In practice these latter types of entry are never used for engine intakes. The flow coefficient of a perfect entry would be 1.0 while the coefficient for a sharp edged entry would be 0.6 and a re-entrant plain pipe 0.5. The acceleration of air flow into a duct is inherently a highly efficient process and the difference between even the crudest radius inlet, and the most aerodynamic shape possible is slight, amounting to no more than a few percent. A longer inlet pipe will create a later intake pressure wave that will help keep the air in the chamber until the intake valve closes. but, it is actually that the intake valve is closing too late and the combustion chamber is simply overfilling and blowing back out the intake port, before the intake valve closes.
It is commonly related that "stand off" (air-fuel mix that gets pushed back out of the port, usually at full throttle / low rpm) is somehow captured by installing a longer intake pipe (stack). Most current aftermarket stacks are designed to be run "in" the airbox and a company that does research well will have some applications that have all the same length and some applications that have differing lengths of stacks on different cylinders. The length of the stack is known to have a direct effect on a particular engine's boosted power range. A properly tuned intake tract produces a rather audible intake noise under high airflow conditions - that is commonly "untuned" to allow the vehicle to pass EPA and DOT noise regulations. OEM automotive manufacturers have many regulations to adhere to.
In amateur and professional racing, aftermarket velocity stacks are often used, as rules allow, and gains in the order of 2% to 4% can be obtained when inlet radii and stack lengths are optimized for that engine.
Modern fuel injection systems with a plenum and single air inlet typically incorporate some sort of radiused entrance, designed to improve power, based on air flow increases. Modified engines often have the original air box and associated ducting removed and velocity stacks are installed as accessories. Modern engines universally have tuned intake tract volumes and associated resonance frequencies, designed to provide higher than atmospheric intake air pressure while the intake valves are open - increasing the density of the trapped air in the combustion chamber (higher compression). Modify the dynamic tuning range of the intake tract by functioning as a resonating pipe which can adjust the frequency of pressure pulses, based on its length, within the tract. It is designed to:Īllow smooth and even entry of air at high velocities into the intake tract with the flow stream adhering to the pipe walls.
Many many many more.Ī velocity stack is a trumpet-shaped device of differing lengths which is fitted to the air entry of an engine's intake system, carburetor or fuel injection. I don't mind EDITING WORDS, or my words being edited, what I do mind are some of these people who basically sabotage your article and argue in the comments to boot. I used to write a lot for Wiki - but - I get tired of the people who "EDIT" so I havent written much for them at all in a while now. I'm not a company, I'm not trying to sell you anything, just give you some ideas and thoughts on products that you may not even know exist.Īnd here is some cool info - may be hard to read due to size:Īnd a quick video. I could get much geekier with the tech speak but.I try not to write what I'm going to say. This is a simple explanation of a velocity stack. I'm pretty OCD, ADD, ADHD and APhD - so I keep track of a lot of STUFF!!! The idea is to spread information on products that a lot of people may simply overlook, or not know about. I plan to add all relevant info in the descriptions and I am not joking when I say that I have HUNDREDS of these types of videos planned. Most of them will contain nothing more than a few jpegs with audio of me giving a description of the product and where you can buy it for the best cost I can find. A majority of these videos on ProjectCarTV2 will be very simply made. The videos will be very simple, very short, and to the point. One of them is ProjectCarTV2 which will be different in that I will do reviews on automotive parts that I have used myself, or have experience with through others. I do have a few Channels that I am working on developing though. I already have the name picked out and everything, FINGERNAIL FRIDAY!!!! My 16th Channel if anyone is interested will be devoted entirely to my birds!!! I'm thinking of a beauty type Channel where I file my fingernails on Friday.
Hello Might圜arMods Forum - I'm trying this new thing where I create a second channel, and a third and a fifteenth.