Downpipes??

[ibizacupra1.8t]

Hi all, looking for a new downpipe for my ibiza. Looking at a&m or milltek I think, any suggestions on either or peoples preference. a&m is 3'' and milltek 2.5'' does it make much difference, and i believe both are 100cel cats. Thinking about k03s soon too, so would one suit the k03s better that another. Any comments would be great.

 

[ibizacupra]

consider blueflame also..

 

[Olly20VT]

IMO the bigger the bore the better, i am happy with the am 3" one but i realy dont think it makes any differance between all the 2.5" ones apart from cost.

 

[GaryM]

Awesome told me to stick with a 2.5" DP with the K03sport, only change to a 3" DP if running a big turbo.
They said changing to a 3" will actually hinder and not help.

 

[cu51pra]

well ive got a 3" dp on my ibiza with a k03 and it helped alot im going to put a ko3s on it in the next week or two so il find out soon but i cant see how it will hinder the turbo?

 

[GaryM]

well ive got a 3" dp on my ibiza with a k03 and it helped alot im going to put a ko3s on it in the next week or two so il find out soon but i cant see how it will hinder the turbo?

Not sure but when I called Awesome to get a price for a 3" DP with decat or 100cell cat I was talked out of it and told to stick with my 2.5" Milltek DP and 200cell cat.

 

[cu51pra]

well thats weired coz am-motorsport sell the 3"dp to use with the k03s they also sell and i have a blue flame turbo back zorst for my ibiza with is going to be the am one then they sell it for the ibiza

 

[Olly20VT]

thats daft, the easyer the air gets out the turbo the better. So 3" DP and 100 cell cat is better flowing than 200cell and 2.5" DP so the turbo is using less power pushing zorst out so will allow the compresor side to work better (spool up quicker and boost longer)
I may be wrong but i cant see how.

 

[m0rk]

thats daft, the easyer the air gets out the turbo the better.

Hark the Engine designer.

what about this for a theory.

3" DP = big space to fill, then you pipe it into a smaller pipe. not smooth at all.

OR

what about back pressure.

 

[GaryM]

Awesome were basing their opinion of figures produced on their dyno which is why I took their advice.
Big is not always best.

 

[Olly20VT]

as i said i may be wrong, so why have people sold them then i.e to me? because if what you say is true then surly the only way to have a 3" DP is if your going to have a 3" de-cat and 3" straight through bore zorst.
Not having a go but i would like to understand it and as i have a 3" DP

 

[m0rk]

People will sell stuff because it's what they think people will buy.

There's only one firm that looks in finite detail at the downpipe you can have on your car, and you took it off. flow rates, pressures all that stuff is something nobody looks at for aftermarket, they just make bigger.

If you could fit a 5" DP on your car, and 5" all the way through - would you?

 

[Olly20VT]

i see what your saying but when modding your car to make it go faster then surly a bigger DP and lesser cell cat and zorst is better air flow.
5" setup would be loud but surly the turbo would work well? i am not an engine designer but is it not just a case of flow?
As i said before im trying to understand this not argue (spelling) it.

 

[GaryM]

i see what your saying but when modding your car to make it go faster then surly a bigger DP and lesser cell cat and zorst is better air flow.
5" setup would be loud but surly the turbo would work well? i am not an engine designer but is it not just a case of flow?
As i said before im trying to understand this not argue (spelling) it.

Awesome reckon not unless you have a huge turbo, not a hairdryer.
They told me you actually need a little back pressure when running the smaller K03 series turbos.

 

[Olly20VT]

realy if the engine is runing then gases are pushing the turbine round wich compresses the gases on the other end, now surly if the zorst gases have to use some of there power to also push them selfs out the zorst then they cant be putting as much through to the compresor side of the turbo? can you see what i mean? could some one exsplain why this is wrong?

 

[cordobabrendy]

I was under the impression that backpressure is good for 8vs, not great for 16vs and a hinderance to turbos.

 

[Olly20VT]

I was under the impression that backpressure is good for 8vs, not great for 16vs and a hinderance to turbos.

Thant was my thought.

 

[Forbez]

No iirc you need back pressure on all engines, to help with the smooth process of the gases being released.
(not in the right mind to go into tech stuff at the mo)

Mork - who are you refereing to, by saying that only one company looks in finite detail into the downpipe?

 

[m0rk]

VW group when the designed the DP.

I'll retract it if any of the DP makers can show me even a page of sums.

 

[ALEX**]

as said if u go too big you loose too much back pressure and hinder performance