Poiseulle's Equation
It is used to describe fluid flow through a rigid, cylindrical vessel (i.e. your charge piping)

Q = [(delta P)(pi)(r^4)] / [( 8 )(L)(n)]

Q = flow rate (cm^3*s^-1)
delta P = pressure difference (dyn*cm^-2)
r = radius of vessel (cm)
L = length of vessel (cm)
n = viscosity (dyn*s*cm^-2)

The units can obviously be converted to the more desirable ones for calculating your flow rate for applying it to a turbocharged vehicle. This only applies to an instantaneous pressure difference. What I wanted to point out was that the r (radius) is raised to the 4th power, having a MUCH larger influence on your flow rate than anything else.
I haven't had time to play with numbers yet, but what it suggests to me is that the sizing of your charge piping plays a bigger role in the power delivery than is given credit. With the flow rate being affected so greatly by a small change in the pipe radius.

I need to play with numbers still, but I would like to experiment with slightly smaller piping diameters to keep the fluid velocity higher without limiting the output flow of the turbo. What I'm saying is that everyone just using 2.25in or 2.5 in piping because its common is probably too large for their applications and would have a much better powerband by decreasing the charge piping size. I don't know though, I haven't tried it yet. I'm sure someone else has already done this math a million times, so I could be retarded, but I hate just doing things without knowing why. My fantastical brain is very scattered right now, and maybe this is all very obvious to everyone else. Thoughts?

 

i think my brain is now scrambled beyond comprehension....... :P

maybe being as sick as i am is affectioning me more than i thought.....

 

abcdefg^2=9 so yeah you're right.

 

going just from 2" to 2.25" pipe is something like, the ability to flow 40% more air, then when going to 2.5", another 70%? i remember either reading or doing this years ago

 

Flow starts to suckass past .3-.4 mach. I'll never run 2 or 2.25" charge pipe on any Honduh, except maybe a foot or so on a small turbo dumping directly into an IC.

My car is targeting 500-550, 2.5" out of the compressor (the scroll is a true 2.5" outlet, unlike a tiny T04E) to the IC, and then 3" from the IC outlet to the TB. If you're super concenred with VE - I'm not - expanding to 3" before the IC is what HT members would do.

 

jd has spoken.

 

Evan, you still have my mapbook, just checking

 

I spoke layman, based on personal experience a lot of people had before I acquired mine. Crunch Evan's numbers and they'll agree - they model reality.

 

so lets speak layman again. is bigger charge piping better and if so how? bottom line i guess.

 

larger pipe = higher pressure, smaller pipe = more velocity. its the basis behind carburetors and venturis