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I've heard both theories, in CFD the reflected waves were very small, nearly negligable. If they were significant from the stepping you would imagine the engine dyno readings would exhibit some crazy outputs as the waves moved from constructive to destructive, and back again.

I have engine simulation software, but its really questionable. Its the performance engine analyzer by performance trends. It sometimes acts very oddly, and often states the pumping loss as negative (as in negative negative or positive) So I'm very skeptical to its use. It got me thinking as...

Alas, I found a topic that didn't have a single reference in this forum. I could hardly believe it. So how do you tune these cacophony of waves caused by a step header? I have Larry Muaex's pipe max software, but whats the real story? All lectures, references, and tirades welcome.

Certainly, but for a good first approach, I always try to use the very best scientific methods and research for a starting point. By the way pedro, I've got it worked out! Does anyone have any definite research articles on relating CFM @ pressure differential to an effect on horsepower? Or...

I just checked it, and its not a flat ellipse and it its not a full ellipse, its some kind of high order polynomial...

Thats what i was saying in not so clear langauge. The flat ellipse doesn't stay a flat ellipse any length of time whenever you step toward the circle. The first movement of dz out from the flat ellipse changes it into a full ellipse. So from that perspective you just start from some defined...

Hrrrm, given what you've written, I think the first dz would create a full oval from the the flat oval, because for every dx/dz and dy/dz of the circle the corresponding dx/dz and dy/dz for the flat ellipse is different. Maybe I could make the first step(.001 in), do a curve interface capture of...

Well my problem is that the area changes between the interpolations. I need to build guide lines which maintain the correct area throughout the transition, otherwise you get the speed up and slow down that causes the turbulence. Its very complicated math it seems. You would have to fit the...

I found your reference in the article pedro, I was a bit confused by what you had said until i read it in the article and its clear now... Just to resolve the transition from oval to round... I wish Larry Meaux was around to explain how he exactly calculated plenum entry area in his pipemax...

haha, I appologize for the misleading title, I didn't even think of the ambiguity. I really appreciate the link, its very interesting. Its the same cfd I was doing, but at a more methodical approach, and time intensive approach. Although it does leave out some amount of specifics. So now that...

I have really tried to pin down runner inlets for combustion engines in order to reduce the coefficient of discharge. I can't quite put my thumb on optimal though and would like any help or expertise you can offer. Here is what I've found...(I think) Round bell mouths exponentially reduce...

I'm looking at applying a rubber laminate to an aluminium pulley that continues to slip. I'm stuck wondering about which rubbers produce the best coefficient of friction against other rubbers. Its a belt driven system i'm not exactly sure of the belts content. Also could anyone clarify the...

With the Miata its not an issue, the cat is rearward fitted (stock location) and in the long gaulley between the engine and the rear wheels. I'm excited to start work on it thank you all for your inputs.

I definitely want to keep a cat in the exhaust... what i was thinking of doing is buying a cat with a very large intake and exhaust pipe (and a hopefully proportionatly larger inner matrix) for minimum back pressure. I know there is no such thing as a high performance cat (well not one for...

T=Time your trying to cut the wave up into small segments where the expansion into atmosphere isnt as violent or concentrated..Similiar to using assymetric tread designs on tires, lots of small individual noises of different frequencies amounts to nothing, but if all the tread tiles were the...

Basically it takes the big puts and cuts them into lots of little puts. What your trying to do is desychronize the wave over t. That is reduce the pressure gradients on each side of the air pellet, and make one nice long static discharge into the atmosphere. As described before the initial hit...

Well yea... we need a complete list of frequency conversion devices though to attack this problem. restriction like a turbocharger is definitely one.

So basically what your trying to do is dissolve the pressure waves... what if you converted them to a frequency that was above or below human hearing... Know of any frequency converting devices like that?

So how does pipe diameter and sound relate to each other? It would seem atleast conceptually that the larger the pipe the lower the frequency emission... so as you increase pipe size you decrease the need to muffle high frequency sound, and increase the need for a muffler that dissapates low...

I'm Looking for an empirical resource of tested bell mouth entries on many different diameters of pipe that show the discharge coefficient of that pipe at different pressures so I have a good rule of thumb to begin testing with, or I guess the alternative (and highly optimistic) approach... is...