Shawn's sread sheet

cboggs · Post by **cboggs** » Wed May 18, 2005 12:13 am

hello,

here's a little sheet i put together to figure cross-sec. and a few other
things. I put Darin's sheet on the second page so you can open them at the
same time. I haven't checked with Darin to see if it's ok to put his spreed
sheet out there yet, but since he has it posted on his site, it might be ok.
Feel free to add to it, as long as you send me a copy!!LOL
thanks,
shawn

http://www.cboggs.com/photos/HeadSpeedcheatsheet.xls

67RS502 · Post by **67RS502** » Wed May 18, 2005 12:48 pm

What air speed are we shootin for?
The formula FPS based on RPM and CA shows - 614.
The formula FPS based on CFM and CA shows - 288.
Could someone elaborate on this for me a bit, whats the optimum air speed?
Thanks to all the gurus on here helpin out the little guys.

shawn · Post by **shawn** » Wed May 18, 2005 3:57 pm

Thanks Curtis!
The " formula FPS based on CFM and CA shows - 288" is just a way to figure out how fast the air is moving through an area.If you stuck your pitot tube in there, in theory, it should show about the same as the formula predicts.Curtis, Darin, and Larry could give you alot more detailed info, and correct me if i'm wrong, but your "measured" velocity shouldn't exceed 350 fps.This is data you would get from plugging the numbers into that calculator, or measuring with your pitot tube. There is also a calculator on there to convert your pitot tube readings at 28" depression to velocity. The other ones help you to find the actual running "choke" point in a motor. These in general shouldn't exceed the 614 fps in a running condition.
shawn

cboggs · Post by **cboggs** » Wed May 18, 2005 4:10 pm

Great little spread sheet, .. but checking the math is
gonna need to be Larry's department, .. I stink at , .. um excuse me, ..
I am not good at math.

Curtis

shawn · Post by **shawn** » Wed May 18, 2005 4:35 pm

I thought you might like it. I seem to remember a post a while back where you or someone else was asking for something like this. Like i said in your email, if someone has something to add to it, great, please do and share it with the other members here. I'm going to have to dig it up, but somewhere i have the math for intake runner wave tuning that would go well on there, too.

68corvette · Post by **68corvette** » Thu May 19, 2005 12:23 am

here is one i picked from net:
(((720-(duration-open))*0,25*flow*2)/(rpm*1))-(area/2)

duration= cam advertised duration:
open= how many degrees valve has been opened before pulse (recommendation ~30):
flow= sound speed in runner (normally 1250-1300fps).
area= port avarage cross section area.

if you change (rpm*2) or (rpm*3) you get second ant third pulse.

SStrokerAce · Post by **SStrokerAce** » Thu May 19, 2005 2:45 am

Curtis,

Sent you a version I did a while ago on discharge coef and Larry's Flow Factor relative to the CFM.

Bret