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View Full Version : larger down pipe on 1.8t ?



gpk_gti
16-11-2006, 01:43 PM
Hi everyone,
Has anyone changed the standard downpipe to a larger more free flowing downpipe? I have noticed on other sites that there seems to be alot of debate about 2.5" or 3".:?
The car has middle muffler removed with a MTM rear box.
I have changed the turbo to the k03s and am waiting on my other bits.
I have been quoted $270 for 2.5" ceramic coated from tuffy in alexandria.
Any advice would be greatly appreciated :)

fuzion
16-11-2006, 01:49 PM
Seb from Euromotive has 3" ones available. Apparently thats the way to go. i think hes bug racer on here.. get in contact with him would be my suggestion!

Bug_racer
16-11-2006, 04:02 PM
I have 1 3 inch exchange here

gpk_gti
16-11-2006, 08:59 PM
thanks bug racer,but what I really wanted to know is is 2.5" or 3" better??:confused: I read on vortex that 3" can cause over spooling http://forums.vwvortex.com/zerothread?id=450388&postid=11249554#11249554
from what I can gather the k03 is more suited to 2.5" and k03s to 3" downpipe? whats your thoughts?

h100vw
16-11-2006, 09:42 PM
I have a 3inch on my A3 with a sport cat and 3 inch system. The turbo will spool quicker as there is less restriction of the exhaust gases leaving the turbo.

The wastegate and electronics control the boost level the engine sees.

You could hear straight away that the turbo spins up quicker/earlier. It whistles nicely now. I have a big turbo planned which is why I went 3 inch over 2.5.


EDIT.
That vortex thread mentions certain chips and downpipes. So not the DP on it's own. Only incorrect code would cause the turbo harm.

Say chip X requests Y boost, knowing full well that the turbo could never spin that fast because of the restrictive DP. You now fit the 3 inch DP allowing the turbo to have a go at reaching Y boost. It may overspeed which is one thing that could damage it. I doubt that any 'off the shelf' code would cause this to happen.

BLKMJC
17-11-2006, 12:12 AM
You'll get less more torque down low with the 2.5" and more HP up top with the 3". I went with 2.5" as I wanted to car to be more zappy around town where I do most of my driving, also GIAC recommends 2.5".

BLKMJC

Bug_racer
17-11-2006, 02:13 PM
2.5 for torque , 3 inch for power . On a KO3 car Id stick with 2.5 but KO3's or KO4 use 3 inch . 2 3/4 is available but more expensive than a 3 inch

VWEAPN
17-07-2007, 07:35 PM
does anyone know how much power gain there is with either a 2.5 or 3" dump pipe?
is it worthwhile?

h100vw
17-07-2007, 08:08 PM
does anyone know how much power gain there is with either a 2.5 or 3" dump pipe?
is it worthwhile?

Very little, if any without changing the chip. The power delivery may change due to the turbo spooling earlier.

Gavin

SoVeReIgN
17-07-2007, 08:25 PM
I have a 3" (courtesy of seb) and I can definently notice the difference.

It isn't amazing but its there, and the turbo spool sound is a little rougher/meaner too :D

VWEAPN
17-07-2007, 10:33 PM
ah ok ye mine is GIAC'd, N75J,air box mod,
now i know theres a bit of a discussion here on whether to go with the 2.5" or 3".
what is recommended?

VWEAPN
17-07-2007, 10:34 PM
ok i have read over the posts again sounds like the 3" is the way to go?

gpk_gti
17-07-2007, 10:40 PM
do a 2 3/4 ,,,best of both sizes!!! thats what I have...:)

h100vw
17-07-2007, 10:47 PM
I agree, 3 is overkill. That's 3/4 over std and an epic increase in cross-sectional area.

Gets calculator out

Gavin

std 2.25inch is 7.95 square inches in diameter.
2.75 would be 11.88 50% increase over std
3 would be 14 76% increase

You just couldn't make use of the extra flow IMO.

Gavin

VWEAPN
18-07-2007, 08:23 AM
well i know the 2 3/4 is pricey due to its size, so im scrapping that one.
i will see what happens on the day, turning to 2.5"

gpk_gti
18-07-2007, 08:29 AM
why is it pricey?? mine was roughly $700 all the way to rear box + ceramic coated dump...thats not alot,is it??:?
whos doing yours?

VWEAPN
18-07-2007, 08:38 AM
well i guess everyones budgets are different, this is the last mod on my car.
3" dump, installed $350-400
euromotive

im not prepared to pay $700

gpk_gti
18-07-2007, 08:40 AM
$700 was for the whole exhaust.so dump would be less than half of that.

VWEAPN
18-07-2007, 08:46 AM
ahhh k, well ill ask around and see how i go, with both sizes

thanks george

gpk_gti
18-07-2007, 08:51 AM
yeah no probs! I didnt shop around too much,so im sure if you do,you will find a good deal.Tell us how you go!:D

fuzion
18-07-2007, 12:02 PM
ive got a 3" on mine (oettinger chipped), mel has a 3" on hers (giac'd) .. made a substancial difference most definately.

i paid $300 and thats stainless steel too.

Cache
18-07-2007, 12:04 PM
Just for some perspective, I payed around $600 for a 2.5' dump, super high flow cat and 2.75' from cat back. You should be able to get the 2.75' dump for $200-$250 considering there isnt that many mandrel bends.

Cheers