The correct intercooler diameter

[3diamond]

If a intercooler outlet pipe is smaller than the throttlebody diameter, what would be the best combination. I'll give a example.

Lets say a intercooler outlet pipe is 1 inches in diameter and the throttlebody is 2.5 inches in diameter, what would be the best size to have this connected.

A. Have the pipe fully 1 inches and have it only to merge into 2.5 inches as close to the throttlebody.

B. Have the intercooler outlet pipe flared straight away to 2.5 inches.

So its either a 1 inch intercooler pipe or 2.5 inches, whats the correct setup that will provide outmost efficiency in regards to flow.

I'm, just thinking that if the intercooler pipe was 1 inche, the throttlebody and engine will have a big restriction sucking all from a little 1 inch diameter pipe.

I have seen at some drag battle meets rotaries with like small turbo outlet pipes that suites the actual diameter of the turbo outlet, but have like massive 3-4 inches of intercooler outlet pipe to throttlebody.

 

[tharaka]

if the diameter of the pipe is smaller, the air is moving through it at a higher velocity
so if the outlet on the intercooler is only 1", shouldn't it be better to have it increase to 2.5" right at the end?

 

[matress]

with a small pipe you may keep the velocity, but you won't be able to flow the volume