Intercooler Piping Diameter.

[Last5Spd]

I got a sc300 pending the 1jzgte swap and was wondering. Would there be a significat different if i used 2.5 inch Piping than 3 Inch piping? I was planning on getting a 3inch outlet Front Mount also. and just using a reducer. My buddy owns a race car fabrication shop and he say he can easily do up to 2.5 inch but 3 he would have to send out.. Iam looking for some opinions.

[dejacky]

I would not do a 3in diameter. 2.5in is a great size for IC piping. If you make the IC piping too wide, you will slow down the velocity of the gasses inside = worse performance. I'm not saying 3in is bad, but 2.5 is a proven standard time and time again. Keep in mind, the sizing WILL depend on your setup and horsepower goals..but again 2.5in is a safe and proven middle ground for the majority of 2JZ turbo setups and common power ranges.

The following is an excerpt from a thread on ClubLexus measuring the outcome of 2.25 IC piping:

Excerpt from Corky Bell's "Maximum Boost" book:
There is probably a magic number that airflow velocity in a tube should not exceed, for reasons of rapidly increasing drag and consequent flow losses. I suspect this number is around Mach 0.4, or about 450 feet per second, since drag, and therefore flow loss, increases significantly after this. Tube size can easily be checked by calculating the maximum airflow attainable, diving by the area of the tube in square feet, and dividing again by 60 to convert to feet per second. An approximate value for maximum airflow can be obtained by multiplying the desired bhp by 1.5.

Example let's assume a goal of 400rwhp, so estiamte 440BHP because of drivetrain loss:
440 BHP x 1.5 = 660 CFM = 660 ft^3/min
Velocity = airflow / area = {[(660 ft^3/min)] / [pi(2.25/2)^2in^2]} x {[(1/60)(min/sec)] / [(1/144)(ft^2/in^2)]} = ~362.166 ft/sec

This value is still less than the 450 ft/sec threshold...so 2.25 inch piping instead of 2.5 inch piping is very feasible. Aside --> if your IC piping is too large of a diameter, it will HURT performance because the air will travel too slow.

CL thread:
http://www.clublexus.com/forums/showthread.php?t=171570&page=4&pp=15

[Last5Spd]

wow cool..

thanks