In the process of buying an air intake system, I found that they are of different diameters. eg, Injen is 2.75", most Ebay intakes are 3", etc.

So, what is the best size. I believe the ID of MAF house is 2.5", while the throttle body ID is 2.75", some think the best size is not 3" but 2.5", which minimizes air speed change. If the pipe is bigger than the throttle body opening, at the step down will create air turbulence and affect flow. I have read here (I can't find now) that the 3" pipe give little dyno gains while the 2.5" was a whole different story. Is this true that bigger is not better? I would appreciate your inputs.

Jerry

Anything bigger than the throttle body doesnt do much.

That being said, it depends on whats going on with the filter as well...

Are you suggesting the 3" is too big for us?

I don't believe the intake needs to be much bigger than the exhaust (2.25" ?). A smooth flow is probably more important.

As am example, Williaty did a "hybrid" intake, replacing the torque box and the oem bellowed piping and he recorded more air flow. I noticed that, although big opening, these oem parts removed all have complicate shape that may disturb airflow?

Problem is no one is making a 2.5" intake to test.
Jerry