Intercooler Pipework (AUM K03S) - 2.25" or 2.5"

[Yohan]

Wasn't sure whether to post this in the Mk2 or Mk4 section.

My friend is putting a 1.8T AUM lump in to a Mk2 Golf and therefore just about every part of this install is custom.

It is time to buy an intercooler and we are trying to decide on the best size for the pipework.

2.25" should be fine as I think that's the factory size, however I was wondering about 2.5" to future proof it a bit.

I know the LCR/S3's use 2.5" (63mm) pipework in standard form (210/225bhp) so 2.5" should be suitable on a Stage 2 K03s surely? I realise it will be laggy in standard form.

So what do you think?

2.25" or 2.5"

[Toby]

Depen how far he plans to go in the end with my ko4 it had to be 2.5"

If he never plans going ko4 n just staying ko3s then 2.25" should be fine!!

[madmanmart]

Ive just finished the intercooler pipework on my mk3 20vt.

I'm using 2.25" all the way but I am keeping the ko3s. The original pipework is 2" in places so its still a upgrade.

[golf-sib]

2.25" standard pipework on a k03 system  whatya been smoking? Its all 2", turbo is 2", it does increase in some parts like one side of the pancake, but then it downsizes again, look at pre the TB, thats 2"... Whats the end power, if over 350bhp then 2.5", if its just a stock setup/remap I'd stick to 2", easier to plumb and fit if you are designing the system yourself and building it.

[Yohan]

Depen how far he plans to go in the end with my ko4 it had to be 2.5"

If he never plans going ko4 n just staying ko3s then 2.25" should be fine!!

Thanks, my thoughts as well but only he will know whether he will end up chasing more power.

Ive just finished the intercooler pipework on my mk3 20vt.

I'm using 2.25" all the way but I am keeping the ko3s. The original pipework is 2" in places so its still a upgrade.

Thanks, I had it in my head it was 2.25" for some reason.

2.25" standard pipework on a k03 system  whatya been smoking? Its all 2", turbo is 2", it does increase in some parts like one side of the pancake, but then it downsizes again, look at pre the TB, thats 2"... Whats the end power, if over 350bhp then 2.5", if its just a stock setup/remap I'd stick to 2", easier to plumb and fit if you are designing the system yourself and building it.

As above for some reason I thought it was 2.25" for some reason. I'll blame my shocking ability to convert inches to mm.

The end power will be a Stage 2 K03s, so realistically around the 230bhp mark.

Your are right about the smaller pipework being easier to route, the engine bay is tight as it is in all the wrong areas.


Thanks for the replies chaps.

[Marc87]

Im going to change the intercooler on my mk4 soon and im going to go 2.25 inch with a medium ish sized intercooler. Dont want it to be too laggy but also dont it to be restrictive at the same time. Im running an aum with a k04-001. May be of no help to you at all lol

[golf-sib]

Im going to change the intercooler on my mk4 soon and im going to go 2.25 inch with a medium ish sized intercooler. Dont want it to be too laggy but also dont it to be restrictive at the same time. Im running an aum with a k04-001. May be of no help to you at all lol

Toyosport audi 1.8T a4 intercooler and 2" pipework is what I went for, nice and easy to get in, as the IC has a 51mm thickness and identical outlets.

[Marc87]

Any pics of ur install anywhere??

[madmanmart]

Mine on the mk3 with AUM engine

[Yohan]

Seems 2.25" is the general opinion. Thanks.