Diameter of 4-1 downpipes

[Mike]

Anyone know the diameter of an average 4-1? The diameter of the 4 pipes from the exhaust ports?

I'd hazard a guess at either 1.75" or 2"

[lynhok]

are we talking internal or external sorry?

[Welsh Dan]

If an uprated exhaust system has a bore of 2", then I'd expect each pipe to be 1" inner diameter when you take the area of the cross section into account.

[garyc]

the od of my BTB 4-1 is 38, my tony law 4-2-1 is 36mm od