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General => The garage => Topic started by: Chris. on 20 June 2012, 22:57

Title: Pipe sizes
Post by: Chris. on 20 June 2012, 22:57

Hi fellow pipe-ists!!

I need a bit of help with pipe sizes.

Im looking at the row highlighted below.

(http://i93.photobucket.com/albums/l42/carsey2006/pipe.jpg)

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

Title: Re: Pipe sizes
Post by: danny_p on 20 June 2012, 23:12

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

Title: Re: Pipe sizes
Post by: Chris. on 20 June 2012, 23:15

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!

Title: Re: Pipe sizes
Post by: golf-sib on 21 June 2012, 09:05

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?

Title: Re: Pipe sizes
Post by: Chris. on 21 June 2012, 10:10

Exhaust manifold mate

Title: Re: Pipe sizes
Post by: golf-sib on 21 June 2012, 10:26

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.

Title: Re: Pipe sizes
Post by: Chris. on 21 June 2012, 13:42

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.

Title: Re: Pipe sizes
Post by: golf-sib on 21 June 2012, 22:24

As google says:

Quote

37 millimetres = 1.45669291 inches

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

Quote

1.25 inch = 31.75 millimetres

Title: Re: Pipe sizes
Post by: Chris. on 22 June 2012, 09:49

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.

Title: Re: Pipe sizes
Post by: golf-sib on 22 June 2012, 11:14

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.

Title: Re: Pipe sizes
Post by: Chris. on 22 June 2012, 22:30

True.  I understand the head is 36.6mm and the exhaust manifold on a stock manifold are 38mm

Title: Re: Pipe sizes
Post by: danny_p on 22 June 2012, 23:41

you actualy want a lip between the head and manifold on exhausts,  runners want to be slightly bigger than the port,  ll to do with pressure aves and refections blagh blagh blangh


also whne it comes to 20vt exaust manifolds  it's practicaly inpossible to make anything thats worse than the oem one

Title: Re: Pipe sizes
Post by: Chris. on 23 June 2012, 13:20

True.  I just dont want a T04e spooling at something like 6k and being crap.  WAnt it spooling as early as possible.