Hey Gents,

New here...

Question about intercooler piping... How do you spec the diametre of your piping for the car? Also, should you use a difference diametre piping on the inlet and outlet side of the intercooler, or does this not matter?

thanks in advance

P.S. Cars I work on are generally diesel utes/trucks.

Ant

 

Coming out of the turbo hot, use a smaller diameter size. The smallest size that doesn't cause the flow rate to approach the speed of sound. For majority of setups 2.5" is sufficient going into the intercooler. The small size helps maintain velocity and reduce turbo lag. It may become turbulent but this head loss is unavoidable due to the design of intercooling cores which force the air to 'brick wall' and suddenly change direction anyways.

After the intercooler a larger size is desirable with pressure drop and it also helps match the size of typical throttle bodies which will assist with laminar flow re-organization of air molecules on the way to the intake manifold. In other words sudden sharp changes in pipe diameter create turbulence which will hurt flow rate far more than the larger size you should be using in the first place to create a seamless transition. The larger volume will hurt pump head but not nearly as much as the intercooler, thus both the intercooler and cold pipe both reduce power potential of the instantaneous flow rate yet this is never an issue because you accounted for that when you sized the tubocharger right? In other words if the pump head is 800CFM some of that is lost to ever inch or every mm or even nm of plumbing volume (it the effect of 3Dimensional flow rate dropping due to friction) thus the pipe walls, contours, corners, shape etc... everything causes a drop in flow rate over time and distance from the compressor head. So technically we want a very short and small volume plumbing, yet the compressor should be capable of flowing more than enough air to compensate for all of these minor head losses which become negligible in the grand scope after running the flow rate math compared with the engine performance goals.

 

I run 2.5 to inter cooler and 3 inch from inter cooler to carb hat.