me to believe you are a very intelligent person, probably a lot smarter than me, but your opening paragraph is incorrect.
With the valves closed, as the piston travels from TDC down the bore, it does take energy, but it takes energy because The atmospheric pressure on the other side of the piston is trying to get into the vacuum area. Of course there’s mechanical losses as well, but essentially it’s the outside pressure pushing on the pistonTrying to fill the vacuum.
@Jaguar, I went there, you’re going to have to be more specific, I have not the desire or the patient’s on the time to find the reference you are, I suppose, making.
Energy is always trying to equalize with its surroundings. Pressure is an effect of Energy often described by Heat. Particles bounce around at varying rates depending on their Temperature (level of Energy). In a closed container the particles bounce off each other and the off walls of their container creating Pressure for a given temperature. Change the temp and the pressure changes. Change the volume and the pressure changes. By introducing a localized difference in pressure within a system, the particles will always move toward Equilibrium (Greatest Entropy). Only if an outside force (loosely used) is acting on the particles/energy within the system, can it be altered.
Correct. A vacuum is an effect, not a force. I think you mistook me quoting @Jaguar (fellow KartPulse memeber) as my words.
You said I was incorrect about a vacuum having no power. Now you’re telling me about heat transfer, well it doesn’t seem to me to be a parallel.
I reject the notion that pressure, and lack of pressure, work together. My scientific vocabulary is lacking in words to describe the condition. Maybe you can describe this power you speak of?
Try this; the definition of “work” is “force over distance”, or something to that effect. A vacuum is just a lack of pressure compared to an adjoining area. Again, my scientific vocabulary is lacking.
Bottom line, and the reason for my post, there’s no such thing as suck, or draw, only push! It’s my contention, it makes a difference how you look at it.
I used the parallel of Heat, because it is a form or Energy most people can relate to. Energy comes in many forms, Kinetic, Potential, Chemical and Thermal (Heat) to name a few. As you stated, Pressure is a term used to describe a difference in Energy States between two or more zones. Power and Energy are somewhat interchangeable terms here. An area of Low Pressure can be considered a Vacuum when compare to an area of High Pressure when referring to Air. Its just a term to used to describe a difference. Is there Power there? In a way, Yes. In the form or Potential. Like a book sitting on a shelf has Potential Energy as Gravity pulls on it and the Shelf resists it. Remove the shelf, gravity applies force and the book falls a distance = Work. Now apply that to air. Imagine two vessels of air connected by a valve between them at the same temperature. One side has more air in it than the other. More molecules = more Pressure vs. fewer molecules = less Pressure on their individual containers. What happens when you open the valve between them? The side containing more air has More Potential Energy (Higher Energy State) than the side with less air (Lower Energy State) and the two Systems become One. The two sides will equalize the pressure between them (Entropy). Energy in container A + Energy In container B is equal to the total Energy of containers A + B. Any vessel with greater “Pressure” than the Atmosphere it is released into will exhibit this effect, from scuba tanks to hair spray. Work was applied to pressurize the vessel and the energy to do so is stored as Potential Energy, like the book on a shelf. Remove the barrier and the Mass (air) moves. Work = moving Mass over a Distance. Call it Foot-Pounds of Torque, Newton Meters or Watts, it does not matter. It is all about moving Mass (Air) over a Distance (filling in the respective void). So, Pressure and Lack of Pressure do Work together or there would be no Movement over a Distance. Two vessels of equal pressure would not exchange air between them when a connecting valve is opened.
Me: Feeling bad this thread has been bolstered by how Air Moves…
not carb 
) and yes I fully understand it. Regardless how you consider the result is the same, air goes in gets burned n gets kicked out, and were off topic a bit (jetting 
)
and good explanation of lean seizure - thanks for that.
