# Thread: Intercooler Pipe Diameter Theory

1. ## Intercooler Pipe Diameter Theory

I saw alot of discussion relative to pipe diameter etc regarding the Seadoos but not so much the SHO platform other than a few posts. I wanted to put this out there and possibly get some "real world" results regarding different size piping from members who possibly tried different diameter piping on the same intercooler, or just your thoughts on this etc. I got bored this morning so I decided to do a little homework and calculate CFM the 1800cc motor (basically 109 ci) This is what I came up with, strictly from what I gathered online. Don't hold me to this , just what I came up with after doing a few minutes of research. I wanted to basically focus on 2-3" piping since that sems to be the most common sizes used. I went on the higher side of boost and rpm and based my setup on 17lbs of boost and 9000rpm to give me some cushion with potential inefficiently with intercooler piping bends etc. With a 109ci motor, spinning 9000rpm and making 17lbs of boost the motor flows 520 CFM.

Here is the flow ration calculator I used....

http://www.cottrell.100megs6.com/CJB/velocity/cfm.html

" *.4 Mach is the point at which air becomes turbulent and losses in efficiency start to occur exponentially. The key is to stay under that speed. You want to use the smallest piping possible that still flows enough to meet your needs. Larger than necessary piping increases lag time with no measurable gain."

The velocities are in miles per hour and mach, and the flow rates are in cfm. Measurements for the piping are in inches.

2" piping
1.57 x 2 = 3.14 sq in
300 cfm = 156 mph = 0.20 mach
400 cfm = 208 mph = 0.27 mach
500 cfm = 261 mph = 0.34 mach
585 cfm max = 304 mph = 0.40 mach

2.25" piping
3.9740625 sq in = 1.98703125 x 2
300 cfm = 123 mph = 0.16 mach
400 cfm = 164 mph = 0.21 mach
500 cfm = 205 mph = 0.26 mach
600 cfm = 247 mph = 0.32 mach
700 cfm = 288 mph = 0.37 mach
740 cfm max = 304 mph = 0.40 mach

2.5" piping
4.90625 sq in = 2.453125 x 2
300 cfm = 100 mph = 0.13 mach
400 cfm = 133 mph = 0.17 mach
500 cfm = 166 mph = 0.21 mach
600 cfm = 200 mph = 0.26 mach
700 cfm = 233 mph = 0.30 mach
800 cfm = 266 mph = 0.34 mach
900 cfm = 300 mph = 0.39 mach
913 cfm max = 304 mph = 0.40 mach

2.75" piping
5.9365625 sq in = 2.96828125 x 2
300 cfm = 82 mph = 0.10 mach
400 cfm = 110 mph = 0.14 mach
500 cfm = 137 mph = 0.17 mach
600 cfm = 165 mph = 0.21 mach
700 cfm = 192 mph = 0.25 mach
800 cfm = 220 mph = 0.28 mach
900 cfm = 248 mph = 0.32 mach
1000 cfm = 275 mph = 0.36 mach
1100 cfm max = 303 mph = 0.40 mach

3.0" piping
7.065 sq in = 3.5325 x 2
300 cfm = 69 mph = 0.09 mach
400 cfm = 92 mph = 0.12 mach
500 cfm = 115 mph = 0.15 mach
600 cfm = 138 mph = 0.18 mach
700 cfm = 162 mph = 0.21 mach
800 cfm = 185 mph = 0.24 mach
900 cfm = 208 mph = 0.27 mach
1000 cfm = 231 mph = 0.30 mach
1100 cfm = 254 cfm = 0.33 mach
1200 cfm = 277 mph = 0.36 mach
1300 cfm max= 301 mph = 0.39 mach

*some material is quoted from other sites regarding velocities etc*
Here is the link that explains it in ALOT more detail. http://www.dsmtuners.com/forums/turb...ping-flow.html

Your thoughts, experiences, tests, results are all welcome. I just thought this may potentially help those in intercooler piping for their particular setups.

2. This is some valuable information for those who are doing custom intercoolers such as the frozen boost. What inch tubing is used in the RIVA Power cooler ?