does 2.5" and 3" downpipe makes any different?

[Sheen]

does 2.5" or 3" downpipe makes different in power bend?
i want to have maximum torque on mid range~
thanks~

[clicht]

if you want low down torque, then go for 2.5". if you plan on getting a larger turbo, then go 3". just my 2 cents worth

[h100vw]

You plan to get a tune as well? Won't do much on it's own without one.

[Sheen]

yea going for a tune straight after

[Sheen]

does mild steel and stainless steel make much of a different?

[noone]

For power, I don't believe so. It's about how long it lasts

[s4mmie]

From my experience, mild steel systems tend to sound deeper than stainless because of the typically thicker wall piping.

[h100vw]

yea going for a tune straight after

What does your tuner recommend?

I reckon you can get away with the smaller one if you have no plans to fit a bigger turbo or wring every last KW from the K03s. Are you buying off the shelf or having one made?

Gavin

Are

[Spec83]

Think testing was done on the K03, 2.5" all the way through was the way to go... 3" gave you no performance gain, other than that impagined in your pants!!

[Guy_H]

When we did all the testing on the 1.8T's (Way back in 2004), it was on the Golf 4 GTI, we ran 2.5", 2.75" & 3" - as above, on a K03, the 3" did nothing up top (turbo out of puff), but lost bottom end torque. 2.5 was nice all the way through, and 2.75" didnt show much benefit over the 3".

We then tested on K04 1.8T's (specifically the S3) with 2.75" & 3" - 3" showed no more top end, even with the K04 - but lost less down low with the bigger turbo.

If it was me building it for a K03 street car, I would run 2.5" - if I was going to go K04 in the future I would run 2.75", I wouldn't personally run 3" as you lose too much.

Problem is most exhaust shops don't carry 2.75" and some don't have 2.5" so they try to sell you 3" piping.

[blitDz]

Speaking of which i think i nabbed the last downpipe and high flow cat from Harding Performance. Looking forward to getting it installed next week by Quattro over here in Perth.

[kaanage]

When we did all the testing on the 1.8T's (Way back in 2004), it was on the Golf 4 GTI, we ran 2.5", 2.75" & 3" - as above, on a K03, the 3" did nothing up top (turbo out of puff), but lost bottom end torque. 2.5 was nice all the way through, and 2.75" didnt show much benefit over the 3".

We then tested on K04 1.8T's (specifically the S3) with 2.75" & 3" - 3" showed no more top end, even with the K04 - but lost less down low with the bigger turbo.

If it was me building it for a K03 street car, I would run 2.5" - if I was going to go K04 in the future I would run 2.75", I wouldn't personally run 3" as you lose too much.

Problem is most exhaust shops don't carry 2.75" and some don't have 2.5" so they try to sell you 3" piping.

This needs to be stickied somewhere - that's great info (as always) Guy.

[bakersdelight]

whats the Polo GTI's stock exhaust diameter anyway? 2.25"?

[Sheen]

yea, 2.25" thanks alot more the information guys!

[Aussiegman]

Too big will definitely loose you low end torque. Under 225kw / 300hp a 2.5" is your best bet but is does depend on the turbo etc.

Also a 3" will be louder.