Pipe sizes

[Chris.]

Hi fellow pipe-ists!!

I need a bit of help with pipe sizes.

Im looking at the row highlighted below.



I know the outside diameter of the 1.25" pipe is 42.4mm, and the wall thickness is 2.6mm.  Doing the maths that leaves 37.2mm in the middle (internal)  but the chart shows its 32mm?

Anyone clear things up who understands pipe.

Chris

[danny_p]

closest standard pipe size  in metric and imperial by the look of it.

the tabel is about ish as well 

some of those inperial / metric sizes are quite diffrent.    inch is 25.4mm

[Chris.]

So that could mean that the 32mm one is too small for my manifold and 40mm is far too big.  36.6mm is the size of the head ports from what ive heard.

Bloody hell!

[golf-sib]

What you trying to do? From top of head TB is 2" on mk4 1.8t, then there's 3mm nipples and a 19 or 16 mm outlet on the side of manifold?

[Chris.]

Exhaust manifold mate

[golf-sib]

Surely then you want 1.5", which is about 38.25mm external, let's say? Plus you lost me with measurements, 1.25" is 32mm approx. I have a spare stock mani indoors that I could measure when I get home.

[Chris.]

People say that 1.5" is too big and will take longer spool.  Which is why I thought 1.25".  The head is about 36.6mm from what I've read so would need pipe close to that as possible.

[golf-sib]

As google says:

37 millimetres = 1.45669291 inches

I'd imagine 1.5" should be fine as you said its 36.6mm

1.25 inch = 31.75 millimetres

[Chris.]

So which one would I go for from the list above?  Since none of their measurements seem to line up with the exact conversions :S

Half tempted to order one of each and see what size turns up at my door.

[golf-sib]

Find out the exact port size in a correct measurement. Then you can work from there giving two dimensions one in inches and one in mm that are completely different isn't making it clear.