I'm having trouble making your math work for the area and circumference, Slvr. I find hard to believe I would need four foot of rope to wrap around a 4" pipe.

 

the gasses will continue to scavenge even after the collectors. I would leave the tubing the same size to avoid halting this effect. Instead of going bigger, which doesnt always mean bigger as slvr showed, go shorter, which ALWAYS means less resistance and better overall flow. A buddy of mine just ran 3" piping off of each collector to a bullet muffler and dumped it after the trans and called it a day. lost several feet of piping in the process. just make sure they are tied down or u will be rubbing them on pavement with every bump

 

I agree with spec, as little piping as necessary...

 

Wow...thanks for pointing that out, I just realized that when I did those calculations I was using a 4 inch radius pipe...oops...nonetheless... [>:]

 

I was beginning to wonder if I had lost some math skills. And yes I agree with what you were trying to say.

 

i noticed that.... he also used the same number twice, probably copy/paste errors from the calc. hell, we all do it. but his message was clear. although, this brings up an interesting point, by increasing diameter only 1 inch, you get a similar cross section as 2 pipes, only slightly less. while it wont benefit in this case, you may want to think about this next time you think aobut doing a 2.5" true dual over a larger ypipe setup. alot of this stuff doesnt actually add up the way it would appear on the surface.

 

Alright, since it's kinda annoying me that I have oodles of wrong stuff (these are the stupid mistakes that come back to bite you in the *** on exams...grrr)

Cross Sectional Area of dual 3 inch: 14.13716694
Cross Sectional Area of single 4 inch: 12.56637061

Circumference of dual 3 inch: 9.424777961
Circumference of single 4 inch: 6.283185307

With 6 feet of tubing:

Surface area of dual 3 inch: 678.5840132
Surface area of single 4 inch: 452.3893421

Volume of a dual 3 inch: 1017.87602
Volume of a single 4 inch: 904.7786842

Volume to surface area ratio:
Dual 3 inch: 1.5
Single 4 inch: 2


Wow, all those calculations to remember that the pi is just going to cancel itself out in the ratio and come back as a radius...funny how much common sense you can loose when you're so used to doing calculus all the time. Nonetheless, the point is still there. I've forgot most of my gas laws and thermal expansion stuff *cough*SPEC*cough* but we could go as far as calculating the changing volume of the gas as it cools off.
*cough*do it spec, I'd like to see the results*cough*

 

please..... just use perv-nert

we would have to know engine conditions (manifold temp, moles gas fumes, manifold pressure, anda base unit for tube volume).

but V variesdirectly as T. you cut your temp in half, you have cut your volume in half.unless you are going to provide me with the thermal conduction of steel headers andheat loss rate to gas flow rates all we can say is that the cooling gasses require less and less pace as they approach ambient temps. that being said: if you use too large of a midpipe the gasses suddenly find themselves in a "void" so to speak. they may only need 2" of pipe to maintain the velocity they had at the block, and now that they are in a 4" chamber, they are met with "idle gasses", so they basically have to push the idle gasses out of the way to continue flowing. you are basically creating a blockage in your pipes, only the blockage is made out of air.




but slvr, i was just gunna agree with u there.. i can integrate and solve a multivariable system, and estimate a multi-electron wavefunction on paper...... but i cant add to save my life [8D]
and yes, many a time I have been plagued by the forgotten minus sign, or a mistyped order of magnitude....... or hell, just forgetting to correct magnitude in constants before using [&:]