How rounding ports affects tuning?

[DylanBunch]

When it comes to bandpass builds you see a lot of of people cutting PVC in half and rounding the edges of their ports. If you do that, how do you calculate the length of the port? Cause since it's rounded, I feel like if it starts at say 4"deep, the rounding shortens that. Is there a way to calculate it?

[jmfrb1]

I was told to measure from the middle of the flare.

[DylanBunch]

I mean how does it affect the length of the port not the width or height

[Joe X]

Posted a few times before but like this:

Compared with a plain PVC of the same length the flared one will tune higher.

[mrd6]

^This, unless you are talking about the ports where is is just one half of PVC making up the entire port so there is no straight length and it is all rounded. Split 4" PVC used as a roundover where your port length is just the 4" PVC will tune very similar to a 1" deep non flared port. Larger roundovers will tune lower, smaller higher.

This will change a lot tho once it is on the car. Just need to test!

[DylanBunch]

those were the answers i was looking for, thanks guys!

[fecupe2001]

those round overs will still change tuning a lot since you would shrink the port area considerably, that´s why you need to test test and test until you find the best port area working on your application, and then, use the round overs in a way that you end up with the same port area that worked better for your application